Sudden pressure drop - Multiphase Flow

koscfd · June 6, 2016, 06:04

Hello,

I created a pipe model in Salome software and imported it in OF for a transient analysis (65s). The flow has two phases and the solver is interFoam. I set the flow from inlet to outlet and run the analysis. The pressure results were reasonable (relatively uniform) for each phase.

When I set the flow the other way round (outlet to inlet), I get sudden and random downward peaks in the pressure field.
For example, at times from 0s to 16.3s pressure results are normal. At time 16.4 the pressure drops significantly (5-6 times less pressure). From times 16.5s to 20.2 results are ok. At time 20.3 the pressure drops significantly. ... and so on.

Do you have any suggestions why could this be happening?

Thank you in advance,
koscfd

katete · July 8, 2016, 06:17

Hello,

I am too working on two-phase pipe flow in interFoam. Could you post the model setup (esp. the boundary conditions)? Then it might be easier to understand your case.

Thanks and best wishes
Katharina

koscfd · July 8, 2016, 07:42

Hello Katharina,

Thank you for your reply.
I have attached the model properties.
I also tried setting 0 pressure (fixedValue) at the pipe outlet, however I still get sudden peaks in pressure results.

Kind Regards,
Kos

katete · August 25, 2016, 08:22

Hey Kos,

I had a look at your case but figured that your simulations are quite different than mine. You are changing the inlet phase as a function of time which I haven't done before. What I could think of since you don't have problems in the positive flow direction: Maybe it is related to the coordinate system? maybe your model has some negative coordinates that might cause problems? Or have you tried turning the whole geometry that the flow is still in positive x-direction? Otherwise I also don't know what you might improve.

Kind regards
Katharina

June 6, 2016, 06:04	Sudden pressure drop - Multiphase Flow	#1
koscfd New Member Join Date: Dec 2015 Posts: 15 Rep Power: 10	Hello, I created a pipe model in Salome software and imported it in OF for a transient analysis (65s). The flow has two phases and the solver is interFoam. I set the flow from inlet to outlet and run the analysis. The pressure results were reasonable (relatively uniform) for each phase. When I set the flow the other way round (outlet to inlet), I get sudden and random downward peaks in the pressure field. For example, at times from 0s to 16.3s pressure results are normal. At time 16.4 the pressure drops significantly (5-6 times less pressure). From times 16.5s to 20.2 results are ok. At time 20.3 the pressure drops significantly. ... and so on. Do you have any suggestions why could this be happening? Thank you in advance, koscfd Last edited by koscfd; June 8, 2016 at 17:59.

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July 8, 2016, 06:17		#2
katete New Member Join Date: Jan 2016 Posts: 10 Rep Power: 10	Hello, I am too working on two-phase pipe flow in interFoam. Could you post the model setup (esp. the boundary conditions)? Then it might be easier to understand your case. Thanks and best wishes Katharina

August 25, 2016, 08:22		#4
katete New Member Join Date: Jan 2016 Posts: 10 Rep Power: 10	Hey Kos, I had a look at your case but figured that your simulations are quite different than mine. You are changing the inlet phase as a function of time which I haven't done before. What I could think of since you don't have problems in the positive flow direction: Maybe it is related to the coordinate system? maybe your model has some negative coordinates that might cause problems? Or have you tried turning the whole geometry that the flow is still in positive x-direction? Otherwise I also don't know what you might improve. Kind regards Katharina