面向粘性流动问题的无网格/直角网格混合算法研究

The hybrid Cartesian grid/gridless method for simulating viscous flows

  • 摘要: 将基于计算区域整体直角网格物面附近局部无网格的无网格/直角网格混合算法发展用于求解粘性流动问题。针对粘性流动,特别是高雷诺数粘性流动边界层薄的特点,在局部无网格布点过程中引入了点距控制函数,使得生成的点云结构能反映粘性流动边界层特点,同时结合无网格区之间的布点干涉机制,将算法拓广到处理多个物体相互干扰的复杂流动问题。对于整体直角网格,采用直角坐标与四叉树加密的方法生成非结构直角网格。由于采用了局部四叉树加密,使得网格区与无网格区之间过渡可控,再结合提出的基于距离和夹角的点云选点策略,保证了网格区与无网格区交界处点云的质量。给出了求解NS方程耦合SA湍流模型的无网格/直角网格混合算法的具体实施方法,数值模拟了NACA0012翼型亚声速和RAE2822翼型跨声速粘性绕流,计算结果与实验数据进行了比较与验证。最后给出了GA(W)-1两段翼型的粘性绕流数值模拟算例,展示了所提方法的可行性。

     

    Abstract: The hybrid Cartesian grid/gridless method is developed to simulate viscous flows. The flow field is basically discretized by Cartesian grids, and local gridless treatment is embedded in the region adjacent to the body. In order to simulate the thin boundary layer of the viscous flows interested in this paper, the cloud of anisotropic points is implemented in the local gridless region. A cloud overlap-free procedure is proposed which enables the hybrid method to treat complex flows involving close-coupled bodies. The unstructured Cartesian grid needed for the hybrid method is generated based on the quadtree data structure, which can help to control the quality of the clouds at the interface between the grid region and the gridless region. The resulting hybrid method is applied to solve two-dimensional compressible NS equations. The viscous flows past a NACA0012 airfoil and a RAE2822 airfoil are first simulated, and the numerical results obtained present a good agreement with available experimental data. The paper ends with a numerical example of the viscous flow past a two-element airfoil, which demonstrates the ability of the present method for treating more complex flows over multi-bodies.

     

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