out flow B.C

Dear all

i want to compute pressure drop in a channel with obstacles. as i know, in palabos we can not define out flow B.C like CFD software (Fluent,OpenFoam,…)

I want to compute velocity (pressure) at out let, only mass balance is considered in the simulation.

can i use Zou/He BC (createZouHeBoundaryConditionXD) for this?

can anyone help me in this problem?


Hi smm

While I haven’t touched LB for a number of months, I think I know how to help you.

So long as you define the inflow condition and leave the outflow boundary as periodic the pressure drop will establish itself and come to a steady state.



Dear Bruce

thank u very much for your kind reply!

do you have any experience with OpenLB?

You can define outflow boundary conditions with Palabos, just like with other CFD software. Check the user’s guide: http://www.lbmethod.org/palabos/documentation.userguide/boundary-conditions.html#zero-gradient-conditions


I am simulating flow in a chamber. i am using Guo’s non-equilibrium extrapolation scheme. I know inlet velocity and at outlet pressure is 1 atm.my Re=200.I have written my inlet BC as
rho[NY-1][i] = rho[NY-2][i];
u_x[NY-1][i] = 0.0;
u_y[NY-1][i] = U = 0.05;
and out flow BC as follows.
rho[NY-1][i] = rho[NY-2][i];
u_x[NY-1][i] = u_x[NY-2][i];
u_y[NY-1][i] = u_y[NY-2][i];
My density is decreasing for every iteration. what went wrong with my code?. i have doubt regarding implementation of BC.
Please help.