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Laminar flow without outlet (mixing with sliding wall) does not find solution
Posted 06.06.2014, 11:39 GMT-4 Fluid & Heat, Studies & Solvers Version 4.4 3 Replies
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Hey,
I have been trying to simulate a system where a sliding wall is causing convection in a closed box.
In brief, the system is a box with one wall sliding at a rate of 0.01 m/s. The other walls are No slip.
The solver seems to solve the problem quite fine, and the result looks reasonable. However, I get the following error message:
Failed to find a solution.
Maximum number of Newton iterations reached.
There was an error message from the linear solver.
The relative error (4e+002) is greater than the relative tolerance.
Returned solution is not converged.
The Solver log looks like this:
============================================================
Number of vertex elements: 4
Number of boundary elements: 462
Number of elements: 10532
Minimum element quality: 0.8176
Number of vertex elements: 4
Minimum element quality: 0.1194
Stationary Solver 1 in Solver 1 started at 6-juin-2014 17:26:14.
Nonlinear solver
Number of degrees of freedom solved for: 19266.
Nonsymmetric matrix found.
Scales for dependent variables:
Pressure (comp2.p8): 0.27
Velocity field (comp2.u8): 1
Iter ErrEst Damping Stepsize #Res #Jac #Sol LinErr LinRes
1 0.034 0.0100000 0.034 2 1 2 0.053 1.2e-015
2 0.032 0.1000000 0.036 3 2 4 0.0055 3e-016
3 0.031 0.2297586 0.038 4 3 6 0.0031 2.4e-016
4 0.035 0.3012911 0.047 5 4 8 0.0029 3.2e-016
5 0.026 0.5186614 0.047 6 5 10 0.0054 5.1e-016
6 0.0033 1.0000000 0.033 7 6 12 0.025 4.4e-014
7 0.00033 1.0000000 0.0037 8 7 14 0.54 1.7e-012
8 9.7e-006 1.0000000 0.00035 9 8 16 9.2 1.6e-011
9 9.2e-007 1.0000000 1e-005 10 9 18 1.8e+002 3.3e-010
10 1.1e-007 1.0000000 7e-007 11 10 20 4.2e+002 9e-010
11 3.3e-007 0.7500000 1.4e-007 20 11 30 3.9e+002 8.1e-009
12 2.3e-007 0.1128516 3.5e-007 23 12 34 3.9e+002 5.8e-009
13 2.6e-007 0.7500000 2.3e-007 32 13 44 4e+002 2e-008
14 2e-007 0.0049796 2.7e-007 37 14 50 4e+002 1.5e-008
15 3.5e-007 0.7500000 2e-007 44 15 58 4e+002 7.6e-008
16 3.5e-007 1.0000000 3.7e-007 45 16 60 4e+002 5.6e-007
17 2.1e-007 0.0798715 3.7e-007 48 17 64 4e+002 3.4e-007
18 1.3e-007 0.2229211 2.2e-007 50 18 67 4e+002 2.5e-007
19 4.7e-007 0.7500000 1.3e-007 59 19 77 4e+002 2.6e-006
20 2.3e-007 0.1053436 4.9e-007 60 20 79 4e+002 1.3e-006
21 1.2e-007 0.0112598 2.4e-007 62 21 82 4e+002 6.6e-007
22 5.6e-007 0.7500000 1.2e-007 70 22 91 4e+002 8.8e-006
23 3.6e-007 1.0000000 5.9e-007 71 23 93 4e+002 4e-005
24 3.3e-007 0.7500000 3.6e-007 80 24 103 4e+002 0.00011
25 2.7e-007 0.0751680 3.5e-007 83 25 107 4e+002 8.9e-005
Stationary Solver 1 in Solver 1: Solution time: 20 s
Physical memory: 1.18 GB
Virtual memory: 1.23 GB
So for some reason ErrEst goes down but LinErr goes up.
Is this just a problem of COMSOL even though the solution is reached, and more importantly, can I trust the result?
Thanks for any comments and suggestions!
