圆柱绕流的三维数值模拟

利用计算流体力学软件CFX－4，对粘性不可压缩流体的圆柱绕流进行了三维数值模拟，采用有限体积法和SIMPLE计算程式，利用不可压缩Navier-Stokes方程，模拟雷诺数在亚临界区内的绕流流动，并计算了流体的水动力特性。为克服数值模拟高雷诺数时的数值不稳定性，计算中采用了QUICK迎风格式,其对流项为三阶精度，其余项如扩散项等为二阶精度，圆柱两端边界采用周期性边界条件。计算结果表明，高雷诺数时圆柱周围的流动具有明显的三维特性，且沿柱长方向不同断面的升力和阻力系数并不相同。同时，对圆柱绕流进行了二维数值模拟，并与三维数值结果进行比较，发现三维模拟的升力和阻力系数均小于二维模拟。

Three-Dimensional Numerical Simulation of Viscous Flowaround Circular Cylinder

A uniform viscous and incompressible flow around a circular cylinder was numerically simulated. The CFX-4 software is used to calculate hydrodynamic characteristics of the flow and the finite volume method for incompressible Navier-Stokes equations is employed in the program. The Reynolds numbers of the simulation are 10 3 and 10 4 respectively. In order to overcome numerical instability for the high Reynolds number flows, quadratic upwind scheme(QUICK) is incorporated for the Navier-Stokes equations, which is of third-order accuracy for the advection and remains only second-order for other terms such as diffusion. Periodic boundary conditions are used at the cylinder ends. It is found that under the high Reynolds number the effect of three-dimensionality of the flow around the circular cylinder is distinct. The changes of the lift coefficients and drag coefficients in each plane along the cylinder span are different. Comparisons between the predicted results based on the three-dimensional(3-D) analysis and the two- dimensional(2-D) analysis were also given.