Propeller Advance Ratio J
Dimensionless speed ratio J = V_A / (n·D) - the horizontal axis of every propeller open-water chart.
Advance ratio J
0.545 -
Formula, assumptions, and limits
V_A = V(1 − w) is the advance velocity (lower than ship speed because of the wake). J typically 0.5–0.9 for merchant ships; lower J = heavier loading, higher KT and KQ.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Advance velocity at propeller disk | m/s | V·(1−w) | |
| Shaft revolutions per second | rev/s | rpm/60 | |
| Propeller diameter | m | propeller drawing | |
| Advance ratio | - | result |