Hello,

I am modeling an object falling into water. The air is compressible and the water is incompressible. Under Specified Operating Density, should I be inputting the density of air, or zero?

One section of the Fluent manual says to input the density of the lowest phase. The section under the inclusion of body forces says that if any phase is compressible, I should input zero.

However, when I do so, I get very different results. The drag curve is very oscillatory for operating density of zero, and it is not for an operating density of air. Which is more accurate?

Thanks, Andrew Wick

Try enabling the "floating operating pressure" option and simply don't specify any operating density in the operating conditions panel.

Hope it helps

Edi.