I have been trying to simulate a system where a sliding wall is causing convection in a closed box.
In brief, the system is a box with one wall sliding at a rate of 0.01 m/s. The other walls are No slip.
The solver seems to solve the problem quite fine, and the result looks reasonable. However, I get the following error message:
Failed to find a solution.
Maximum number of Newton iterations reached.
There was an error message from the linear solver.
The relative error (4e+002) is greater than the relative tolerance.
Returned solution is not converged.
The Solver log looks like this:
============================================================
Number of vertex elements: 4
Number of boundary elements: 462
Number of elements: 10532
Minimum element quality: 0.8176
Number of vertex elements: 4
Minimum element quality: 0.1194
Stationary Solver 1 in Solver 1 started at 6-juin-2014 17:26:14.
Nonlinear solver
Number of degrees of freedom solved for: 19266.
Nonsymmetric matrix found.
Scales for dependent variables:
Pressure (comp2.p8): 0.27
Velocity field (comp2.u8): 1
Iter ErrEst Damping Stepsize #Res #Jac #Sol LinErr LinRes
1 0.034 0.0100000 0.034 2 1 2 0.053 1.2e-015
2 0.032 0.1000000 0.036 3 2 4 0.0055 3e-016
3 0.031 0.2297586 0.038 4 3 6 0.0031 2.4e-016
4 0.035 0.3012911 0.047 5 4 8 0.0029 3.2e-016
5 0.026 0.5186614 0.047 6 5 10 0.0054 5.1e-016
6 0.0033 1.0000000 0.033 7 6 12 0.025 4.4e-014
7 0.00033 1.0000000 0.0037 8 7 14 0.54 1.7e-012
8 9.7e-006 1.0000000 0.00035 9 8 16 9.2 1.6e-011
9 9.2e-007 1.0000000 1e-005 10 9 18 1.8e+002 3.3e-010
10 1.1e-007 1.0000000 7e-007 11 10 20 4.2e+002 9e-010
11 3.3e-007 0.7500000 1.4e-007 20 11 30 3.9e+002 8.1e-009
12 2.3e-007 0.1128516 3.5e-007 23 12 34 3.9e+002 5.8e-009
13 2.6e-007 0.7500000 2.3e-007 32 13 44 4e+002 2e-008
14 2e-007 0.0049796 2.7e-007 37 14 50 4e+002 1.5e-008
15 3.5e-007 0.7500000 2e-007 44 15 58 4e+002 7.6e-008
16 3.5e-007 1.0000000 3.7e-007 45 16 60 4e+002 5.6e-007
17 2.1e-007 0.0798715 3.7e-007 48 17 64 4e+002 3.4e-007
18 1.3e-007 0.2229211 2.2e-007 50 18 67 4e+002 2.5e-007
19 4.7e-007 0.7500000 1.3e-007 59 19 77 4e+002 2.6e-006
20 2.3e-007 0.1053436 4.9e-007 60 20 79 4e+002 1.3e-006
21 1.2e-007 0.0112598 2.4e-007 62 21 82 4e+002 6.6e-007
22 5.6e-007 0.7500000 1.2e-007 70 22 91 4e+002 8.8e-006
23 3.6e-007 1.0000000 5.9e-007 71 23 93 4e+002 4e-005
24 3.3e-007 0.7500000 3.6e-007 80 24 103 4e+002 0.00011
25 2.7e-007 0.0751680 3.5e-007 83 25 107 4e+002 8.9e-005
Stationary Solver 1 in Solver 1: Solution time: 20 s
Physical memory: 1.18 GB
Virtual memory: 1.23 GB
So for some reason ErrEst goes down but LinErr goes up.
Is this just a problem of COMSOL even though the solution is reached, and more importantly, can I trust the result?
Thanks for any comments and suggestions!
3 Replies Last Post 26.01.2015, 08:19 GMT-5
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Posted:
1 decade ago
Hello Pekka,
Are you specifying the pressure anywhere? If not, your model is mathematically ill-posed as there are an infinite number of pressure fields (differing from one another only by a constant pressure) that satisfy the equations. If that's the problem, simply specify the pressure at one point (any point) and that should fix it.
