Learning Forum

[MrFCA]

Hello

I am trying to simulate 3D (steady) impeller of a centrifugal pump for get the performance curves. However, in the result you can see negative absolute pressures on the surface of the blade. What in happening whit that? Negative absolute pressures are not possible in the reality.

 

[Amine Ben Hadj Ali]

1/Bad convergence behavior

2/Negative Absolute Pressure might tell that water is cavitating inside the Pump.

[MrFCA]

Hello! The first problem was solved (it was due to the boudary conditions). However, the second problem not. Why is it cavitating in this stranger zone? I have followed the step of two videos upload in YouTube (ANSYS How To Videos). This are the links followed:

https://www.youtube.com/watch?v=nBs4Zs3rCRQ

https://www.youtube.com/watch?v=1Mhwtv4DlHY&t=4s

[MrFCA]

Do not you have manuals on centrifugal pumps to follow the steps and solve the problem correctly?

[Amine Ben Hadj Ali]

No I do not have the manuals for that. The videos are sufficient.

Which 2nd Problem are you now meaning? The negative Aboslute pressure?

[MrFCA]

Yes, I refer to the negative absolute pressure. How can I solve that? 

[MrFCA]

I have been traying a lot of things, but in this zone of the blade I always have this problem. I hace tried with different geometries and it always happens. 

[Amine Ben Hadj Ali]

If all settings are correct and convergence is now excellent, then as I said it probably seems cavitating.

[MrFCA]

Ans also, every tima I simulate I have this error:

 

[MrFCA]

But in real life, negative absolute pressures are not possible. Why the program give me this result?

[Amine Ben Hadj Ali]

That is why one requires modeling cavitation to avoid negative absolute pressure. Absolute Pressure is only limited for material properties.

[Amine Ben Hadj Ali]

Make some more tutorials especially one related to cavitation.