Dg shock capture #1595
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Dg shock capture #1595
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voferreira
approved these changes
Jul 29, 2025
| @@ -35,6 +35,10 @@ subsection physical properties | |||
| end | |||
| end | |||
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| subsection stabilization | |||
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applications_tests/lethe-fluid/dg_tracer_advection_tanh_bdf2.prm
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| // We define the cutoff function from the Moe paper using a lambda function. | ||
| // It's a bit weird this cutoff function, but YOLO I guess. Why do we divide y | ||
| // by 1.1? I do not know, I believe it to be one of the mysteries of life. |
hepap
approved these changes
Jul 30, 2025
| "scalar limiter", | ||
| "none", | ||
| Patterns::Selection("none|moe"), | ||
| "Type of scalar limiter. The limiters are only appropriate with the DG versions of the solvers and should only be used for advection-dominated problem."); |
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I don't know if we need to say that it's only available for the tracer here.
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I'll implement it soon for the VOF equation, so I don't think it's required :)
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| // 3. Calculate the value of the theta limiting using the max, min and | ||
| // mean values as well as the bounds. | ||
| const double max_value = | ||
| max_value_per_cells.at(cell->global_active_cell_index()); | ||
| const double min_value = | ||
| min_value_per_cells.at(cell->global_active_cell_index()); | ||
| const double mean_value = | ||
| mean_value_per_cells.at(cell->global_active_cell_index()); | ||
| double y_max = | ||
| (upper_bound - mean_value) / ((max_value - mean_value) + 1e-16); | ||
| double y_min = | ||
| (lower_bound - mean_value) / ((min_value - mean_value) + 1e-16); |
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So upper/lower bounds are from the neighbor values and min/max are from the cell values?
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Yes exactly. The max/min/avec are in the cell and the upper and lower bounds are from the neighbours
Co-authored-by: Victor Oliveira Ferreira <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
Co-authored-by: hepap <[email protected]>
etiennemarin
pushed a commit
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Jul 30, 2025
Description The DG implementation of the tracer was not very adequate for pure advection if the DG order was larger than 0 (so DG Q1 and above). This is because we did not have any sort of limiter in place. This PR adds a Moe limiter (see documentation for reference) which is an a posteriori limiter that works quite well for scalar equations. It is not very invasive and not very expensive and I have managed to get very adequate results with it. Testing The DG advection test has been changed to use the limiter and I have added a new test with BDF2 which really requires the limiter to get adequate results. Documentation Since the limiter is generic for all scalar equations, I have documented it in the stabilization section where I believe it adequately belong. Co-authored-by: Victor Oliveira Ferreira <[email protected]> Co-authored-by: hepap <[email protected]>
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Description
The DG implementation of the tracer was not very adequate for pure advection if the DG order was larger than 0 (so DG Q1 and above). This is because we did not have any sort of limiter in place. This PR adds a Moe limiter (see documentation for reference) which is an a posteriori limiter that works quite well for scalar equations. It is not very invasive and not very expensive and I have managed to get very adequate results with it.
Testing
The DG advection test has been changed to use the limiter and I have added a new test with BDF2 which really requires the limiter to get adequate results.
Documentation
Since the limiter is generic for all scalar equations, I have documented it in the stabilization section where I believe it adequately belong.
Miscellaneous (will be removed when merged)
Checklist (will be removed when merged)
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