Table of contents

2020 the 4^th International Conference on Fluid Mechanics and Industrial Applications (FMIA 2020: http://www.icfmia.org) includes original and peer-reviewed research papers and held online on June 27-28, 2020. This conference was sponsored by Asian Union of Information Technology, and was attended by academicians, researchers, entrepreneurs, government agencies and policy-makers, postgraduates.

FMIA 2020 is the annual international conference devoted to the discussion of recent developments and applications of parallel computing in the field of fluid mechanics, CFD, fluid power, fluid flow and related disciplines. The field of fluid mechanics is vast and covers numerous and diverse applications. The conference covered a wide range of topics, including basic formulations and their computer modelling as well as the relationship between experimental and analytical results. The meeting provided a forum for discussing new work on fluid mechanics and in particular for promoting the interchange of novel ideas and the presentations of the latest developments in this field. This conference will also provide an ideal environment to develop new collaborations and meet experts on the fundamentals, applications, and products of the mentioned fields.

FMIA 2020 received 379 manuscripts, and 92 submissions had been accepted by our reviewers. By submitting a paper to FMIA 2020, the authors agreed to the review process and understood that papers would undergo a peer-review process. Manuscripts were reviewed by appropriately qualified experts in the field selected by the conference committee, who took detailed comments and-if the submission was accepted-the authors would submit a revised version that took into account this feedback. All papers were reviewed using a double-blind review process: authors declared their names and affiliations in the manuscript for the reviewers to see, but reviewers did not know each other's identities, nor did the authors receive information about who had reviewed their manuscript. The committees of FMIA 2020 invested great efforts in reviewing the papers submitted to the conference and organizing the sessions to enable the participants to gain maximum benefit.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

□ Type of peer review: Single-blind / Double-blind / Triple-blind / Open / Other (please describe)

Double-blind. By submitting a paper to FMIA 2020, the authors agreed to the review process and understood that papers would undergo a peer-review process. Manuscripts were reviewed by appropriately qualified experts in the field selected by the conference committee, who took detailed comments and-if the submission was accepted-the authors would submit a revised version that took into account this feedback. All papers were reviewed using a double-blind review process: authors declared their names and affiliations in the manuscript for the reviewers to see, but reviewers did not know each other's identities, nor did the authors receive information about who had reviewed their manuscript.

□ Conference submission management system: Conference Management Toolkit (sponsored by Microsoft Research) and Email

□ Number of submissions received: 379

□ Number of submissions sent for review: 371

□ Number of submissions accepted: 92

□ Acceptance Rate (Number of Submissions Accepted / Number of Submissions Received X 100): 24.3

□ Average number of reviews per paper: 2

□ Total number of reviewers involved: 32

□ Any additional info on review process: Fluid mechanics is a very small division of physics. Therefore, there are fewer research institutions and researchers. Although it is a blind review, reviewers and authors often know each other.

□ Contact person for queries: Jun Xiao

This paper conducts a detailed numerical investigation to study the evolutions of flow topology and aerodynamic losses in a low-aspect ratio compressor rotor operating from freewindmill condition (near stall point) to highly loaded windmill condition (near choke point). Firstly, a simplified numerical calculation method based on energy transfer between rotor blade and working fluid is employed to capture the windmill points at low rotational speeds. Then, the influences of windmill on tip leakage loss are analyzed. At windmilling conditions, the tip leakage flow travels across the clearance from suction to pressure side and causes blockages near the pressure surface in the casing end-wall region, which is quite different from the flow phenomenon at freewindmill conditions. Finally, the influences of windmill on flow separations are investigated. In tip region, with the rotor operating from freewindmill to highly loaded windmill condition, the flow separation switches from suction surface separation to pressure surface separation, and both the intensity and size are increased. Unlike near the tip, the hub separations always appear on the suction surface and a radial growth is observed near the trailing edge at the highly loaded windmilling condition, which is not presented at both the near stall and windmill points.

Tilt-rotor aircraft is a new type of aircraft which can take off and land vertically and cruise at high speed. It can be used to perform specific tasks by special departments such as public security or fire rescue. The terrain environment and threat of tasks are complex and changeable. In order to ensure flight safety, the flight trajectory should be planned in advance. As a global optimization algorithm simulating biological evolution process, genetic algorithm is mostly used in two-dimensional flight path planning. In this paper, the three-dimensional digital map is preprocessed according to the actual mission environment and constraints of the tiltrotor aircraft. The related genetic operators and individual evaluation function of the genetic algorithm are improved to reduce the calculation of the trajectory planning and effectively avoid the partial optimal solution. The simulation results show that after preprocessing the 3D digital map, a 3D mission trajectory with the best cost in the complex mission environment can be successfully planned by the improved genetic algorithm.

Dredging engineering is widely used in port and waterway construction, water conservancy facilities construction, environmental protection dredging, land reclamation, subsea tunnel excavation and deep-sea mining, among which drag suction dredger is an important tool for dredging operation. During the process of its construction, the mud overflow process is an important link to realize the mud treatment of excavation. According to the actual engineering conditions, the loading and overflow process is an important part of the treatment of excavated slurry. With the increasing requirements of environmental protection, the related ecological pollution caused by dredging has become a hot spot today, and the diffusion of overflow slurry is one of the sources of pollution generated by dredging suction dredgers. Therefore, combining with actual engineering conditions, this paper adopts the theory of computational fluid dynamics (CFD) to study the diffusion characteristics, diffusion range, and influencing factors and proposes construction strategies to reduce its pollution impact.

Based on the hybrid methods of cavitation transient simulation of multiphase flow and the boundary element numerical acoustic calculation, the noise of contrarotating propellers in states of cavitation and non-cavitation is calculated, the increase quantity of the noise spectrum level in cavitation relative to in non-cavitation condition is analyzed; the calculated noise value and the tested value are compared. The multiphase flow transient simulation includes three simulations: unsteady Reynolds-averaged Navier-Stokes method (URANS), scale adaptive simulation (SAS) and detached eddy simulation (DES). The testing result shows that the open water performance curve of propellers coincides well with the experimental result in the range of large range of feed coefficient. SAS presents a comparable ability with DES in capturing the pulsating pressure of cavitation and can respond well to the unsteady load noise. RANS (Reynolds-averaged Navier-Stokes) is appropriate for the low frequency noise. The calculating error of line spectrum cavitation volume pulsation 1 kHz is less than4.23 dB, and the average error of spectrum level 1/3 Octave band is less than1.83dB in the frequency band of 1 kHz-3kHz, and the predicted error of the total sound pressure level is less than 2.74dB, And the attenuation coefficient of sound pressure level with is calculated by simulation, which can provide certain help for the design and the noise prediction of propellers.

In this paper, based on the Eulerian Lagrangian model, the non-phase change flow process of the coarse particle slurry in the horizontal pipeline is studied. The particle motion state is tracked, the dynamic characteristics of the coarse particle slurry in the pipeline transportation are explored, and the resistance characteristics of the pipeline and the operation stability under different conditions are analyzed. The comparison of the results of velocity distribution, concentration distribution and pressure curve with the empirical formula and experimental data shows that the simulation results are in good agreement with the calculation results of wasp formula and the experimental values of Roco&Balakrishnam, and the simulation can better describe the flow characteristics in the basin. In addition, the flow characteristics of particles are further analyzed according to the key factors such as the flow stability, the transition process and the critical deposition velocity of particles in different positions of the pipeline.

Bubble atomization technology, originated in the 1990s, has the advantages of simple structure, good atomization effect, low influence of liquid viscosity on atomization effect and low energy consumption. At present, it is widely used in the fields of combustion, spraying and fire fighting. In order to further expand the application field of bubble atomization, the possibility of applying bubble atomization to cooling and cooling is studied in this paper. In this paper, six types of bubble atomization nozzles with different structures are designed and a special experimental platform is built to measure the data of six types of nozzle. The flow characteristics, droplet size distribution, droplet velocity distribution and other parameters of six kinds of bubble atomizing nozzles were studied, and the experimental results were compared and analyzed. On this basis, Fluent simulation software was used in this paper to simulate the gas-liquid two-phase distribution, velocity distribution and spray velocity distribution at the nozzle outlet of the mixing chamber structure, so as to supplement and verify the experimental results. Different nozzle structures have great influence on the atomization effect of the bubble atomization nozzle. This conclusion will play a certain role in the design of the bubble atomization nozzle in the future.

