基于DES的二维和三维空腔流动特性研究

Numerical Simulation of 2D/3D Cavity Flows Using DES

空腔流动广泛存在于航空航天工程中,对其流动特性的研究具有十分重要的工程意义。采用数值方法对比模拟了二维和三维空腔流动,控制方程采用N-S方程,空间离散采用有限体积方法,对流通量计算采用Roe格式,非定常时间离散采用双时间步长方法,湍流粘性计算采用基于SA模型的DES方法。数值计算所得的三维空腔底面压强分布与实验结果一致,所得的二维和三维空腔内的流动结构与相关文献中的分析相吻合。将二维和三维的计算结果进行比较,发现空腔底部压强分布、空腔内的压强振荡、空腔内部流线图及声压级等均有所不同,得出在空腔宽度有限时,横向流动简化了流动结构,削弱了振荡幅值,但使振荡过程复杂化,其三维效应不能忽略。

Cavity flow problems exist widely in aerospace engineering, so it is very important to study the flow physics of the cavity flow oscillations. The unsteady Navier- Stokes equations in both two and three dimensions are solved humerically to simulate two and three dimensional cavity flows, using detached- eddy simulation （DES） method in Spalart- Allmaras one equation modes. Spatial discretization is performed with finite volume scheme, time integration is implemented by a dual time - stepping approach and numerical fluxes are computed with Roe scheme. The pressure coefficients on 3D cavity floor eoincide with experimental dates, and the flow structures in 2D and 3D cavity agree well with physical analyses in other articles. The results of two dimensional and three dimensional computations are compared to each other, differences between them are observed in terms of pressure distribution, the amplitude of the fluctuations, the streamlines and the sound pressure level （SPL） in the cavity. The results suggest that when the width of the cavity is finite and is of same order than the length of the cavity ,three-dimensional effects cannot be neglected.