Rotating Arm Simulation
 

Hi everyone,

I am trying to simulate a sphere rotating about a point, submerged in water. I have defined a domain around the sphere as fluid. Now I proceeded to solve for the forces etc. on the sphere in the following two ways:

Approach 1:
At the Inlet, defined the fluid velocity as angular, of the appropriate magnitude, and with the apt rotation axis. All this in absolute terms.

Approach 2:
At the Inlet, defined the fluid velocity as angular, of the appropriate magnitude, and with the apt rotation axis. Also, defined the sphere as rotating about the rotation axis. All this in absolute terms.

Could you please help me out over here and tell me which approach is correct? Would all the extra terms due to the circular motion (centrifugal force etc) be included in approach 2 and not 1? Please can anyone help me out with this?

By approach 2, wouldnt the viscous force increase? Because the velocity of the fluid relative to the sphere will increase and become the (velocity of the sphere + Tangential velocity of the fluid) right? So does that make the first approach correct? Does it take into account the centrifugal forces too?

Thank you in advance..