The aero-thermal-elastic coupled simulations of an air-cooled turbine vane were carried out by a developed coupled solver, HIT3D, employing the finite difference method. The pressure on the vane surface and the temperature in the solid vane were obtained by the coupled heat transfer simulation, then the single-way aero-elastic and thermal-elastic analysis on the turbine vane were performed. It shows that the predicted profile temperature employing the transition model agrees well with the measured one, the blade deformation caused by aerodynamic force is negligible, and that the greater thermal deformation and thermal stress locate at the blade leading edge pressure side and at the blade trailing edge, as the result of the strong temperature gradient and the constraint at the vane endwalls.

Implementing the producing degree of reserves in the developed area is of great significance for timely understanding of oil and gas development trends in the developed area, and then taking targeted adjustment measures to improve oil and gas producing efficiency. On the basis of the analysis of different scale pore percolation capacity of reservoir and the study of four kinds of porosity (connected porosity, effective porosity, flowing porosity, filling porosity) and their corresponding calculation models of oil saturation, a quantitative characterization parameter - "oil and gas producing efficiency" of the producing degree of reserves in the developed area is proposed, and its theoretical discussion and case analysis are carried out. Research shows: 1) Oil and gas producing efficiency is the ratio of the reserves involved in percolation to geological reserves in the developed area of the oilfield, which is finally expressed as the ratio of the product of the flowing porosity and the original oil saturation of the flowing pores to the product of the connected porosity and the original oil saturation of the connected pores. 2) Reservoir flowing porosity and the original oil saturation of flowing pores are a function of displacement power, while the original oil saturation of connected pores is a function of reservoir forming power. Therefore, the oil and gas producing efficiency is essentially a coupling function of displacement power and reservoir forming power. 3) When the displacement power is greater than the reservoir forming power, the oil and gas will be fully developed, and the oil and gas producing efficiency will be 1; when the displacement power is less than the reservoir forming power, the oil and gas will be partially developed, and the oil and gas producing efficiency will be less than 1. 4) The calculation examples of X oilfield in Ordos Basin show that the connected porosity is 11.2%, the original oil saturation of the connected pores is 57.1%, the flowing porosity is 5.32%, the oil and gas producing efficiency is 0.832, and the oil and gas are partially developed. If the oil and gas are to be fully developed, the production pressure difference can be increased from 4.1MPa to 6.2MPa. 5) The study of oil and gas producing efficiency deepens the understanding of reserves producing status in the developed area of the oilfield, and has guiding significance for the targeted production adjustment and production pressure difference optimization of the oilfield.

Taking the aerodynamic calculation of high-speed aircraft as an example, this paper introduces the modelling and application of computational fluid dynamics in aircraft design. The application of computational fluid dynamics in the design of aircraft is accompanied by the development of computer technology and aerodynamics. From the earlier solution of the Euler equation and the NS equation from a macro perspective, to the solution of the NS equation with chemical reactions and ionization that considers the influence of real gases, and from the micro perspective, the Monte Carlo method is used to directly simulate and solve the gas molecule motion, that is, It represents the development of computational dynamics theory and is also the result of the development of computer technology today. This article discusses the application of computational fluid mechanics, including the selection of mathematical models, the selection of calculation methods, and its application to special problems in aircraft design.

In order to maximize the energy extraction potential from the marine resource, the primary task is to improve the power generation efficiency of multi-unit turbine arrays. There are many factors that affect the power generation efficiency of hydro turbine arrays. This paper mainly studies the influence of the effects of array structure parameters on the flow structure of the near-wake flow field and the energy utilization. The numerical simulation results are compared with the experimental data to verify the reliability of the numerical model. The double-row staggered arrangement of the turbine array is selected, and the size of the array structure parameter, the horizontal distance Dx and the vertical distance D_y, is changed to calculate a series of working conditions. The analysis of the results shows that when the horizontal distance D_x is 2.5RD and the vertical distance D_y is 2RD, the energy efficiency of the turbine array will reach the highest.

This study investigated the Computational Fluid Dynamics (CFD) simulation of pollutant emission in a natural draft dry cooling tower (NDDCT) with flue gas injection. In order to predict the diffusion and distribution characteristics of the pollutant more accurately, Large Eddy Simulation (LES) was applied to predict the flow field and pollutant concentration field and compared with Reynolds Average Navier-Stokes (RANS). The relationship between pollutant concentration pulsation and velocity pulsation is emphatically analyzed. The results show that the maximum value of LES is about 43 times that of RANS for the prediction of pollutant concentration in the inner shell of cooling tower. Compared with RANS, LES can simulate flow field pulsation with a smaller scale and higher frequency.

The small propeller with serrated trailing edge of the UAV has the characteristics of low aerodynamic noise. In this paper, based on the momentum-leaf theory and modified the airfoil parameters, the aerodynamic performance calculation method of the propeller with a serrated tail structure is put forward. Combined with the CDF technology of three-dimensional aerodynamic performance analysis of small propeller blades at low Reynolds number, this method was used to calculate the aerodynamic performance of the small propeller with serrated tail structure, and the calculation results were experimentally verified. The experimental results show that, using the modified airfoil parameters, the established aerodynamic performance calculation method of the tail serrated structure propeller hover state has a good effect.

Different from traditional aircraft, morphing wing aircraft can change their own wingspan in the process of flying, so as to adapt to different environments and tasks, and reduce the space they occupy in transportation and storage. In this paper, a reasonable analysis of the aerodynamic layout of the aircraft wing is carried out, and a large number of data research is done on the most important aileron. Based on the basic theory, the working mechanism of the aileron is analyzed, and finally the optimal position of the aileron is obtained, i.e. the position of relative span 15.4% - 57.4%, relative span is up to 42%. Finally, the surface streamline of the aircraft in flight is studied by CFD simulation, and the skin scheme is determined based on it. Profili, a professional airfoil analysis software is applied to analyze parameters of airfoil, it finally results that the change of wingspan of rectangular wing has no effect on lift coefficient, drag coefficient and lift drag ratio, but it has obvious effect on lift, it proves that the aerodynamic layout of the wing is reasonable. Through the load test, it shows that the increase of lift is consistent with the theoretical prediction by about 50%. After a series of ground and flight tests, the practicability and safety of the morphing wing aircraft are proved.

The cyclone is an important part of the combustion chamber of the gas turbine and has a direct impact on the combustion performance in the combustion chamber. Therefore, it is of great value to study the structural characteristics of the cyclone. This paper firstly analyses the structural characteristics of cyclone that have the greatest impact on the performance of the combustion chamber through the relevant data and the structural parameters of the actual combustion chamber. Then appropriately simplifies the structure of the combustion chamber, designing a F-class combustion chamber with cyclone. Numerical simulation method is compared with the actual combustion chamber data to verify whether the design of the cyclone meets the requirements, thus preliminary determining the blade installation structure and the number of blades of the combustion chamber cyclone. In the end, using the model combustion chamber as a blueprint, adjust the blade characteristics of the cyclone for different installation angles (40°, 45°, and 50°) and the number of blades (6, 8, and 10). The combustion chamber model is simulated to determine that the flow field of the combustion chamber is the best when the angle is 45°and the number of blades is 8.

The material loss and equipment failure caused by erosion wear is a serious problem in solid-liquid mixture flow in the mechanical, metallurgy, energy, building materials, transportation, aviation, aerospace, military and other industrial departments. Therefore, understanding the erosion wear mechanism, the influencing factors, and how to set up mathematical model are very important. Since the 1950s, the research on the erosion wear made great development. The purpose of this paper is to give a comprehensive review about previous research work of erosion wear. Firstly, the mechanism and influencing factors of erosion wear are introduced. Secondly, the forces of particle caused by fluid are analysed and several erosion models which tested by experimental with good results are introduced. Thirdly, the method of erosion numerical simulation combining computer software and CFD theory is introduced. Finally, based on the conclusion, some useful conclusions are drawn and the future research direction is prospected.

