直升机旋翼桨-涡干扰状态非定常气弹载荷高精度预估

为准确计算直升机旋翼在复杂的桨-涡干扰(BVI)状态下的气弹载荷,在刚性旋翼计算流体力学方法中引入桨叶弹性变形的影响,建立了一套适合于弹性旋翼BVI状态气动特性分析的计算流体力学/计算结构力学(CFD/CSD)耦合方法.CFD模块对Reynolds averaged Navier-Stokes(RANS)/Euler方程进行求解,并采用双时间法推进和Baldwin-Lomax(B-L)湍流模型.CSD模块采用中等变形梁假设的有限元模型,通过Newmark-Beta方法求解桨叶运动方程.通过代数变换方法进行桨叶网格变形,并建立一个适于流场/结构信息交换的CFD/CSD耦合方法.在分别验证CFD和CSD模块的有效性的基础上,开展UH-60A直升机旋翼的BVI状态载荷分析,并与飞行测试数据进行了对比.计算结果表明:相比于旋翼综合分析中的升力线理论和刚性旋翼CFD方法,耦合的CFD/CSD方法可以更准确地预测BVI状态气弹载荷,并有效地模拟桨叶前行侧方位角和后行侧方位角附近的BVI现象,对BVI导致的升力波动幅值和相位的计算结果均与试验值吻合良好.

High-precision prediction on unsteady aeroelastic loads of helicopter rotors under blade-vortex interaction condition

In order to obtain accurate aerodynamics loads of helicopter rotors under complex blade-vortex interaction (BVI) condition, blade deflections were introduced into rigid rotor CFD analysis and a computational fluid dynamics/computational structural dynamics (CFD/CSD) coupling method suitable for aerodynamic characteristics analysis of elastic rotors under BVI condition was developed. The CFD module solved Reynolds averaged Navier-Stokes (RANS)/Euler equations based on dual time-stepping algorithm and Baldwin-Lomax (B-L) turbulence model. The CSD module employed finite element model of moderate deflection beam theory, and the blade equations of motion were calculated by using Newmark-Beta method. Blade deformations were accomplished through algebraic grid deformation method and a CFD/CSD coupling strategy was developed for exchanging fluid/structure information. The established CFD and CSD modules were validated by UH-60A elastic blade respectively, and aerodynamics loads of UH-60A rotor were analyzed under BVI condition and compared with flight test data. The calculated results demonstrated that coupled CFD/CSD method can acquire more accurate aerodynamics loads under BVI condition than lifting-line method in rotor comprehensive analysis and rigid rotor CFD method, and the flow phenomena near azimuth of advancing blade and azimuth of retreating blade under BVI condition are well captured in detail. The calculated results of the lift's phase and amplitude caused by BVI agree well with the experimental data.