Question: A thin flat disc of diameter D is rotated about a spindle through its center, at a speed of ω radians per second, in a fluid of density ρ and kinematic viscosity ν. Show that the power P needed to rotate the disc may be expressed as
Note: For (a) solve in terms of the index of ν and for (b) solve in terms of the index of ω. Further, show that ωD2/ν, PD/ρν3, and P/ρω3D5 are all nondimensional quantities.