Learning Forum

[javat33489]

Hi all.

I watched a wonderful video on how cavitation was calculated for a centrifugal wheel:

https://www.youtube.com/watch?v=9E3Q-cqhkVw

 

Question about boundary conditions for calculating cavitation when using a mixture. At the inlet pressure, volume fraction of steam = 0. At the outlet, steam mass flow = 0. Water comes in and only water comes out.

 

So the question is, is it permissible to also count evaporation? At the inlet pressure, volume fraction of steam = 0. At the outlet, steam mass flow = 0. Water comes in and only water comes out.

 

Thank you.

[javat33489]

What do you say? It is acceptable? I think yes.

[Rob]

The boundary conditions need to set to suit the models and conditions. 

And in Admin mode: please contain your questions that cover one subject/model to one topic/thread. 

[javat33489]

>>The boundary conditions need to set to suit the models and conditions. 

That's why I asked, is the task of evaporation similar to cavitation under equal conditions?

[Rob]

Similar. Try running the model and see how it behaves. 

[javat33489]

1.Sir. It seems I managed to find the cause of the problem. When calculating mixtures when indicating mass flow rates, you need to be very careful. Mass flow is kg/s. The density of the phases may be different. For example, water is 1000 kg, and gas is 0.1 kg. Therefore, when specifying mass flow, the flow rate for both phases must be calculated correctly. If there were volumetric flow it would be easier, but this is not the case in Fluent.
2.I used the inlet pressure and outlet pressure found when calculating the water. Everything goes perfectly, but after about 1000-1500 iterations, a sharp jump in all graphs occurs and the calculation stops. I'm doing different tests, I'll write how successful it is.