
[Sponsors] 
May 6, 2013, 12:01 
not solve all components of a vector (velocity)

#1 
Member
Join Date: Nov 2012
Posts: 66
Rep Power: 5 
hi,
im currently running an axisymmetric case (1 cell thick). But all Direction of the velocity are solved, which results in the problem that i need longer calculation times and the Uz compoent are calculated wrong. the wrong solution of the Uz direction should affect the solver accuarcy. They could simply be set to zero(i know how to do this). it would be way more elegant to simply not solve in the zdirection so valueable calculation time could be saved. My only approach for now is (that a haven't test yet) to manipolate the fvmesh.SolutionD and fvmesh.geometricD. Both of those function are const so i could manipolate them with a pointer over another variable. The problem here is i don't know where these functions are used as well. Does anyboy know if there is a more elegant approach? Best regards Henning 

May 6, 2013, 14:09 

#2 
Senior Member
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 727
Rep Power: 20 
OpenFOAM already has in built ways to deal with 2D problems. Did you set your boundaries on the front and back to "empty" and your axis to "axis"?


May 6, 2013, 17:22 

#3 
Member
Join Date: Nov 2012
Posts: 66
Rep Power: 5 
thanks for the response
the frontSide and backSide are declared as wedge and the axis is declared as empty. But the axis has no faces. But if i dont delete the faces (collapseEdge) and set the boundary condition of the axis to empty. OpenFoam calculates Ux and Uz but not Ux and Uy. is there a boundary conditions called axis? 

May 6, 2013, 19:55 

#4 
Senior Member
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 727
Rep Power: 20 
Sorry, I was inaccurate. The boundary condition you should use is "symmetryPlane" (see the movingCone tutorial in for pimpleDyMFoam). Also, how are your coordinate planes oriented?


May 7, 2013, 03:56 

#5 
Member
Join Date: Nov 2012
Posts: 66
Rep Power: 5 
sadly that doesn't solve the problem.its 3D after all and there are really slow velocity in the Uz direction after some times steps.
In my probelm theses begin to add up after 500000 iteration the can't be neglected anymore. Definition of a 2D mesh is made in the class polymesh. It can only be 2D if the BC empty and wedge are used. i think Is there some solver option in the fvsolution dict to block one direction? 

May 7, 2013, 08:12 

#6 
Member
Join Date: Nov 2012
Posts: 66
Rep Power: 5 
it works:
you can say the solver to not solve on set of equation by typing this Code:
Vector<label>& geoP = const_cast<Vector<label>&>(mesh.geometricD()); geoP.x()=1; geoP.y()=1; geoP.z()=1; Vector<label>& solP = const_cast<Vector<label>&>(mesh.solutionD()); solP.x()=1; solP.y()=1; solP.z()=1; PS hope that solution doesn't cause some major troubles. 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
solve equation  michaelsmit  OpenFOAM Running, Solving & CFD  4  March 24, 2011 06:35 
Solve Flow or VOF simultaneously ?  Ramsey  FLUENT  1  February 16, 2011 14:16 
Linearized NS euqations: how to solve them?(problem with Matrix operations..)  matteoL  OpenFOAM Running, Solving & CFD  0  November 18, 2009 07:58 
Using Compressible Solver (sonicFoam) to solve subsonic flows  ezsoal  OpenFOAM  0  October 27, 2009 10:13 
MAC method solve for pressure at boundry  Ron  Main CFD Forum  2  January 28, 2006 03:14 