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-   -   Turbidity current (http://www.cfd-online.com/Forums/fluent/103756-turbidity-current.html)

julien.n June 25, 2012 19:12

Turbidity current
 
Hello everyone,

I am working in a lab where we make some experiments on turbidity currents,
so I am trying to modelize a turbidity current with Fluent to compare the numerical results with the experimental ones.


I've got some difficulties to obtain a good model which is matching
with reality.
I'm using fluent 14 with a simple geometry (a flume 0.580x5x0.4m or
0.580x5m in 2d) meshed with Gambit (40 000 cells approximately).
I've put water in the flume.

I tried to introduce a turbidity current by a
velocity inlet in the left side, 0.5 m/s for velocity, 0.1 for volume
fraction of sediment, and 20% for the turbulence intensity.

(I also tried to patch a sediment suspension in the left part of the flume
(density 2500 kg/m3) with a volume fraction of 1 then 0.4, 0.2, 0.1
with water and 20% for turbulence intensity I tried all of them.
Then I've injected water by the left side, I tried different
velocities 10m/s 1m/s 0.5m/s 0.1m/s 0.01 m/s).

I used a pressure based transient model with gravity, and an implicit
Eulerian multiphase model.
For turbulence I used k-epsilon model with RNG, standard wall
functions and dispersed turbulance multiphase model.
Then I've put the granular option in the sediment phase with a
syamlal-obrien interaction with water.

When I solve this problem, I have not got the billows or just the
first one in the head but not in the body.
I posted some movies and pictures here :
https://docs.google.com/folder/d/0B7...VEk/edit?pli=1

What I want to obtain is a model with all the billows of the turbidity current like we can see on this videos for exemple : http://video.google.com/videoplay?do...40257860282305


I tried a lot of different model, parameters, turbulence options ... and I always have an imprecise model (without the billows) so I would like to understand what is wrong with my approach.


Thank you.

Julien


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