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Old   February 25, 2016, 08:14
Default problem with velocity and pressure fields
  #1
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Caro
Join Date: Jul 2014
Posts: 14
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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               ; 
 }
this is what the end of my log file looks like before the simulation stops:
Quote:

Courant Number mean: 1.77976e-08 max: 0.117738
deltaT = 6.26454e-43
--> FOAM Warning :
From function Time:perator++()
in file db/Time/Time.C at line 1055
Increased the timePrecision from 47787 to 47788 to distinguish between timeNames at time 0.00754415
Crank angle = 90.5298 CA-deg
deltaZ = 0
clearance: 0.0581264
Piston speed = 0 m/s
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for Ux, Initial residual = 3.60105e-17, Final residual = 3.60105e-17, No Iterations 0
DILUPBiCG: Solving for Uy, Initial residual = 3.70568e-17, Final residual = 3.70568e-17, No Iterations 0
DILUPBiCG: Solving for Uz, Initial residual = 5.57992e-17, Final residual = 5.57992e-17, No Iterations 0
DILUPBiCG: Solving for h, Initial residual = 5.95157e-16, Final residual = 5.95157e-16, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.06467e-06, global = 5.284e-07, cumulative = 0.0760969
DILUPBiCG: Solving for h, Initial residual = 5.952e-16, Final residual = 5.952e-16, No Iterations 0
GAMG: Solving for p, Initial residual = 1.40164e-15, Final residual = 1.40164e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.40164e-15, Final residual = 1.40164e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.40164e-15, Final residual = 1.40164e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.40164e-15, Final residual = 1.40164e-15, No Iterations 0
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.06467e-06, global = 5.284e-07, cumulative = 0.0760974
DILUPBiCG: Solving for h, Initial residual = 5.952e-16, Final residual = 5.952e-16, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.66551e-15, Final residual = 1.66551e-15, No Iterations 0
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.06467e-06, global = 5.284e-07, cumulative = 0.0760979
DILUPBiCG: Solving for epsilon, Initial residual = 1.7532e-17, Final residual = 1.7532e-17, No Iterations 0
DILUPBiCG: Solving for k, Initial residual = 2.05059e-17, Final residual = 2.05059e-17, No Iterations 0
Mean pressure:105735
Mean temperature:311.055
Mean u':3.07951
ExecutionTime = 35699.6 s ClockTime = 36008 s


Courant Number mean: 1.03968e-08 max: 0.0687785
deltaT = 7.17536e-43
--> FOAM Warning :
From function Time:perator++()
in file db/Time/Time.C at line 1055
Increased the timePrecision from 47788 to 47789 to distinguish between timeNames at time 0.00754415
Crank angle = 90.5298 CA-deg
deltaZ = 0
clearance: 0.0581264
Piston speed = 0 m/s
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for Ux, Initial residual = 4.49422e-17, Final residual = 4.49422e-17, No Iterations 0
DILUPBiCG: Solving for Uy, Initial residual = 4.63692e-17, Final residual = 4.63692e-17, No Iterations 0
DILUPBiCG: Solving for Uz, Initial residual = 6.98229e-17, Final residual = 6.98229e-17, No Iterations 0
DILUPBiCG: Solving for h, Initial residual = 7.81953e-16, Final residual = 7.81953e-16, No Iterations 0
GAMG: Solving for p, Initial residual = 1.46715e-15, Final residual = 1.46715e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.46715e-15, Final residual = 1.46715e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.46715e-15, Final residual = 1.46715e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.46715e-15, Final residual = 1.46715e-15, No Iterations 0
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.06467e-06, global = 5.284e-07, cumulative = 0.0760984
DILUPBiCG: Solving for h, Initial residual = 7.81097e-16, Final residual = 7.81097e-16, No Iterations 0
GAMG: Solving for p, Initial residual = 1.18901e-15, Final residual = 1.18901e-15, No Iterations 0
GAMG: Solving for p, Initial residual = 1.18901e-15, Final residual = 1.18901e-15, No Iterations 0
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Old   March 19, 2016, 15:25
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Vinícius da Costa Ávila
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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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