直升机前飞旋翼桨尖涡定常质量射流控制计算

针对直升机前飞状态开展了旋翼非定常桨尖涡的模拟,采用定常桨尖空气质量射流(TAMI)控制方式对旋翼桨尖涡进行了控制。建立了一个适用于前飞旋翼桨尖涡高精度捕捉和质量射流控制模拟的数值方法,在该方法中,采用有限体积法进行空间离散,应用5阶Roe-WENO(weighted essentially non-oscillatory)格式进行流场重构及控制面对流通量计算;采用双时间方法进行时间推进,伪时间步上应用隐式LU-SGS(lower upper symmetric Gauss-Seidal)格式;引入射流边界条件对质量射流进行模拟;采用运动嵌套网格方法对前飞旋翼桨尖的挥舞运动进行模拟,并对桨叶网格和背景网格进行针对性加密。基于所建立的方法对前飞状态旋翼非定常桨尖涡及其质量射流控制进行了模拟,计算结果表明:前飞状态下旋翼桨尖涡存在较大的前后差异,桨盘前侧的桨尖涡涡核强度远小于桨盘后侧;桨盘前侧旋翼桨尖涡的涡核强度很难由定常质量射流控制来减弱,而桨盘后侧的旋翼桨尖涡则可以通过定常质量射流得到有效控制。

Control calculation of helicopter rotor tip vortex in forward flight using steady air mass injection

A high-accuracy numerical method was established to simulate the rotor flowfield of rotor tip vortex with tip air mass injection (TAMI) control in forward flight. In the existing method, the finite volume method was used for spatial discretization. The upwind Roe scheme with a fifth-order WENO (weighted essentially non-oscillatory) scheme was employed to calculate convective fluxes on control faces. A dual-time method was utilized in time marching and the high-efficiency implicit LU-SGS (lower upper symmetric Gauss-Seidal) scheme was applied to every pseudo time step. A surface boundary condition which may effectively simulate the effect of TAMI was introduced into this method. The moving overset grid method of refining the blade grid and background grid pertinently was adopted to simulate the blade flapping and rotating motions. Based on the presented method, rotor tip vortex with TAMI control in forward flight was calculated. It demonstrated that there existed obvious difference between the tip vortex induced at the front side of rotor disk and that induced at the rear side. The core strength of tip vortex induced at the front side was smaller than that at the rear side. Tip vortex induced at the front side of the rotor disk cannot be weakened. However, tip vortex induced at the rear side can be effectively weakened by the steady TAMI.