Best,
Jeff
Are you specifying the pressure anywhere? If not, your model is mathematically ill-posed as there are an infinite number of pressure fields (differing from one another only by a constant pressure) that satisfy the equations. If that's the problem, simply specify the pressure at one point (any point) and that should fix it.
Best,
Jeff
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Posted:
1 decade ago
Thanks Jeff, this solved the issue!
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Posted:
10 years ago
Hi Jeff, I have encountered the same issue with Pekka even with my pressure constraint included. Because I am coupling the laminar flow with electric current modules, and for the electric current modules, I also use periodic condition (electric potential continuity) on the inlet and outlet. There is no such a constrain condition in ec module like the pressure constrain in laminar flow module. So in this case, what do you think about the error message from my linear solver that the : the relative error is greater than the relative tolerance. returned solution is not converged.
My log message is also pasted below. Any information would be greatly appreciated. Thank you
Stationary Solver 1 in Solver 1 started at 26-Jan-2015 01:13:30.
Nonlinear solver
Number of degrees of freedom solved for: 529517.
Nonsymmetric matrix found.
Scales for dependent variables:
Electric potential (comp1.V2): 2.3e-007
Pressure (comp1.p): 0.025
Velocity field (comp1.u): 0.02
Iter ErrEst Newton Cauchy Stepsize #Res #Jac #Sol LinErr LinRes
1 0.00071 1.0000000 0.0000000 7 2 1 1 16 1.5e-014
Scales for dependent variables:
Electric potential (comp1.V2): 1.1e-006
Pressure (comp1.p): 0.41
Velocity field (comp1.u): 3.6e-005
2 3.3e-005 1.0000000 0.0000000 0.21 3 2 2 1.1 7.2e-013
3 1.4e-005 1.0000000 0.0000000 0.029 4 3 3 0.39 2.3e-013
4 5.5e-006 1.0000000 0.0000000 0.022 5 4 4 0.0035 1.7e-013
5 4.1e-006 1.0000000 0.0000000 0.011 6 5 5 0.005 4.5e-014
6 3.2e-006 1.0000000 0.0000000 0.007 7 6 6 0.023 8.6e-014
7 1.7e-006 0.4369750 0.0000000 0.0018 9 7 7 0.0028 4.8e-014
8 1.1e-006 0.7839243 0.0000000 0.0018 10 8 8 0.083 9.7e-014
9 3.2e-007 1.0000000 0.0000000 0.0014 11 9 9 0.049 7e-014
10 2.8e-007 1.0000000 0.0000000 0.00057 12 10 10 0.032 3.7e-014
11 2e-007 1.0000000 0.0000000 0.00051 13 11 11 0.0059 4e-014
12 1.3e-007 1.0000000 0.0000000 0.00048 14 12 12 0.017 3.7e-014
13 9.4e-008 1.0000000 0.0000000 0.00046 15 13 13 0.0081 4e-014
14 7.9e-008 1.0000000 0.0000000 0.00044 16 14 14 0.068 4.3e-014
15 6.3e-008 1.0000000 0.0000000 0.00044 17 15 15 0.055 3.4e-014
16 5e-008 1.0000000 0.0000000 0.00043 18 16 16 0.00076 3.8e-014
