Hi Folks,

I have written a code in D2Q9 and I have wall on the top and bottom, my flow is basically in channel, where I have given inlet condition of constant velocity and outflow conditions at the outlet i.e.

at outlet:

X=Xmax+1

do y= 2,Ymax

f(3,x,y) = 2.*f(3,x-1,y)-f(3,x-2,y)

f(6,x,y) = 2.*f(6,x-1,y)-f(6,x-2,y)

f(7,x,y) = 2.*f(7,x-1,y)-f(7,x-2,y)

end do

The grid that I have taken is (500,100)

Uinlet =0.0667lu/ts

tau=0.8 (approx.)

Re=100.

I am using simple Bounceback boundary conditions at the walls.

My problem is at the outlet (exit) I should get Umax=0.1lu/ts(i.e. at the center) as inlet given is 0.0667 lu/ts, but I am getting maximum velocity as Umax = 0.092 lu/ts, hence the results are not matching with the theoretical results. I have checked the code many a times but I have not found any error in collision or bounce back or propagation.

I have just used constant inlet velocity and the outlet condition I have written in the above part of post. Kindly help me out with this, I am really puzzled.

regards

Prateek