Transverse Water Jet Thruster Arrangement and Thrust Creation
(a) Arrangement of a Transverse Water Jet Thruster:
A transverse water jet thruster is a maneuverability-enhancing device typically mounted on the sides of a vessel below the waterline. Here’s a breakdown of its arrangement:
- Intake: A submerged opening in the hull that allows water to enter the system. It’s often protected by a grating to prevent debris from entering.
- Water Pump: A centrifugal pump powered by an electric motor or a hydraulic motor. It draws water in through the intake and pressurizes it.
- Delivery Duct: A sturdy pipe or channel that carries the pressurized water from the pump to the thruster unit.
- Transverse Thruster Unit: This underwater unit houses a directional nozzle and other components.
- Directional Nozzle: A movable nozzle within the thruster unit that can be directed to port or starboard. It controls the direction of the water jet for maneuvering.
- Outlet: The opening at the end of the directional nozzle where the high-pressure water exits the thruster unit.
(b) Thrust Creation in a Water Jet Thruster:
Water jet thrusters operate based on Newton’s Third Law of Motion (for every action, there is an equal and opposite reaction). Here’s how thrust is created:
- Water Intake: The pump draws in water through the intake at the bottom of the vessel.
- Water Acceleration: The pump impeller rapidly accelerates the water, converting kinetic energy into pressure.
- High-Pressure Flow: The pressurized water is then channeled through the delivery duct to the thruster unit.
- Directional Nozzle Control: The operator controls the directional nozzle within the thruster unit, directing the water flow to port or starboard.
- Jet Force: The high-pressure water exiting the nozzle at high velocity creates a powerful jet force in the opposite direction of the water flow (per Newton’s Third Law).
- Transverse Thrust: This jet force pushes against the surrounding water, generating a lateral thrust force perpendicular to the vessel’s direction of travel. By directing the nozzle port or starboard, the thruster can create a pushing force in the desired direction, aiding in maneuvering during docking, station keeping, or low-speed operations.
Additional Considerations:
- Reversible Thrust (Optional): Some water jet thruster designs may incorporate a reversing mechanism within the directional nozzle. This allows for reversing the water flow direction, creating a braking effect or thrust in the opposite direction for even more precise maneuvering control.
- Gimbal Mounting (Optional): In some installations, the thruster unit might be mounted on a gimbal, allowing for some angular movement of the nozzle. This provides additional flexibility in directing the water jet, especially on vessels with significant hull curvature.
Overall, transverse water jet thrusters offer a powerful and efficient way to enhance a vessel’s maneuverability by utilizing a pump, directional nozzle, and the principles of fluid mechanics to generate a controllable lateral thrust force.