Quasi-propulsive coefficient η_D = η_H × η_O × η_R - the ratio between effective power (EHP) and delivered power (DHP).
Formula
$$ \eta_D = \eta_H \eta_O \eta_R = \frac{1-t}{1-w} \eta_O \eta_R $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $t$ | Thrust deduction | - | ship-propeller interaction |
| $w$ | Wake fraction | - | Taylor or Harvald |
| $\eta_O$ | Open-water efficiency | - | propeller chart |
| $\eta_R$ | Relative rotative efficiency | - | model test |
Sources
- Rawson & Tupper Vol 2.