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Time dependent values for Sus,Bed, Susw and Bedw

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zahra moosavi, modified 3 Years ago.

Time dependent values for Sus,Bed, Susw and Bedw

Youngling Posts: 21 Join Date: 12/22/14 Recent Posts
Dear all,
As i found in order to reach the bar and berm profiles during the storm and calm wave condition, using Delft3D model, we need to define different values of Sus, Bed, Susw and Bedw in each condition. I would really appreciate if anybody help me to know is there anyway to define time dependent values for Sus,Bed, Susw and Bedw or not?
Best Regards
Ben Williams, modified 3 Years ago.

RE: Time dependent values for Sus,Bed, Susw and Bedw (Answer)

Jedi Knight Posts: 114 Join Date: 3/23/11 Recent Posts
Hi Zahra,

If you are running a wave time series via a wavecon file then you will not be able to define time-varying Sus, Bed, Susw and Bedw. These are simply scaling parameters, defined in the MOR file , that help one control the overall magnitude of suspended and bedload transport, and the direction in which it moves (i.e. current direction vs wave direction). In this way they are useful calibration parameters, although the default values for Susw and Bedw are not realistic and generally do not lead to satisfactory results in the nearshore when wave activity is important.

If you splitt your simulation in to a series of smaller model runs each considering a certain period of wave conditions, with the end point of each simulation acting as the 'hotstart' for the next, then you will be able to define values as you choose for each individual simulation, This however seems somewhat laborious and I'm not sure of the physical meaning of undertaking such an exercise.

If you are looking at bar dynamics (no tidal currents) then SusW and BedW are the calibration factors that give most 'bang for buck' . You can get a reasonable estimate of what kind of values don't result in horrible instabilities by undertaking a sensitivity analysis over a smootly varying range of values for these two parameters (in the range 0 - 1), and looking at either sediment transport observations (if you have any) or comparing the skill of the model in reproducing some final bathymetry.

Good luck.

Ben
ZM
zahra moosavi, modified 3 Years ago.

RE: Time dependent values for Sus,Bed, Susw and Bedw

Youngling Posts: 21 Join Date: 12/22/14 Recent Posts
Hi Ben,

Thank you so much for your really valuable comments.

Best wishes