open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

I try to correctly prescribe the BC at the downstream boundary in an estuary.

At the flood, the water is entering into the domain by the downstream BC (inflow). In this situation, I would try to prescribe an hydrograph (negative discharge) instead of increasing stage. I want to try that to solve mass conservation issue due to poor imposition.

At the ebb, the water leaves the domain by the downstream BC. In this case I would prefer to impose stage curve.

How can I impose at the same boundary, a discharge condition (at the flood) and a stage condition at the ebb?

Hi,

When I impose a water level at the downstream boundary of my estuary, at the flow (when the water level increase) the flow is negative (-> water enter in the domain).
I can't find any information about the treatment of BC where varying water level is imposed.
It looks like the discharge is always the same changing the Stickler coefficient... does it mean that the discharge is just calculated from the water level variation (mass conservation???).

In this case,is advection (caused by the flow) canceled ?

Hello,

With a level imposed and with the flow entering the domain, the problem is not well posed, it is the nagging difficulty of estuaries. A general advice is to put the open boundary in deep waters, so that the velocity remains small. Many tidal studies are done like this. When it is not sufficient the Thompson boundary conditions must be used, and the theory of characteristic hopefully gives the correct conditions (but actually if the velocities and elevations are not both prescribed there is still a small risk).

With best regards,

Jean-Michel Hervouet

Thank you very much for your advice Jean-Michel.

I would definitely apply that but it only works with Telemac. I would like to do this kind of imposition with Mascaret. I perfectly understand your advice but I can only give information on discharge or elevation and nothing exist to apply Thompson (I don't know if it makes sense in 1D).

I wish that an extension seaward can improve the dynamic but my first tests doesn't look better.

Thanks again.
Alexis

Hello,

Sorry, I did not understand it was for Mascaret...

JMH