Hi guys,
so far i used Reynolds-numbers > 1, and everything looked like fine, but now i need to use Re < 1 and i get some weird results.
Here are my Input values:
I apply an external field, with deltaP_ex = 5 Pa/m, with an x-axis lenght of lx_p = 6.9E-4 m.
-> deltaP_p = deltaP_ex * lx_p = 3.5E-3
and my velocity in x-direction is therefore:
ux_p = sqrt (2*deltaP_p / rho_p) = 1E-3 m/s
with:
rho_p = 7000 kg/m³
lx_p = 6.9E-4 m
ly_p = 4E-4 m
lref = 4E-4 m
visc_p = 7.13E-7 m² /s
N = 200.
therefore i end up with a Reynoldsnumber Re = (ux_p * lref) / visc_p = 0.557 which is ok.
The above values lead to visc_lb = 7.17 (and also geLatticeNu() does).
With BGK-dynamics, tau = visc_lb/c_s² + 0.5 should be true (c_s = sound speed in the lb system), which leads to an tau = 22.093 and this looks like the reason for my problems.
But on the other hand, if I calculate the Mach number with Ma = ux_p / c_s
and use
Ma / Re = 1/sqrt(3) * (tau - 0.5) / N
I end up with
tau = 1.07
getTau() also produces the 22.093, so I guess the Ma of my System isnt the value I come up with from the above equation.
But where do I define it in palabos, or what else I am doing wrong ?
thx for any input,
Cheers,
Chris