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I'm new to TELEMAC, so perhaps this is an easy question to answer: Is it necessary to specify inlet velocity (UBOR) values in the .cli file if the inlet is an "open boundary with prescribed Q"?

If an inlet is specified as LIHBOR=4 (free depth), LIUBOR=5 (U based on Q), LIVBOR=5 (V based on Q), how is velocity calculated if it is not specified (given that depth is "free")?

With or without specifying UBOR values in the .cli file, I am getting the following error:

PROBLEM ON BOUNDARY NUMBER 1
GIVE A VELOCITY PROFILE
IN THE BOUNDARY CONDITIONS FILE
OR CHECK THE WATER DEPTHS

Could someone please explain? I've tried all the different velocity profile options.

Hi

If there is no water on the discharge boundary Telemac cannot compute an area which is required to compute the velocity (to impose the discharge).
For subcritical flow, the water level on upstream boundary comes from downstream. To impose a discharge, you just have to impose the velocity at the entry.
For supercritical flow, you must impose Velocity and Water level otherwise this will crash...

Regards

I understand that a velocity (or depth) is initially needed along with the imposed discharge. I think my problem is that I'm not using a hotstart, so my model is initially dry. Hence, my condition of LIHBOR = 4 (free depth) and LIUBOR/LIVBOR = 5 (based on discharge) is under-prescribed because there is no depth yet.

To try to fix this, I set LIHBOR = 5 (prescribed depth) and set HBOR = 1 (as an arbitrary depth) for all inlet boundary points in the .cli file. I kept LIUBOR/LIVBOR = 5. I also changed my hydrograph in the .liq to ramp up very slowly. In this configuration I get the following error:

SL: MORE PRESCRIBED ELEVATIONS ARE REQUIRED
IN THE PARAMETER FILE
AT LEAST 1 MUST BE GIVEN.

It seems that my HBOR specification is being ignored...am I missing something? Thanks and sorry if this is something trivial!

Hi

As you have 2 boundary conditions in your model, you should give at least 2 values in the line prescribed elevations even only one will be use.

regards

Thanks. I ended up changing the initial conditions to CONSTANT ELEVATION and the set the INITIAL ELEVATION to something that would wet the u/s boundary. That gave the upstream boundaries a depth to start from - simple enough. Still not quite sure why specifying an HBOR value in the boundary file didn't work...