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usker July 1, 2008 20:05

scalar meaning
What is the meaning of "Void Fraction" scalar in the scalar data output panel of Star-CD?

Thank you

Polly Eda July 4, 2008 06:10

Re: scalar meaning
It's the fraction of the volume of the cell that is occupied by the disperesed phase in an euler-lagrange calculation.

usker July 4, 2008 21:26

Re: scalar meaning
Hi Polly Eda, thank you for the help.

Does it mean that, for example, if the injection pressure of the liquid is increased the void fraction will be higher at higher injection pressures, because the liquid material will be more dispersed. And since euler-lagrange calculation takes into account coupled two-phase flow, at the start of injection, before atomization occurs, the void fraction value will be lower, because there is a liquid phase only, and as the spray progresses the void fraction will increase, because the liquid will be more dispersed.

Thank you very much

Andrea July 6, 2008 11:26

Re: scalar meaning
Hi usker,
it's difficut to say how will be the void fraction in general when varying the injection we're speaking of a scalar that has a value for each cell!
Generally higher injection pressure means higher cone angle and so more dispersed liquid phase in your combustion chamber...I think that in general you're right, but only considering the mean void fraction of the cell occupied by the spray at a particular crank angle.

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