Power number
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The power number Np (also known as Newton number) is a dimensionless number relating the resistance force to the inertia force. In engineering, this number, along with the Reynolds number, is one of the most widely employed dimensionless numbers.
The power-number has different specifications according to the field of application. E.g., for stirrers the power number is defined as:
<math> N_{p} = {M_{t}\over \rho n^{3} d^{5}} <math>
with
- Mt: torque
- ρ: fluid density
- n: rotational speed
- d: diameter of stirrer