Marine Propeller Open-Water Thrust & Power Calculator
Calculate propeller advance coefficient (J), thrust coefficient (KT), torque coefficient (KQ), open-water efficiency, and delivered power via ITTC standards.
Propeller Geometry & Operating Speeds
Water Density & Hub Submergence
Thrust, Torque & Delivered Power
| Advance Coefficient (J): | -- |
| Thrust Coefficient (KT): | -- |
| Torque Coefficient (10 × KQ): | -- |
| Shaft Torque (Q): | -- kN·m |
| Delivered Shaft Power (PD): | -- kW |
| Effective Thrust Power (PT): | -- kW |
| Keller Cavitation Min EAR: | -- |
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Frequently Asked Questions
What is the propeller advance coefficient J and why is it crucial?
The advance coefficient J = Va / (n * D) is the non-dimensional kinematic parameter describing the ratio of propeller forward axial speed through water (Va) to propeller blade tip circumferential rotational speed (n * D). Open-water propeller performance curves universally plot thrust coefficient KT, torque coefficient KQ, and efficiency eta_0 against J.
How does the Keller cavitation criterion determine the required blade area ratio (EAR)?
The Keller formula calculates the minimum expanded blade area ratio (AE/A0) needed to avoid excessive sheet cavitation based on total thrust load, ambient hydrostatic pressure at the shaft centerline, and blade count. If propeller blade loading exceeds the Keller threshold, low pressure on the blade back causes seawater to flash into vapor cavities, causing pitting erosion, loss of thrust, and severe hull structural vibrations.
What is the relationship between ship speed (Vs) and advance velocity (Va)?
Because a ship drags a boundary layer of water along with it as it moves, the water entering the propeller disk is moving forward relative to still water. The effective speed of water into the propeller disk is the advance speed Va = Vs * (1 - w), where w is the Taylor wake fraction (typically 0.15 - 0.35 for single-screw displacement hulls).