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-   -   no converge - for Low Re Porous media seepage flow (http://www.cfd-online.com/Forums/cfx/24467-no-converge-low-re-porous-media-seepage-flow.html)

lee August 29, 2007 05:18

no converge - for Low Re Porous media seepage flow
 
Hi,

I am doing seepage flow simulation using Domain Interface method (Translational Periodicity). When pressure difference around 80Pa & flow velocity around 0.1m/s, the results agree well with the lab measured values.

However, as pressure difference decreases, e.g. delta_P=12 Pa, the simulation never converged, even though the mass flow rate fluctuated around an averaged value which is near to the experimental value (error, around 13%)

Can any one help figure out why no converge for low Re ??

I even using laminar model, still no converge.

Thanks in advance for your kind advice !

By the way, how much can we trust the averaged mass flow rate, it seems acceptable as the error is only around 13% ?


lee August 29, 2007 11:15

Re: errors from solver ...
 
+--------------------------------------------------------------------+ | ERROR #002100004 has occurred in subroutine Out_Scales_Flu. | | Message: | | The Reynolds number is outside of the range expected based on the | | Option selected for the TURBULENCE MODEL. Check this setting, | | the values of the properties, mesh scale, consistency of units | | and solution values in the input file. Execution will proceed. | +--------------------------------------------------------------------+


Glenn Horrocks August 29, 2007 18:12

Re: errors from solver ...
 
Hi,

Don't worry about the Reynolds number warning. The solver works out this reynolds number using a relation which may not have any bearing on your simulation. Do a search on this forum and you will find explanations of the exact equation it uses.

You should work out the Reynolds number of the flow based on physically relevant length, velocity and fluid property scales and decide based on that whether the flow really is laminar or turbulent.

Glenn Horrocks

lee August 31, 2007 01:12

Re: errors from solver ...
 
thanks Glenn !

it works out when using smaller local timescale factor, my problem is a steady case, and with seperated flow & also maybe due to poor mesh aorund the edge



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