Zero Gradient for Volume fraction at inlet
 

Hi, Could some answer the following question for me. Thanks so much.

What does the 'zero gradient' option for the Volumer Fraction mean for a multiphase flow simulation while specifying the inlet boundary condition?

Regards, Kushagra

I was baffled by this too and just dug it up from the user's guide.


14.2.3.2.*Fluid Values: Volume Fraction
Volume Fraction > Option can be set to:
Value
If set to Value, you must enter a numeric value or an expression for the volume fraction for each fluid. Note that the total volume fractions of the fluids in the list box must be equal to 1.
Zero Gradient
The volume fraction can also be set to Zero Gradient, which implies that the volume fraction gradient perpendicular to the boundary is zero. This setting can be useful for subcritical free surface flow when the free surface elevation is specified (via a pressure profile) at the outlet.