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-   -   Need help: 7 times more Mass Flow out than in (http://www.cfd-online.com/Forums/star-ccm/103240-need-help-7-times-more-mass-flow-out-than.html)

simonart7 June 14, 2012 11:31

Need help: 7 times more Mass Flow out than in
 
Hello!

I want to simulate the Battery-Cooling of a formula student car.
I implemented a radial fan, like in the rigid body motion tutorial

Inlet: Velocity (15m/s)
Outlet: Pressure
Implicit unsteady
Ideal Gas
K-Epsilon Turbulence
Gravity
Three Dimensional
Surface Remesher
Polyhedral Mesher
Prism Layer Mesher (2)

If I try Coupled Energy, the outgoing Mass Flow is going to be 7 times bigger than the incoming Mass flow.
It is still increasing.

Please help me!

Enjoy it.
Have a nice day!

( Please excuse my bad English)

simonart7 June 14, 2012 11:37

How can I put pictures in here?

simonart7 June 14, 2012 11:38

http://www.cfd-online.com/Forums/dat...BJRU5ErkJggg==

husker June 15, 2012 03:33

Hi,

Try to monitor mass flow rate with manual reports of density and velocity.

Regards

abdul099 June 15, 2012 15:42

A mass flow report at each inlet and outlet should be fine to judge the mass imbalance.
How long did you run it? What about your time step size? Is it small enough? What about the convective courant number? Residuals? How does the flow field look like, is it reasonable?
In my experience, the coupled solver needs a long time until a reasonable flow field has established. So although CD-adapco recommends the coupled solver when ressources are no issue, I would stick to the segregated solver when there are no high mach numbers involved. Or at least try to initialise as good as possible.

When the setup is right and you run it long enough, the coupled solver will give you the same mass flow in and out for sure (assumed, you're looking on average values over a long enough period).


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