17 3.6e-008 1.0000000 0.0000000 0.00043 19 17 17 0.017 4e-014
18 3e-008 1.0000000 0.0000000 0.00042 20 18 18 0.034 4.1e-014
19 2.3e-008 1.0000000 0.0000000 0.00042 21 19 19 0.0091 4.1e-014
20 2.1e-008 1.0000000 0.0000000 0.00042 22 20 20 0.01 3.9e-014
21 1.5e-008 1.0000000 0.0000000 0.00041 23 21 21 0.0023 4.2e-014
22 1.3e-008 1.0000000 0.0000000 0.00041 24 22 22 0.024 3.8e-014
23 9.8e-009 1.0000000 0.0000000 0.00041 25 23 23 0.013 5e-014
24 9.2e-009 1.0000000 0.0000000 0.00041 26 24 24 1.3e+002 2e-012
25 7.6e-009 1.0000000 0.0000000 0.0004 27 25 25 0.0092 5.6e-014
26 6.3e-009 1.0000000 0.0000000 0.0004 28 26 26 0.058 3.7e-014
27 4.9e-009 1.0000000 0.0000000 0.0004 29 27 27 0.022 3.8e-014
28 4.6e-009 1.0000000 0.0000000 0.0004 30 28 28 0.0022 3.5e-014
29 4.4e-009 1.0000000 0.0000000 0.00039 31 29 29 0.02 3.9e-014
30 3.8e-009 1.0000000 0.0000000 0.00039 32 30 30 0.029 3.4e-014
31 3.1e-009 1.0000000 0.0000000 0.00039 33 31 31 0.0098 4.3e-014
32 3e-009 1.0000000 0.0000000 0.00039 34 32 32 0.0055 3.6e-014
33 2.8e-009 0.4700411 0.0000000 0.00018 36 33 33 0.082 3.6e-014
34 2.8e-009 0.4714406 0.0000000 0.00018 37 34 34 0.027 4.4e-014
35 2.7e-009 0.4728424 0.0000000 0.00018 38 35 35 0.019 3.7e-014
36 2.6e-009 0.4742503 0.0000000 0.00018 39 36 36 0.024 4.4e-014
37 2.6e-009 0.4756627 0.0000000 0.00018 40 37 37 0.0061 3.9e-014
38 2.6e-009 0.4770840 0.0000000 0.00018 41 38 38 0.021 4.2e-014
39 2.6e-009 0.4785110 0.0000000 0.00018 42 39 39 0.011 4.6e-014
40 2.6e-009 0.0000000 0.9999998 1.8e-011 64 40 40 0.017 3.8e-014
41 2.6e-009 0.0000000 0.9999999 4.3e-012 67 41 41 0.023 3.6e-014
42 2.6e-009 0.0000000 0.9999999 4.3e-012 68 42 42 0.024 4.3e-014
43 2.6e-009 0.0000000 1.0000000 1.9e-015 78 43 43 0.047 3.5e-014
Stationary Solver 1 in Solver 1: Solution time: 5686 s (1 hour, 34 minutes, 46 seconds)
Physical memory: 14.65 GB
Virtual memory: 15.62 GB
My log message is also pasted below. Any information would be greatly appreciated. Thank you
Stationary Solver 1 in Solver 1 started at 26-Jan-2015 01:13:30.
Nonlinear solver
Number of degrees of freedom solved for: 529517.
Nonsymmetric matrix found.
Scales for dependent variables:
Electric potential (comp1.V2): 2.3e-007
Pressure (comp1.p): 0.025
Velocity field (comp1.u): 0.02
Iter ErrEst Newton Cauchy Stepsize #Res #Jac #Sol LinErr LinRes
1 0.00071 1.0000000 0.0000000 7 2 1 1 16 1.5e-014
Scales for dependent variables:
Electric potential (comp1.V2): 1.1e-006
Pressure (comp1.p): 0.41
Velocity field (comp1.u): 3.6e-005
2 3.3e-005 1.0000000 0.0000000 0.21 3 2 2 1.1 7.2e-013
3 1.4e-005 1.0000000 0.0000000 0.029 4 3 3 0.39 2.3e-013
