Study On Formation Mechanisms And Aerodynamic Characteristics Of Ground Vortex Under Crosswind Conditions

The ingestion of ground vortex into the intake could make the loss of total pressure which can decrease the thrust of the engine and cause surge in severe cases.And particles carried by the intake vortex current will also wear the fan blades,erode the bearing seals and plug the cooling holes of the turbine,which greatly affects the safe operation of the aero-engine.Therefore,it is of great value in engineering application to study the mechanisms and characteristics of ground vortex and obtain effective information which is helpful to the prediction and prevention of ground vortex.In this paper,the scaled intake was taken as the object,and the numerical simulation was used to study the aerodynamic characteristics of the ground vortex under crosswind conditions.And the factors affecting the development of ground vortex was explored,and empirical model for the characteristics of ground vortex under crosswind conditions was established.Firstly,the influence of inflow velocity,ground clearance and yaw angle on ground vortex was analyzed when there is no taxiing.It was found that the vortex strength increases first and then decreases with the increase of inflow velocity and increases monotonously with the decrease of ground clearance and the increase of yaw angle.While the index DC₆₀at fan face increases rapidly with the increase of wind velocity and enlargement of yaw angle,but ground clearance has no significant effect on the inflow distortion.Secondly,the influence of aircraft taxiing was considered.The results show that with the wind velocity and taxiing speed increase the vortex strength will decrease rapidly which makes the ground vortex difficult to form.Taxiing speed is the main factor affecting non-dimensional vortex strength?^*,while distortion index DC₆₀ is mainly affected by inflow velocity.Besides,relative magnitude of the taxiing speed and inflow velocity can affect the structure of ground vortex.Then,the formation mechanisms of ground vortex under crosswind conditions were explored,and the following conclusions were drawn:the relationship between velocity ratio and ground clearance will affect the interaction between sucked streamtube and ground,thus affecting the formation of ground vortex.The ground boundary layer is the main source of vorticity,but it can't determine the generation of ground vortex.Relative taxiing weakens the convergence of ambient vorticity before the inlet and makes it difficult to generate vortex.Finally,based on the aerodynamic self-similarity of the vortex characteristic parameters,an empirical model of the ground vortex characteristics under crosswind conditions was established,and numerical examples were applied to verify the model.The verification results show that the non-dimensional vortex strength curve obtained by the model is in good agreement with the CFD results,while the distortion index DC₆₀ coincides with the simulation results to great extent both in numerical value and overall trend.