Final work : Numerical investigation of the ground vortex ingestion into the intake under crosswind

Abstract

Aiming to increase aircraft fuel efficiency, Ultra High By-pass ratio (UHBR) engines are gaining popularity. When operated under static or near static conditions, subject to crosswind, UBHR engines can experience a lip separation on the windward side of the intake, and the formation of a ground vortex extending from the stagnation point on the ground into the intake called a ground vortex. These vortices create considerable stagnation pressure losses and flow distortion at the engine fan face affecting the efficiency of the engine and structural integrity of the fan. Furthermore, the ground vortices can generate forces that can suck debris from the ground into the intake, mainly over poorly maintained runways. This Foreign Object Digestion (FOD) can lead to compressor blades’ erosion, reducing the engine’s service life. Considering the advantages of numerical analysis over full and scaled model experiments, the ground vortex ingestion is studied numerically. The present work aims to provide the best numerical setup to analyse this phenomenon using the experimental data for validation. Initially, a few studies are conducted to determine the appropriate turbulence model and the significance of the boundary layer profile for simulations. A grid sensitivity study is performed using steady-state RANS, and the vortex is learned to be stable in low crosswind conditions. URANS is solved for medium and high crosswind conditions to fully understand the vortex’s unsteadiness using coarse mesh. The temporal convergence study determines the time stepping for the unsteady simulation. This research demonstrated periodic vortex motion in medium and high crosswind conditions at ≈10 Hz and ≈22 Hz, respectively. Furthermore, the separation exists in high crosswind conditions, and the shear layer oscillates at a broadband frequency rather than a single or narrow band. Good agreement is found between the time-averaged URANS results and the experiment data using coarse mesh. The proposed numerical setup can therefore be used for further analysis of ground vortex ingestion studies.