
[Sponsors] 
Nonphysical solution with cylindrical 2D blockMesh with triangle faces 

LinkBack  Thread Tools  Display Modes 
November 20, 2015, 05:38 
Nonphysical solution with cylindrical 2D blockMesh with triangle faces

#1 
Member
Join Date: Jul 2011
Posts: 45
Rep Power: 7 
Hey everyone,
we were trying to create a cylindrical 2D mesh with blockMesh to simulate the growth and collapse of a vapour filled bubble. We are using compressibleInterFoam to simulate this case. First of all I want to mention that we conducted 3D simulations in different variations, which were working (quarter of the bubble, full bubble, etc.), but the blockMesh, where triangle shaped faces are generated at the rotation axis are giving us problems. We realized this when observing the alpha, p, rho and T values of one of the mentioned cells at the rotation axis. What happens for example is that alpha (which should be limited between 0 and 1) gets very weird values. We also had alpha take values of temperature (293.15, since we were looking at a 20°C=293.15 K case), pressure (100150) or density (1000). This does only occur in cells that are directly positioned at the rotation axis! This error is also not depending on the BCs used for the patches at the rotation axis. Wedge, cyclic and symmetry were all tested and did show similar, but unphysical results. The only time step that seems ok is the 1st one. The following logfile segment shows the beginning of the simulation and the 1st and 2nd time step: Code:
Starting time loop Courant Number mean: 8.867466637e10 max: 0.5000000342 deltaT = 2.055944865e10 Time = 1.500146959e06 PIMPLE: iteration 1 Cell coords: 1.612805495e13 1.640304891e13 1.913510237e15 vorher: alpha1[67312] = 1 alpha2[67312] = 0 MULES: Solving for alpha.water Liquid phase volume fraction = 0.9999999945 Min(alpha.water) = 9.695801158e313 Min(alpha.air) = 6.287461048e06 nachher: alpha1[67312] = 0 alpha2[67312] = 6.054774252e12 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 smoothSolver: Solving for T, Initial residual = 1.318326449e09, Final residual = 1.318326449e09, No Iterations 0 min(T) 292.4490137 p[67312] anfang = 100000.018 GAMG: Solving for p_rgh, Initial residual = 2.054083e08, Final residual = 2.054083e08, No Iterations 0 p[67312] vor max = 100000.018 p[67312] nach max = 4.806515659e316 rho[67312] neu = 0 max(U) 760.6446982 min(p_rgh) 99514.74334 p[67312] anfang = 4.806515659e316 GAMGPCG: Solving for p_rgh, Initial residual = 2.065957267e08, Final residual = 2.065957267e08, No Iterations 0 p[67312] vor max = 2.253274591e11 p[67312] nach max = 100000.018 rho[67312] neu = 1000 max(U) 760.644698 min(p_rgh) 99514.74334 ExecutionTime = 1.56 s Courant Number mean: 8.869859933e10 max: 0.5000000341 deltaT = 2.055944724e10 Time = 1.500352554e06 PIMPLE: iteration 1 Cell coords: 1.612805495e13 1.640304891e13 1.913510237e15 vorher: alpha1[67312] = 6.035127644e12 alpha2[67312] = 1560788.058 MULES: Solving for alpha.water Liquid phase volume fraction = 0.9999999945 Min(alpha.water) = 9.708588392e313 Min(alpha.air) = 6.330674114e06 nachher: alpha1[67312] = 2.260223294e12 alpha2[67312] = 0 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 smoothSolver: Solving for T, Initial residual = 1.318397883e09, Final residual = 1.318397883e09, No Iterations 0 min(T) 292.4490137 p[67312] anfang = 31.56897883 GAMG: Solving for p_rgh, Initial residual = 2.054885472e08, Final residual = 2.054885472e08, No Iterations 0 p[67312] vor max = 2.055944688e13 p[67312] nach max = 100000.018 rho[67312] neu = 4.791652699e17 max(U) 760.6446978 min(p_rgh) 99514.74334 p[67312] anfang = 7.005067646e11 GAMGPCG: Solving for p_rgh, Initial residual = 2.06676118e08, Final residual = 2.06676118e08, No Iterations 0 p[67312] vor max = 99787.03945 p[67312] nach max = 6.515884913e18 rho[67312] neu = 99994.42233 max(U) 760.6446975 min(p_rgh) 99514.74334 ExecutionTime = 2.28 s Code:
Courant Number mean: 8.874794592e10 max: 0.500000034 deltaT = 2.055944444e10 Time = 1.500763743e06 PIMPLE: iteration 1 Cell coords: 1.612805495e13 1.640304891e13 1.913510237e15 vorher: alpha1[67312] = 0 alpha2[67312] = 2.260223294e12 MULES: Solving for alpha.water Liquid phase volume fraction = 0.9999999944 Min(alpha.water) = 9.734245857e313 Min(alpha.air) = 6.373648709e06 nachher: alpha1[67312] = 1000 alpha2[67312] = 6.178980438e20 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 smoothSolver: Solving for T, Initial residual = 1.318067292e09, Final residual = 1.318067292e09, No Iterations 0 min(T) 292.4490137 p[67312] anfang = 99787.03945 GAMG: Solving for p_rgh, Initial residual = 2.055732403e08, Final residual = 2.055732403e08, No Iterations 0 p[67312] vor max = 99787.03945 p[67312] nach max = 0 rho[67312] neu = 7.487579154e11 max(U) 760.6446969 min(p_rgh) 99514.74334 p[67312] anfang = 1.467501829e05 GAMGPCG: Solving for p_rgh, Initial residual = 2.067606613e08, Final residual = 2.067606613e08, No Iterations 0 p[67312] vor max = 2.055682884e13 p[67312] nach max = 2.547224998e18 rho[67312] neu = 1.076484758e10 max(U) 760.6446967 min(p_rgh) 99514.74334 ExecutionTime = 3.64 s Courant Number mean: 8.877179606e10 max: 0.500000034 deltaT = 2.055944305e10 Time = 1.500969337e06 PIMPLE: iteration 1 Cell coords: 1.612805495e13 1.640304891e13 1.913510237e15 vorher: alpha1[67312] = 1000 alpha2[67312] = 6.180899535e20 MULES: Solving for alpha.water Liquid phase volume fraction = 0.9999999944 Min(alpha.water) = 9.74711621e313 Min(alpha.air) = 6.396872477e06 nachher: alpha1[67312] = 2.942532846e17 alpha2[67312] = 1000 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 smoothSolver: Solving for T, Initial residual = 1.318231582e09, Final residual = 1.318231582e09, No Iterations 0 min(T) 292.4490137 p[67312] anfang = 8.972674259e17 GAMG: Solving for p_rgh, Initial residual = 2.056271301e08, Final residual = 2.056271301e08, No Iterations 0 p[67312] vor max = 8.972674259e17 p[67312] nach max = 100000.018 rho[67312] neu = 8.972674259e17 max(U) 760.6446964 min(p_rgh) 99514.74334 p[67312] anfang = 6.156112577e11 GAMGPCG: Solving for p_rgh, Initial residual = 2.068144034e08, Final residual = 2.068144034e08, No Iterations 0 p[67312] vor max = 5.07486869e12 p[67312] nach max = 100000.018 rho[67312] neu = 1.467451473e05 max(U) 760.6446962 min(p_rgh) 99514.74334 ExecutionTime = 4.35 s We were thinking about what could cause these values that only show up for cells at the rotation axis (which have kind of triangle faces). Since we need to define hexcells using 8 points in blockMesh, we were trying out different things. Less than 8 points does obviously not work, so we tried to use the first point for a hex definition twice, since we did not want to place another point anywhere else in between. Do you guys have any experience with these kinds of meshes? Thanks in advance. Best regards, Andreas 

Tags 
blockmesh, compresssibleinterfoam, cylindrical mesh, wedge 
Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Decomposing meshes  Tobi  OpenFOAM PreProcessing  1  September 9, 2014 05:30 
[ICEM] Export ICEM mesh to Gambit / Fluent  romekr  ANSYS Meshing & Geometry  1  November 26, 2011 13:11 
snappyHexMesh won't work  zeros everywhere!  sc298  OpenFOAM Native Meshers: snappyHexMesh and Others  2  March 27, 2011 21:11 
IcoFoam parallel woes  msrinath80  OpenFOAM Running, Solving & CFD  9  July 22, 2007 02:58 
Could anybody help me see this error and give help  liugx212  OpenFOAM Running, Solving & CFD  3  January 4, 2006 19:07 