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The internal cavity is widely used on new generation aircraft. However, there are some new aerodynamic and acoustic issues accompanied with the internal cavity. Store separation is a challenge when separated from a high-speed cavity, the store usually generates nose-up pitch moment due to the separated flow and large static pressure gradient, which is a threat to store separation safety. Leading edge spoiler is an effective passive flow control method to improve the store separation characteristics, however the effects of varisized leading edge spoiler on store separation characteristics are still unknown. In this paper, a parameterized leading edge spoiler model is established to investigate the store separation characteristics by leading edge spoilers flow control before supersonic cavity, a small aspect ratio fly-wing aircraft and a simplified store model are employed to simulate the store separation characteristics. Numerical results show that the leading edge spoiler lifts the shear layer and significantly changes the pressure distribution inside the cavity, which makes the store a nose down pitch angle during separation. The height of leading edge spoiler greatly influences the store separation characteristics for it changes the shear layer and vortex structure. The angle of spoiler and the gas between spoiler and aircraft also have great effects on store separation, larger angle and smaller gas lead to less nose-up angle.

Surface texture technology has been proven to be an effective way to improve the lubrication performance of friction surfaces. In order to obtain the optimal surface texture distribution parameters, taking the spherical crown pit texture model as the research object, and selecting the unequal rectangular control unit to establish the surface texture distribution model with different horizontal and vertical distribution distances (densities).According to the principle of fluid dynamic pressure lubrication, a two-dimensional Reynolds equation based on the N-S equation is established and solved by the multigrid method to study the effect of texture distribution parameters on the surface hydrodynamic lubrication under plane motion. The results show that when the texture unit Lx is 3.4r and the aspect ratio Ly / Lx is 0.82, the optimal oil film bearing capacity can be obtained. When the control unit of the boundary pit is appropriately increased so that the left and right sides of the pit at the boundary are about 3.4r, the oil film pressure stability can be effectively improved.

The element free Galerkin method (EFG) is much interest in recent years due to its merits of only node information needed in constructing shape functions and high precision. However, its low computational efficiency becomes a technical issue in the simulation of realistic problems. To develop a more efficient and accurate method, the point interpolation method using quadratically consistent three-point integration scheme (PIM-QC3) is proposed, based on consistency framework for meshfree nodal shape function and its derivatives. And the shape functions along with corrected nodal derivatives at integration points, adopt quadratic basis, meet the differentiation of the approximation consistency (DAC) and the discrete divergence consistency (DDC). In addition, they possess Kronecker delta property and could enforce displacement boundary conditions simply. The T6-Scheme is utilized for node selection in constructing approximation, to avoid the singular moment matrix and make the computation of shape functions simple. Numerical results show the excellence of the proposed method in accuracy and efficiency of all tested methods. Specially, it is more efficient than three-point integration scheme based on element-free Galerkin method. The research in this paper could provide an efficient and reliable tool for analysis of engineering structure.

Single bubble formation behaviours which develops from submerged nozzle under the quasi-static mode in stagnant deionized water in a rectangular column are studied. Bubble formation behaviours are captured by a digital high-speed camera and information of the induced adjacent flow field is synchronously obtained via the particle image velocimetry (PIV) system. Interactions of induced bubble adjacent flow patterns with bubble formation behaviours are investigated at each stage of a three-stage bubble formation model. Results indicate that recirculation of the continuous phase near the bubble base accelerates rapid detachment of the bubble and the dynamic pressure variation in the liquid induced by bubble behaviours is the main reason why such flow pattern appears.

Aiming at the problems of short spray distance and poor atomization effect in pesticide spraying. In addition, in order to enhance the initial velocity of the droplets and the secondary atomization of the droplets, a new air-driven combined electrostatic nozzle based on the Venturi effect is designed in this paper. And a method for accelerating and atomizing mist droplets using the Venturi effect is proposed. Combined with the distribution of airflow from the venturi, the acceleration and atomization effects of the nozzle were verified and analyzed. Using the factor design test method, three structural parameters, namely the distance A from the nozzle outlet to the venturi mouth, the retracting radius B of the venturi mouth, and the extension distance C of the venturi mouth were tested, and the following conclusions were drawn. At the 1% significance level, the single factors A, B, and C have significant effects on the average velocity of the venturi throat. The interaction of two factors, AB, AC, and BC, had no significant effect on the average velocity of the venturi throat. The interaction of three factors ABC has a significant effect on the average velocity of the venturi throat.

The Kriging-based genetic algorithm applied to aerodynamic optimization design encounters a problem of unexpected sample size. In this paper, an adaptive method is proposed that the search space moves with the local optimum. The automatic division and hierarchical approximation of search space are realized by taking the selection of refinement samples into account. The typical function optimization and transonic supercritical airfoil drag reduction design are performed using this method. Results show that the number of samples required is greatly reduced, and the aerodynamic performance of the airfoil is efficiently improved.

In order to reduce the moisture content of flue gas in coal-fired power plants, this paper puts forward a novel spraying system with upward spraying and downward gas flow (ST-UD). And the heat and mass transfer models of ST-UD in fluent were validated against experiment data. Then orthogonal simulation experiment was carried out to get the relationship between the four influence factors and the two evaluation indices. Through the range analysis and trend analysis, it can be found that the influence degree and the influence trend of factors on evaluation indices. The conclusion of this paper provides a reference for the heat-transfer performance optimization of other spray towers.

The goal of this paper is to implement an accurate and robust solver for compressible Navier-Stokes equations coupled with the Spalart–Allmaras model, which possesses the capability of shock-capturing and predication of boundary layer and separated flow. In a given stencil width, a WENO-Z scheme equipped with Roe flux difference split method is used to calculate the inviscid flux, and central differencing scheme for the viscous terms are employed. The explicit Runge-Kutta is adopted for the temporal discretization. The simulation results of selected cases are given to verify the validation of the solver.

Planning an automatic detection system of the air tightness of medicine box is very necessary for growing demand for storage of pharmaceutical products. In this study, the high-fidelity CFD study is performed for the air tightness of the medicine box, using the LBM algorithm. The high-fidelity results indicate that after about 5.24 s, the stable value of the average static pressure of the ring cavity remains at about -9414 Pa. The slit flow in the early stage of micro-leakage is very complicated, especially for the initial stage. The location of the micro-leakage is concentrated in the directions of 1 o'clock, 4 o'clock, 7 o'clock and 11 o'clock along such edge of the end cap, therefore, the sealed end cover needs to be further improved. Additionally, the idea of this research work can provide a good basis and reference for the subsequent series of related airtightness studies.

Many industrial applications involve the measurements of the velocity and size for the design of the products. Examples of such products are kitchen ventilator, water pump, household appliances and industrial oriented nozzles for fire suppression and paint. In the area of industrial safety, validation of the face mask for leakage is also an important aspect of the mask design. Fire suppression, paint nozzle, and mask filter are items which we encounter and rely on in our daily life. The design of products of those items to provide the best and optimal outcome is a critical aspect of the research and development in many industries. This paper covers two laser based techniques, Phase Doppler Particle Analyzer (PDPA) and Particle Image Velocimetry (PIV), for the design of fire suppression nozzles, paint nozzles, and N95 filter mask. The results of velocity profiles and droplet size distributions provided the critical information to evaluate the design and to allow corrections of deficiency in the process. Both the PDPA and PIV are non-invasive laser based techniques which introduce no disturbance to the flow and particle fields to be measured, giving the true representation of the measurement results.

Recently reduce in fuel consumption and concern regarding the ground vehicle safety, automotive engineers are faced with the immediate task of introducing more efficient aerodynamic performance vehicles. Hence, the rear spoiler attached on the ground vehicle was presented. Rear spoiler is a device commonly found on road vehicle for improving their aerodynamic performance. Review on the research effects of the rear spoiler aerodynamic analysis on ground vehicle performance is reported in this paper. This review intends to enhance the stability and safety by attaching the rear spoiler on ground vehicle. The review mainly focus on aerodynamic analysis and control of the rear spoiler for different types ground vehicle in term of improving vehicle performance. Researches carried out by a number of researchers with regard to analyze and control the rear spoiler of ground vehicle and their effect on ground vehicle performance. Aerodynamic analysis i.e. computational fluid dynamics(CFD), design optimization, drag coefficient (C_d) and lift coefficient (C_l) and control methods i.e. passive control and active control had been reviewed. Meanwhile, progressive research on the rear spoiler aerodynamic analysis was observed due to its flexibility for wide range of application in the different type vehicles.

