hi all
I have run program anb.f in many lx and ly
but pressure is not correct while u and v seems to be correct
I have this question:
whether press have meaning or not in p=rho*cs^2 ?

when we use incompressible we must became rho=constant

with compressibility error of LBM in density, how I can find pressure gradient in domain?

I understand lbunits and those conversion to physical units but pressure with conversion and without conversion is incorrect

thanks

maybe you can find something help in the paper:On pressure and velocity boundary conditions for the lattice Boltzmann BGK model(Zou/He).
good luck@@

dear aass277
hi
I was read that paper previous time and I review that again now
but I have my problem again now
is it possible to you to help me
have a nice time
mehdi

but pressure is not correct while u and v seems to be correct

• Which problem are you simulating?
• Is it simply that the amplitude of the pressure is wrong, or do you get an entirely unexpected pressure profile?
• If you are simulating a steady problem: are you sure the simulation has reached a steady state?

I have this question:
whether press have meaning or not in p=rho*cs^2 ?

• Yes, this equation has a physical meaning. You can use it to compute the pressure.

when we use incompressible we must became rho=constant

• In theory yes, but in practice we allow small density variation as a way to solve the physics of the pressure term.

dear Jonas Latt
I try to prepare a 3D code in LB but in this time I want to compare my 2D code answers with others answers.
I try to run 2d cavity flow and channel flow.

amplitude of pressure is incorrect and also that have very oscillation in domain.

I am not sure to reach steady state , how I can sure to reach steady state? I run program 200000 iteration.
I see mean velocity in one cross section and if that value not changed for long time I stop the program.

in p=rhocs^2 I find very small pressure change in real unit because rhocs^2 is about=1/3 in lb units.
what is this p? is it a difference or ratio of pressure?

my problem is flow between two stationary wall
lx=402 ly=82
widthreal=0.1m
rho=997.1 kg/m^3
dxreal=0.1/80
dtreal=dxreal**2*nulb/nureal
nureal=0.897d-6
rholb=1
re=10
mach=1/(ly-2)=1/80
dx=1
dt=1

thanks
have a nice time
mehdi