From impeller-specific power curves (Rushton, etc.): [ P = N_p \cdot \rho \cdot N^3 \cdot D^5 ] Typical Np values (turbulent regime):
Torque is derived from the absorbed power and rotational speed:
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$$P = N_p \cdot \rho \cdot N^3 \cdot D_i^5 / (16 \times 10^4) \text h.p.$$