In this contribution, we described a Dynamic Mode Decomposition (DMD) analysis of a turbulent channel flow database at a moderate friction Reynolds number Re_τ ≈ 950. More specifically, a composite-based DMD analysis was conducted, employing hybrid snapshots assembled by skin friction C_f(t_k) and either instantaneous Reynolds stress $({u}^{^{\prime} }{v}^{^{\prime} }(\overrightarrow{x};{t}_{k}))$ or streamwise velocity fluctuation $({u}^{^{\prime} }(\overrightarrow{x};{t}_{k}))$ fields. The DMD modes thus obtained were sorted according to its relevance to the C_f: less than 2% of the modes suffice to reconstruct accurately either the streamwise velocity or the Reynolds stress profiles near the wall. Furthermore, we aim to extend our preliminary work on the analysis of the turbulent database, by considering snapshots encompassing a larger spatial subdomain and covering a longer temporal span. However, this study involved data matrices significantly larger than that one, which the memory footprint of this problem exceeds a typical workstation. Accordingly, we have resorted to the parallel, memory distributed DMD algorithm as a reinforcement. With this enhanced composite DMD algorithm, flow features of moderate and even large turbulent channel problems could be identified and characterized.

This paper performs the effect of solid volume fractions (0.09< SVF<0.64) on the flow through and around a square cylinder array at Re=63832. A delayed vortex shedding occurs in 8x8 array (SVF) while the Strhoul number is slightly higher than the solid one. For the intermediate SVF (0.25<SVF<0.49), the separated shear layers (SSLs) contain large-scale turbulent eddies but their ends cannot interact to generate wake billows. The maximum of root mean square of transverse velocity along wake center-line decreases monotonously as SVF decreases, and several ways of defining the spatial extent of the wake region are discussed.

Aimed at the improvement of ability of the high altitude test (HAT) facility for rocket engine, a new designed secondary-throat diffuser with ejection of low total pressure and supersonic cold air is proposed. The main structural characteristic of the new-designed diffuser is that: a groove is added to the start of the secondary throat of diffuser, and the supersonic cold air with low total pressure is ejected into diffuser to form the gas film, which leads to a reduction of the wall temperature and thermal load of the new-designed diffuser, and an improvement of the ability of diffuser holding shock train. The effects of cold air on flow characteristics and performance of diffuser are numerically investigated in detail under different conditions including total pressure and Mach number. The results show that the wall temperature along the diffuser increases with an increase of Mach number, and decreases with an increase of total pressure; with an increase of Mach number, the starting position of pressure rise moves upstream to the inlet of diffuser; and with an increase of total pressure, the starting position of pressure rise moves downstream to the end of diffuser.

Valve leakage is a very important factor affecting the normal operation of pressure piping system. In this paper, based on the analysis of the mechanism of acoustic emission detection in the valve, under the condition of laboratory, the experimental platform and acoustic emission detection devices are designed and built. The experimental results show that acoustic emission technique can be used to detect leakage and evaluate leakage rate, which is very important for the real-time monitoring and quantitative detection of leakage in the pressure pipeline valve.

The two-dimensional numerical simulation for NACA0015 airfoil and S325 airfoil were conducted with k-ω SST turbulence model. For the k-ω SST turbulence model could not predict the airfoil stall characteristics accurately, the non-equilibrium turbulence transport nature was systematically analyzed. The study showed that: the turbulent viscosity scope simulated by the original k-ω SST turbulence model was smaller which resulting in the model could not accurately simulate the turbulence transport properties in the separation zone; By increasing β^* or decreasing α₁ can improve the capabilities for predicting the transport characteristics of non-equilibrium turbulent, and then improve the accuracy of numerical simulation for stall characteristics of the airfoil, it also helps to improve the accuracy of numerical simulation of wind turbine blades.

The movement and distribution of the airflow field of the sprayer are very important for the distribution and penetration of the droplets. It is the focus and difficulty of the research to find the airflow field distribution of the fan outlet that matches the parameters of the canopy of the fruit tree. In order to study the influence of the angle change of the deflector of the orchard air-driven sprayer on the three-dimensional spatial distribution of the external air velocity field, this paper numerically simulated the external flow field based on computational fluid dynamics. The spray requirements of different fruit tree crown shapes were analyzed. The ICEM CFD software was used to model the external flow field. In order to improve the calculation efficiency, the model was divided into mixed grids. The k-ε turbulence model and Fluent solver are used for numerical solution. The flow fields of different deflectors are analyzed, and the influence of different positions and different sizes of deflector angles on the external flow field is determined.

In order to investigate the effect of the air deflector sprayer deflector angle on the droplet drift, this paper based on the particle tracking technology of the discrete phase model of CFD, studied the characteristics of droplets at different positions of the deflector angle. In this paper, six groups of nozzles are set at the air outlet in the cuboid calculation area with the conditions of 4000mm × 2000mm × 3300mm. Under the same wind conditions, the sprayer's deflector changes and the droplet motion characteristics are analyzed. The results show that the droplets are accelerated by the high-speed airflow, and the velocity gradually becomes smaller as the distance increases. The speed is stable at a position close to the canopy of the fruit tree, and the speed is roughly between 8m / s-15m / s, which is almost the same as the wind speed delivered.

Four different design of FDM molding chamber with hot air circulation were proposed to meet the requirements of temperature uniformity of FDM rapid prototyping equipment. Fluid and solid domain model of FDM molding chamber was established by finite numerical simulation method in order to analyze the influence of the heating rod, blower, air inlet and outlet position on the temperature uniformity and air flow. The results show that the temperature uniformity and air velocity evenness are highest when the heating rod is located on both sides of the molding chamber, the blower is lied at the bottom, the air inlet is located above the left side, and the air outlet is above the right side. And the temperature uniformity is up to 99%. FDM molding chamber prototype was developed according to the simulation results. Air flows evenly, and temperature uniformity is as high as 97.66%, which verified the accuracy and effectiveness of the simulation results deeply.

The flying-wing aircraft is a promising concept for the mid or long-term commercial aviation due to its excellent performance in aerodynamic and structure, which has been studied by a number of investigators both experimentally and computationally. However, the conditions in wind-tunnel testing do not necessarily reflect those observed in free flight, the support structure interference is an important factor to affect experimental data collected from wind tunnels. Support interference characteristics of a flying-wing model from subsonic to supersonic speed is investigated by numerical simulation methods. Results show that grid convergence is obtained with the series of grids, which implies that the solutions are in the asymptotic range. The support has a relatively small effect on aerodynamic characteristics of flying-wing aircraft at low speed while has a relatively large effect on drag at transonic speed and supersonic speed.

The stochastic characteristic of lid-driven cavity flow under the condition of Re=100 is investigated in this paper by a non-intrusive polynomial chaos method. The lid-driven velocity and viscosity coefficient are assumed to be two independent stochastic input variables with Gaussian distributions. The velocities at every grid points are the response of interest and no longer deterministic but stochastic. Their stochastic characteristics are represented by Hermite polynomials with interaction effects between two input variables considered. The statistical results, including mean value, variance and the relative contribution of each input variable to the variance of outputs are analysed. It is found that the variance of velocity shows similar structures with its magnitude of mean value and the correlation coefficient is larger than 0.96. The nearly linear correlation coefficient shows that the lid-driven velocity is the main factor affecting the velocity distribution and the influence of viscosity coefficient on most regions is unimportant. The analysis of stochastic flow field helps understand the inherent mechanism in the lid-driven cavity flow.

