mappedPatch BC

vigges · February 20, 2012, 08:42

Hi all!!

I'm having a hard time setting up the boundary conditions for my 2D case.
I'm using OF 2.1.0 and simpleFoam.

What I need is a mapped patch at the inlet in order to get a fully developed turbulent flow before entering a diffuser.
I adjusted my constant/polyMesh/boundary and 0/U as followed:

Code:

    inletPatch
    {
        type            mappedPatch;
        nFaces          8;
        startFace       45368;
        sampleMode        nearestCell;
        sampleRegion    region0;
        samplePatch        none;
        offsetMode        uniform;
        offset            (0.035 0 0);
    }

Code:

    inletPatch
    {
        type                        mapped;
        value                        uniform (30.22 0 0);
        interpolationScheme            cell;
        setAverage                    true;
        average                        (30.22 0 0);    
    }

Unfortunately, it's not working.
Any ideas or suggestions what I could change?

Thanks

stevenvanharen · February 20, 2012, 10:20

What do you exactly mean when you say it is not working?

I am not sure about version 2.1 but in 1.7 you should have directMappedPatch as type in the boundary file. And directMapped in the field file.

Did you check the tutorials? Or you sure this type is correct?

vigges · February 22, 2012, 03:38

Problem solved.
After converting my 3D sHM mesh into 2D using extrudeMesh and autoPatch, I forgot to reassign the properties to the inletPatch in constant/polyMesh/boundary.

samiam1000 · May 9, 2012, 03:45

Hi all,

just a question: does the mappedPatch type allow you to set the interface between 2 fluid regions??

Thanks a lot,

Samuele

Djub · March 15, 2013, 06:39

Hi Vigges,
May I ask you what is your 0/p boundary conditions for your inlet ?
Do you map also the pressure field or use a classic "zerogradient" condition?
For me, the NS equations are linking both fields. You should not take V without P! Nevertheless, tutorial are making this (U=mapped and p=zeroGradient ). What is your opinion about this?
For example, there is a under-pressure in the core of a large vortex. Don't you have to map it in the inlet? Or the NS solver is able to reconstruct it thanks to U-field?
I am still doubtfull, because within the calculated domain, from where you extract the V field, pressure field has no reason to be zerogradient!
How to deal with this?

hrvig · March 8, 2015, 11:34

I am asking the exact same questions as you Djub. What I have done so far is to place my sample patch sufficiently long away from the outlet, so that the type of BC here does not influence on the sample patch.

Did you find a way to solve your problem?

I am having convergence problems when mapping the pressure field from outlet to inlet. This approach does as well require you to specify a reference pressure inside the domain, which shouldn't be a problem.

February 20, 2012, 08:42	mappedPatch BC	#1
vigges Member Join Date: Oct 2011 Posts: 36 Rep Power: 14	Hi all!! I'm having a hard time setting up the boundary conditions for my 2D case. I'm using OF 2.1.0 and simpleFoam. What I need is a mapped patch at the inlet in order to get a fully developed turbulent flow before entering a diffuser. I adjusted my constant/polyMesh/boundary and 0/U as followed: Code: inletPatch { type mappedPatch; nFaces 8; startFace 45368; sampleMode nearestCell; sampleRegion region0; samplePatch none; offsetMode uniform; offset (0.035 0 0); } Code: inletPatch { type mapped; value uniform (30.22 0 0); interpolationScheme cell; setAverage true; average (30.22 0 0); } Unfortunately, it's not working. Any ideas or suggestions what I could change? Thanks

February 20, 2012, 10:20		#2
stevenvanharen Senior Member Steven van Haren Join Date: Aug 2010 Location: The Netherlands Posts: 149 Rep Power: 15	What do you exactly mean when you say it is not working? I am not sure about version 2.1 but in 1.7 you should have directMappedPatch as type in the boundary file. And directMapped in the field file. Did you check the tutorials? Or you sure this type is correct?

February 22, 2012, 03:38		#3
vigges Member Join Date: Oct 2011 Posts: 36 Rep Power: 14	Problem solved. After converting my 3D sHM mesh into 2D using extrudeMesh and autoPatch, I forgot to reassign the properties to the inletPatch in constant/polyMesh/boundary.

May 9, 2012, 03:45		#4
samiam1000 Senior Member Samuele Z Join Date: Oct 2009 Location: Mozzate - Co - Italy Posts: 520 Rep Power: 18	Hi all, just a question: does the mappedPatch type allow you to set the interface between 2 fluid regions?? Thanks a lot, Samuele

March 15, 2013, 06:39		#5
Djub Senior Member Julien Join Date: Jun 2012 Location: France Posts: 152 Rep Power: 13	Hi Vigges, May I ask you what is your 0/p boundary conditions for your inlet ? Do you map also the pressure field or use a classic "zerogradient" condition? For me, the NS equations are linking both fields. You should not take V without P! Nevertheless, tutorial are making this (U=mapped and p=zeroGradient ). What is your opinion about this? For example, there is a under-pressure in the core of a large vortex. Don't you have to map it in the inlet? Or the NS solver is able to reconstruct it thanks to U-field? I am still doubtfull, because within the calculated domain, from where you extract the V field, pressure field has no reason to be zerogradient! How to deal with this?

March 8, 2015, 11:34		#6
hrvig New Member Jakob Hærvig Join Date: Sep 2012 Location: Aalborg, Denmark Posts: 27 Rep Power: 13	I am asking the exact same questions as you Djub. What I have done so far is to place my sample patch sufficiently long away from the outlet, so that the type of BC here does not influence on the sample patch. Did you find a way to solve your problem? I am having convergence problems when mapping the pressure field from outlet to inlet. This approach does as well require you to specify a reference pressure inside the domain, which shouldn't be a problem.