## Postprocessing

#### How to create a volume location in CFD Post based on coordinates

• FAQ
Participant

In order to define a volume location in CFD Post, one can use expression-based variables. There are two procedures:

1a) define an expression which has the value of 1 in the region to be defined as volume location, and value of 0 anywhere else.
For instance, expression which has a value of 1 in the region 0.25m < z < 0.75m and -0.025m < x < 0.025 can be defined as:
step((Z-0.25[m])/(1[m])) * step((0.75[m]-Z)/(1[m])) * step((X+0.025[m])/(1[m])) * step((0.025[m]-X)/(1[m]))
The function step(x) returns 1 when the x is positive, otherwise 0.
1b) define an expression based on the if function: if(Z<0.75 [m] && Z>0.25 [m] &&X<0.25 [m] && X>-0.25 [m],1,0)
2. define a new variable, select “Expression” as “Method” and choose the expression defined in step 1.
3. Insert -> Location -> Volume; select “Isovolume” as Method; Variable -> select the variable defined in step 2; Value = 1 Keywords: CFD Post, Volume, Iso-Volume, coordinates