[manos1990]

Hello,

Im running a centrifugal pump with a rotating levitated impeller
pressure-based transient solution
Model: SST-kw
with pressure inlet and outlet
impeller speed: 3000 rpm
Methods: SIMPLE, PISO

I have tried both SIMPLE and PISO with URFs reduced but my residuals keep osciliating in a every time step. Additionally the continuity is high. Even though the solution is converging im not sure about the quality of my results.

The minumum orthogonal quality is 0.15 in a few cells and the majority is above 0.6.

Attached a screenshot to take a glimpse.

Any thoughts on how to reduce the continuity and skip the oscillation?

Much appreciated,
Manos

[LuckyTran]

Where is the oscillation? It looks to be converging nicely.

Residuals will and should spike to very high values whenever a new time-step starts. You should get a saw-tooth looking like behavior, which I see here. It looks to me like you are doing 400 iteration per time-step.

[manos1990]

Originally Posted by LuckyTran

Where is the oscillation? It looks to be converging nicely.

Residuals will and should spike to very high values whenever a new time-step starts. You should get a saw-tooth looking like behavior, which I see here. It looks to me like you are doing 400 iteration per time-step.

Sorry for the late reply i was off.
Thank you for your message and the information.
Yeah is 400 iterations/time-step. I prolonged them now to converge.
Do you think the continuity is abnormal?