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-   -   Mass flow rate at outlet (http://www.cfd-online.com/Forums/fluent/34873-mass-flow-rate-outlet.html)

Leon October 18, 2004 13:54

Mass flow rate at outlet
 
Is there a way to specify a mass-flow boundary condition (e.g. mass flow rate at outlet)? The inlet mass-flow rate is out of the question due to many considerations (compressibility effects with Mach number around 0.8 being one of them). Imagine a vacuum cleaner for which mass flow rate is known and you are required to estimate its efficiency in terms of what area it covers and how much of dust it sucks in.

SAM October 18, 2004 17:07

Re: Mass flow rate at outlet
 
yes it is

/define/boundary-conditions/target-mass-flow-rate-settings>

there are two ways to define it . please refer to fluent users guide for description

regards


Leon October 19, 2004 10:28

Re: Mass flow rate at outlet
 
Thank you, SAM. It seems fairly easy indeed. Although a further step is required - an unsteady targeted mass flow rate at outlet. I have tried to hook up a udf procedure normally used for mass-flow_inlet and failed :(.

SAM October 19, 2004 10:36

Re: Mass flow rate at outlet
 
i have no idea for udf and unsteady flow fenomena

:(


Leon October 19, 2004 11:10

UDF with Targeted mass flow rate
 
1) A scalar was defined.

Then: 2) define -> boundary conds -> pressure ... [standard points] and:

Use profile for scalar value [no]? yes

Profile name [""] "udf"

data name [""] suck_in_rate

!!! And then it prompts: specify targeted mass-flow rate !!! What am I supposed to do?


Chetan Kadakia October 21, 2004 20:25

Re: UDF with Targeted mass flow rate
 
If you know the mass flow at the outlet, just call it a massflow-inlet, but specify the direction to exit at the outlet.

Chetan Kadakia October 21, 2004 20:31

Re: Mass flow rate at outlet
 
And in that case, you can use a 0 pressure inlet too, since you are sucking in from atmospheric conditions. I use that all the time: pressure inlet at inlet, and mass flow inlet for the outlet.

Leon October 22, 2004 07:36

Re: UDF with Targeted mass flow rate
 
Good suggestion. Thanks. Tried it in the first place though. Convergence was pretty awful. And it never worked with the coupled solver.


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