基于隐式算法的悬停旋翼粘性绕流高效CFD分析方法

Highly-efficient CFD calculations on viscous flow of hovering rotor based on the implicit algorithm

  • 摘要: 为显著提高旋翼粘性绕流CFD模拟效率, 建立了一套高效的基于隐式LU-SGS算法和OpenMP并行策略的旋翼悬停流场求解方法。首先, 求解Poisson方程生成桨叶剖面翼型的贴体正交网格, 并通过剖面网格插值、翻折方法生成桨叶C-O型贴体网格;在此基础上, 采用基于“扰动衍射”挖洞方法与“Inverse map”相结合的洞边界划定与贡献单元搜索方法, 解决了嵌套网格技术中的相关瓶颈问题。然后, 以非惯性系下耦合S-A湍流模型的RANS方程为流场主控方程, 对流通量采用三阶Roe-MUSCL格式进行离散, 时间推进采用高效的隐式LU-SGS方法, 同时采用基于数据共享的OpenMP并行策略加速流场求解。最后, 运用所建立的方法分别对不同旋翼翼型和悬停状态“Caradonna-Tung”以及UH-60A旋翼的流场及气动特性进行了计算, 并给出了根据涡核位置加密网格来提高桨尖涡捕捉精度的方法, 同时将计算结果与试验值进行了对比, 验证了该方法在旋翼CFD流场模拟中的高效性和高精度特征。

     

    Abstract: To improve the CFD compute efficiency on the viscous flow of helicopter rotor, a highly-efficient implicit LU-SGS algorithm and OpenMP parallel strategy have been employed for predicting the aerodynamic characteristics of hovering rotor. Firstly, the orthogonal and body-fitted grid around rotor blade is generated by using Poisson equations and folding approach; then the “disturbance diffraction method”(DDM) and “Inverse map” method are utilized in the identification of hole cells and searching the donor cells respectively, thus to solve the bottleneck problem of the embedded grid technique. On these bases, the RANS equations coupled S-A turbulence model in a rotating frame are used as the governing equations, and the three-order scheme of ROE-MUSCL is used for spatial discretization of convective fluxes, and the highly-efficient implicit scheme of LU-SGS is adopted for temporal discretization, and data sharing OpenMP parallel strategy is employed to accelerate the calculation as well. Finally, the flowfield and aerodynamic characteristics of several rotor airfoils and hovering rotors(C-T and UH-60A rotor) have been simulated by the presented method. At the same time, a refined grid strategy according to the position of vortex core has been conducted to improve the capturing accuracy of blade-tip vortex. By comparisons of numerical results with experiment data, high-efficiency and high-accuracy abilities of the present method on the simulation of the rotor flowfield is demonstrated.

     

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