Bent Lower Rudder Section for Twin-Propeller Wake Drag Reduction
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Solution Overview
Problem
Large rudders on twin-propeller ships cause significant drag and turbulence, negatively impacting efficiency and fuel consumption.
Innovation Solution
A rudder design for twin-propeller ships comprising an upper and lower section, where the lower section is angled or bent, reducing the exposed surface area and turbulence in the propeller wake, with a transition area at the propeller axis level, and featuring suction and pressure sides to counteract lateral lift forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If large rudders are used to generate sufficient steering lift, then steering effectiveness is improved, but drag and flow resistance increase negatively impacting efficiency and fuel consumption
Solution Approach 1:
The rudder is divided into an upper rudder section and a lower rudder section separated by a gap. The upper section is positioned above the propeller axis while the lower section is positioned below the propeller axis. This segmentation allows the rudder to utilize the propeller wake more effectively, generating sufficient steering lift with a smaller overall rudder area, thereby reducing drag and fuel consumption.
Solution Approach 2:
The invention positions the rudder sections in different vertical dimensions relative to the propeller axis. The upper rudder section operates in the region above the propeller axis while the lower section operates below the propeller axis. This dimensional arrangement allows the rudder to capture energy from both the upper and lower parts of the propeller wake, improving steering effectiveness without increasing rudder size and associated drag.
2Force
If large rudders are deployed to improve steering capability, then steering effectiveness increases, but the exposed surface area and turbulence in the propeller wake increase
Solution Approach 1:
By segmenting the rudder into upper and lower sections with a gap between them, the invention reduces the continuous surface area exposed to the propeller wake. The gap allows the wake to pass through more smoothly, reducing turbulence generation while still providing sufficient surface area in both upper and lower regions to generate the required steering lift.
Solution Approach 2:
Positioning rudder sections in different vertical dimensions (above and below the propeller axis) allows the invention to distribute the steering lift generation across different vertical zones of the wake. This reduces the concentration of turbulence in any single region while maintaining overall steering effectiveness.
3Object-generated harmful factors
If the lower rudder section is bent or angled to one side, then turbulence in the propeller wake is reduced, but the symmetry of the rudder design is changed
Solution Approach 1:
The invention deliberately introduces asymmetry by bending or angling the lower rudder section to one side relative to the upper rudder section. This asymmetric configuration is specifically designed to reduce turbulence in the propeller wake by allowing the wake to flow more smoothly past the rudder. The asymmetric shape is optimized for its specific operating condition (in the propeller wake) rather than maintaining general symmetry.
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
Reduces flow resistance and turbulence, enhancing rudder efficiency, allowing for a shorter and thinner design with lower manufacturing costs and improved steering behavior.
Implementation Method 1
a buoyancy force acting laterally in the direction of a ship's median plane, caused by an influence on the wake by a hull of the twin-propeller ship, is counteracted
Implementation Method 2
The hull influences the water flow in the area of the propellers and rudders, which are mounted laterally on the hull, causing additional turbulence in the currents, particularly in the propeller wakes
Data Source
Figure 1~2
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Figure 5
AI summary
In order to provide a rudder for ships, in particular for double propeller ships, using which the flow resistance of the rudder and the turbulence of the wake of a propeller are reduced, a rudder (100, 100a, 100b) for ships, in particular for double propeller ships (200), is proposed, wherein: the rudder (100, 100a, 100b) is designed to be positioned in the wake of a propeller (211, 212) of a ship; the rudder (100, 100a, 100b) comprises an upper rudder section (10, 10a, 10b) and a lower rudder section (11, 11a, 11b); the lower rudder section (11, 11a, 11b) is bent or angled towards one side (12) of the rudder; and precisely one lower rudder section (11, 11a, 11b) is provided.