Boat Propulsor Plate with Holes for Sink Vortex Attenuation
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Solution Overview
Problem
Duct-type boat propulsors generate a large vortex, known as the 'sink vortex,' which affects the maneuverability of the hull by causing it to move diagonally sideways instead of laterally, despite intended maneuvering commands.
Innovation Solution
A boat propulsor design featuring a duct with a rotatable propeller and an upper plate extending from the duct, containing multiple holes that attenuate water streams, reducing the formation and impact of the sink vortex, thereby improving maneuverability. The plate is strategically positioned above the rotation axis, curved, and symmetrically arranged to minimize weight and resistance, and its holes are designed to merge vortices effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a duct-type boat propulsor is used, then propulsion efficiency is improved, but maneuverability deteriorates due to sink vortex generation
Solution Approach 1:
The plate is divided into multiple segments with holes arranged in specific patterns, creating segmented flow paths that break up the formation of large-scale vortices while maintaining overall propulsion efficiency
Solution Approach 2:
The plate with holes acts as an intermediary element between the duct and the water, modifying the water stream flow to prevent sink vortex formation without directly interfering with propeller operation
2Ease of operation
If a plate with multiple holes is added to the duct, then maneuverability is improved by attenuating water streams, but device complexity increases
Solution Approach 1:
The plate with holes serves multiple functions simultaneously: it attenuates water streams to prevent sink vortex formation, maintains structural strength, and can be integrated with existing duct designs, making it a multi-functional component that addresses multiple problems at once
Solution Approach 2:
The plate is designed with a porous structure containing multiple holes, allowing water to pass through while attenuating the water streams and preventing vortex formation, rather than using a solid barrier that would be more complex
3Object-affected harmful factors
If the plate extends from the entire circumference of the duct, then sink vortex attenuation is maximized, but weight increases
Solution Approach 1:
The plate is positioned at specific locations on the duct (upper portion or upper half circumference) rather than extending from the entire circumference, providing sink vortex attenuation where it is most needed while minimizing unnecessary weight
4Stability of the object's composition
If the plate is asymmetrically shaped, then flow variations are addressed, but unequal left-right forces are generated
Solution Approach 1:
The plate is designed with asymmetric hole arrangements or shapes that specifically address flow variations on different sides of the duct, creating balanced forces by compensating for asymmetric flow conditions rather than using a symmetric design that would not address the asymmetric problem
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively decreases or prevents the reduction in maneuverability caused by the sink vortex, allowing the boat to move laterally with high accuracy and reducing weight and resistance, while maintaining structural strength against downward forces.
Implementation Method 1
Water streams passing around and along the duct are attenuated as the water streams pass through the plurality of holes in the plate. Thus, the boat propulsor is able to decrease or prevent a reduction in maneuverability of the hull caused by the sink vortex generated in a vicinity of the duct.
Data Source
AI summary
A boat propulsor includes a duct, a propeller in the duct and rotatable around a rotation axis extending along an axial direction of the duct, and a rotator to rotate the propeller. An upper portion of the duct includes a plate extending from the duct in the axial direction and including holes. Water streams passing around and along the duct are attenuated as the water streams pass through the holes in the plate.