The Reynolds number Re for a sphere moving through a fluid is given as Re = ÏvD/μ, where D is the sphere diameter, Ï is the density of the fluid, μ is the viscosity of the fluid, and v is the speed of the sphere.
Here the exponent is an integer.
At low Reynolds number Re, the drag coefficient for a moving sphere varies with Re as caRe.
Here a is an integer.