基于非惯性系的悬停状态旋翼CFD/CSD耦合气动分析

CFD/CSD coupling analysis on aerodynamic characteristics of rotor in hover based on non-inertial frame

旨在提高先进旋翼气动特性的分析精度,在旋翼高精度CFD分析中耦合气动弹性效应,取代传统方法中的刚性桨叶假设,并考虑悬停状态旋翼流场准定常的特性,在非惯性坐标系下建立了一套适合于悬停状态旋翼气动特性计算的CFD/CSD耦合分析方法。旋翼气动载荷通过求解三维Navier-Stokes方程求得,空间离散及通量计算采用Jameson中心格式,时间方向则选用五步Runge-Kutta迭代求解,湍流模型采用B-L模型;基于Hamilton原理建立了描述旋翼弹性运动的非线性微分方程,针对旋翼悬停状态的工作特点,采用Raphson迭代方法求解获得旋翼桨叶的弹性变形量。在CFD/CSD耦合计算中,旋翼桨叶交接面载荷及变形信息通过CFD与CSD模块进行传递,同时为提高桨叶弹性变形后贴体网格生成的效率和质量,采用基于网格点坐标转换的网格变形方法。在CFD和CSD程序分别验证基础上,采用建立的旋翼CFD/CSD耦合分析方法计算了先进的UH-60A直升机旋翼的表面压强及气动载荷。计算结果表明,与刚性旋翼CFD模拟结果比较,本文建立的CFD/CSD耦合分析模型可以更准确地预估旋翼气动载荷和性能。

In order to enhance the analytical accuracy of advanced rotor aerodynamic characteristics,the aero-elastic effects are coupled into high fidelity CFD analysis method instead of rigid blade assumption.Con-sidering the quasi-steady characteristics of rotor flowfield in hover,a CFD/CSD coupling analysis model for the helicopter rotor is developed based on the non-inertia frame.Airloads are obtained through solving 3-D Navier-Stokes equations with Jameson central difference scheme used in spatial discretization,five-step Runge-Kutta method adopted in temporal integration and B-L turbulent model.Based on the Hamilton prin-ciple,nonlinear differential equations which describe the elastic motions of the rotor are formulated and then calculated by Raphson iteration method.During the process of coupled CFD/CSD calculations,airloads and deformation information are exchanged between CFD and CSD module,and grid deformation method based on the direct coordinate transformation is adopted to improve grid deformation efficiency.Finally,the sur-face pressure distributions and airloads of UH-60A helicopter in hover are calculated,and it is demonstrated that the present CFD/CSD coupling model can predict rotor airloads more accurately compared to CFD meth-od with rigid rotor assumption.