Session: 06-15-01 Unsteady Hydrodynamics, Vibrations, Acoustics and Propulsion

Submission Number: 157473

Integrated Four Quadrant Propeller Maneuvering Model and Power Systems for Twin-Shaft Ships 

Traditional maneuvering models for ships typically consider first-quadrant propeller motion, where the ship operates solely in the forward direction. These models do not account for scenarios in which a ship may need to decelerate, halt, or operate in reverse, limiting their applicability and robustness. In reality, ship propulsion involves dynamic interactions across all four quadrants of propeller operation, especially during emergency or reverse maneuvers. Previous efforts by the authors have focused on a 4-DOF maneuvering model based on first-quadrant propeller curves, using a 1/49 scale model of the Office of Naval Research (ONR) Tumblehome vessel, equipped with twin propellers and twin rudders in calm water. This maneuvering model was validated against experimental data and CFD simulations to demonstrate the model’s accuracy in predicting ship dynamics under forward motion. 

This paper presents an extended maneuvering model for twin-shaft ships that integrates four-quadrant propeller dynamics and power system dynamics to simulate both forward and astern operations, including crash stop and astern maneuvers. Building on the earlier combined maneuvering and seakeeping model for the ONR Tumblehome vessel, this work incorporates detailed propulsion equations to capture ship dynamics across all four quadrants of propeller operation. The four-quadrant propeller model is derived using experimental data from open-water tests of propellers similar to the one used on the ONR Tumblehome vessel, as the specific propeller details are not publicly available. The study relies on the well documented Wageningen B-series propellers, which provide extensive data for modeling propeller performance in all four quadrants. The extension to astern and crash stop conditions allows for a more comprehensive assessment of ship performance in emergency and reverse operations, enhancing the understanding of transient responses such as sudden deceleration or astern motion. 

Furthermore, the maneuvering model is integrated with a power systems model to investigate the interactions between hydrodynamics, propulsion, and power generation, with a particular focus on propeller-hull-engine dynamics. Previous efforts have determined the torque and thrust generated by the propellers, as well as the speed and trajectory of the vessel for a given RPM. This model has now been extended to account for the rotational speed of the shaft and the torque generated by the engine in response to power commands. The extension compares the torque generated by the propeller during a maneuver against the engine's power output and factors for discrepancies. 

Additionally, the integration accounts for the dynamics of the propeller and shaft system, including the added inertia and damping effects due to the water interacting with the propeller. These factors are incorporated to accurately represent the behavior of the propulsion system, thereby enhancing the robustness of the model. This more comprehensive representation of the propulsion system improves the overall fidelity of the maneuvering simulations, particularly in transient conditions. The practical applicability of the integrated model is evaluated through traditional maneuvers such as straight-line, turning circle, and zigzag tests. Results are compared with available experimental data to validate the accuracy and reliability of the integrated model across a wide range of operating conditions.

Presenting Author: Omotayo Oladele Virginia Tech

Presenting Author Biography: Omotayo is a doctoral candidate at Virginia Tech, specializing in the hydrodynamics of surface and underwater vessels. His current research examines the asymmetry in propeller loads during maneuvering in water for twin-shaft ships, with a particular focus on the propulsive performance differences between the port and starboard sides of the vessel.