open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

As far as I know, Telemac3d uses the classical Sigma transformation for the 3D-grid generation. Could this method affect the numerical results in case of gravity currents or salinity transport especially in tideless estuaries, to be more specific, the classical sigma transformation may cause artificial density flows in the absence of source or sink terms (no tides). If this is the case, how can such problem avoided.

Kind regards,
Mohamed

I do not think this is the case. Have a look at the lock exchange problem (part of the validation examples). It is a direct application of gravity current without tide.

Note that TELEMAC-3D has more than one option for vertical meshing. The latest available is the AMR method (limiting diffusion), an application of which to the lock excahnge problem is detailed in the proceedings of the XVIIIth TELEMAC Conference paper (pp137-141), "Adaptive vertical layering in TELEMAC-3D" available on this website.

Hope this helps,
Sebastien.

The lock exchange case is for flat bottom, the presence of steep bottom like in the nature could make big differences, and the stratification is not very high, if you refer to the following paper:

'Decoene, A. and Gerbeau, J.F., Sigma transformation and ALE formulation for three-dimensional free surface flows, Int. J. Num. Meth. in Fluids (2009), 59, 357–386.'

you will find illustration for the problem starting from page 363.

Concerning the adaptive mesh, I did not actually use, I am not sure if it is available in version 6.1 because Telemac3d in version 6.2 is full of problems.