泊肃叶流动

1058343691

泊肃叶流动用D2Q9模型来模拟，关于粘度和Re数的关系，u=U*Lx/Re,它的U是怎么确定的？在演化处理过程中，我是添加的外力项。

luo@odu.edu

For the Poiseuille flow with a GIVEN Reynolds number Re, the following formula for the maximum velocity

U = F N^2 / 8 v

where v is the viscosity, F is the forcing magnitude, and N is the number of grid point across the channel. Also, the following condition must be satisfied for numerical stability in practice:

U / c_s < 0.3

Therefore, you will have the following upper bound for the forcing:

F = 8 U^2/(Re*N) < 0.24 / (Re*N)

where c_s^2 = 1/3 has been used. Once the forcing F is determined, so is U.

1058343691

谢谢，罗老师。

1058343691

谢谢，罗老师

luo@odu.edu

Does my comment help at all?

1058343691

我觉得还是有些不明白的。查了一些资料也没查到，罗老师你说的。按我的理解
U = F N^2 / 8 v，假设Nx=50， v=0.0135，F=密度*加速度，加速度取,0.005，密度取0.1，
代入F = 8 U^2/(Re*N) < 0.24 / (Re*N)中，不满足条件。感觉这个条件很难满足啊，我想根本问题是我理解有误。

luo@odu.edu

Mean density rho_0 should be set to 1.0 (because rho is NOT a meaningful
quantity in the incompressible flow), thus F = rho_0 a = a (a is the acceleration),
and you should use the following formula to pick a value of "a":

a < 0.24 / (Re*N)

That is: pick a value of viscosity nu, and a channel width N, then you can compute
Re, with Re and N, you can decide the approximated upper bound for the acceleration
(or force).

[ 本帖最后由 luo@odu.edu 于 2013-5-25 09:51 编辑 ]

DelvonLiu

罗老师，对于加速度就是重力加速度（重力驱动），我格子中的加速度怎么取呢？