I'm trying to use the one seventh power law for velocity profile between two parallel plates in cfx. The problem is that the expression covers only half of the flow, from the center of the flow to the wall. I know it is mirror image from the center to the other wall and I have two deferent expressions for the complete profile but how can I give this profile from wall to wall to cfx when it takes only one expression?

thanks!

If the equation for your power law originates from an origin of zero, it is probably that the equation only works for anything > zero. I am guessing the zero origin is at center of your channel, that's why you were only getting half of the profile. You can perhaps try offsetting the origin to make your expression work.

However, if you have two different expressions for the upper and lower half of the channel, you might want to try looking at specifying your velocity profile through user routine (See User Fortran section in Modelling Guide)

Good luck!

thank you for your response!

If you have two different expressions (unlikely), the step function can also be used to activate one for y>0 and the other for y<0, without resorting to User Fortran.