I want to know the operations
 

I want to know the operations needed for micro-gravity simulation.

Thanks.

That's a painfully general que
 

That's a painfully general question. It's general enough that there isn't a useful answer, besides referring you to the User's Guide.

Since the User's Guide doesn't explicitly refer to micro-gravity conditions, the following may be useful as well:

Most OpenFOAM solvers do not include a gravitational force, and thus are valid for micro-gravity flows without any changes. For the solvers which do include gravity, there is usually a way to set the direction and strength of the gravity vector; for instance, in the Breaking-Dam example from the user's manual, the gravity force vector is set in the "environmentalProperties" file in the "constant" subdirectory of the case directory. Other solvers will have the gravity vector stored in a similar location. To do a micro-gravity simulation, simply change the force vector's magnitude to zero (or the appropriate very small number).

Beyond that simple change, everything else in the User's Guide will apply directly.