why do I get velocity entering a wall boundary?

bhqasx · August 19, 2021, 21:33

Hello, I'm a beginner on openFoam. I downloaded an application called gravityCurrentFoam from here https://github.com/psu-efd/gravityCurrentFoam. There is a case in the repo which simulating gravity current in a rectangular flume. In that case, there is a hole (inlet) on the bottom of the flume which is represented as a boundary with a fixed inflow velocity. Now I'm modifying that case to simulate another experiment from a paper. I deleted that boundary but still found velocity around that area.

The case I'm working on is here.
https://github.com/bhqasx/Learning-openFoam-case

piu58 · August 20, 2021, 01:18

As far as I see you have fixed value for all boundaries for U.

Normally this is not recommended. If you use it, inflow and outflow have to contain the same volume stream. That is not the case, as far as I can see.

bhqasx · September 10, 2021, 09:11

Thanks Pilz. I have added an outlet with fixed pressured and the problem is fixed.

August 19, 2021, 21:33	why do I get velocity entering a wall boundary?	#1
bhqasx New Member Zach Join Date: Jun 2021 Posts: 5 Rep Power: 4	Hello, I'm a beginner on openFoam. I downloaded an application called gravityCurrentFoam from here https://github.com/psu-efd/gravityCurrentFoam. There is a case in the repo which simulating gravity current in a rectangular flume. In that case, there is a hole (inlet) on the bottom of the flume which is represented as a boundary with a fixed inflow velocity. Now I'm modifying that case to simulate another experiment from a paper. I deleted that boundary but still found velocity around that area. The case I'm working on is here. https://github.com/bhqasx/Learning-openFoam-case

August 20, 2021, 01:18		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	As far as I see you have fixed value for all boundaries for U. Normally this is not recommended. If you use it, inflow and outflow have to contain the same volume stream. That is not the case, as far as I can see. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

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September 10, 2021, 09:11		#3
bhqasx New Member Zach Join Date: Jun 2021 Posts: 5 Rep Power: 4	Thanks Pilz. I have added an outlet with fixed pressured and the problem is fixed.