use 3DDP solver....
parameter u.r of momentum and pressure by default...
results:
after iteration 9 AMG Solver still serro...
according to the cfdfluent.com (discussion) says that need to use u.r one by one .... still don't have pattern or formula how to set the discretization methods....
parameter u.r of momentum and pressure by momentum=0.39 and pressure=0.31...
after iteration 4139 error AMG solver...
parameter u.r of momentum and pressure by momentum=0.39 and pressure=0.61...
after iteration 1 error AMG solver...
parameter u.r of momentum and pressure by momentum=0.61 and pressure=0.39...
after iteration 937 error AMG solver...
so try about BC's of the Simulation.....
Showing posts with label FLUENT-Airflows-Single-Phase. Show all posts
Showing posts with label FLUENT-Airflows-Single-Phase. Show all posts
Sunday, June 24, 2007
Saturday, June 23, 2007
equisize-skew->-0.97
Meshing success? but EquiSIZE SKEW >0.97 (11 or 16 cells)?
May have to re-fine meshing of the geometry...by:
*. coarse mesh then if need more fine mesh have to try methods below...
Because Meshing in GAMBIT automatically generated mesh (especially in 3-D) in most cases, can not provide uniformly high quality in un-structured mesh (hexahedral or tetrahedral) for complex geometry.
On the surface, the unstructured mesh does have advantages to cover large areas of complex geometry, but, in reality, a high quality mesh is always hard to obtain.
One says that need to go back to the blocking of the geometry (meshing process): to divide the geometry into smaller pieces and re-create the surface geometry so that can avoid the highly skewed cells.
**. have to try long iteration until 10^-6 criterion meet.... (already done, but still not convergence)....
have to try one by one....
And .... just an information from CFD source: it must take more time in Meshing Process and Convergence Process......
May have to re-fine meshing of the geometry...by:
*. coarse mesh then if need more fine mesh have to try methods below...
Because Meshing in GAMBIT automatically generated mesh (especially in 3-D) in most cases, can not provide uniformly high quality in un-structured mesh (hexahedral or tetrahedral) for complex geometry.
On the surface, the unstructured mesh does have advantages to cover large areas of complex geometry, but, in reality, a high quality mesh is always hard to obtain.
One says that need to go back to the blocking of the geometry (meshing process): to divide the geometry into smaller pieces and re-create the surface geometry so that can avoid the highly skewed cells.
**. have to try long iteration until 10^-6 criterion meet.... (already done, but still not convergence)....
have to try one by one....
And .... just an information from CFD source: it must take more time in Meshing Process and Convergence Process......
Friday, June 22, 2007
Under-relaxation-momentum
About:....
Error: AMG Solver ...temperature
Solution:
* by Modification of Under-relaxation of Momentum become less than default (0.7) have to try become 0.6....or: 0.5, 0.4, 0.3, 0.35, 0.39....
for 0.5: 500iteration success but after iteration 701 error AMG Solver again...
for 0.4: error after iteration 1185...
for 0.3: error afater iteration 359...
for 0.35: error after iteration 763...
for 0.39: error after iteration 1750...
for 0.396 or 0.389: have to simulate beside check about Meshing or Coupled Solver and not Segregated...
for 0.396: error after iteration 197...
for 0.389: error after iteration 857...
for 0.37: error after iteration 456...
So, want to check it up of coupled...
conclution for u.r. of momentum is about=0.39 and for pressure is about=0.3
but ok before fixed it...need to set the under-relaxation of Pressure....the default is 0.3 but i have to try the 0.28, 0.29 and 0.32 to know influence of this value...
for this use the same convergence criteria that is 1.0e-06 for all graphics...
for 0.28: error after iteration 1086...
for 0.29: error after iteration 264...
for 0.3: error after iteration 1750...already done
for 0.31: error after iteration 2229...
for 0.32: error after iteration 838...
So, the best configuration based-on under-relaxation of pressure and momentum is 0.31 and 0.39 for this case eventhough it's still has error in AMG solver: temperature.
Now, before try coupled solver....need to try to change the the BC's becouse one says that AMG solver and Reversed flow come from settings in BC's....
Error: AMG Solver ...temperature
Solution:
* by Modification of Under-relaxation of Momentum become less than default (0.7) have to try become 0.6....or: 0.5, 0.4, 0.3, 0.35, 0.39....
for 0.5: 500iteration success but after iteration 701 error AMG Solver again...
for 0.4: error after iteration 1185...
for 0.3: error afater iteration 359...
for 0.35: error after iteration 763...
for 0.39: error after iteration 1750...
for 0.396 or 0.389: have to simulate beside check about Meshing or Coupled Solver and not Segregated...
for 0.396: error after iteration 197...
for 0.389: error after iteration 857...
for 0.37: error after iteration 456...
So, want to check it up of coupled...
conclution for u.r. of momentum is about=0.39 and for pressure is about=0.3
but ok before fixed it...need to set the under-relaxation of Pressure....the default is 0.3 but i have to try the 0.28, 0.29 and 0.32 to know influence of this value...
for this use the same convergence criteria that is 1.0e-06 for all graphics...
for 0.28: error after iteration 1086...
for 0.29: error after iteration 264...
for 0.3: error after iteration 1750...already done
for 0.31: error after iteration 2229...
for 0.32: error after iteration 838...
