新手求教自然对流中无量纲化问题

st2yang

我的问题解决了。后面结果又乱了的原因是u/c取的0.1，没有满足低马赫数假设。将网格增加为128x128，特征速度取0.05，得到结果正确。谢谢@埋葬过往的耐心解答！

埋葬过往

哈，不客气，

gerok

能否請問你的TauF 跟TauG 分別是怎麼計算的呢

st2yang

gerok 发表于 2015-5-14 12:36
能否請問你的TauF 跟TauG 分別是怎麼計算的呢

求出运动粘度和热扩散系数就可以确定无量纲松弛时间了，适用于自然对流的模型里面是
tau_f=3*niu+0.5;
tau_g=3*X+0.5;（省略了t等取1的量）

luo@odu.edu

st2yang 发表于 2015-5-13 20:40
我的问题解决了。后面结果又乱了的原因是u/c取的0.1，没有满足低马赫数假设。将网格增加为128x128，特征速 ...

If you use the MRT model, it would be much more stable and accurate. We can use small mesh of 41*41 for Ra = 10**6. See the following papers:

J. Wang, D.H. Wang, P. Lallemand, and L.-S. Luo.
Lattice Boltzmann simulations of thermal convective flows in two dimensions.
Computers and Mathematics with Applications 65(2):262-286 (January 2013).

D. Contrino, P. Lallemand, P. Asinari, and L.-S. Luo.
Lattice-Boltzmann simulations of the thermally driven 2D square cavity at high Rayleigh numbers.
Journal of Computational Physics 275:257-272 (15 October 2014).

which can be downloaded from my website.

haisenberg

您好，楼主，请问如何将运动粘度和热扩散系数无量纲化呢