*jeff*

The feedback value usually has to be pretty high. Impulse force to counteract the mass of the object that you wish to float. Try values between 50-2000 if the sim fits on the default Houdini grid.

This has actually changed for H12, since the FLIP Solver now takes into account fluid density (which defaults to water = 1000) when solving for pressure, which in turn scales the feedback force. The H11 solver was equivalent to treating fluid density as 1.

From the Feedback Scale parameter doc:

A scale factor used in applying feedback forces to other objects. A value of zero prevents any feedback from occurring.

The default RBD object has the same density as water, so to balance with the default fluid density a value of 1 should be used.

Also, the “DensityViscosity” FLIP example shows a combination of variable density, variable viscosity, and a floating RBD object.