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How to move background mesh with body in overset mesh method? |
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July 5, 2020, 08:17 |
How to move background mesh with body in overset mesh method?
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#1 |
Member
Antoni Alexander
Join Date: Nov 2009
Posts: 43
Rep Power: 17 |
Hello everyone! I am trying to simulate a boat accelerating case with v1806 which contains overset mesh method. In the case, the accelerating phase is most concerned. The acceleration can be realized by rotating the propeller. However, because the boat moving distance is very long, to save grid I want to simulate the motion by making background mesh follow the boat in x-direction. So how to do that?
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July 8, 2020, 22:15 |
rigidBodyDynamics seems to be the entry.
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#2 |
Member
Antoni Alexander
Join Date: Nov 2009
Posts: 43
Rep Power: 17 |
As OpenFOAM uses the rigidBodyDynamics lib to handle multi-body motions within overset mesh, it seems that the rigidBodyDynamics needs to be modified.
I am currently working on it. |
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July 13, 2020, 00:12 |
Background mesh movement is done!
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#3 |
Member
Antoni Alexander
Join Date: Nov 2009
Posts: 43
Rep Power: 17 |
I have successfully made the background mesh moving by adding a restraint in rigidBodyDynamics. From the flowing picture, we can see the background moving to the left.
An other question is rising, that is the inlet boundary condition. I used the condition same as the DTCHull tutorial. But the water is flowing away during the simulation. However, if i set the value from to 0 to 1 in the alpha.water file, there is a thin layer of water covering the whole inlet boundary cell, which is still not what I want. So, how to set he water level at inlet boundary when moving the background mesh? The following picture is the result of my 2D floating case. |
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July 13, 2020, 12:24 |
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#4 |
New Member
Felix Weiler
Join Date: Nov 2016
Location: Bremen
Posts: 22
Rep Power: 10 |
Hi Antoni,
did you use the "setFields" command and "setFieldsDict", respectively? That should set separate the inlet faces between air (0) and water (1) in alpha.water. Best regards |
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July 13, 2020, 22:46 |
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#5 |
Member
Antoni Alexander
Join Date: Nov 2009
Posts: 43
Rep Power: 17 |
Hi Felix, thanks for your reply.
Yes, I used the setFields command in the preprocess, and the setFieldsDict is as follow: Code:
defaultFieldValues ( volScalarFieldValue alpha.water 0 volScalarFieldValue zoneID 123 ); regions ( boxToCell { box ( -100 -100 -100 ) ( 100 0.1 100 ); fieldValues ( volScalarFieldValue alpha.water 1 ); } cellToCell { set c0; fieldValues ( volScalarFieldValue zoneID 0 ); } cellToCell { set c1; fieldValues ( volScalarFieldValue zoneID 1 ); } ); alpha.water: Code:
dimensions [0 0 0 0 0 0 0]; internalField uniform 0; boundaryField { #includeEtc "caseDicts/setConstraintTypes" inlet { //type fixedValue; //value uniform 0; type variableHeightFlowRate; lowerBound 0; upperBound 1; value $internalField; } outlet { type variableHeightFlowRate; lowerBound 0; upperBound 1; value $internalField; } stationaryWalls { type zeroGradient; } atmosphere { type inletOutlet; inletValue uniform 0; value uniform 0; } floatingObject { type zeroGradient; } bgFrontAndBack { type empty; } frontAndBack { type empty; } } Code:
FoamFile { version 2.0; format ascii; class volScalarField; object p_rgh; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [1 -1 -2 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type fixedFluxPressure; value $internalField; //type zeroGradient; } outlet { type zeroGradient; } oversetPatch { type overset; } stationaryWalls { type fixedFluxPressure; } atmosphere { type totalPressure; p0 uniform 0; U U; phi phi; rho rho; psi none; gamma 1; value uniform 0; } floatingObject { type fixedFluxPressure; value $internalField; } overset { patchType overset; type fixedFluxPressure; } bgFrontAndBack { type empty; } frontAndBack { type empty; } } Code:
FoamFile { version 2.0; format ascii; class volVectorField; object U; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Umean 0; mUmean 0; dimensions [0 1 -1 0 0 0 0]; internalField uniform ($mUmean 0 0); boundaryField { #includeEtc "caseDicts/setConstraintTypes" inlet { //type pressureDirectedInletOutletVelocity;//freestreamVelocity;//fixedValue; //value $internalField; //freestreamValue (0 0 0); //inletDirection (1 0 0); //value uniform (0 0 0); type fixedValue; value $internalField; } outlet { //type outletPhaseMeanVelocity; //alpha alpha.water; //Umean $Umean; // value $internalField; type pressureDirectedInletOutletVelocity; inletDirection (1 0 0); value $internalField;// uniform (0 0 0); } stationaryWalls { type movingWallVelocity;// fixedValue; value uniform (0 0 0); } atmosphere { type pressureInletOutletVelocity; tangentialVelocity $internalField; value uniform (0 0 0); } floatingObject { type movingWallVelocity; value uniform (0 0 0); } bgFrontAndBack { type empty; } frontAndBack { type empty; } } Any ideas which combinations for p_rgh and U could work when fixing the inlet alpha.water level? Hints are highly welcome! Antoni |
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July 15, 2020, 06:59 |
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#6 |
New Member
Felix Weiler
Join Date: Nov 2016
Location: Bremen
Posts: 22
Rep Power: 10 |
If a more complex mesh blows up the simulation, I'd assume that the mesh is responsible, not the boundary conditions.
Is the quality of the mesh acceptable? In particular with respect to overset, a suitable interpolation area must be given. |
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September 25, 2020, 12:14 |
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#7 |
New Member
saeed barzegar
Join Date: Feb 2012
Posts: 19
Rep Power: 14 |
Hi Antoni,
Can you please share more detail on how you managed to get moving mesh as background mesh in the overset mesh method? I have a NWT with a moving paddle at the inlet (dynamic mesh), and I need to add a moving ship interacting with the incoming wave as well. Thank you, Saeed |
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