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

  • 摘要: 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。

     

    Abstract: 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. Considering 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 principle, 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 surface 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 method with rigid rotor assumption.

     

/

返回文章
返回