Based on the principle of forced convection heat transfer in a single tube with air transverse sweep, an experimental device of forced convection heat transfer with equilibrium point tracking was developed. The device controls wind speed, heating power and other experimental working parameters by MCU, synchronously adjusting, collecting and analyzing working parameters in real time, to realize the tracking of thermal balance point. Newton cooling formula and criterion relation are adopted to calculate Nusselt number and Reynolds number automatically, to fit criterion relation and to display correlation curve automatically, and to realize automatic data analysis. The test results show that the experimental results are in good agreement with the empirical correlation formula within the Reynolds number range of 40 ~ 4000, which realizes the automatic tracking of thermal equilibrium point and meets the requirements of real-time automatic measurement in forced convection heat transfer experiment.

The bubbly wake characteristics of the underwater vehicle are the basic of wake homing techniques. The bubbly wake of the underwater vehicle caused by the side exhausting is simulated based on the Mixture model and the Multiple Reference Frames technology. The results show that due to the side exhausting of the underwater vehicle, a wake with lots of bubbles appears in the sailing through area. The bubbly wake of the underwater vehicle lasts for a long time. As a result, the bubbly wake can be observed in the area far away from the underwater vehicle, which is signification enough to be detected by the bubbly wake detector. Besides, the bubbly wake characteristics for the cases of the underwater vehicle with/without the propeller are much different.

To control the separation of flow past an airfoil with a simple jet mechanism, based on the Large Eddy Simulation from Favre, a suction-blowing combined jet is studied with holes placed on a NACA0012 airfoil's upper surface and Re = 10⁴ attack angle α = 6°. The results show the control mode of front-hole suction and back-hole blowing is effective. It can suppress the disturbance in the flow field and increase the lift-to-drag ratio of the airfoil at the same time.

A three-dimensional model and finite element model of the diesel engine SCR catalytic converter were established by using ANSYS software. The numerical simulation of the internal flow field for the diesel engine SCR catalytic converter was performed. The results show that the pressure loss of the catalytic converter is larger and the velocity distribution in the front of substrate is nonuniform. On this base, the effects of the diameters and lengths of the substrate on the catalytic converter's internal flow field characteristic were studied. The results show that when the substrate's length increases, the pressure loss increases and the velocity distribution uniformity in the front of substrate becomes worse. When the diameter of substrate increases, the pressure loss decreases and the velocity distribution uniformity in the front of substrate becomes better. Therefore, the structure of catalytic converter was optimized. Through the optimization of the structure, the velocity distribution in the front of substrate is more uniform. The passing capacity of substrate is increased. The conversion efficiency of catalytic converter is improved. The back pressure is reduced.

In order to obtain the drag coefficient in accuracy, it needs to correct the model's buoyancy drag coefficient in the high-speed wind tunnel test. However, there are several methods on calculating the buoyancy drag coefficient, each will generate a result differently. Three types of methods are studied in this paper, the formulas are derived, the buoyancy drag coefficients are calculated, and the results are compared in the end. It shows that the most exact method is the one based on pressure fitting function, it's suitable for correcting the model's drag coefficient with high accuracy requirement.

To solve the problems of secondary flow, turbulent vortex, and instability of the flow field in the elbow of the water flow standard device, some 3D geometric models of the elbow were established, and the flow field numeral calculations of the elbows were carried out based on the 3D models. The study shows that appropriately increasing the turning angle and the number of deflectors has a significant effect on improving the flow field quality in the elbow. While it is not obvious that the effect of increasing the thickness of the deflector on the flow field quality, and which may increase the requirements for the power source of the standard device. It is concluded that the elbow with a 135°turning angle and 2 pieces deflectors may be the optimal choice.

In the design stage of an anti-icing system for an aircraft, the heat load on a protection surface must be correctly calculated. In this study, the heat load calculation method for an aircraft wing model was analyzed. The calculation process was presented and the correctness of the method was validated using existing published experimental data. And the effect of variation of incoming flow speeds, flight altitudes, and temperatures on the surface heat-load distribution was given. The results show that the heat load is mainly located at the leading edge of the wing. The maximum value of the heat load can reach 3500w/m2 and the closer to the tip of the wing, the larger the heat load value will be. The heat load curve has a trough in the middle and two shoulders at each side. The range of the non-zero region and the amplitude of the heat load is in proportion to the flow speed. However, the variation of altitude has a non-obvious effect on the heat load results. As the temperature rises, the amplitude of the heat load increases, but the distribution characteristic of the curve remains the same.

In this paper, the temperature change curve of the casting and frozen sand mould during the solidification process of the A356 aluminum alloy in the frozen sand mould is tested. According to the actual temperature change curve of the casting surface and the sand mould surface, the interface heat transfer coefficient between the frozen sand mould and the A356 aluminum alloy could be reversed analysis. The results show that when the casting temperature is lower than 550 °C, the interface heat transfer coefficient remains about 750 W.(m2.K)-1; When the casting temperature is between 550 °C and 610 °C, the interface heat transfer coefficient increases significantly; when the casting temperature is higher than 610 °C, the interface heat transfer coefficient reaches the maximum value, which is about 2300W. (m2.K) -1. At this time, this study simulates the solidification temperature field of aluminum alloy hub parts in the frozen sand mould according to the interface heat transfer coefficient calculated by inverse analysis, and the temperature field of resin sand mould casting was used as for comparison. The results show that: under the same solidification time, the temperature field of A356 aluminum alloy hub parts in frozen sand mould is lower than that of resin sand casting, freezing casting can realize the high-speed solidification process of different parts of complex castings.

In order to deeply understand the heat transfer characteristics of water and foam at high temperature with different inclination angles and initial surface temperature, pure water and foam were selected to conduct experimental research on high temperature surface liquid flow with inclination angles of 45 ° and 70 ° and initial surface temperature of 110 ° C, 210 ° C, and 310 ° C. It is found that the difference between the flow pattern and heat transfer of pure water and foam on the surface of high temperature metal plates is more obvious when the surface initial temperature is higher. The water flow form horseshoe-shaped low temperature region with the lateral width increasing and the longitudinal length decreasing on the higher temperature surface. The foam on the high-temperature surface is mainly cooled by the strip shaped area flowing in the mainstream direction; the length of the cooling area covered by the foam of the high-temperature surface is significantly longer than pure water.

To compare the aerodynamic characteristics of flame stabilizer by supersonic jet and flame stabilizer by subsonic jet, this article studies the size and length/width ratio of recirculation zone, size of jet trajectory at both supersonic and subsonic jet under the same geometry and boundary conditions in the ANSYS Fluent software program. The result shows that under supersonic jet the size, length/width ratio of recirculation zone and size of jet trajectory are bigger than under subsonic jet. Due to the size of recirculation zone is related to the burning range, that means using supersonic jet as a flame stabilizer can enlarge the stable burning range of a combustion chamber. It would make a big difference when the jet flame stabilizer apply to the gas turbine aircraft engine.

In order to study the fluid flow characteristics of the key components in hydraulic excited rotary valve,and then determine the area where the vortex and negative pressure to find the weak link in th e structure and analyze the performance of the valve. Simulate the flow field in the rotary valve by Fluent fluid analysis software, and setting different opening degrees under the same boundary condi tions. Studies showed that the velocity at the exit junction of the fluid in the rotary valve, and the vortex degree of pressure is large at the oil groove. When the opening degree is small, the nega tive pressure is large, the vortex is obvious. With the opening becomes large, and the negative pressure and the vortex are improved. The research provides a theoretical basis for the optimization and improvement of the rotary valve. Studies have shown: The velocity of the flow channel calculated under the turbulence RNG k − ε model is the largest, Realizable. The velocity of the flow channel calculated under the model is the smallest. For different models, the values of the low speed region are different, where Realizable k − ε Minimum model speed, The RNG k − ε model has the highest speed and standard. The speed of the k − ε model is in the middle; The high speed area is mainly concentrated in the corner area of the oil tank and valve mouth, The area of high speed area of the RNG k − ε model is smaller than that of the other two models, and the standard of the model is smaller than that of the other two models. The k − ε Model and the Realizable k − ε is no significant difference in the area of high speed area calculated by the model. The comparison draws the following conclusions: The results of the turbulence RNG k − ε model and the other two groups of models are more accurate when calculating the low velocity flow field. The Realizable k − ε Model and the RNG k − ε has the calculation results of the model are similar.

