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TOPIC: Error in volume balance during resuspension
Error in volume balance during resuspension 6 months 3 weeks ago #44681
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Hi all!
In a recent application of Telemac3D + GAIA (v8p4r0) we had an issue with resuspension. This happened under specific circumstances and I am unfortunately not able to share my model. I am not looking for a direct solution, but hopefully the flagging of this issue will allow it to be fixed in the future. I have a model where we judge the far field fine sediment plume (SSC and deposition) of a dredging project. Every 4 hours we release over 200 kg/s of sediment (over 4 classes) at a source point under a period of 10 minutes. Most of this fine sediment stays in suspension for a longer period before depositing far away from the source point. During storms with strong bed currents some of this sediment might be resuspended. For one of the meteorological periods that we investigated, we had an issue with our volume balance. In the attached screenshot I have included some time series from the GAIA/Telemac3D mass balance in the sortie-file. The model results are perfectly fine until day 9. Both the SSC ("Tracer Quantity" from Telemac3D) and the bed deposition ("Sediment Total Mass" from GAIA) gradually increase over time. At day 9, we suddenly see a peak in SSC (the heavier sediment classes 3 and 4) due to resuspension and shortly after a large increase in bed deposition. We have not found the source of this issue but expect something might be off in the volume balance of the resuspension. Investigation of the source code has not helped. It appears that the error propagates from nodes where little sediment is available. The quick fix that we applied in our project was to disable resuspension (by setting C_eq = 0 in the Fortran routines) which was not that much of an issue for this project. Has anybody come across this issue before? Additional details on the model: - Bed load transport is disabled. - Stratified model (salinity and temperature) - Also coupled to WAQTEL to achieve stratification during the entire period (disabling WAQTEL does not solve the issue)
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