This is not correct. The physical velocity is u[sub]p[/sub] = 0.4 m/s, the lattice constant dx = 0.000154 m (1cm/65) and your time step dt = 0.0002 s. The lattice velocity u[sub]l[/sub] then is u[sub]p[/sub] * dt / dx = 0.519, which is too large. The lattice velocity should not exceed 0.1. You have to rechoose your time step.
By the way, my approach usually is to first set the characteristic lattice velocity and lattice viscosity (to ensure reasonable values), and then the time step. But everybody has different preferences. Important is that in the end everything is working nicely.
We want a grid consisting of 6565390 =>
I choose tau=0.5009
(I would like to use tau=0.8-0.9, but it’s quite difficult to tune so for u_p=0.4 m/s and nu_p=8.5510^-7 m2/s)
The lattice velocity
u_LB=u_pdt/dx=0.4m/s(8.32*10^-6 s)/(0.000154 m)=0.02161<0.1
Could you please help me check the processes one more time?
And is this u_LB the inlet velocity in the LB program coding if the Zou/He velocity BC’s is applied?
Another question here. I read the paper ‘Shear Stress in Lattice Boltzmann simulations’, equation (45)
s_ab=-3/(2taurho)summation(ciacib-delta_ab/3ci dot ci)f_neq