open TELEMAC-MASCARET The mathematically superior suite of solvers

Dear all,

I have been trying to get my simulation to work and have attached a picture of the geometry file. The case looks into simulating the flow passing through a turbine and has a weir to the left.

The first simulation runs without the turbine installed and I’ve made the geometry at 25m to block the flow so that all water flows through the weir. I’ve put a flowrate of 41 at entrance (top) and put a boundary with prescribed H on the exit. I then wait for the geometry to fill up with water and reach a steady state, the initial depth is 0.8. The problem is a steady state isn’t reached and the flow rate is not conserved at the end of simulation. I have attached the relevant simulation files to this post.

On the next simulation, I’ve made a closed line of 18.5m around the bottom half of the geometry and made this a separate simulation. I’ve then at the top prescribed a flow rate coming from the weir of 37 and then a flowrate of 5 from the turbine. I’ve also put a free velocity boundary (444) at the exit. Upon running and waiting for a steady state, the simulation crashes with the following error:

GIVE A VELOCITY PROFILE
IN THE BOUNDARY CONDITIONS FILE
OR CHECK THE WATER DEPTHS.
OTHER POSSIBLE CAUSE:
SUPERCRITICAL ENTRY WITH FREE DEPTH
IN THIS CASE GIVE A POSITIVE DEPTH
IN THE INITIAL CONDITIONS
OR PRESCRIBE THE DEPTH AT THE ENTRANCE.

I’ve attached a copy of the simulation files in next comment. Also I don’t know how I can make a closed line so that it’s 20.5m on the hill by the weir and 18.5m on the exit.

I don’t know if anyone was able to help me out please?

These are the files for the second case.

Hi,

I don't know how you did for creating your mesh but it is of poor quality at boundaries, at your dam and along the shorelines.

I would spend time fixing this before going further with simulations. Blue Kenue is a good mesher for such geometries and there are good tutorials available on this website/forum!

Good luck!

Best regards
PL

Dear pilou1253,

thank you for your reply.

I did use Blue kenue and have done the baxter tutorial.

in the first case, I used the close line tool with a value of 25m along the outside of the river and then created a triangular mesh using the xyz data and the closed line as a constraint. For the second case I did this with a value of 18.5m but around the bottom half of the geometry.

I don't know if there was a more effective way of doing this in order to select the computational domain.

Best Regards

Paul

Dear Paul,

I would create a mesh from an outline and density polygons instead. In this way you can select the mesh size in a approriate way for the different parts of your model. You can even include piers etc with closed (soft or hard) lines, if needed. Look at the Blue Kenue manual it is very well explained.

Then, once you're satisfied with your mesh, you can interpolate the elevation at nodes using the 2D interpolator or any other methods (from a ASCII grid raster, ...). This is also well explained in the Blue Kenue manual.

Good luck!

Best regards
PL

Dear PL,

thank you for your help, I will try and do this method and see if it helps my telemac simulation.

Many Thanks

Paul