空化流动隐式求解方法研究

发布时间：2018-02-02 10:56

本文关键词： 空化预处理隐式求解数值模拟源项　出处：《空气动力学学报》2017年01期 　论文类型：期刊论文

【摘要】：空化流动问题本质上是可压缩流动,应用可压缩方法开展数值模拟研究更符合物理实际。气体和液体压缩性的显著差别使得低速空化流动数值模拟的刚性问题非常突出,通过引入预处理技术解决低速问题中由于特征值量值不一致导致的收敛刚性问题,提高收敛速度。同时,以预处理后的特征值构造Roe格式耗散项,提高低速流动计算精度。鉴于自然空化流动中气液组分转换现象和物质输运现象并存,且气体和液体的密度在常温状态下存在显著差别,预处理后的源项雅克比矩阵的特征值与无粘通量雅克比矩阵的特征值存在量级的差异,这会使得求解过程不稳定或收敛速度极慢,即出现"源项刚性"问题。为此,本文系统推导了预处理框架下的气液两相流隐式求解方法,采用点隐式方法处理源项,通过直接求逆的方式增强算法的稳定性。研究中分别考察了三种不同的算子分裂方式在LU-SGS(Lower-Upper Symmetric-Gauss-Seidel)隐式迭代中的模拟效果,并提出适用于DDADI(Diagonally Dominant Alternating Direction Implicit)的算子分裂方式,在NACA0015水翼空化算例模拟中综合比较了上述四种隐式迭代方式对低速空化问题收敛性的影响。最后,应用本方法对三维尖锥自然空化算例进行了考核模拟,捕捉到自然空泡流场中的主要特征,计算结果与试验测量结果吻合。
[Abstract]:Cavitation flow is essentially a compressible flow. The application of compressible method in numerical simulation is more in line with the physical reality. The rigid problem of numerical simulation of low-velocity cavitation flow is very prominent due to the obvious difference between the compressibility of gas and liquid. In this paper, the preprocessing technique is introduced to solve the problem of convergence rigidity caused by the inconsistency of eigenvalues in low speed problems, and the convergence speed is improved. At the same time, the dissipative term of Roe scheme is constructed from the pretreated eigenvalues. In view of the coexistence of gas-liquid component conversion phenomenon and mass transport phenomenon in natural cavitation flow, the density of gas and liquid varies significantly at room temperature. There is an order of magnitude difference between the eigenvalues of the source term Jacobian matrix and that of the viscidity flux Jacobian matrix, which makes the solution process unstable or the convergence speed extremely slow. For this reason, the implicit solution method of gas-liquid two-phase flow under the preprocessing framework is systematically derived, and the point implicit method is used to deal with the source term. The stability of the algorithm is enhanced by direct inversion. Three different operator splitting methods are investigated in LU-SGS. respectively. Simulation effect in Lower-Upper Symmetric-Gauss-Seidel implicit iteration. It is also suggested that it is suitable for DDADI(Diagonally Dominant Alternating Direction Implicitity. To split the operator. In the NACA0015 hydrofoil cavitation simulation, the effects of the four implicit iteration methods on the convergence of the low-speed cavitation problem are comprehensively compared. By using this method, the main characteristics of natural cavitation flow field are captured, and the calculated results are in good agreement with the experimental results.
【作者单位】：中国空气动力研究与发展中心计算空气动力研究所;
【分类号】：O35
【正文快照】： part,the natural cavitation case of 3-D(three-dimension)cone is simulated by the current meth-od,capturing the main characteristic of the natural cavity flow field,and attaining agroup ofsimulating data that matches well with the experiment data.0引言随

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