4 5.5e-006 1.0000000 0.0000000 0.022 5 4 4 0.0035 1.7e-013
5 4.1e-006 1.0000000 0.0000000 0.011 6 5 5 0.005 4.5e-014
6 3.2e-006 1.0000000 0.0000000 0.007 7 6 6 0.023 8.6e-014
7 1.7e-006 0.4369750 0.0000000 0.0018 9 7 7 0.0028 4.8e-014
8 1.1e-006 0.7839243 0.0000000 0.0018 10 8 8 0.083 9.7e-014
9 3.2e-007 1.0000000 0.0000000 0.0014 11 9 9 0.049 7e-014
10 2.8e-007 1.0000000 0.0000000 0.00057 12 10 10 0.032 3.7e-014
11 2e-007 1.0000000 0.0000000 0.00051 13 11 11 0.0059 4e-014
12 1.3e-007 1.0000000 0.0000000 0.00048 14 12 12 0.017 3.7e-014
13 9.4e-008 1.0000000 0.0000000 0.00046 15 13 13 0.0081 4e-014
14 7.9e-008 1.0000000 0.0000000 0.00044 16 14 14 0.068 4.3e-014
15 6.3e-008 1.0000000 0.0000000 0.00044 17 15 15 0.055 3.4e-014
16 5e-008 1.0000000 0.0000000 0.00043 18 16 16 0.00076 3.8e-014
17 3.6e-008 1.0000000 0.0000000 0.00043 19 17 17 0.017 4e-014
18 3e-008 1.0000000 0.0000000 0.00042 20 18 18 0.034 4.1e-014
19 2.3e-008 1.0000000 0.0000000 0.00042 21 19 19 0.0091 4.1e-014
20 2.1e-008 1.0000000 0.0000000 0.00042 22 20 20 0.01 3.9e-014
21 1.5e-008 1.0000000 0.0000000 0.00041 23 21 21 0.0023 4.2e-014
22 1.3e-008 1.0000000 0.0000000 0.00041 24 22 22 0.024 3.8e-014
23 9.8e-009 1.0000000 0.0000000 0.00041 25 23 23 0.013 5e-014
24 9.2e-009 1.0000000 0.0000000 0.00041 26 24 24 1.3e+002 2e-012
25 7.6e-009 1.0000000 0.0000000 0.0004 27 25 25 0.0092 5.6e-014
26 6.3e-009 1.0000000 0.0000000 0.0004 28 26 26 0.058 3.7e-014
27 4.9e-009 1.0000000 0.0000000 0.0004 29 27 27 0.022 3.8e-014
28 4.6e-009 1.0000000 0.0000000 0.0004 30 28 28 0.0022 3.5e-014
29 4.4e-009 1.0000000 0.0000000 0.00039 31 29 29 0.02 3.9e-014
30 3.8e-009 1.0000000 0.0000000 0.00039 32 30 30 0.029 3.4e-014
31 3.1e-009 1.0000000 0.0000000 0.00039 33 31 31 0.0098 4.3e-014
32 3e-009 1.0000000 0.0000000 0.00039 34 32 32 0.0055 3.6e-014
33 2.8e-009 0.4700411 0.0000000 0.00018 36 33 33 0.082 3.6e-014
34 2.8e-009 0.4714406 0.0000000 0.00018 37 34 34 0.027 4.4e-014
35 2.7e-009 0.4728424 0.0000000 0.00018 38 35 35 0.019 3.7e-014
36 2.6e-009 0.4742503 0.0000000 0.00018 39 36 36 0.024 4.4e-014
37 2.6e-009 0.4756627 0.0000000 0.00018 40 37 37 0.0061 3.9e-014
38 2.6e-009 0.4770840 0.0000000 0.00018 41 38 38 0.021 4.2e-014
39 2.6e-009 0.4785110 0.0000000 0.00018 42 39 39 0.011 4.6e-014
40 2.6e-009 0.0000000 0.9999998 1.8e-011 64 40 40 0.017 3.8e-014
41 2.6e-009 0.0000000 0.9999999 4.3e-012 67 41 41 0.023 3.6e-014
42 2.6e-009 0.0000000 0.9999999 4.3e-012 68 42 42 0.024 4.3e-014
43 2.6e-009 0.0000000 1.0000000 1.9e-015 78 43 43 0.047 3.5e-014
Stationary Solver 1 in Solver 1: Solution time: 5686 s (1 hour, 34 minutes, 46 seconds)
Physical memory: 14.65 GB
Virtual memory: 15.62 GB