Hi, I have a cylinder where I want the radius to be a function of time, like: r = A*sin(t), using a moving mesh. I know that there is a bondary condition called "Mesh motion - specified displacement - XYZ components" but I want to use polar coordinates. One solution is to use a CEL-expression to calculate the cartesian components of the motion from polar coordinates, but then I need r and theta. I know that they are predefined in CFX but when I use them I get ALL the coordinates in the domain, and not just the ones on the wall.

So my question would be... is there a way to specify which coordinates to use, like Rwall = sqrt((x@wall)^2+(y@wall)^2) and Thetawall = atan(y@wall/x@wall)??

cheers Jonas

Hi Jonas,

You don't need to worry about getting ALL the coordinates. CFX will only evaluate the expression where it is used. If it is called on the boundary region, only the boundary region variables are calculated, not the entire domain.

-CycLone

Hi,

Thanks, apparently CFX is smarter than I thought

/Jonas