# 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

## References

1. ^ J Wei, J L Anderson, K B Bischoff Advances in Chemical Engineering, Volume 17 Academic Press (1991) ISBN 0-12-008517-8 page 44