I have loaded a state file (.pvsm) of a turbulent channel flow solved using DNS and I want to visualise vortical structures using the Q-criterion but it’s not working out.
I’m not sure what I’m missing because the tutorials seem straightforward.

The velocity components are all stored as points in 3 different arrays (u,v,w) but I can’t seem to be able to calculate the velocity magnitude with the Calculator filter. I use the equation Umag= sqrt(u^2+v^2+w^2) to find the velocity magnitude.

Any help will be appreciated and I am happy to give more information about the setup

Well, assuming the research I have made is correct, the first step is to create an array (Umag) with the three velocity components (u,v,w) using the calculator filter.

I have been struggling to do this, then you use the Gradient of Unstructured Dataset 1 filter to calculate vorticity and Q criterion.

So, while my main goal is to calculate the Q criterion I haven’t been lucky to find the Umag. I get a blank box when I apply the calculator filter as shown in the image below:

I get a blank box when I apply the calculator filter as shown in the image below:

This is an outline, switch representation to surface to see the surface instead of the outline

the first step is to create an array (Umag) with the three velocity components (u,v,w) using the calculator filter.

The first step is to create a Vector with the three velocity components (u,v,w) using the calculator filter or the dedicated filter, MergeVectorComponents