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February 25, 2016, 08:14 
problem with velocity and pressure fields

#1  
New Member
Caro
Join Date: Jul 2014
Posts: 14
Rep Power: 4 
Hello,
I'm using coldEngineFoam and I have inlet areas as valves on the cylinderhead. When the piston is moving down and air is entering the cylinder, the simulation stops at some point saying maximum number of iterations exceeded.If I look at the log file everything seems to be converging nicely, but the time steps get smaller and smaller until the simulation stops. For a really coarse mesh I didn't get the problem, but if the mesh is a bit more refined the pressure and the velocity seem to do something strange. There are a few points inside the cylinder where the pressure is a lot lower than in the rest and the velocity is huge >300m/s. Since my maximum piston speed is 10 m/s and the open area is 30% I don't expect these high velocities. I'm not sure if it is a mesh problem (it works with a very coarse mesh) or a problem with my fvSchemes. I have tried changing the numbers of correctors, but it doesn't seem to have any infuence. Can anyone give me some advice please? The fvSchemes I'm using is: Code:
ddtSchemes { default Euler; } gradSchemes { default Gauss linear; } divSchemes { default none; div(phi,h) Gauss upwind; div(phi,U) Gauss upwind; div(phi,K) Gauss upwind; div(phid,p) Gauss upwind; div(meshPhi,p) Gauss upwind; div(phiv,p) Gauss upwind; div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; div(phi,R) Gauss upwind; div(R) Gauss linear; div(phiXi,Xi) Gauss upwind; div(phiXi,Su) Gauss upwind; div(phiSt,b) Gauss limitedLinear01 1; div(phi,ft_b_ha_hau) Gauss multivariateSelection { fu limitedLinear01 1; ft limitedLinear01 1; b limitedLinear01 1; ha limitedLinear 1; hau limitedLinear 1; ea limitedLinear 1; eau limitedLinear 1; }; div(U) Gauss linear; div((Su*grad(b))) Gauss linear; div((U+((Su*Xi)*grad(b)))) Gauss linear; div((muEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear limited corrected 0.5; } interpolationSchemes { default linear; } snGradSchemes { default limited corrected 0.5; } fluxRequired { default no; p ; } Quote:


March 19, 2016, 15:25 

#2 
Member
Vinícius da Costa Ávila
Join Date: Jul 2015
Location: Porto Alegre, Brazil
Posts: 61
Rep Power: 3 
The only difference between the simulation that work and the one that didn't is the mesh? Could you please post checkMesh logs for both meshes and pictures of them?
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Vinícius dC.A. 

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coldenginefoam, pressure and velocity 
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