Reversed flow in pressure inlet

lehoanganh07 · January 17, 2014, 20:51

Dear fluent user,

I am modeling 3D flow in Nozzle with boundary condition at inlet and outlet is pressure. But after 5000 iteration, I got the warning: reversed flow in pressure inlet, and the number of faces which got that problem is increase.

Any one know how to fix this problem and it will cause the incorrect result?

Also I set total pressure 164560 Pa, when I got this messenger, I check pressure inlet, it show static pressure equal total pressure.

LDA · January 18, 2014, 19:36

This is quite common in the first few iterations but after 5000 iterations ...

Do you have to use a pressure inlet BC? Try to use velocity inlet instead if you can. For a nozzle problem I think you surely can. If you cannot, that means your under relaxation factors need to be reduced.

There are other solutions too but as I do not know about your specific goal I cannot comment more about it neither.

lehoanganh07 · January 19, 2014, 04:58

Thank you, LDA

Yes, I am using pressure inlet BC. I am modeling two phase flow, so the density is not constant. Therefore, using velocity inlet will give unphysical result.
Also, URF I set small 0.1 for all value except pressure 0.5, density 0.5, body weight 1

lehoanganh07 · January 19, 2014, 05:17

Also, this is the result I checked (still calculate). The result seem very strange, and also different from out experiment.
The method I use: PISO transcent, second order for pressure, least square cell base for gradient, QUICK for all other.

Can anyone suggest the solve for this result?

LDA · January 19, 2014, 13:17

Are you sure you adequately satisfy a LES simulation's requirements in terms of mesh resolution principally?

lehoanganh07 · January 19, 2014, 19:35

I think it OK. The mesh for LES, yplus less than 1.
Also I have same result with K-e and K-o

January 17, 2014, 20:51	Reversed flow in pressure inlet	#1
lehoanganh07 Member le hoang anh Join Date: Oct 2012 Posts: 96 Rep Power: 14	Dear fluent user, I am modeling 3D flow in Nozzle with boundary condition at inlet and outlet is pressure. But after 5000 iteration, I got the warning: reversed flow in pressure inlet, and the number of faces which got that problem is increase. Any one know how to fix this problem and it will cause the incorrect result? Also I set total pressure 164560 Pa, when I got this messenger, I check pressure inlet, it show static pressure equal total pressure.

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January 18, 2014, 19:36		#2
LDA New Member Join Date: Jan 2014 Posts: 5 Rep Power: 12	This is quite common in the first few iterations but after 5000 iterations ... Do you have to use a pressure inlet BC? Try to use velocity inlet instead if you can. For a nozzle problem I think you surely can. If you cannot, that means your under relaxation factors need to be reduced. There are other solutions too but as I do not know about your specific goal I cannot comment more about it neither.

January 19, 2014, 04:58		#3
lehoanganh07 Member le hoang anh Join Date: Oct 2012 Posts: 96 Rep Power: 14	Thank you, LDA Yes, I am using pressure inlet BC. I am modeling two phase flow, so the density is not constant. Therefore, using velocity inlet will give unphysical result. Also, URF I set small 0.1 for all value except pressure 0.5, density 0.5, body weight 1

January 19, 2014, 13:17		#5
LDA New Member Join Date: Jan 2014 Posts: 5 Rep Power: 12	Are you sure you adequately satisfy a LES simulation's requirements in terms of mesh resolution principally?

January 19, 2014, 19:35		#6
lehoanganh07 Member le hoang anh Join Date: Oct 2012 Posts: 96 Rep Power: 14	I think it OK. The mesh for LES, yplus less than 1. Also I have same result with K-e and K-o