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Dear all,

Would it be possible to get some documentation or details about the option 3 for treatment of tidal flats (i.e, wetting and drying)? I would like to know how this porosity coefficient is implemented and if the value really corresponds to the definition of the total porosity.

Kind regards,

Jean-Philippe

Hello Jean Philippe,

The porosity option is used for tidal flat treatment with options :TIDAL FLATS =YES and OPTION FOR THE TREATMENT OF TIDAL FLATS =3.
The idea behind this technique can be summerized as follows: for partially dry elements (caused by partial flooding or the presence of obstacles with size lower than the element length such as buildings or trees etc. ) the percentage of area occupied by water is expressed by the mean of a porosity.
Consequently, in a numercial point of view, we have:
1 - in the continuity equation: we solve for d(theta h)/dt + div(theta hu) = 0 in stead of d(h)/dt + div(hu) = 0 (theta is the porosity)

2- in the momentum equation, theta is introduced only in the dispersion term (h is repalced by theta h), however, the effect of porosity can be considered by adding a drag force F = (-D/(2A))*Cd*||u||u (where D is the diameter of the obstacle, A is its active area, Cd is the drag coefficient and u is the velocity vector)

You can introduce or modify th porosity by editing the subroutine CORPOR.f


I hope that this helps

With my best regards,

Riadh

Hello,

The porosity for tidal flats is computed in subroutine poro11.f (library telemac-2D). It is a rough evaluation of the percentage of element occupied by water. It gives a slightly different dynamics of flood waves.

Regards,

Jean-Michel Hervouet