Centrifugal pump boundary conditions

[Anonymous]

Hi Team,

I have been going through your tutorial models and I came across the centrifugal pump model where I can't seem to figure out.

Here's a video from your AU class: http://au.autodesk.com/au-online/classes-on-demand/class-catalog/classes/year-2017/simulation-cfd-36... (you might want to go to timestep 19:00 where the boundary conditions are applied).

Also go through this tutorial of a similar pump model: https://knowledge.autodesk.com/support/cfd/learn-explore/caas/CloudHelp/cloudhelp/2014/ENU/SimCFD/fi...

In the video, can you explain why we have a zero pressure inlet and but specified flow rate for the outlet. Taking into account that we have specified the parameters of the rotating region. Isn't this model over-constrained? 

The set up in the tutorial page makes more sense since we specified a zero pressure inlet and outlet. We allow the flow to be generated (only) by the rotating region.

Please, what am I missing?

Thanks,

Nnaemeka 

[Jon.Wilde · Accepted solution]

Hi Nnaemeka, welcome to our CFD forum 🙂

Pumps generate a pressure rise and so there should be a higher pressure at the outlet than the inlet.

We tend to pull flow out and have a P=0 at the inlet, then CFD predicts the outlet pressure.

If we swap the conditions, we get into negative pressures, which are not as simple for the solver.

You can also run P=0 at both, this is simply an open flow condition which represents a different point on the pump curve.

Assigning various outlet flow rates simply gives you a different point on the curve. These models are not over constrained.

Does that answer your question?

Thanks!

Jon

[Anonymous]

Yes, thanks Jon