Power number

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

{{For|use in arithmetic and algebra|Exponentiation}}

The power number N_p (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:

:$N\_\backslash mathrm\{p\}\; =\; \backslash frac\{P\}\{\backslash rho\; n^\{3\}\; D^\{5\}\}$

with

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