open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,
Though the manual provides technical informations about the solver options, i wish to confirm my understandings by having the following discussion.

I wish to use tidal flats where i came across the option such as 'TREATMENT OF NEGATIVE DEPTHS' which have
0 : no treatment,
1 : smoothing of negative depth,
2 : Flux control.

1) Firstly, what is mean by 'NEGATIVE depth'? If so then what will be POSITIVE DEPTH? With reference to what datum these are fixed with signs?

2) Help me in understanding the process done by SMOOTHING OF NEGATIVE DEPTH and FLUX CONTROL.

3) Would you brief me about the mechanism of the options 'H CLIPPING' and 'MINIMUM VALUE OF DEPTH' and how are they related to "TREATMENT OF NEGATIVE DEPTHS"

Thanks in advance,
Sathya

Hello,

Depth is free surface elevation minus bottom elevation so there is no reference to datum. This physical depth should remain positive, though nothing in equations really prevents depth from becoming negative. Practically we allow slightly negative depths in one option (1), and in this case depths are kept only slightly negative by smoothing them, and we ensure positive depths in the other option (2). I would recommend that H CLIPPING =YES using the MINIMUM VALUE OF DEPTH is not used though it is an available option, it is indeed used by many other programs but this is not mass conservative, every time you cancel a negative depth or impose a minimum depth you wrongly add water in the domain.

With best regards,

Jean-Michel Hervouet