The aerodynamic performance of wind turbine blades is of great significance and value to the power output of wind turbines. Correct evaluation of blade performance is beneficial to the design and design of wind turbines. In the operating environment, the aerodynamic load on the blade is a combination of the aerodynamic pressure of the air and the additional force generated by its own rotation. Under different environmental conditions, the aerodynamic load on the wind turbine blades will be significantly different. Using advanced fluid mechanics, the developed program is used to perform aerodynamic simulation on a certain type of wind turbine blade calculation example to obtain the flow field and blade surface pressure coefficient distribution. The calculated results are in good agreement with the experiment, and the developed program can be used for aerodynamic analysis of engineering wind turbine blades, which is conducive to the development of wind turbine design.

In this paper, ANSYS FLUENT was used to simulate the gas-liquid two-phase flow in the process of micro-nano bubble aeration and optimized the central air intake aeration conditions. The particle size of microbubbles was 2 μm, the Eulerian model was used in multiphase flow model, and the standard k - ε model was used in turbulence model. The gas-liquid two-phase flow field with different aeration velocity was simulated. The effects of aeration time on gas holdup were studied. The results showed that the aeration effect was better with the increase of aeration speed, stronger turbulence, two-phase mixing and oxygen mass transfer.

Based on the China Knowledge Network Database (CNKI), a literature measurement analysis of the domestic computational fluid dynamics (CFD) application research was conducted. The results show that from 1973 to 2019, the number of articles published by CFD research has increased significantly year by year. The earliest literature on CFD published in the database was published in 1973, and more than 10 articles have been published annually since 2005. The text-issuing institutions are mainly well-known universities in China, among which Tianjin University has the most. Many masters and doctors in this university obtain degrees through researches related to computational fluid mechanics. CFD theory and software are mainly studied in Engineering technology and basic and applied basic research, and more research has been supported by the National Natural Science Foundation.

With the continuous integration of artificial intelligence technology and management disciplines, the emergence of new technologies and new concepts put forward new requirements for the cultivation of cross-disciplinary talents in management disciplines. At the same time, strengthening the development of cross-disciplinary integration is also a vital part of the "Double First-Class" universities construction. This article points out that the application direction of artificial intelligence technology in innovative talents of management discipline can be divided into three levels: computational intelligence, perceptual intelligence, and cognitive intelligence. Based on the three levels, formulated innovative talents in the management discipline cross-cultivation model that integrates innovation quality orientation, innovation performance orientation and innovation contribution orientation, designed a talent training operation mechanism based on multi-subject collaboration, facing the new education ecology in the era of artificial intelligence.

Design of a cryogenic heat exchanger for kerosene rapid cooling is carried out, and the heat transfer mode and structural form of the heat exchanger are preliminarily designed by theoretical calculation. The corresponding physical and numerical models are established, and the cooling characteristics of aerospace kerosene were studied by numerical calculation method. By comparison with experimental data, the validity and accuracy of the numerical simulation results are verified, which provide theoretical guidance for further research.

Aiming at the problem of optimal design of take-off quality in the process of missile overall design, on the basis of establishing the optimization model of missile take-off quality, three different optimization algorithms are used to optimize the calculation of missile take-off quality, by comparing the effects of the three algorithms on the takeoff mass optimization and aerodynamic parameters, the models and algorithms for different types of missiles are obtained.

The throttling ring plays an important role in the normal performance of the gun. The inner diameter of the throttling ring directly affects the gun's recoil stress law and recoil motion parameters. It is of great significance to study the failure mode and failure mechanism. By means of spectral test and analysis technology, wear particle analyzer and ICP-MS and FAAS method are used to test and analyze the content of abrasive particles and ions in the use environment of throttling ring, and to study and determine the failure mechanism of throttling ring.

In order to meet the heat dissipation requirements of outdoor transformers equipped with sound-absorbing barriers, this paper uses the finite element analysis software ANSYS Fluent to simulate the temperature field of outdoor transformers. Firstly, the simulation calculation model is established according to the actual typical outdoor transformer, and the finite element mesh is divided accurately. Secondly, the simulation parameters are set according to the field operation. Then, the distribution of the temperature field of the outdoor transformer and the effect of noise barrier on heat dissipation of outdoor transformer are obtained by the simulation calculation model. The simulation results in this paper provide a preliminary reference for the design of noise barriers of outdoor transformers.

Aiming at the complex flow phenomena with multiple speed scales and the high computational cost constraints of the rotor's finite ground effect, the momentum source methods to satisfy the computational accuracy and efficiency are developed. Combined with the preconditioning methods, which cope with multiple speed scales, a numerical simulation method for the finite ground effect of the rotor is presented. On this basis, the validity of the numerical method is verified by hovering case firstly. The thrust only slightly increases by 3.26% compared with the experiment. Then, the effects of rotor deviation and height on the aerodynamic performance of the rotor are studied, and a surrogate mode with finite ground effect is established, which is tested by the testing samples on its prediction accuracy. The conclusion shows that the momentum source method can be applied to the analysis and prediction of the finite ground effect of rotor hovering, and the finite ground effect has a significant impact on the overall aerodynamic performance of the rotor.

Numerical investigations of NASA Common Research Model under stochastic inflow conditions are analysed in this paper by Non-intrusive Polynomial Chaos (NIPC) method. Reynolds number, Mach number and temperature of inflow conditions are assumed to be independent stochastic variables. It is found that predicted drag mainly depends on Mach number of incoming flow. The contribution of Reynolds number and temperature to the variance of drag is negligible. The mean value of drag shows consistent convergence with grid refinement. The investigation of this paper quantitates the uncertainty induced by stochastic inflow conditions to drag prediction and recognizes the most significant input variable. This will help the validation of numerical methods with experiment.

Numerical simulations based on computational fluid dynamics are used to study the Magnus effect. The cross force can be obtained through solving the governing equations of the flow around rotating cylinder. Through analyzing the characteristics and structure of the flow field, the Magnus effect can be enhanced by using endplates to change the flow pattern. Numerical results prove the effectiveness and practicality of the improvement.

In the design of fish way, the flow pattern of the pool is an important design basis. Many factors need to be considered in the preliminary test of fish way in the laboratory. This paper introduces the design method and preliminary results of flow measurement test of fish way pond chamber. The results show that the layout and porosity of the partition wall should be considered in the design of natural fish way. Different partition arrangements and porosities have obvious influence on the flow pattern in the pool. In the flow pattern of the pool chamber, there is a clear main flow, but the flow rate is low behind the partition wall and near the side wall of the pool chamber.

Performance evaluation is an important part of simulated training, and also a challenging project in the development of simulators for aerial mechanist training. In this paper, the evaluation method is explained in detail, and then the evaluation model is put forward, and finally the application of comprehensive fuzzy evaluation is discussed in this paper.

With the development of new energy vehicles, thermal management of power batteries has become a hot research topic. Power battery thermal management has a very important impact on battery life, safety, charging, and other performance. In this paper, the heat transfer performance of a cooling process is studied by establishing a three-dimensional thermal management model of power battery. The results showed that the proportion of heat in the battery taken directly from the coolant was 91.6%, and the proportion of heat absorbed and dissipated into the environment by the components outside the cell by heat transfer and so on was 8.6%.

The flow field characteristics of increased velocity (Invelox) system under different wind direction were studied by computational dynamic fluid (CFD) method. Since the Invelox wind turbine system needs to be placed in external space to operate, the atmospheric boundary layer (ABL) wind profile must be considered. The Invelox system was simulated with uniform velocity inlet and exponential wind profile inlet. The results show that when the wind direction is more than 90 degrees from the axis of the venturi pipe, the power generation efficiency of the system will decrease sharply. When the Angle exceeds 120 degrees, the system does not generate electricity. After considering ABL, the speed ratio (SR) of the system will decrease.

Radiation hydrodynamics problem is mulitphysics field coupled and challenge in mathematics. A new scheme, IMEX, is put forward in solving RHD equations when the explicit method have an extremely small time step and implicit method have a complicated and high cost solver. RHD equations are solving by splitting the explicit operator and implicit operator with IMEX scheme. The results of Riemann problems are plotted and the scheme shows the effect to lower the computation cost.

