Tugboat Stern Stabilizing Device for Vortex Control
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Solution Overview
Problem
Watercraft, particularly tugboats, experience instability and controllability issues due to the formation of Karman vortex streets in the stern area, especially with round or pointed stern designs, which complicates vortex shedding and affects yaw stability and steerability.
Innovation Solution
A stabilization device with flow-influencing elements is integrated into the stern area of the hull, featuring a protruding body with a flow-guiding surface that extends vertically along a theoretical arrangement line, disrupting vortex formation and reducing counter-rotating vortex pairs, thereby altering the shedding frequency and improving yaw stability and controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a rounded or pointed stern design is used, then the hull shape is streamlined and aesthetically pleasing, but Karman vortex streets form causing severe instability and uncontrollability
Solution Approach 1:
The invention converts the harmful Karman vortex street phenomenon into a beneficial effect by deliberately inducing controlled flow separations at specific locations on the hull. These controlled separations disrupt the formation of dangerous vortex streets while maintaining the aesthetic rounded stern design, thus transforming a harmful flow phenomenon into a stabilizing mechanism
Solution Approach 2:
The invention introduces intermediate flow-separating elements (such as fins or protrusions) at strategically chosen locations on the hull. These intermediaries act as mediators between the streamlined hull shape and the water flow, preventing direct formation of Karman vortex streets by creating alternative flow paths and separation zones
2Reliability
If symmetric fins are arranged on both sides of the central longitudinal plane, then yaw stability is improved, but the construction becomes very complex
Solution Approach 1:
The invention employs asymmetric flow control elements positioned at specific non-symmetric locations on the hull. By strategically placing single asymmetric elements or unequal pairs of elements, the patent achieves effective vortex suppression and stability improvement while avoiding the complexity of symmetric fin arrangements on both sides of the hull
3Reliability
If guide plates are added to a transom stern, then flow continuation is achieved, but the device complexity increases
Solution Approach 1:
The invention applies flow control measures locally at specific critical zones on the hull rather than adding comprehensive guide plate systems to the entire transom stern. By targeting only the essential flow separation points with minimal localized elements, the patent achieves flow continuation while keeping the overall device complexity low
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 prevents the formation of Karman vortex streets, enhancing the controllability and yaw stability of watercraft with minimal impact on ship resistance and allowing for easy retrofitting, regardless of the hull design.
Implementation Method 1
Under certain flow conditions, a Karman vortex street is created behind the hull, particularly in the stern area. The resulting vortices, with opposite directions of rotation on the sides of the hull located on either side of the central longitudinal axis, detach from the hull as the flow coefficient increases.
Implementation Method 2
This separation results in severe instabilities when traveling straight ahead. Particularly in designs with a rounded stern, the location and size of the flow separations are often unpredictable
Data Source
Figure 1a~1c
Figure 2a~6b
AI summary
The invention relates to a water vehicle (1), comprising a ship body (1) and a stabilizing device arranged in the stern region (3). According to the invention, the stabilizing device (8) has, on each of both sides of the center longitudinal plane (MLE) of the ship body (2), at least one flow-influencing element (9.1, 9.2), which lies flush against the ship hull (7) and which, examined proceeding from a base (B) on the ship bottom (6), extends over at least a partial region of the ship hull (7) in the height direction along a theoretical arrangement line (A1, A2) and which has an incident flow surface (10.1, 10.2) formed around the arrangement line (A1, A2).