Learning Forum

[scabo]

Hi
I have a 3D flow and I want to create equidistant stramlines on a slice. For that i am using the surface streamline function, but how can i create streamlines that has constant spacing of streamfunction values? Streamline is generating slightly more random streamlines but I want them to be seperated by constant streamfunction values.
Also how can i calculate the streamfunction from the flow on a 2D slice extracted from the 3D flow?
thanks

[Petros]

Hi, the first question is a duplicate to this one and is already answered.

Regarding the second question you can calculate it using an expression based on the definition of stream function. Stream function is only defined for 2D flows and it wouldn't make physical sense to slice a 3D domain and plot it there. The only situation where this would apply is if the flow is confined to that plane, so there is no significant velocity component out of the plane.

[scabo]

Hi, But i have seen papers calculate streamfunction for a 3D flow on a 2D slice of the cross-section. Can i not calculate it after extracting the velocity components from a 2D plane? Means how is CFDPost plotting streamlines on a surface? It must be calculating the streamfunction first?

[Petros]

Again, if the velocity component normal to the plane is not significant then it can be approximated on that plane in the case of a 3D solution.

Documentation covers how streamlines are computed. Stream function is not needed to calculate them.

[scabo]

Okay but what if i want to calculate the maximum value of streamfunction, because i want the exact distance of the vortex centre on the 2D plane?

[Petros]

Maybe you can calculate the maximum value of the vorticity swirling strength on the Plane, then export that variable on the plane in a .csv file and look for it. You will get the coordinates.