[ehsan1363]

Good day for everyone!
I am modeling a multiphase steady state flow on a propeller with free surface model. i have two domains: a rotating(with propeller) and a stationary domain.propeller is assumed to operate in depth of 130 cm.
According to the picture below,the gravity vector is Z and axis of rotation is X. But i see an error at the beginning of the solution which says that the gravity vector must be aligned with the axis of rotation.But i'm confused, because i did not understand it.for a free surface flow involved a rotating propeller near the free surface i do not know why gravity vector can not be Z.