So, the best configuration based-on under-relaxation of pressure and momentum is 0.31 and 0.39 for this case eventhough it's still has error in AMG solver: temperature.
Now, before try coupled solver....need to try to change the the BC's becouse one says that AMG solver and Reversed flow come from settings in BC's....
AMG-Solver-Temperature
Message in the screen.....when simulate in FLUENT after GAMBIT process....
Error: divergence detected in AMG solver: temperature
Error Object: ()
Is it about computer?
One suggest me to:
*Make sure about Under-Relaxation:.....I have to try to do it....
*the message indicates that doing something wrong in settign up the case (boundary conditions)...
*Make up Coupled Solver.
*check about mesh.
I have to do it....hope fully it become succeesfull
About the reversed flow pressure outlet.....please to make sure about the BCs and ICs...Because: In fact (real conditions), there should be no backflow at the pressure outlet in the converged solution. But, backflow occurs during the iteration. If so what should I do?
Error: divergence detected in AMG solver: temperature
Error Object: ()
Is it about computer?
One suggest me to:
*Make sure about Under-Relaxation:.....I have to try to do it....
*the message indicates that doing something wrong in settign up the case (boundary conditions)...
*Make up Coupled Solver.
*check about mesh.
I have to do it....hope fully it become succeesfull
About the reversed flow pressure outlet.....please to make sure about the BCs and ICs...Because: In fact (real conditions), there should be no backflow at the pressure outlet in the converged solution. But, backflow occurs during the iteration. If so what should I do?
Wednesday, June 20, 2007
reversed-flow
...
reversed flow in 8 faces on pressure-outlet 9.
reversed flow in 9 faces on pressure-outlet 13.
6009 3.3860e-04 1.7957e-01 3.4764e-01 1.9047e-01 5.7751e-04 0:00:00 0
why not displayed word "CONVERGENCE" in the monitor (althought the simulation already done for 1000 iteration = 13minutes and 33seconds --> 81 minutes and 3 seconds)?
[Check the CONVERGENCE status……….by:]
1. Compute from: no need to set… (because already set from geometry by GAMBIT)
2. Solve-Control-Solution—Under-relaxation
Solve-Control-Solution—Pressure-Velocity Coupling
Solve-Control-Solution—Discretization; or
3. Solve-Monitor-Residual--Convergence Criteria; or
4. Meshing process about Equisize SKEW > 0.97 (11, 16 or … by Tet/Hybrid- TGrid and Hexcore
:-)smile
reversed flow in 8 faces on pressure-outlet 9.
reversed flow in 9 faces on pressure-outlet 13.
6009 3.3860e-04 1.7957e-01 3.4764e-01 1.9047e-01 5.7751e-04 0:00:00 0
why not displayed word "CONVERGENCE" in the monitor (althought the simulation already done for 1000 iteration = 13minutes and 33seconds --> 81 minutes and 3 seconds)?
[Check the CONVERGENCE status……….by:]
1. Compute from: no need to set… (because already set from geometry by GAMBIT)
2. Solve-Control-Solution—Under-relaxation
Solve-Control-Solution—Pressure-Velocity Coupling
Solve-Control-Solution—Discretization; or
3. Solve-Monitor-Residual--Convergence Criteria; or
4. Meshing process about Equisize SKEW > 0.97 (11, 16 or … by Tet/Hybrid- TGrid and Hexcore
:-)smile
divergence-in-AMG-solver
after running the simulation for airflows I see only an error:
...
reversed flow in 23 faces on pressure-outlet 4.
reversed flow in 31 faces on pressure-outlet 5.
reversed flow in 35 faces on pressure-outlet 6.
reversed flow in 38 faces on pressure-outlet 7.
reversed flow in 52 faces on pressure-outlet 8.
reversed flow in 8 faces on pressure-outlet 9.
reversed flow in 8 faces on pressure-outlet 13.
Error: divergence detected in AMG solver: temperature
Error Object: ()
why?.....how to fixed it?.....
solution for that error: in windows of FLUENT click SOLVE then click Initialize-Initialize-set Velocity Magnitude = 1 or other values then click Reset-Apply-Close.
Another solution is to click Initialize-Initialize- then click Init...
...continuousimprovement of lasmanp's thesis...
...
reversed flow in 23 faces on pressure-outlet 4.
reversed flow in 31 faces on pressure-outlet 5.
reversed flow in 35 faces on pressure-outlet 6.
reversed flow in 38 faces on pressure-outlet 7.
reversed flow in 52 faces on pressure-outlet 8.
reversed flow in 8 faces on pressure-outlet 9.
reversed flow in 8 faces on pressure-outlet 13.
Error: divergence detected in AMG solver: temperature
Error Object: ()
why?.....how to fixed it?.....
solution for that error: in windows of FLUENT click SOLVE then click Initialize-Initialize-set Velocity Magnitude = 1 or other values then click Reset-Apply-Close.
Another solution is to click Initialize-Initialize- then click Init...
...continuousimprovement of lasmanp's thesis...
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