直升机/舰船耦合流场的数值模拟

发展了一套基于雷诺平均Navier-Stokes(RANS)方程的直升机/舰船耦合流场数值模拟方法,采用ROEMUSCL格式对交接面通量进行重构,并采用k-ε湍流模型以提高对涡流场的捕捉精度,直升机旋翼等旋转部件的模拟使用动量源模型。然后,以具有典型驱护舰结构的LPD-17及ROBIN直升机的组合为研究对象,从涡量场、速度场及压力场等方面分析了直升机、舰船耦合情形下的流场特征。研究表明,当来流速度V_∞≥4m/s时,舰船流场进入雷诺数自准区,流场速度无因次化量基本保持不变;直升机着舰时,旋翼会与舰船艉部的涡回流区以及甲板两侧的舷涡发生较强的"涡-涡干扰",在上述干扰以及舰面效应的共同作用下,旋翼拉力产生显著的振荡,并呈现出先减小、后增大的变化特征;当着舰位置向舰尾移动时,艉部回流区的影响减弱,旋翼拉力振荡幅度相应减小。最后,对全机状态下的耦合流场进行了模拟,结果显示机身和尾桨对舰艉流场的主要结构影响较小,可用旋翼/舰船耦合流场来进行直升机安全着舰分析,这将显著缩短计算时间。

Numerical simulatin of coupled flow field of helicopter/ship

A computational method based on Reynolds-Averaged Navier-Stokes (RANS) equations is developed for the study of aerodynamic interaction between helicopter and ship,wherein ROE-MUSCL scheme is used to reconstruct the flux at the interface,and k-ε turbulence model is used to improve the simulation precision for flow structure.Actuator disk method is used to simulate the main rotor and tail.A scaled LPD-17 ship and ROBIN helicopter are then used to simulate the coupled flow field.The coupled flow field characteristics are analyzed,inlucing vorticity,velocity and pressure fields.Analysis results indicate that when the freestream velocity is greater than 4 m/s,Reynolds number of ship flowfield comes into the prospective area of Reynolds number the normalized velocity components of the ship flow field remain unchanged;during the landing process,the main rotor will interact with the large recirculation zone and the deck-edge vortices,and these interactions as well as ground effect cause the rotor thrust to oscillate,and the oscillation shows a regularity of increase first and then decrease.When the landing spot moves to the stern,the effect of the recirculation zone diminishes,thus causing reduction of the amplitude of thrust oscillation.Simulation of the interaction between full aircraft and ship is conducted.Results show that fuselage and tail have slightly influence on the characteristics of the main flow field;therefore,the coupled flow field of rotor/ship can be used to analyze the safety during shipborne operations,and the computation time can thus be shortened significantly.