interDyMFoam deltaT drops nonstop
Hi everyone,
Below is my setup for controlDict to run interDyMFoam. My concern is now (after 10 iterations) the deltaT is in the order of e05 and continue to drops. I have tried to tighten pcorr to 1e12 and with Gauss upwind for convection and also try Gauss linear limited 0.7 for laplacian. Also, decrease underelaxation for k and epsilon to 0.5. Still does not see the light. In this case, I also do the checkMesh and all look okay as indicated below. My PISO setting for Courant no. is also provided below. Considered this stage, my concern is time is not marching any way due to extremely small deltaT. Any suggestion will be greatly appreciated. // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // application interDyMFoam; startFrom latestTime; startTime 0; stopAt endTime; endTime 0.1; deltaT 0.005; writeControl adjustableRunTime; writeInterval 0.01; purgeWrite 0; writeFormat ascii; writePrecision 12; writeCompression uncompressed; timeFormat general; timePrecision 10; runTimeModifiable yes; adjustTimeStep yes; maxCo 0.5; maxAlphaCo 0.5; maxDeltaT 0.005; libs ( "libincompressibleRASModels.so" "libfvMotionSolvers.so" "libforces.so" ); // ************************************************** *********************** // // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create polyMesh for time = 0 Time = 0 Mesh stats points: 599829 faces: 1728840 internal faces: 1677599 cells: 565109 boundary patches: 6 point zones: 0 face zones: 0 cell zones: 0 Overall number of cells of each type: hexahedra: 556015 prisms: 629 wedges: 0 pyramids: 0 tet wedges: 20 tetrahedra: 0 polyhedra: 8445 Checking topology... Boundary definition OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces ... Patch Faces Points Surface topology sidewall 16384 16770 ok (nonclosed singly connected) inlet 4096 4225 ok (nonclosed singly connected) outlet 4096 4225 ok (nonclosed singly connected) floor 8192 8385 ok (nonclosed singly connected) ceiling 8192 8385 ok (nonclosed singly connected) floatingObject 10281 11433 ok (closed singly connected) Checking geometry... Overall domain bounding box (2 1.5 2) (4 2 2) Mesh (nonempty, nonwedge) directions (1 1 1) Mesh (nonempty) directions (1 1 1) Boundary openness (2.96151165684e16 4.64197183787e17 9.36902725343e15) OK. Max cell openness = 2.53757529159e16 OK. Max aspect ratio = 4.49379234381 OK. Minumum face area = 2.09352045e05. Maximum face area = 0.00341828125. Face area magnitudes OK. Min volume = 4.3804331189e07. Max volume = 0.0001602417. Total volume = 83.9563743795. Cell volumes OK. Mesh nonorthogonality Max: 51.5433563696 average: 3.4337367223 Nonorthogonality check OK. Face pyramids OK. Max skewness = 3.44827063315 OK. Mesh OK. End # PISO { momentumPredictor no; nCorrectors 3; nNonOrthogonalCorrectors 2; nAlphaCorr 1; nAlphaSubCycles 3; cAlpha 1; correctPhi yes; } 
sorry, I thought I should also post the progress of the simulation too. now is dropping to e6.
Interface Courant Number mean: 3.57569768064e05 max: 0.347384454161 Courant Number mean: 0.00346227188823 max: 1.05310016844 deltaT = 1.11396410976e05 Time = 0.006390756284 Centre of mass: (0.499906589644 0.24999904487 1.20104643514) Linear velocity: (0.627710873661 0.0852525959485 26.4966964046) Angular velocity: (12.8920948858 833.985757923 0.00690366308419) GAMG: Solving for cellDisplacementx, Initial residual = 0.0551572903235, Final residual = 8.88849915274e06, No Iterations 3 GAMG: Solving for cellDisplacementy, Initial residual = 0.0385918438553, Final residual = 3.13337111456e06, No Iterations 4 GAMGPCG: Solving for pcorr, Initial residual = 0.0250926042783, Final residual = 4.94159179989e07, No Iterations 7 GAMG: Solving for cellDisplacementz, Initial residual = 0.0460431089478, Final residual = 3.81392093508e06, No Iterations 4 Execution time for mesh.update() = 12.13 s time step continuity errors : sum local = 2.5407120133e11, global = 3.00220714219e12, cumulative = 2.86158988517e07 GAMGPCG: Solving for pcorr, Initial residual = 0.00341457758679, Final residual = 7.82092422324e07, No Iterations 4 time step continuity errors : sum local = 