open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I am trying to simulate the scour around a cylinder in coupled T2D-Sisyphe. The purpose is to analyze the bed evolution.

The Sisyphe results of bed evolution (scour) around a cylinder are not satisfactory. I am getting maximum scour depth as just 2 to 3 mm. Which is not comparable to experimental results, where maximum scour depth was found 8 cm.

I tried these bed load formula: 1-MPM, 2-EB, 7-VR.
I tried to change the values of different parameters such as skin friction correction, the ratio between skin friction and mean diameter, slope effect, morphological factor, minimal value of the water height, friction angle of sediment, sediment slide, and different time steps ranging from 0.005 to 0.1












Can anyone help in solving this problem?

Thank you.

Regards,
Parth

Hi Parth,

Are you happy with the flow results? The scour around monopiles is dominated by enhanced turbulence around the structure, which can only be resolved with a good turbulence model. From your telemac steering file, I see that

You are using constant viscosity, which is never going to get close enough.

FREE SURFACE GRADIENT COMPATIBILITY =0.8, which might smooth the free surface too much

You are using telemac2d, which in itself might be reducing the turbulence. You may have to switch to 3D

Thanks for your reply, Sir.

Initially, I am working in T2D, if it gives approximate results, then I can move on T3D.

I have changed the turbulence model and free surface gradient compatibility. Flow field around piles is improved. But still, I am not getting the good results of bed evolution.

Is there any problem in sisyphe parameters, time step, or mesh?


Your suggestions will be helpful in solving the issue. Thanks in advance.

Regards,
Parth

Hello everyone,

I would appreciate a lot if anyone suggests necessary steps to solve the earlier posted problem.

Thanks.
Parth

Having run your model, it looks like the flow velocities (peak velocity <0.2m/s are not high enough to move the .45mm sand (critical velocity 0.28 m/s). Your 2D flow model is ignoring variations in the turbulence (the default is constant viscosity), so of all the scour causing mechanisms, you only have the acceleration around the object. Not the enhanced turbulent viscosity, and not the 3D downwelling effect around a surface piercing object.
Changes in the Sisyphe settings are not going to correct that.