open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

I have two classes of sediments, one cohesive and another non-cohesive. I must prescribe the cohesive sediments as suspended sediment at the inlet boundary and non-cohesive sediments as bed load or solid discharge. Therefore, I would like to know if it is possible to prescribe both suspended sediment concentration (g/l) and solid discharge (kg/s) at the inlet.

Also, to simplify my problem, I tried to prescribe both classes of suspended sediment concentration in g/l at the inlet. However, I am getting large depositions at the inlet, and the simulation crashes after some time due to super-critical flow at the inlet.

I would really appreciate some suggestions. Thank you.

Hello Ravi,

I didn't try your case so far, but I think it is possible.
I don't simulate cohesive sediments. So I am not completely sure for this part.

I assume that your cohesive sediment is first class, and the non-cohesive is 2nd class.
The amount of solid discharge can be described with the keyword "PRESCIBED SOLID DISCHARGE".
Which classes are imposed is determined by the initial condition at the inlet. So If you have
only class 2 (non-cohesive) at the initial boundary, only class 2 will be come in.
You can give the initial distribution by the keyword "CLASSES INITIAL FRACTION = 0.0; 1.0"
or in an previous sedimentological computation file.


The sediments in suspension are treated in telemac2d as additional tracers.
So the first one will be the cohesive one which should have suspension inlet and the 2nd should not have some input.
With the keyword PRESCRIBED SUSPENDED SEDIMENTS CONCENTRATION VALUES you can give for each boundary and each class the value.
Here you have to be certain that you don't put in the 2nd class.
In the mass-balance you can check how much sediments come into the system as bedload and suspension.
So you can see if your description of your boundaries was correct.

The problem you described that you have too much deposition directly at tbe boundary happens very often.
It is not easy to guess the reasons. Mostly the hydrodynamic doesn't fit to the morphodynamic.
This means that your sediment input at the bottom and at the water is too high (or your velocity too small).
I would do it step by step. First only the non-cohesive class, second only cohesive class and finally both together.
With this procedure it is hopefully easy to understand what the program is doing.

I hope this helps you.
Best regards,
Rebekka