复杂旋翼流场的耦合欧拉-拉格朗日数值方法

针对影响旋翼流场求解精度的关键因素“桨叶复杂近体流动”和“尾迹涡畸变”,结合计算流体力学(CFD)方法和黏性涡方法,发展了一套适合于复杂旋翼涡流场分析的耦合欧拉-拉格朗日数值方法:为捕捉桨尖三维效应、激波等细节流场特征,在桨叶近体区域采用CFD方法对其进行求解;针对高雷诺数旋翼流场中桨尖涡的紧凑结构特点,引入黏性涡方法建立了高分辨率的尾迹求解模型;两计算域间的信息交换采用了集中涡源法和边界修正法.应用所建立的计算方法,以旋翼CFD标准验证试验(Caradonna-Tung旋翼)为算例,对尾迹影响明显的悬停状态进行了数值模拟,通过对比耦合边界处流场特征及桨叶表面压力系数分布,验证了方法的有效性.此外,还从旋翼尾迹捕捉精度、涡量耗散特征及计算时间等方面对不同计算方法进行了对比分析,结果表明耦合方法可充分发挥CFD和黏性涡方法各自的优点,在旋翼流场数值模拟方面具有独特的优势.

Coupled Eulerian-Lagrangian Method for Complicated Rotor Flow Field Prediction

A hybrid Eulerian-Lagrangian solver is developed by coupling the computational fluid dynamics (CFD) method with viscous vortex particle method for complicated rotor vortex field analysis. In order to capture the detailed features of a flow field such as its three-dimensional blade tip effect, shock wave, etc., the CFD method is adopted to compute the near-body flow, while a high revolution model is established using the viscous vortex particle method to track the wake since the tip vortex has compact structural characteristics in a high Reynolds number rotor flow field. The "integrated vorticity source method" and the "boundary surface method" are used to exchange the information between the two computational domains. Using the proposed method, a standard test (Caradonna-Tung rotor) for CFD method verification is performed as an example, and numerical simulation is carried out for a hover condition in which the wake plays a more obvious role than in other flight conditions. By comparing the flow characteristics in coupled boundary and pressure coefficient distribution of the blade surface, the validity of the method is verified. Furthermore, different methods are comparatively analyzed from the aspects of the accuracy of capturing the rotor wake, vorticity dissipation characteristics and calculation time. The results show that the hybrid method possesses the advantages of both the CFD method and the Viscous Vortex Particle Method, and has a unique advantage in the rotor flow field numerical simulation.