A CFD/experimental comparative database to feed a predictive model for ground vortex characteristics

Most modern aircraft engines rely on the use of high Bypass Ratios (BPR) turbofans to achieve both high thrust and low specific fuel consumption. However, such configurations are prone to the formation of ground vortices during low-speed operations. This phenomenon arises under specific combinations of wind direction, velocity or inlet air speed, generating engine vibrations and leading to the suction of damaging abrasive particles. Its characterization in early design stages is crucial. In this work, a joint experimental and numerical exploration of operating conditions leading to ground vortex presence is carried out on a scaled wind tunnel configuration. Flow details are investigated for several working points obtained from a specific set of input parameters (intake speed, wind speed, ground clearance). A methodology suitable for both experimental and Computational Fluid Dynamics (CFD) works is developed to extract vortex characteristic quantities, based on a local pressure minimum and Q-criterion contours topology. A very good agreement is obtained when comparing vortex predictions stemming from CFD and experiments. This database shall be used to transpose experimental data probed outside of the nacelle to data within the nacelle using data analytics techniques, paving the way for future data driven predictive models.