5.13383490686e17, global = 6.06255486822e18, cumulative = 2.86158988523e07 MULES: Solving for alpha1 Liquid phase volume fraction = 0.189772205184 Min(alpha1) = 1.18791754256e07 Max(alpha1) = 0.999999999995 MULES: Solving for alpha1 Liquid phase volume fraction = 0.18976775217 Min(alpha1) = 6.93200240088e07 Max(alpha1) = 0.999999999995 MULES: Solving for alpha1 Liquid phase volume fraction = 0.189763302103 Min(alpha1) = 1.54970255717e08 Max(alpha1) = 0.999999999995 GAMGPCG: Solving for pcorr, Initial residual = 1, Final residual = 9.03507236794e07, No Iterations 7 GAMG: Solving for p_rgh, Initial residual = 0.00890734579531, Final residual = 7.26500211696e05, No Iterations 6 GAMGPCG: Solving for pcorr, Initial residual = 0.0250926042783, Final residual = 4.94159179989e07, No Iterations 7 GAMG: Solving for p_rgh, Initial residual = 0.00105150500514, Final residual = 8.00369639837e06, No Iterations 4 GAMG: Solving for p_rgh, Initial residual = 0.00017536985361, Final residual = 7.89000651154e07, No Iterations 5 time step continuity errors : sum local = 4.97052999835e09, global = 5.82771123844e10, cumulative = 2.86741759647e07 GAMGPCG: Solving for pcorr, Initial residual = 0.00341457758679, Final residual = 7.82092422324e07, No Iterations 4 time step continuity errors : sum local = 5.13383490686e17, global = 6.06255486822e18, cumulative = 2.86158988523e07 GAMG: Solving for p_rgh, Initial residual = 0.000409536855082, Final residual = 2.87332492538e06, No Iterations 4 GAMG: Solving for p_rgh, Initial residual = 0.000139728476782, Final residual = 8.59664788755e07, No Iterations 3 MULES: Solving for alpha1 Liquid phase volume fraction = 0.189772205184 Min(alpha1) = 1.18791754256e07 Max(alpha1) = 0.999999999995 MULES: Solving for alpha1 GAMG: Solving for p_rgh, Initial residual = 7.45188594154e05, Final residual = 4.79430381896e07, No Iterations 3 Liquid phase volume fraction = 0.18976775217 Min(alpha1) = 6.93200240088e07 Max(alpha1) = 0.999999999995 time step continuity errors : sum local = 2.98207714667e09, global = 2.88815783222e10, cumulative = 2.86452943864e07 MULES: Solving for alpha1 Liquid phase volume fraction = 0.189763302103 Min(alpha1) = 1.54970255717e08 Max(alpha1) = 0.999999999995 GAMG: Solving for p_rgh, Initial residual = 7.61552247514e05, Final residual = 4.57831986712e07, No Iterations 3 GAMG: Solving for p_rgh, Initial residual = 6.13199105298e05, Final residual = 3.69433582136e07, No Iterations 3 GAMG: Solving for p_rgh, Initial residual = 0.00890734579531, Final residual = 7.26500211696e05, No Iterations 6 GAMG: Solving for p_rgh, Initial residual = 0.00105150500514, Final residual = 8.00369639837e06, No Iterations 4 GAMGPCG: Solving for p_rgh, Initial residual = 5.91885010226e05, Final residual = 4.4902425514e09, No Iterations 3 time step continuity errors : sum local = 2.79184843811e11, global = 1.68961681819e13, cumulative = 2.86452774902e07 GAMG: Solving for p_rgh, Initial residual = 0.00017536985361, Final residual = 7.89000651154e07, No Iterations 5 DILUPBiCG: Solving for epsilon, Initial residual = 0.0153215890859, Final residual = 7.67678370387e11, No Iterations 4 time step continuity errors : sum local = 4.97052999835e09, global = 5.82771123844e10, cumulative = 2.86741759647e07 DILUPBiCG: Solving for k, Initial residual = 0.039579350528, Final residual = 8.93676390673e10, No Iterations 5 ExecutionTime = 809.69 s ClockTime = 1950 s Interface Courant Number mean: 7.49421107175e05 max: 0.495849330153 Courant Number mean: 0.00643486555823 max: 0.795353004364 deltaT = 6.99465836359e06 Time = 0.006397750943 
Alpha1 image at timestep=0 is posted below after running setFields.
http://www.cfdonline.com/Forums/mem...rdhexmesh.htm http://www.cfdonline.com/Forums/mem...dhexmesh.html 
1e6 is not necessarily *extremely* small, it depends on your setup. What is the maximum flow velocity you're expecting? Compare that to your smallest cell size. Running with 1e06s, how does the solution look like? Does it make sense?

Hi,
some comments:
Good luck, Jan 
momentumPredictor no;
set the momentumPredictor to yes 
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