| Wake vortex,as a natural by-product of lift generated by aircraft,is an important factor affecting the safe operation of aircraft and restricting the growth of terminal airspace capacity.The past shows that the mechanism of wake vortex evolution mainly focused on the effects of atmospheric turbulence and stratification stability.Recent research results pointed out that the atmospheric wind field also has an important influence on the wake vortex decay.Based on Reynolds averaged numerical simulation method,this paper systematically studies the influence of crosswind on wake vortices in the final approach segment and the decision altitude,and explores the physical mechanism of its influence from the perspectives of the decay characteristics,the horizontal motion characteristics and the vertical motion characteristics of the wake vortices.This research shows that crosswinds can promote wake vortices decay,which is manifested in that crosswind changes the relative velocity between vortex cores and the surrounding flow field,se and promotes the attenuation of vorticity at wake vortices core;the fusion of crosswind and the wake vortex induces the wake vortices triggering instability mechanism,shortens the time when wake vortices enters the rapidly decay phase,and accelerates wake vortex decay.For wake vortices near ground,due to the combined effect of ground effect,crosswinds can also cause the separation of the surface boundary layer near the wake vortices to form secondary vortices,and make a reverse winding motion around the primary vortices,which can induce the wake vortices to trigger the instability mechanism,shorten the time to enter the rapidly decay phase,and accelerate wake vortex decay.The analysis of the horizontal motion characteristics of wake vortices shows that the transport of crosswind can induce the horizontal displacement of wake vortices,and the displacement range of wake vortices varies with the intensity of the crosswind.Low-speed crosswinds can only push the downwind vortex out of the runway area,while the upwind vortex will remain in the runway area until it completely dissipates due to the influence of crosswind and wake vortices induction.High-speed crosswinds can effectively push wake vortices out of the runway,shorten the time when the wake vortices exit the airport runway and reduce the wake turbulence separation between the lead and trail aircraft.For the near-ground wake vortices,when the wind speed reaches 5 m/s,wake turbulence separation standards of heavy aircraft can be reduced by 35.7%.In terms of the vertical motion characteristics of wake vortices,crosswinds can accelerate wake vortices pair descent by intensifying the vortex induction.In the final approach segment,wake vortices are sinking out of the bottom boundary of glide slope under strong crosswind and it reduce the impact on the subsequent aircraft.In the near-ground segment,it presents an asymmetric rebound trend for wake vortex under the combined influence of crosswinds and ground.It behaves as crosswinds restrain the rebound motion of upwind vortex and make the rebound distance of upwind vortex decrease with the increase of crosswind velocity.When the wind speed reaches 7m/s（about 4.8 timesw0）,the rebound motion of upwind vortex is completely suppressed.When the wind velocity reaches 5 m/s（about 3.5 times w0）,the rebound distance of downwind vortex reaches its maximum value.Then,with the further increase of the wind speed,the rebound distance of the downwind vortex begins to decrease,and the promotion of crosswind wear off.However,the rebound distance of the downwind vortex is always higher than that of the upwind vortex. |
