Abstract
Turbulence: Out of troubled waters?
Turbulence is often referred to as the last unsolved problem in classical physics. This leads to the discouraging impression that turbulence is an almost impossible challenge, where fundamental progress is hardly possible, and where problems of applied importance can be only treated using ad-hoc approximations.
Over the last few years, however, there has been very pronounced progress in understanding the fundamentals of turbulence. Many deep theoretical results have been obtained in the problem of mixing of a passive scalar by a turbulent flow, opening new perspectives on the turbulence problem itself. This progress is intrinsically related to the very stimulating developments in Lagrangian measurements and theory. These recent achievements have brought to light further fundamental problems, making the subject more diverse, and in scientific terms, even more interesting. The old problem as to whether small scales become isotropic at high Reynolds number is currently the subject of renewed debate and the existence of the relationship between anisotropy and intermittency is being examined in the light of the new evidence. The issue of the dependency of the small scales on the large scale boundary conditions is beginning to be systematically explored. And how modelling, such as Large Eddy Simulations, can deal with solid boundaries and with small scale anomalies is still an open question, but one in which there is great activity.
The purpose of this issue in New Journal of Physics is to address these and other basic questions in turbulence theory, experiment, computation and modelling, highlighting where progress has been achieved, and where it can be reasonably expected within the next few years. Listed below are the first contributions. Further articles from other leading groups in the field will appear in the near future.
Elastic turbulence in curvilinear flows of polymer solutions Alexander Groisman and Victor Steinberg
Small-scale anisotropy in stably stratified turbulence Yukio Kaneda and Kyo Yoshida
Ten questions concerning the large-eddy simulation of turbulent flows Stephen B Pope
Anomalous scaling and universality in hydrodynamic systems with power-law forcing L Biferale, M Cencini, A S Lanotte, M Sbragaglia and F Toschi
On conditional scalar increment and joint velocity–scalar increment statistics Hengbin Zhang, Danhong Wang and Chenning Tong
Statistics of a passive scalar in homogeneous turbulence Takeshi Watanabe and Toshiyuki Gotoh
Markovian properties of passive scalar increments in grid-generated turbulence M Tutkun and L Mydlarski
Entropy production and extraction in dynamical systems and turbulence Gregory Falkovich and Alexander Fouxon
Eulerian and Lagrangian studies in surface flow turbulence John R Cressman, Jahanshah Davoudi, Walter I Goldburg and Jörg Schumacher
Conditional scalar mixing statistics in homogeneous isotropic turbulence B L Sawford
A low-dimensional model for turbulent shear flows Jeff Moehlis, Holger Faisst and Bruno Eckhardt
Particle pair diffusion and persistent streamline topology in two-dimensional turbulence Susumu Goto and J C Vassilicos
Active and passive fields face to face Antonio Celani, Massimo Cencini, Andrea Mazzino and Massimo Vergassola
Advances in wave turbulence: rapidly rotating flows C Cambon, R Rubinstein and F S Godeferd
Experimental and numerical study of the Lagrangian dynamics of high Reynolds turbulence Nicolas Mordant, Emmanuel Lévêque and Jean-François Pinton
Reynolds number scaling of particle clustering in turbulent aerosols Lance R Collins and Arun Keswani
Unifying ideas on mixing and atomization Emmanuel Villermaux
Progress in studying small-scale turbulence using 'exact' two-point equations L Danaila, R A Antonia and P Burattini
Lagrangian statistics for fluid particles and bubbles in turbulence Irene M Mazzitelli and Detlef Lohse
On the distribution of Lagrangian accelerations in turbulent flows A M Reynolds, N Mordant, A M Crawford and E Bodenschatz
Zellman Warhaft, Cornell University, NY, USA Alain Pumir, Institut Non Linéaire de Nice Sophia Antipolis, France