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解二维辐射输运问题时,对于矩形网格,用Sn菱形(diamond)格式处理十分简单有效,但该格式不能直接用于非矩形网格,而辐射流体力学计算往往要求在非矩形网格上进行.本文讨论任意四边形网格的辐射输运数值方法,给出一种全正的子网格平衡计算格式,并进行数值计算,与矩形网格Sn菱形格式结果比较,得出本方法可行性结论. 相似文献
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文章给出了一种真正多维的HLL Riemann解算器.采用AUSM分裂将通量分解成为对流通量和压力通量, 其中对流通量的计算采用迎风格式, 压力通量的计算采用HLL格式, 且将HLL格式的耗散项中的密度差用压力差代替, 从而使得格式能够分辨接触间断.为了实现数值格式真正多维的特性, 分别计算了网格界面中点和角点上的数值通量, 并且采用Simpson公式加权组合中点和角点上的数值通量得到网格界面的数值通量.为了减少重构角点处状态时的模板宽度, 计算中采用基于SDWLS梯度的线性重构获得2阶空间精度, 而时间离散采用2阶保强稳Runge-Kutta方法.数值实验表明, 相比于传统的一维HLL格式, 文章的真正多维HLL格式具有能够分辨接触间断, 以及更大的时间步长等优点.与其他能够分辨接触间断的格式(例如HLLC格式)不同, 真正多维的HLL格式在计算二维问题时不会出现激波不稳定现象. 相似文献
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从最小势能原理出发,使用变分-差分方法构造带有弯曲边梁的薄板的小挠度弯曲问题的差分格式,所得格式仅依赖板面网格结点,从而避免了由于引入虚拟网格结点而带来的问题;编制求解差分方程组的MATLAB程序,给出数值模拟结果. 相似文献
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利用双曲守恒律的Hamilton-Jacobi方程形式,应用Taylor公式与Galerkin有限元给出了求解双曲守恒律的计算方法。采用TVD差分格式的构造思想,对数值通量作修正,在等距网格情形下有限元方法得到的计算格式满足TVD性质,并给出了数值例子。 相似文献
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非正交网格上的九点格式在热传导问题中的改进 总被引:1,自引:1,他引:0
对文献[1]在二维Lagrange流体力学网格上构造的扩散方程九点差分格式做了进一步的讨论和改进,给出了一般形式边界条件的计算格式。数值试验的结果表明,这些改进提高了原格式数值结果的精度。 相似文献
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边界条件对对流扩散方程数值稳定性的影响 总被引:2,自引:0,他引:2
本文利用数值计算方法对采用均分网格的一维线性无源的对流-扩散方程在各种边界条件下的稳定性进行了分析,燕求出了不同边界条件下一维问题的中心差分和QUICK格式的临界网格Peclet数。指出按现有方法得出的临界网格Peclet数是判别差分格式对流数值稳定性的最苛刻的要求。对中心差分和QUICK格式,除两点边值问题以外的其它边界条件下的稳定性范围均不小于或远远大于两点边值问题的稳定性范围。通过计算还得出了格式的数值稳定性主要取决于计算区域下游侧的边界条件类型而与计算区域上游侧的边界条件类型无关的结论。 相似文献
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QUICK与多种差分方案的比较和计算 总被引:9,自引:3,他引:6
本文用QUICK和多种差分方案计算了四个流动与换热问题.计算结果表明。对于强制流动问题,QUICK用较粗网格就能得到其他差分方案用较细网格才能得到的结果。对稳态自然对流,QUICK与其他差分方案的计算结果相近,但QUICK方案能预测出所计算的低Pr数流体自然对流的物理振荡,而其他几种方案不能. 相似文献
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A high-order incompressible flow solver with WENO 总被引:1,自引:0,他引:1
A numerical method for solving the incompressible Navier–Stokes equations with a 5th-order weighted essentially non-oscillatory (WENO) scheme is presented. The method is not based on artificial compressibility and is free of tunable parameters such as the artificial compressibility parameter. The method makes use of the fractional-step method in conjunction with the low-dissipation and low-dispersion Runge–Kutta (LDDRK) scheme to improve temporal accuracy of the scheme. The use of a WENO scheme makes it possible to obtain stable solutions for discontinuous initial data and resolve difficult applications with strong shear such as Kelvin–Helmholtz instability or turbulence. Good convergence rate is established for the velocity variables and numerical solutions of the present method compare well with exact solutions and other numerical results. 相似文献
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低Prandtl数水平流体层自然对流的振荡和分歧 总被引:7,自引:3,他引:4
本文用具有QUICK方案的有限差分法对底部加热的低Prandtl数水平流体层自然对流换热进行了数值计算,研究了这种问题中存在的振荡和分歧问题。结果显示,在Ra的一定取值区间,有4涡型流场和5涡型流场两个解的分支。但在这个区间以外,最终的结果没有出现分歧。在所发现的两个解的分支中,问题由稳态转变为非稳态的临界Racr是不同的。 相似文献
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The artificial compressibility method for the incompressible Navier–Stokes equations is revived as a high order accurate numerical method (fourth order in space and second order in time). Similar to the lattice Boltzmann method, the mesh spacing is linked to the Mach number. An accuracy higher than that of the lattice Boltzmann method is achieved by exploiting the asymptotic behavior of the solution of the artificial compressibility equations for small Mach numbers and the simple lattice structure. An easy method for accelerating the decay of acoustic waves, which deteriorate the quality of the numerical solution, and a simple cure for the checkerboard instability are proposed. The high performance of the scheme is demonstrated not only for the periodic boundary condition but also for the Dirichlet-type boundary condition. 相似文献
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三维不可压N-S方程的多重网格求解 总被引:2,自引:0,他引:2
应用全近似存储(Full Approximation Storage,FAS)多重网格法和人工压缩性方法求解了三维不可压Navi-er-Stokes方程.在解粗网格差分方程时,对Neumann边界条件采用增量形式进行更新,离散方程用对角化形式的近似隐式因子分解格式求解,其中空间无粘项分别用MUSCL格式和对称TVD格式进行离散.对90°弯曲的方截面管道流动和4:1椭球体层流绕流的数值模拟表明,多重网格的计算时间比单重网格节省一半以上,且无限制函数的MUSCL格式比TVD格式对流动结构有更好的分辨能力. 相似文献
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The broken dam problem flow is tested to check accuracy of different procedures for gas-liquid interface resolution based
on solution of the additional equation for the volume fraction of liquid phase. The study is focused on the numerical schemes
used to approximate advection fluxes of this equation. In particular, the MUSCL scheme with QUICK interpolants and compressive
minmod TVD limiters with the slope modification technique for the volume fraction fluxes is applied, as well as the upwind-downwind
donor acceptor procedure designed in the VOF method. As the first stage, the quite simple and explicit procedure adopting
the artificial compressibility method is used to solve the velocity and pressure equations. Computations are initially performed
with a careful grid and time step independence studies. Importance of the wall boundary condition is also discussed. To present
free surface motion, results of numerical investigation are shown in terms of contour plots for the volume fraction at successive
times, as well as surge front and column height positions versus time.
The work was financially supported by the President of the Russian Federation (NSh No. 454.2008.1), Russian Foundation for
Basic Research (Grant No. 06-01-00724), Integration Project of SB RAS (No. 2-16), and National Scientific Council of Taiwan
(NSC, R.O.C., contract NSC-92-2212-E006-102). 相似文献