直升机与舰船耦合流场的旋涡与分离特性

Vortex and separation of coupled flow field between helicopter and ship

直升机的舰面起降安全性问题一直受到广泛关注,舰船尾流和旋翼涡流的相互干扰耦合,对舰载直升机的操纵产生了极大威胁。为了克服稳态计算和动量源法的局限性,采用重叠网格法模拟旋翼的转动,对直升机舰面悬停和下降过程中的非定常耦合流场进行了数值计算。结果表明,重叠网格法能够更准确地捕捉旋翼涡流场的细节。直升机舰面悬停过程中,旋翼拉力系数逐渐收敛并表现为稳定的周期性波动,桨尖涡呈螺旋状脱落,与机库后方回流区及舷涡发生干扰,流场的非定常效应明显;直升机着舰过程中,回流区的再附点先向舰尾方向移动然后逐渐向舰首方向移动,桨尖涡与舰面旋涡的挤压碰撞加剧,使得旋翼拉力系数产生显著振荡,耦合流场的湍流度急剧增加且振荡幅度越来越大,加大了着舰的风险性。

The safety of helicopter’s take-off and landing on ship has been widely concerned.The coupling of ship airwake and rotor vortex has a great threat to the operations of shipborne helicopter.In order to overcome the limitation of steady simulation and momentum source method,the overset mesh method was used to numerically solve the unsteady flow field where helicopter is hovering or landing on a ship.The results show that the overset mesh method can capture the details of rotor vortex more accurately.During the hovering,the rotor thrust coefficient gradually converges and appears as stable periodic fluctuations.The tip vortex falls off spirally and interferes with the recirculation zone behind hangar as well as the ship side vortex,which shows strong unsteady effect of the flow field.During the landing,the reattachment point of recirculation zone first moves towards the stern and then moves towards the bow.The rotor thrust coefficient violently oscillates due to the collision between tip vortex and ship vortex intensifies.The turbulence intensity of the coupled flow field increases sharply and the oscillation amplitude becomes larger and larger,which adds risk to land on the ship.