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July 2, 2008, 11:08 
how to define restituition coefficient using UDF?

#1 
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hi, everyone~~~
in many simulations for gassolid flows, the restituition coefficient (e) is always treated as a constant. But some researchers considered that e was the function of voidage, so I want to know how to modify the restitution coefficient using UDF. I check the help files provided by Fluent, but cannot find the solution. Could anybody help me? thanks very much~~~~ 

July 2, 2008, 11:24 
Re: how to define restituition coefficient using U

#2 
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I'm not sure but try
DEFINE_EXCHANGE_PROPERTY Paul 

July 2, 2008, 21:45 
Re: how to define restituition coefficient using U

#3 
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thanks~~~
which file in src can we find the definition of restitution coeff.? 

July 2, 2008, 22:58 
Re: how to define restituition coefficient using U

#4 
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I don't know where in the src could you find the definition of the restitution coefficient.
In GUI the restitution coefficient could be changed at Phases>Interactions>Collisions. In a UDF you could change the restitution coefficient by changing the model of interactions in phases. Anyway this is how I would try to define a variable restitution coefficient: The interaction drag between two solid phases is modeleted in Fluent by symlalobriensymmetric, this model uses the constant restitution coefficient provided by you in GUI at Collisions. Pick the relations for this model, implement the model in a UDF as a DEFINE_EXCHANGE_PROPERTY and use your relation for the restitution coefficient. Then you could hook your function instead of the classic symlalobriensymmetric. Paul 

July 7, 2008, 00:38 
Re: how to define restituition coefficient using U

#5 
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Hi,
An alternative is to rewrite the whole REFLECT particle boundary condition model using DEFINE_DPM_BC (can be foudn in the UDF manual). The example given in the UDF manual corresponds to the REFLECT condition. You can then add your mathematical description of the restitution factor in the UDF. Might or might not be the best way. Do let us know. Best regards, Woo 

July 8, 2008, 22:46 
Re: how to define restituition coefficient using U

#6 
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thanks, but the model I use is EulerianEulerian, not DPM


July 9, 2008, 23:26 
Re: how to define restituition coefficient using U

#7 
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can anyone help me? thanks


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