What is/are the advantage(s) of a cyclone separator?

The product of the cross-sectional area of flow in the river and the average velocity of flow is known as _________.

As compared to a laminar flow, the boundary layer thickness in a turbulent flow is:

A body is fully submerged in a surrounding fluid. If the flow speed corresponds to a ratio U√(E / ρ) ≤ 0.3 (incompressible flow) and change in density is insignificant, which forces/numbers can be neglected in dimensional analysis to derive drag and lift coefficients?