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