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twray August 21, 2012 12:15

UDF for turbulence models
 
Hello all,

Can a completely new turbulence model be implemented with a UDF? Specifically I'm interested in the zeta-f, v2-f, and RSA models.

My understanding so far is that it is possible to do the zeta-f and v2-f models because they also use the original k-epsilon transport equations. However, in the RSA model, k and epsilon have algebraic relations and are not defined by transport equations. Since this is a different implementation of k and epsilon I'm unsure if the use of a UDF is possible for the RSA model.

Any insight is appreciated,
Tim

eng_s_sadeghi August 22, 2012 06:34

You may could model it by entering sources, changing variables in turbulent models panel. Or, write two user defined scalars for turbulent parameters.

pratikddhoot March 24, 2016 14:48

Quote:

Originally Posted by eng_s_sadeghi (Post 378138)
You may could model it by entering sources, changing variables in turbulent models panel. Or, write two user defined scalars for turbulent parameters.

Hi,

I am new to using UDF but I wanted to build a zero equation turbulence model and use it in FLUENT. Can you help me with this?

alinik October 26, 2016 20:09

Quote:

Originally Posted by eng_s_sadeghi (Post 378138)
You may could model it by entering sources, changing variables in turbulent models panel. Or, write two user defined scalars for turbulent parameters.

Hi,

I am struggling with implementing a new intermittency transport equation that I have derived in fluent and you seem to be a very knowledgable person in this regard.

I understand that I have to use UDS. But I am not sure how I should change the value of intermittency inside the UDF? I am guessing that I have to use DEFINE_ADJUST for that reason but then again I do not know how to access (read) the value of intermittency from the solver.

Also two other problems:
1) For adding source terms to intermittency can I simply add it through the sources tab in the fluids window or it has to be done through UDF as well.

2) Diffusion term: This is the part that I literally do not have any clue about. Any help is much appreciated.

Sorry if my problems sound childish to you. I have been using CFX for quite a while and I know how to work with that but I am quite a newbe in fluent.

I would really really appreciate it if you can help me with that. I am lost and do not have much time.

Thanks a lot,

Ali

mahipal parmar October 29, 2016 10:13

energy residual convergence problem
 
hello frnds..
give the suggestion to e for my problem..

my analysys is double pipe heat exchanger with two different turbulator inserts.
and i used
counterflow arrangement
turbulent k-epsilon(2 eq) stand wall fun.
hot inlet-413 k,1.3 kg/s
cold inlet-298k,1.3 kg/s
solution scheme-pressure-velocity based
simple,
second order
my problem is..during my solution in fluent cfd energy residual is not converged and its value increases and reach to 1e+08..
plz gys give me the suggestion..
thanks in advance

alinik October 29, 2016 12:56

Quote:

Originally Posted by mahipal parmar (Post 623405)
hello frnds..
give the suggestion to e for my problem..

my analysys is double pipe heat exchanger with two different turbulator inserts.
and i used
counterflow arrangement
turbulent k-epsilon(2 eq) stand wall fun.
hot inlet-413 k,1.3 kg/s
cold inlet-298k,1.3 kg/s
solution scheme-pressure-velocity based
simple,
second order
my problem is..during my solution in fluent cfd energy residual is not converged and its value increases and reach to 1e+08..
plz gys give me the suggestion..
thanks in advance

This does not fall under the topic of this thread. Please see other threads focusing on obtaining convergence in fluent.
My guess is your mesh or your BC is wrong.

mahipal parmar November 1, 2016 02:14

energy residual convergence problem
 
my boundary condition is:
hot inlet-413k,1.3 kg/s
hot outlet-pressure based
cold inlet-298k,1.3 kg/s
cold outlet-pressure based
all wall boundarries except outer pipe are copper material.
and outer pipe is of aluminium.
inserts wall are also of copper.
mesh quality:
min orthogonal quality-1.23155e-01
maxi. aspect ratio- 3.34364e+01

and again i dont get convergence in energy residual it increasing and goes toward... e+8.
can any one help me..
thanks in advance frnds.


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