[mariam.sara]

Hello I am tried to wright if statement to set velocities of two fluids (one at the bottom of the pipe and the other on the upper part) I tried use CEL expression and I use in it If expression to distribute the velocity between the phases as below:

if(y>0.01 [m],if(y<=0.01 [m],12.5 [m s^-1],0.0066 [m s^-1]),0 [m s^-1])

where y vertical distance
0.01 m is the free surface level
knowing that the velocities at walls are zero (no slip condition).

when I try test the expression above before run in cfx-pre it gives zero velocity everywhere along y direction so what the problem? may somebody tell me? is the expression incorrect? I read at the documentations about IF statement but not find similar example to my case?

[Lance]

if(cond_expr,true_expr,false_expr)

Do you want 12.5 m/s above 0.01 m and 0.0066 m/s below 0.01?
if(y>0.01 [m],12.5 [m s^-1],0.0066 [m s^-1])

[mariam.sara]

Yes when y>0.01 m velocity is 12.5 m/s
But when y<=0.01 m velocity is 0.0066 m/s
When y=0 & y=0.0985 m (at lower and upper walls respectively) velocity is 0 m/s
with the above conditions how the expression will be?
Thanks

Originally Posted by Lance

if(cond_expr,true_expr,false_expr)

Do you want 12.5 m/s above 0.01 m and 0.0066 m/s below 0.01?
if(y>0.01 [m],12.5 [m s^-1],0.0066 [m s^-1])

[Lance]

The expression I gave you will work. At the walls the velocity will be zero unless you have defined a free-slip wall.