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为了细致捕捉直升机旋翼桨尖涡的生成和演化过程,建立了一个基于高精度网格和高阶通量计算格式的旋翼桨尖涡计算流体力学(CFD)求解方法。在该方法中,流场求解选取旋转坐标系下的Navier-Stokes方程为控制方程;空间离散采用迎风Roe格式,并采用低耗散的5阶WENO(Weighted Essentially Non-Osciltatory)格式进行对流通量的计算;时间推进则采用双时间法,在伪时间步上使用隐式LU-SGS(Lower-Upper Symmetric Gauss-Seidel)推进格式;应用嵌套网格方法实现桨叶网格和背景网格的数据交换。应用所建立的方法对悬停状态的旋翼桨尖涡流场进行了高精度模拟,在桨叶网格上精细地捕捉到了桨尖涡的具体生成过程,在背景网格上捕捉到了更多圈数的桨尖涡尾迹,并对桨尖涡的演化机理进行了深入研究。结果表明:建立的高精度数值方法能够有效地对旋翼桨尖涡的生成和演化过程进行细致模拟;悬停状态下旋翼桨尖气流在上下表面压力梯度的作用下经历了边界层增厚、逐渐卷起形成涡核以及最终脱离桨叶形成桨尖涡的过程。
In order to carefully capture the generation and evolution of helicopter rotor blade tip vortices, a computational fluid dynamics (CFD) solving method of rotor blade tip vortex based on high-precision grid and high-order flux calculation format was established. In this method, the Navier-Stokes equation is selected as the governing equation in the flow field solution; the windward dispersion Roe format is used for the spatial discretization and the Weighted Essentially Non-Oscillation (WENO) The time advance method uses the double time method and the pseudo-time step uses the implicit LU-SGS (Lower-Upper Symmetric Gauss-Seidel) propulsion format. The nested grid method is used to implement the grid of the blades and the background grid Data exchange. The established method is used to simulate the hovering rotor tip vortex field with high accuracy. The generation of tip vortex is captured finely on the blade grid and more cycles are captured on the background grid Of the blade vortex wake trace, and the evolution of the tip vortex mechanism in-depth study. The results show that the established high-precision numerical method can simulate the generation and evolution of rotor tip vortex efficiently. The hovering rotor tip air flow experiences thickening of the boundary layer under the pressure gradient of the upper and lower surfaces, Roll up to form a vortex core and finally leave the blade to form a blade tip vortex.