Non-dimensional torque KQ = Q / (ρ·n²·D⁵). Open-water charts typically tabulate 10·KQ to keep KQ and KT on the same chart scale.
Formula
$$ K_Q = \frac{Q}{\rho \cdot n^2 \cdot D^5} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $Q$ | Shaft torque | N·m (input as kN·m) | torsionmeter |
| $ρ$ | Sea-water density | kg/m³ | 1025 |
| $n$ | Shaft rev/s | rev/s | rpm/60 |
| $D$ | Propeller diameter | m | drawing |
| $KQ$ | Torque coefficient | - | result |
Sources
- Carlton - Marine Propellers and Propulsion.