Increasing maximum velocity of poiseullie 2D flow

Hi every one,

Actually, I wrote a code by C++ language. Modeling a 2D Poiseullie flow in a pipe. I used Zou and He velocity and pressure Boundary Condition for inlet and outlet respectively and bounce-back BC for stationary walls. However, maximum velocity is increasing during the channel after the flow becomes fully develop.

I do not know where the problem is. I used collision and streaming of this code for the periodic Boundary condition case and it worked perfectly, but with this new boundary condition, the maximum velocity is increasing during the channel.

Does anyone have any suggestion?

Thank you in advance,

Dear atefeh,

My code suffers from the same problem as yours and there is no mass conservation. Actually I wrote a code by FORTRAN language. Did you find out your problem?
I appreciate if you let me know about the treatment that you implemented.