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M. Riffai April 17, 2008 10:12

Free Surface Flow with Sediment Transport
Hello CFX Folks,

I am trying to simulate flow over an embankment weir (small trapezoidal dam) where as the bed is mobile. I was successful in simulating the hydrodynamic part, but now I would like to include the effects of the mobile bed. So I believe it is possible to simulate the transport of sediment in three ways:

1- Eulerian-Eulerin Multiphase 2- Lagrangian Particle Transport (although CFX won't let me include two Eulerian-Eulerian models or two continuos phases like air and water with a dispersed phase like solid particles using the Lagrangian model) 3- Create a new material (water and sediment) and an additional variable such as concentration and solve a transport equation (e.g. Poisson or diffusive transport)

I would like some advice on how to define each phase in each of the cases above (if possible. I have a feeling the Lagrangian Particle Transport will not work because the air and water phase cannot both be continuous wtih a dispersed solid phase. I know this has been done before, and I'm sure there is a way around it).

Your help is very much appreciated. Thanks!

Regards, M. Riffai

Glenn Horrocks April 17, 2008 19:51

Re: Free Surface Flow with Sediment Transport

This sounds like it would be best done as a discrete element model. These type of models can account for particle size and packing, settling and motion. At the moment you need to couple to a package like EDEM to do this, but I hear that CFX V12 has some capability in this area. Not sure if it will do what you are looking for.

Regards, Glenn

CFD_UJI December 1, 2011 18:23

Hello M. Riffa,

Finally, how did you define this model?
Option 1, 2 or 3? I'm really interested in this system.

I had several problems with option 2 as well, but I think it's the best approach. I wouldn't define solid particles as a "solid dispersed". On the other hand, air and water continuous phases are necesary.

Thanks a lot

mdallali September 5, 2013 09:45

I wanna model the pickup rate as expression mentioned by van.Rijn as follow:
P=0.00033(tet-tet_cr/tet_cr)^1.5 * (s-1)^0.6 *g^0.6 *d^0.8/nu^0.2

which ni is diffusivity and s is ratio of densities and d is particle diameter.
How could I nondimensional this expression and relate it to froud-Numbewr and Reynold?


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