排序方式: 共有18条查询结果,搜索用时 15 毫秒
1.
2.
M. Parsani G. Ghorbaniasl C. Lacor E. Turkel 《Journal of computational physics》2010,229(14):5373-5393
The filtered fluid dynamic equations are discretized in space by a high-order spectral difference (SD) method coupled with large eddy simulation (LES) approach. The subgrid-scale stress tensor is modelled by the wall-adapting local eddy-viscosity model (WALE). We solve the unsteady equations by advancing in time using a second-order backward difference formulae (BDF2) scheme. The nonlinear algebraic system arising from the time discretization is solved with the nonlinear lower–upper symmetric Gauss–Seidel (LU-SGS) algorithm. In order to study the sensitivity of the method, first, the implicit solver is used to compute the two-dimensional (2D) laminar flow around a NACA0012 airfoil at Re = 5 × 105 with zero angle of attack. Afterwards, the accuracy and the reliability of the solver are tested by solving the 2D “turbulent” flow around a square cylinder at Re = 104 and Re = 2.2 × 104. The results show a good agreement with the experimental data and the reference solutions. 相似文献
3.
Evelyn Otero Peter Eliasson 《International Journal of Computational Fluid Dynamics》2015,29(2):133-149
The implicit lower–upper symmetric Gauss–Seidel (LU-SGS) solver is combined with the line-implicit technique to improve convergence on the very anisotropic grids necessary for resolving the boundary layers. The computational fluid dynamics code used is Edge, a Navier–Stokes flow solver for unstructured grids based on a dual grid and edge-based formulation. Multigrid acceleration is applied with the intention to accelerate the convergence to steady state. LU-SGS works in parallel and gives better linear scaling with respect to the number of processors, than the explicit scheme. The ordering techniques investigated have shown that node numbering does influence the convergence and that the orderings from Delaunay and advancing front generation were among the best tested. 2D Reynolds-averaged Navier–Stokes computations have clearly shown the strong efficiency of our novel approach line-implicit LU-SGS which is four times faster than implicit LU-SGS and line-implicit Runge–Kutta. Implicit LU-SGS for Euler and line-implicit LU-SGS for Reynolds-averaged Navier–Stokes are at least twice faster than explicit and line-implicit Runge–Kutta, respectively, for 2D and 3D cases. For 3D Reynolds-averaged Navier–Stokes, multigrid did not accelerate the convergence and therefore may not be needed. 相似文献
4.
A Fast,Matrix-free Implicit Method for Computing Low Mach Number Flows on Unstructured Grids 总被引:2,自引:0,他引:2
HONG LUO JOSEPH D. BAUM RAINALD LÖHNER 《International Journal of Computational Fluid Dynamics》2013,27(2):133-157
A fast, matrix-free implicit method has been developed to solve low Mach number flow problems on unstructured grids. The preconditioned compressible Euler and Navier-Stokes equations are integrated in time using a linearized implicit scheme. A newly developed fast, matrix-free implicit method, GMRES + LU?SGS, is then applied to solve the resultant system of linear equations. A variety of computations has been made for a wide range of flow conditions, for both in viscid and viscous flows, in both 2D and 3D to validate the developed method and to evaluate the effectiveness of the GMRES + LU?SGS method. The numerical results obtained indicate that the use of the GMRES + LU?SGS method leads to a significant increase in performance over the LU?SGS method, while maintaining memory requirements similar to its explicit counterpart. An overall speedup factor from one to more than two order of magnitude for all test cases in comparison with the explicit method is demonstrated. 相似文献
5.
Stability Analysis of a Fully Coupled Implicit Scheme for Inviscid Chemical Non-Equilibrium Flows
下载免费PDF全文
![点击此处可从《advances in applied mathematics and mechanics.》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Von Neumann stability theory is applied to analyze the stability of a fully
coupled implicit (FCI) scheme based on the lower-upper symmetric Gauss-Seidel (LU-SGS)
method for inviscid chemical non-equilibrium flows. The FCI scheme shows excellent
stability except the case of the flows involving strong recombination reactions,
and can weaken or even eliminate the instability resulting from the stiffness problem,
which occurs in the subsonic high-temperature region of the hypersonic flow field. In
addition, when the full Jacobian of chemical source term is diagonalized, the stability
of the FCI scheme relies heavily on the flow conditions. Especially in the case of high
temperature and subsonic state, the CFL number satisfying the stability is very small.
Moreover, we also consider the effect of the space step, and demonstrate that the stability
of the FCI scheme with the diagonalized Jacobian can be improved by reducing
the space step. Therefore, we propose an improved method on the grid distribution
according to the flow conditions. Numerical tests validate sufficiently the foregoing
analyses. Based on the improved grid, the CFL number can be quickly ramped up to
large values for convergence acceleration. 相似文献
6.
7.
8.
任登凤;谭俊杰;张军 《力学与实践》2006,28(5)
采用非结构网格的LU-SGS隐式算法计算三维Euler方程,数值模拟了不同
马赫数以及不同攻角下某空心弹丸绕流流场,分析了流场的波系结构及其升阻力特性,计算
结果表明空心弹丸的阻力系数比同口径的普通弹丸的阻力系数大约小30{\%},空心弹丸的
阻力系数以及升力系数随攻角的变化规律与普通弹丸一致. 相似文献
9.
10.
We propose an efficient and robust algorithm to solve the steady Euler equa- tions on unstructured grids.The new algorithm is a Newton-iteration method in which each iteration step is a linear multigrid method using block lower-upper symmetric Gauss-Seidel(LU-SGS)iteration as its smoother To regularize the Jacobian matrix of Newton-iteration,we adopted a local residual dependent regularization as the replace- ment of the standard time-stepping relaxation technique based on the local CFL number The proposed method can be extended to high order approximations and three spatial dimensions in a nature way.The solver was tested on a sequence of benchmark prob- lems on both quasi-uniform and local adaptive meshes.The numerical results illustrated the efficiency and robustness of our algorithm. 相似文献