I am trying to model a system in which cubes of about 2 cm in size are floating in a circular water thank of about 30 cm in diameter. The cubes move around under the influence of the fluid flow induced by four inlets that point toward the center of the tank, and are located at the positions $0$, $\pi/2$, $\pi$, and $3\pi/2$. The flow velocity ranges from 0 to 10 cm/s, with an average velocity around 6 cm/s.
My questions are the following:
- What would be the Reynolds number of the system? In particular, should I take as characteristic length the size of the cubes, or that of the tank?
- For such a system, what is the limit Reynolds number for the turbulent regime?
- What would be the correct form of the drag force, and do you intuitively think that the orientation of the blocks is negligible from a drag coefficient point of view?
Thanks for your help!