Collector is one of the key parts of the high-speed free-jet wind tunnel, which directly affects the performance of wind tunnel. In this paper, a small high-speed free-jet wind tunnel is used as the test platform to carry out the start-up and operation characteristics test of wind tunnel. Start-up pressure characteristics were obtained at various Mach number, and the influence of the collector throat heights and collector positions on start-up pressure and matching pressure was preliminarily studied. The results show that the high collector throat height can meet the requirements of wind tunnel start-up and pressure matching. The closer the collector is to the nozzle, the smaller the corresponding starting pressure and matching pressure. However, this trend weakens with the decrease of Mach number, which lays a foundation for the development of large high-speed free jet equipment.

Haemodynamic conditions play a crucial role in the pathological development of aortic dissection (AD). However, it is challenging to quantitatively and precisely capture the flow features in vivo. In this study, a mock circulation loop (MCL) embedded with patient-specific aortic phantoms was proposed. In order to evaluate perfusion characters, a normal aortic model and an AD model were established with twelve main branches. The system is capable of replicating the aortic geometry, vascular compliance, characteristic resistance, and peripheral resistance of the cardiovascular system. By altering controlling parameters, it can mimic various cardiovascular conditions. The physiological healthy rest cardiac condition was reproduced and the rationality and accuracy of the system was confirmed by comparing the measured flow data from the MCL with a normal aortic phantom and the in vivo ultrasound velocimetry of healthy volunteers (maximum discrepancy was 4.69%). Different flow features between the normal and AD phantoms were quantitatively compared by pressure sensors and ultrasonic flow sensors under the same condition. Therefore, the proposed MCL can be applied as a research tool for in vitro haemodynamic analysis of the aorta. Moreover, it can be applied to evaluate the performance of interventional devices and to provide a realistic platform for trainings on interventional treatments.

For a methane (CH4) bubble rising in liquid, knowledge of bubble rising characteristics is crucial for the comprehension of methane dissolution rate and the inter-phase mass transfer. Here, the investigation of a methane bubble was performed using the computational fluid dynamics (CFD) technique and the volume of fluid (VOF) two-phase model. The deionized water of 13 MPa and 5°C was used as the carrier of the rising bubble. Bubbles with diameters ranging from 3.0–6.0 mm were selected. The results show that the bubble instantaneous liquid velocity distribution and the wake structure manifest unique characteristics under such a high-pressure and low-temperature condition. The bubbly flow involves complicated vortex structures. Moreover, the bubble velocity is relatively low relative to those obtained under general conditions. A non-dimensional analysis of the bubble behavior indicates that the results obtained here deviate significantly from available results obtained under general conditions. The bubble diameter significantly influences the drag coefficient.

Aiming at the problem of dynamic displacement of mixed gas in laser transmission pipeline, by selecting a typical section of the pipeline, the problem can be simplified to study the filling of binary mixed gas in a relatively closed cavity with the single entrance and exit. The finite volume method is used to simulate the flow field of this section of pipeline, and the velocity distribution of the binary mixed gas filling process is simulated by using the incompressible N-S equation and the standard k-epsilon turbulence model; the molar concentration distribution of the binary mixed gas over time is simulated. Furthermore, the distribution of flow field and the change of gas composition inside the pipeline were calculated under different inlet velocity conditions. Through the above simulations, the change of flow field distribution in the pipeline with time is described; the formation, development and extinction process of vortex at different time or at different positions in the pipeline are simulated. Based on the works above, the basic research idea and theoretical basis of the study on the mixed gas filling progress of large scale laser transmission pipeline are provided. By comparing and analyzing the characteristics of flow field distribution at different inlet velocity or at different time periods of the same inlet velocity, it will also have certain reference value to guide the implementation and optimization of the gas filling project of laser transmission pipeline.

Aiming at the problem that the output force of the cylinder is small, this paper studies a method based on the simulation technology to obtain the larger output force and realize the stepless control of the output force. Through the simulation analysis, it can be seen that the system can achieve a more stable output force control when the system damping is large. There will be a certain amount of impact when each stage of cylinder is started.

The current microfluidic chip design generally forms a stagnation point in the exit flow area of the microfluidic chip. The presence of the stagnation area can cause problems such as choke of channel and sample purity degradation. For this problem, a microfluidic chip with converse fluid was designed. The converse sheath liquid can avoid the adverse effects caused by the presence of the stagnation point. It can prevent the cells from contacting the wall surface, and avoid the blocking problem of cell. At the same time, the introduction of the converse sheath liquid can also focus the sample flow in the sorting channel and the waste channel again, which is convenient for the detection of the sorted sample. The fluid flow state in this microfluidic chip was also simulated, and it verified the benefit of introducing converse sheath fluid, which has reference value for the design of microfluidic chip for cell analysis and sorting.

Battery packs are extensively used in electrical vehicles (EV) to avoid environmental pollution. The safety, aging and life of battery cell are significantly related to its thermal behavior. This work concerns with thermal analysis and measurement of an EV battery cell of 153Ah. The Bernardi's heat generation model is employed and the reversible heat is taken into account. The reversible heat is related to the entropy coefficient and it is tested and presented as a relation to SOC. The specific heat capacity and the relationship between the heat and the temperature rise of battery cells are tested by the EV-ARC. The heat generation model is validated by tests at 0.2 C, 0.67 C and 1.2 C discharging rates. It reveals that the reversible heat is not negligible especially at low rate discharge. Then the heat generation model is applied to a cell model to verify the temperature of the cell. The numerical results from this thermal modeling of the battery cell are in good agreement with the test results.

Based on the oil-water two-phase liquid flow model, with equal-viscosity and water-wet unequal-diameter parallel channels, the previous researches on the retention mechanism of "residual oil in the form of oil droplets or oil column" during water flooding, and they stated that "residual oil in the form of oil droplets (or oil column)"can be retained in both large and small channels. Re-examination of the model shows that "residual oil in the form of oil droplets (or oil column)" cannot be retained in large channels, but only in small channels. By changing the wettability and oil-water viscosity (variable viscosity) of this model, the small channel retention characteristics of "residual oil in the form of oil droplets (or oil column)" remain unchanged. This research shows that: (1) When the oil-water phase flows in the unequal-diameter parallel channel model, the flow velocity of the large channel is always greater than the small channel, and the "residual oil in the form of oil droplets (or oil column)" is always retained in the small channel. (2) The retention of small channels of "residual oil in the form of oil droplets (or oil column)" is general, and is not affected by changes in factors such as pressure difference, capillary force, total flow, wettability, and oil-water viscosity ratio.

The present study on battery thermal management performance is mainly based on the research conducted in a single-pack environment, without considering the impact of the vehicle driving environment on the thermal performance of the power battery. Therefore, this paper conducts a research on the thermal management performance of the power battery and considers the effect of heat exchange under the driving conditions of the whole vehicle. In addition, the ohmic heat generation method of a battery pack in the process of charging and dis-charging is established in this paper. The complete heat exchange condition of a liquid cooling power battery is obtained and the research of thermal management performance is carried out. The results indicated that the tested temperature values at sensor NTC position are in good agreement with the predicted data. The maximum temperature deviation between numerical results and experiment data at the same temperature sensor (NTC) position is 1.4 °C, which demonstrates that the prediction accuracy of numerical simulation methods adopted in this paper is significantly high.

Battery pack is one of the most important components of electrical vehicles (EV). The safety, aging and life of battery packs are significantly related to its thermal behavior. This work concerns with thermal behavior of an EV battery pack for realistic engineering applications. The Bernardi's heat generation model with the consideration of reversible heat is employed and validated by tests and numerical simulation on battery cells. Then the validated cell model is applied to an EV battery pack with cooling system underneath for the study of thermal behavior in a realistic operation condition, and numerical results are in good agreement with the test results.

By using the simulated software FLAC^3D, triaxial creep simulation experiments are conducted on soft and hard interbedded rock bodies under different stress levels and loading paths, and the effects of stress state and loading method on the time-dependent characteristics of soft and hard interbedded rock bodies are studied. The established model is analyzed with the method of 3-D visco-elasto-plastic numerical simulation. The results have shown that under the same stress level the deformation and volumes of plastic zone of rock mass will expand when the amounts of soft rock layers increase or the gradient of soft rock layers is steeper.

