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svenki7 April 18, 2013 10:31

Problem during Residence time distribution in fluent

I am doing "Residence Time Distribution" by pulse input method in fluent.But
i am getting tracer (area weighted average) concentration greater than 1. I did experiments also. I compared with simulation results with experimental. The simulation results are less than 5 time the experimental results. In simulations, sum of tracer concentration is greater than 1. The simulation results are (mean residence time) is less than theoretical residence time.

Can anybody help me please.

Thanks in advance

billwangard April 19, 2013 15:46

Residence Time in FLUENT
Easy way to do residence time in fluent (without particles):

1. Define a User-scalar
2. Set its diffusivity to very small: 1E-11 or so should work
3. Use default flux vector and unsteady term

Compille the following UDF and hook it to the SOURCES for the UDS:

#include "udf.h"
dS[eqn] = 0;
return C_R(c,t);

Set the UDS to 0 at the inlet.

Then, when you solve, the UDS will have the value of residence time.

Bill Wangard
Engrana LLC

svenki7 April 20, 2013 03:31

Problem during Residence time distribution in fluent
1 Attachment(s)
Thank for your reply Mr.Billwangard,
I am newer to UDF that why i choose the pulse method. I don't much about UDF.I attached my geometry.The above one is my geometry. Its converging-converging end is inlet and one end is outlet. Total length of my channel is 68 mm.The Inlet dia 1 mm

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