open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello Telemac community!

I have asked a similar question before but I am revisiting it and I am still looking for ideas/a solution.

The task - model fast tidal flows in a tidal channel and calibrate the model w.r.t ADCP data.

The problem(s)

1) Using TPXO you really have to increase the 'COEFFICIENT TO CALIBRATE TIDAL RANGE' to 1.4 to get realistic velocities. However, then the elevations are too high. Has anyone had any experience like this?

2) Free surface and velocity instabilities. I have tried most of the suggestions I have read on here but nothing removes them completely. Maybe there is no solution in some cases? i.e. for steep bathymetry and fast currents.

In the middle of the channels I can get relatively smooth solutions but close to the land boundary the oscillations are extreme and have large magnitudes. Lowering the resolution fixes some of the issues but then I want to resolve some regions to 25m. I ran a FV version which gives a smooth solution but the velocities are way too low. Has anyone had experience with calibrating the FV solver for velocities?

I have also tried Quasi-Bubble elements but it made the solution worse.

I have attached the setup to this message. If anybody has any ideas or opinions, I would be most grateful!

Best regards,
John

Hi
I didn't look your files but there is something strange in your message.
You use COEFFICIENT TO CALIBRATE TIDAL RANGE = 1.4 in order to have realistic velocities but this leads to too high elevations
I would say that's sounds logical as you increase the tide range by 40%

There is the same keyword for TIDAL VELOCITIES so why don't you use it?

Hi thanks for your response. Good point! I just did a quick test and I will either need to increase the velocities by more than 1.4 to get the right magnitudes or maybe a mixture of increasing the velocities and the elevations will work.

However, it still doesn't solve my problem with oscillations.

Thanks,
John

Hello John,

Christophe is right, the COEFFICIENT TO CALIBRATE TIDAL VELOCITIES is the right one to tune velocities at the maritime boundaries, not COEFFICIENT TO CALIBRATE TIDAL RANGE. This latter should have less influence for velocities. You can also change the LAW OF BOTTOM FRICTION and/or FRICTION COEFFICIENT.

For your 2nd issue, can you show figures to illustrate what you see please? e.g. velocity fields + mesh together.

Best regards,

Chi-Tuan