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This page demonstrates the spatial convergence rates of diffusion schemes.

Configurations

A 2D cavity of unit length is used and the spatial mesh is reduced, at constant time step, for testing convergence. The schemes are verified in

See also
Explicit and implicit schemes comparison.

Temporal schemes

In order to suppress most temporal errors, the most precise temporal scheme has to be used.

Analysis

The precise spatial convergence analysis is somehow complex as temporal errors also occurs and cannot be completely removed. Hence, we have chosen numerical parameters such that the effective schemes' convergence rate appear in the range. Absolute values of error can be compared between schemes.

Implicit schemes

All schemes exhibit the expected convergence rate.

Explicit schemes

All schemes exhibit the expected convergence rate.

Results

Implicit schemes

o2_centered

Mesh Temperature L1 error order Temperature L2 error order Temperature Linf error order
32×4 1.2935846888020158e-07 n/a 1.4275968501959712e-07 n/a 1.9801337136637898e-07 n/a
64×8 3.230845164493845e-08 2.001 3.5828048794521865e-08 1.994 5.042452899672867e-08 1.973
128×16 8.075433294014566e-09 2.000 8.965949536945098e-09 1.999 1.2664493231895335e-08 1.993
256×32 2.019007121605303e-09 2.000 2.2423279166181104e-09 1.999 3.1701760105917742e-09 1.998
512×64 5.050139275168642e-10 1.999 5.609153766074666e-10 1.999 7.931948431405544e-10 1.999
1024×128 1.2652285164893096e-10 1.997 1.4053067184465362e-10 1.997 1.9873691581295816e-10 1.997
2048×256 3.190051783580694e-11 1.988 3.543250949391376e-11 1.988 5.010980519415398e-11 1.988
4096×512 8.243448220815388e-12 1.952 9.156162657506196e-12 1.952 1.294897522541305e-11 1.952

Explicit schemes

o2_centered

Mesh Temperature L1 error order Temperature L2 error order Temperature Linf error order
32×4 1.2935811613719317e-07 n/a 1.4275929581424112e-07 n/a 1.98012831797989e-07 n/a
64×8 3.230809235031315e-08 2.001 3.5827650431421577e-08 1.994 5.042396944432426e-08 1.973
128×16 8.075072590793802e-09 2.000 8.965549007459253e-09 1.999 1.2663928239398103e-08 1.993
256×32 2.018646414562726e-09 2.000 2.2419273306497303e-09 2.000 3.1696093527600055e-09 1.998
512×64 5.046539177145401e-10 2.000 5.605155005289335e-10 2.000 7.926290734872055e-10 2.000
1024×128 1.2616297654602127e-10 2.000 1.4013095327324698e-10 2.000 1.9817114615960918e-10 2.000
2048×256 3.154069960819504e-11 2.000 3.503284918082218e-11 2.000 4.954359145159515e-11 2.000
4096×512 7.885168823422693e-12 2.000 8.758216893810434e-12 2.000 1.2386203174230559e-11 2.000

o4_centered

Mesh Temperature L1 error order Temperature L2 error order Temperature Linf error order
32×4 2.636976562456206e-09 n/a 2.910160810021556e-09 n/a 4.0365091269478626e-09 n/a
64×8 1.657192965753146e-10 3.992 1.8377232667874604e-10 3.985 2.5864177466417004e-10 3.964
128×16 1.0371753748818907e-11 3.998 1.151550938092588e-11 3.996 1.626543344457332e-11 3.991
256×32 6.484509110227243e-13 4.000 7.201783604850409e-13 3.999 1.018185535883731e-12 3.998
512×64 4.04939923010373e-14 4.001 4.4971269538839685e-14 4.001 6.361577931102147e-14 4.000
1024×128 2.5002769359029273e-15 4.018 2.784012498112694e-15 4.014 4.3298697960381105e-15 3.877

References