Start-up process of the ground vortex ahead of the engine intake with crosswind

The ground vortex formed within the crosswind degrades the power output of the aero-engine and threatens the flight takeoff safety. Considerable amounts of experiments have been conducted to investigate the flow mechanism for the formation of the ground vortex. However, the detailed transient start-up process of the ground vortex is still unclear due to the limitations of the measurement techniques. In this work, high-fidelity delayed detached eddy simulations are performed to investigate the underlying mechanism of the ground vortex formation ahead of the intake with the occurrence of crosswind. A thorough validation is conducted first to compare the simulation against the experimental data. By gradually increasing the mass flow into the intake, a near-ground shear vortex formed around the intake due to its blockage to the crosswind is enhanced by the suction of the intake and gradually approaches the highlight plane. Multiple ground vortex filaments are generated from the shear vortex at the boundary between the crosswind and the suction flow. The vortex filaments merge into one single ground vortex, and it moves upwind along the intake lip together with the lower trailing vortex. It takes 0.9-1.0 s for the ground vortex to be formed with a velocity ratio of 4.7-5.0. The formation process found in this study is different from previous research in which the ground vortex is evolved from the trailing vortex or the ambient vorticity.