interFOAM air_water interface strange behaviour

anubasu · December 8, 2023, 14:34

Hi I have modeled partially filled flow in a pipe as shown, but when the water strikes the floor, it breaks the surface and it shows strange behaviour. I have reduced the timestep and Co and also refined the mesh but it causes no change in results. Do I need to change anything in fvSchemes? or something else. Because in fluent the same problem, the air-water interface is coming perfectly smooth. I attached the picture.

Thanks

2538sukham · December 11, 2023, 07:15

What are the fvScheme and fvSolution? I guess solver is interFoam.

anubasu · December 11, 2023, 14:25

Quote:

Originally Posted by 2538sukham

What are the fvScheme and fvSolution? I guess solver is interFoam.

Hi Michael, Yes solver is interFOAM. Schemes are ddtSchemes=Euler, gradSchemes=Gauss linear, divSchemes=Gauss linearUpwind grad(U), for alpha=Gauss vanleer,div(phirb, alpha) =Gauss linear, laplacianSchemes=Gauss linear corrected, interpolation=linear.

fvSolution=alphawater=smoothsolver, pcorr=PCG, p_rgh=GAMG, PIMPLE=momentum predictor=no.

Do I have to choose any other schemes?

2538sukham · December 13, 2023, 05:34

Maybe its the interface compression. cAlpha in PIMPLE/PISO parameter in case of foamExtend or alpha.water in fvSolutions where the compression factor is given. try 0 and try 1 (there are reports where higher cAlpha results in oscillations). Although cAlpha = 0 would give a diffused alpha field, that would be a start to your problem.

anubasu · December 14, 2023, 19:23

Hi,
I tried with calpha =1 but it is same but I will try with calpha=0. Do you think that it is something to do with schemes? of div U or alpha or something with the MULES setting in alphawater?

Thanks

2538sukham · December 15, 2023, 01:52

Try running with the dam break case settings provided.Your schemes seem fine. Which version are you using? The simulation doesn't seem that heavy so maybe I can try running in my machine and see it.
With regards

anubasu · December 15, 2023, 04:59

Hi,

Yea i am using OpenFOAM-7. Yea i have tried damBreak settings although I will try again. I tried attaching mesh but it is very large. I am writing the BCs for you. Inlet-just water inlet with some flow rate, Mass flow rate=3.3, Outlet pressure outlet, and walls no slip. I have used similar BCs as angledDuct in the tutorials within interFOAM but with only inlet, outlet and walls for different components like velocity, alpha.water, etc. If you need any details please ask me. I can share the zip with you email if yu want.
Thanks.

anubasu · December 15, 2023, 05:00

What i am noticing is when the water falls from the height it causes some air-water interface problems, but when it just flows thru a pipe it is coming smooth.

2538sukham · December 28, 2023, 06:23

I am at a lost, but then try curving the geometry at the junction, instead of a sharp 90 degree turn.

December 15, 2023, 01:52		#6
2538sukham Member Michael Sukham Join Date: Mar 2020 Location: India Posts: 79 Rep Power: 6	Try running with the dam break case settings provided.Your schemes seem fine. Which version are you using? The simulation doesn't seem that heavy so maybe I can try running in my machine and see it. With regards Last edited by 2538sukham; December 15, 2023 at 04:33.

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December 11, 2023, 07:15		#2
2538sukham Member Michael Sukham Join Date: Mar 2020 Location: India Posts: 79 Rep Power: 6	What are the fvScheme and fvSolution? I guess solver is interFoam.

December 13, 2023, 05:34		#4
2538sukham Member Michael Sukham Join Date: Mar 2020 Location: India Posts: 79 Rep Power: 6	Maybe its the interface compression. cAlpha in PIMPLE/PISO parameter in case of foamExtend or alpha.water in fvSolutions where the compression factor is given. try 0 and try 1 (there are reports where higher cAlpha results in oscillations). Although cAlpha = 0 would give a diffused alpha field, that would be a start to your problem.

December 14, 2023, 19:23		#5
anubasu Member Anurag Join Date: Feb 2023 Posts: 66 Rep Power: 3	Hi, I tried with calpha =1 but it is same but I will try with calpha=0. Do you think that it is something to do with schemes? of div U or alpha or something with the MULES setting in alphawater? Thanks

December 15, 2023, 04:59		#7
anubasu Member Anurag Join Date: Feb 2023 Posts: 66 Rep Power: 3	Hi, Yea i am using OpenFOAM-7. Yea i have tried damBreak settings although I will try again. I tried attaching mesh but it is very large. I am writing the BCs for you. Inlet-just water inlet with some flow rate, Mass flow rate=3.3, Outlet pressure outlet, and walls no slip. I have used similar BCs as angledDuct in the tutorials within interFOAM but with only inlet, outlet and walls for different components like velocity, alpha.water, etc. If you need any details please ask me. I can share the zip with you email if yu want. Thanks.

December 15, 2023, 05:00		#8
anubasu Member Anurag Join Date: Feb 2023 Posts: 66 Rep Power: 3	What i am noticing is when the water falls from the height it causes some air-water interface problems, but when it just flows thru a pipe it is coming smooth.

December 28, 2023, 06:23		#9
2538sukham Member Michael Sukham Join Date: Mar 2020 Location: India Posts: 79 Rep Power: 6	I am at a lost, but then try curving the geometry at the junction, instead of a sharp 90 degree turn.