open TELEMAC-MASCARET The mathematically superior suite of solvers

hi,everyone,
The user mannual shows that there are propagation, advection of u/v, diffusion and source terms in the dynamic equations, but I have never heard the propagation. What is it specifically? Whether the waves are included, there is propagation term?

Hello,

The propagation is the propagation of waves at the celerity sqrt(gh). Basically the propagation term in the momentum equation is the term -g*grad(free surface). It can be shown also in the shallow water continuit equation, by eliminating the velocity. Then a wave equation appears with the celerity sqrt(gh). This is why the depth in the term div(hu) in the continuity equation is called propagation depth.

With best regards,

Jean-Michel Hervouet

Thank you, JMH
As I understand it, ∂(u)/∂t+u▽(u)=-g*grd(free surface)+(diffusion term) + (source term), so the -g*grd(free surface)is the propagation term?

That's it.

JMH

Thank you very much!

In addition, I have encountered a problem. ve. I want to solve an advection–diffusion equation with a unit (negative) source term in the control region.

In a first step, I use the hydrodynamic model to generate the velocity and turbulence fields
as usual, and the intermediate results are stored. Then, in a second step,the equation I want to solve is integrated backward in time using the hydrodynamic fields computed in the first step.

So I read the velocity and turbulence fields in the telemac2d.f, and set the time step as negative,and add a unit (negative) source term via TIMP%ADR(1)%P%R(I)=-1.D0. The results is negative, and I wonder if I was wrong?