Power number


 * For Newton number, see also Kissing number in the sphere packing problem.

The power number Np (also known as Newton number) is a commonly used dimensionless number relating the resistance force to the inertia force.

The power-number has different specifications according to the field of application. E.g., for stirrers the power number is defined as:


 * $$ N_\mathrm{p} = \frac{P}{\rho n^{3} D^{5}} $$

with
 * P: power
 * ρ: fluid density
 * n: rotational speed in revolutions per second
 * D: diameter of stirrer