open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi

I'm working on a project where I'm simulating the effect of mooring lines on the seabed. I'm modelling the erosion due to the movements of the mooring lines as a localised increase in bed stress on the bed. I've programmed this in the tob_gaia.f subroutine and all seems to be working (was seeing the expected values in the output results.

However, whilst I'm seeing a small impact where expected, I was only seeing 1 mm of erosion after almost 30 days. So was playing with increasing the bed shear stress 5 N/m2 vs 17 N/m2) but was seeing the exactly the same result leading to my suspicion it wasn't working as intended. Granted both levels of bed shear stress were above the critical threshold of erosion to induce motion but I was still expecting the higher value to erode faster.

So my question was: is bed shear stress taking into account in the bed load transport equation? Looking at bedload_soulsby.f (the transport formula I was using) it doesn't appear to?

That or I've modelled a perfect condition where the equilibrium inflow conditions means the bedload transport upstream is almost perfectly balancing out the erosion!

Many thanks for any insight.

Cheers

David

So appear to have answered my own question, yes it appears the Soulsby bedload doesn't consider bed shear stress. Owing to a combination of coupling telemac-tomawac-gaia and a multi-layer bed, have used the Bailard bedload formula instead and am suddenly seeing much greater erosion.

David