The method of ducted propeller design is used to design the impeller of water jet propeller. The method of space transformation is used to transform the two-dimensional NACA airfoil into three-dimensional airfoil. The flow field model of water jet propeller is generated by structured grid. The SST model is using for calculation and the maximum thrust is 170.4N when the rotation speed is 4000R / min and the inlet velocity is 2m / s.

Feed water pumps play an important role in floating nuclear power plant system equipment, and their safe and reliable operation directly affects the safety and reliability of the entire power plant. The movement status of floating nuclear power plants under sea conditions will change, and additional inertial forces are generated on the pipelines of the water supply system, which may cause cavitation of the feed water pump. This paper deduces the additional force on the fluid at the inlet pipe of the feed pump under the marine environment, establishes a mathematical model of the fluid flow at the inlet pipe of the feed pump under the influence of ocean conditions, and calculates the stable operation of the feed pump under the ocean conditions once in a century according to the layout plan. The requirements of effective cavitation allowance and necessary cavitation allowance provide theoretical calculation basis for design and layout optimization of feed pumps for floating nuclear power plants.

Compared with 8-node and 4-node isoparametric element, the 9-node isoparametric element is more flexible and higher rate of convergence. Based on state-space techniques, the 9-node isoparametric element of piezothermoelastic material under orthogonal curvilinear coordinate system is established. Finally, the example shows the practicability and accuracy of the 9-node isoparametric element of piezothermoelastic material under orthogonal curvilinear coordinate system.

Improving the aerodynamic characteristics of racing cars is one of the important means to improve the performance of FSAE.This paper completed the FSAE car body and aerodynamics device design and development, based on the CFD technology in the car's aerodynamic characteristics are studied.Through the analysis of the aerodynamic characteristics of the car body with and without aerodynamic devices, and the comparative analysis of airflow pressure and velocity distribution around the car body and aerodynamic devices, the simulation results show that the aerodynamic devices effectively improve the aerodynamic characteristics of the car, and better improve the control stability and driving safety of the car.

Based on the requirements of Formula Student China racing rules, the maximum diameter of the restrictor valve is 20mm in the intake system. In order to improve the engine charge coefficient and reduce the impact on performance caused by uneven air intake of each cylinder, it is quite necessary to redesign and analyse the air intake system under. Firstly, we calculate the volume of the pressure stabilizing chamber and the length of the intake manifold applied theoretical knowledge. Secondly, we redesign the model of intake system using UG software, which includes the parameter of the throttle angles for inlet and outlet, the intake manifold length, the volume of the pressure stabilizing chamber. By comparing and analysing the different data of inlet-outlet angles for the restrictor valve and the height of the baffle located in the stabilizing chamber, we can came to a conclusion after using CFD software that it is the optimal value when the inlet angle for throttle is 14 degree, the outlet angle is 22 degree and the height of the baffle is 10mm, the intake unevenness of each cylinder is 1.4%, and the total intake air is increased by 5.5%.

The spectral theory of differential operators is one of the basic problems of differential operator theory. It has been an important tool in quantum mechanics and other fields. For the Sturm-Liouville Problems with weighted functions, the spectral theory of right-definite problems with self-adjoint boundary condition has been accomplished. But the spectral structure of indefinite problems, is quite different from and more complicated than that of right-definite problems. Compare with second order case, much less known for the fourth order indefinite differential operators. The present paper discusses a class of fourth order discontinuous differential operators. We obtained the estimate on the non-real eigenvalues, under separated boundary condition and the condition that weighted functions change signs for only once or any times.

Because of the advantages of small installation space, good cavitation performance, low cost and easy maintenance, the open channel pump station is widely used in agricultural production, flood control and ecological construction. In the process of operation, large-scale vortices such as wall vortex, bottom vortex and surface vortex easily appear. Under special working conditions, the head and efficiency of the pump station will be reduced, cavitation will occur at the blades, shafting will move, and the unit will vibrate, which will reduce the service life and safety of the pump station. In this paper, the head, efficiency, flow characteristic and free surface vortex of a mixed flow pump device model in pumping station under different water level and flowrates are studied numerically and experimentally, providing experience and theoretical reference for the design of the pumping station.

The paper aims to measure half-wave voltage of KDP crystal irradiated by a 532 nm red laser. This paper explores a safe and easy way to measure the electro-optic coefficient, and then calculates the electro-optic coefficient of the KDP crystal. It provides a feasible way to measure the half-wave voltage and electro-optic coefficient of different electro-optic crystal materials by laser with different wavelengths.

In this paper, the Eulerian model and Mixture model are used to study the free surface, internal flow and mass transfer in the aeration tank. The two multiphase models affect the liquid velocity, internal flow and oxygen mass transfer coefficient (k_La) of the tank. Eulerian model than the Mixture model significantly higher simulates the liquid velocity near the impeller, and the range of the main longitudinal circulation vortex is smaller than Mixture model. The error between the simulated k_La of Eulerian model and the experimental value is smaller than Mixture model. The results show that the Eulerian model is more suitable for the simulation of the gas–liquid two-phase flow in the aeration tank.

Although fog harvesting technology was firstly invented in the 1980s, the theoretical research is still in its infancy. To enhance the collection efficiency of fog harvester, lots of work have been done such as surface modification and 3D structure of the fibres of the fog harvester. In this study, based on observation of daily phenomenon, relationships between the angle of crossed fibres of the fog harvester between collection efficiency are discussed. Results show that as the angle of fibres changes, the effective collection rate per unit length of the fibre keeps unchanged, except near the maximum/minimum limits of the angle, where the collection rate drop significantly, caused by clogging according to the experimental observations. It is also found that the existence of fibre node will influence the collecting process of fog harvester, which can explain why harp-like fog harvester performs well in fog collection.

Gas transport and storage mechanism in gas reservoirs with complex pore size distribution play a key role in gas production. In the nano-scale, during the process of density disturbance caused by depressurization development, notable output gas collides with the wall as they convey along the channel. The continuum assumption of fluid flow is therefore invalid, and taking the influence of particles to collide with solid walls into account is necessary. The effective viscosity and slip boundary conditions were introduced in the simulation. Meanwhile, because of the adsorption effect is one of the most important intrinsic properties of shale, the impact of surface adsorption on the solid wall by using Langmuir adsorption kinetics was also involved in our investigation. In this work, a unified LB model was developed for gas multiple transports and surface adsorption in nanopores. In the model, the double distribution function was employed for a coupled bulk flow and gas diffusion model. The model is valid within the range of the continuum regime to the transition regime and has been verified by the analytical solution and the results of some previously published works. The results show that (1) the driven force of the fluid, the combination coefficient of slippage and the Knudsen number of the flow have an impact on the adsorption rate, (2) adsorption effect only directly influence the local small region of the solid surface, and the induced concentration gradient makes the global concentration variation, (3) once acting the surface adsorption on the boundary, the flux falls more significant as Knudsen number increases.

For the problem of the pressure drop loss and the equivalent length calculation of elbows in submarine high pressure pipelines, the flow processes of ultra-high pressure gas in 90° elbows were numerically simulated by the way of CFD. The inner flow area was meshed with structured hexahedral grid, and by means of the numerical solution to deal with the RANS equations closed by RNG k-ε turbulence model, the flow field characteristics inside the pipe was studied, and the pressure distribution was obtained. The calculated results are consistent with the numerical simulation and model experiment results carried out by other scholars. Simulation results show that the total pressure loss of the pipe will be increased greatly due to the partial pressure loss caused by elbows. Besides, the feasibility and availability of simulating the flow characteristics of the ultra-high pressure gas inside the elbows by RNG k- turbulence model were verified.

This paper introduces the method of calculating the thermal resistance and thermal resistance of high-power water-cooled radiators in cooling towers of thermal power plants using computational fluid software (CDF) Fluent. By solving the three-dimensional unsteady flow field and thermal field, the thermal resistance and thermal resistance value of the water cooling radiator of the cooling tower of the thermal power plant under different flow rates are calculated, which provides the temperature calculation for the steady state and dynamic process of the high-power inverter in accordance with.