Inflatable Liferaft Drag Reduction via Segmented Floatation Tubes
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Solution Overview
Problem
Large inflatable liferafts face difficulties in moving through water due to high drag forces, making them impractical for towing at required speeds, especially when loaded with passengers, as they become inefficient and difficult to maneuver.
Innovation Solution
The design incorporates non-rigid floatation tubes with optimized spacing, drag-reducing end shapes, water-ablative coatings, and strategically placed propulsion means to reduce drag and enhance mobility, along with seating arrangements on the air side for stability and buoyancy, allowing for a higher capacity and larger size while maintaining mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the floatable liferaft is increased in size to carry more passengers, then the passenger capacity is improved, but the drag force from water increases making it impossible to move through water with sufficient speeds
Solution Approach 1:
The floatable liferaft is divided into multiple separate floatation tubes instead of using a single large rigid structure. This segmentation reduces the overall drag coefficient by allowing water to flow between the tubes, while still providing sufficient buoyancy for increased passenger capacity. The non-rigid nature of individual tubes further reduces drag compared to a solid structure of equivalent size.
Solution Approach 2:
The patent employs non-rigid floatation tubes made from flexible materials instead of rigid structures. These flexible shells deform with water flow, significantly reducing form drag and turbulence. The thin-film construction allows the structure to adapt to hydrodynamic pressures while maintaining buoyancy, enabling larger size without proportionally increasing drag forces.
2Quantity of substance
If the floatable liferaft is increased in size to match vessels with increasing passenger capabilities, then the capacity is improved, but the force required for towing increases requiring large engine powers
Solution Approach 1:
By segmenting the liferaft into multiple independent floatation tubes, the patent reduces the overall drag coefficient, which directly lowers the power required for towing. The segmented structure creates less resistance to water flow compared to a solid structure of equivalent capacity, reducing the engine power needed to achieve required towing speeds.
Solution Approach 2:
The patent changes the physical parameters of the floatation structure by using non-rigid, flexible materials with optimized geometry. This parameter change reduces the drag coefficient and improves hydrodynamic efficiency, thereby reducing the towing power required to move a large-capacity liferaft at speeds of 2-3 knots as required by SOLAS regulations.
3Length of moving object
If non-rigid vessels are increased in size to certain dimensions, then the capacity is improved, but they become practically impossible to move through water with sufficient speeds due to extremely high drag forces
Solution Approach 1:
The patent uses flexible, non-rigid floatation tubes that can deform with water flow, significantly reducing form drag and turbulence. This flexibility allows the vessel to maintain higher speeds through water compared to rigid structures of equivalent size, as the flexible surfaces adapt to hydrodynamic pressures and reduce resistance.
Solution Approach 2:
By dividing the large vessel into multiple smaller floatation tubes, the patent reduces the overall drag coefficient. The segmented structure allows water to flow through and around the tubes more efficiently, reducing turbulence and drag forces that would otherwise prevent movement at sufficient speeds. This segmentation enables the large vessel to move through water at the required 2-3 knots.
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 achieves a drag coefficient below 0.5 at speeds over 4 knots, enabling efficient towing and movement of large liferafts with multiple passengers, ensuring safety and compliance with regulatory requirements.
Implementation Method 1
a plurality of non-rigid floatation tubes (3) arranged beneath the non-rigid bottom element (2), extending in the longitudinal direction to provide buoyancy
Implementation Method 2
The inflatable floatable liferaft may have a drag coefficient C d below 1 at a speed of more than 3 knots, and more preferably a drag coefficient C d below 0.75 at a speed of more than 3.5 knots, or even more preferably a drag coefficient C d below 0.5 at a speed of more than 4 knots
Data Source
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AI summary
The present invention relates to an inflatable floatable liferaft (1) for marine rescue which in its deflated state is capable of being stored in a container on board a ship, vessel or sea installation, and which is inflatable when deployed into the water, the fully inflatable floatable liferaft (1) extending in a longitudinal direction and comprising a non-rigid bottom element (2) having a water side (2a) and an air side (2b). The inflatable floatable liferaft (1) further comprises a plurality of non-rigid floatation tubes (3) arranged beneath the non-rigid bottom element (2), the non-rigid bottom element (2) extending in the longitudinal direction and being arranged with an intermediate distance (ID1) between neighboring non-rigid floatation tubes (3). The present invention further more relates to improved propulsion through the water of such an inflatable liferaft (1).