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-   -   mass flow rate computation in fluent (http://www.cfd-online.com/Forums/fluent/45162-mass-flow-rate-computation-fluent.html)

Kishore June 26, 2007 01:53

mass flow rate computation in fluent
 
hi .. I ran a simulation for an inverted Y - shaped duct which has one inlet and two outlets. though the exit areas are equal , the duct is unsymmetrical , that is the geometry is such that the 2 exits have different pressure and velocity distributions. while post processing in fluent, i used Report>Surface Integrals..>mass flow rate , and it showed equal mass flow on both outlets.

I feel it is physically impossible. with different pressure and velocity distributions obviously the mass flow should differ for the two exits.

Now is this a problem with the computation using fluent or is it something else? kindly help me out in this regard.

Expecting your valuable suggestions, Kishore

ritmat June 26, 2007 03:15

Re: mass flow rate computation in fluent
 
if both pressure at the outlet are equal you shouldnt get same mass flow, but in this case i dont know why

prakash June 26, 2007 05:31

Re: mass flow rate computation in fluent
 
if it is compressible flow it might be possible to get same mass flow rate at the both outlets.

1. otherwise you can check the volume flow rate at the outlets and compare the results. 2. check the pressure at the junction and outlets and estimate the flow. this can give idea about results.


Neil June 26, 2007 09:35

Re: mass flow rate computation in fluent
 
Have you applied a surface monitor at the exits to see whether mass flow rate is constant during iterations. A converged solution does not always mean the mass flow rates have settled to steady values.

bashu June 26, 2007 11:30

Re: mass flow rate computation in fluent
 
if you use outlet bc, fluent split the flow between the outlets. try pressure outlet bc.

Rola June 27, 2007 03:53

Re: mass flow rate computation in fluent
 
Hi

I think your problem is in the dimension you have a large dim from the main to the dividing two legs. try to decrease this length and you will find your target. I studied this in what we call fluidics.

I made a VB program to simulate this case but on contrary this didn't divided equal just like you because this length I'm talking about was very short

Need to hear what had happen from you !!

Rola


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