Selective Riblet Surface Layout for High-Friction Flow Regions
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Solution Overview
Problem
Existing methods for reducing frictional resistance on objects moving through fluids, such as aircraft, are costly and inefficient due to the difficulty in applying riblets uniformly across varying cross-sections, leading to high production costs that outweigh the fuel savings benefits.
Innovation Solution
Apply riblets only in specific partial regions where the cumulative frictional resistance exceeds a certain threshold, optimizing the surface by calculating and minimizing the required material coverage to achieve a significant reduction in frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If riblets are applied uniformly across the entire surface of objects with varying cross-sections (such as aircraft), then frictional resistance is reduced, but production costs increase significantly
Solution Approach 1:
The patent applies riblets only in specific regions where the local skin friction coefficient exceeds a threshold value, rather than uniformly across the entire surface. This selective application is achieved by calculating the local skin friction coefficient distribution and identifying high-friction zones, thereby reducing material costs while maintaining effective friction reduction where it matters most.
Solution Approach 2:
The patent implements partial action by applying riblets only to portions of the surface where they are most effective (regions with high local skin friction coefficient). The method determines optimal coverage areas through calculation, applying riblets selectively rather than excessively across the entire surface, thus achieving cost-effective friction reduction.
2Use of energy by moving object
If riblets are applied to reduce frictional resistance, then fuel consumption decreases, but material costs and production complexity increase
Solution Approach 1:
The patent reduces material consumption by applying riblets only in regions where the local skin friction coefficient exceeds a predetermined threshold. This selective application based on local friction characteristics ensures that materials are used only where they provide the most benefit, optimizing the balance between fuel savings and material costs.
Solution Approach 2:
The patent implements partial action by determining the optimal extent of riblet application through calculation of the local skin friction coefficient distribution. Rather than applying riblets excessively across the entire surface, the method identifies and treats only the necessary portions, reducing material costs while maintaining effective fuel consumption reduction.
3Object-affected harmful factors
If riblets are applied to complex surfaces with varying cross-sections, then frictional resistance is reduced, but manufacturing difficulty increases
Solution Approach 1:
The patent segments the surface into distinct regions based on the local skin friction coefficient distribution. By calculating and identifying high-friction zones separately from low-friction zones, the method enables selective riblet application on complex surfaces with varying cross-sections, thereby reducing manufacturing difficulty compared to uniform full-surface application.
Solution Approach 2:
The patent addresses manufacturing complexity by applying riblets with local quality - differentiating between regions that require riblets (high local skin friction coefficient) and regions that do not (low local skin friction coefficient). This selective approach simplifies the manufacturing process for complex surfaces by focusing treatment only where necessary.
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
Achieves a substantial reduction in frictional resistance with reduced material costs by strategically applying riblets in high-friction areas, balancing efficiency and cost-effectiveness.
Implementation Method 1
these riblets ensure that a turbulent flow in the near-surface region of a skin of a shark is prevented, or at least reduced, so that there is also a less turbulent flow, and a flow which therefore increases a frictional resistance to less of an extent
Data Source
AI summary
A method for producing an object with riblets on and/or in the surface, around which object a fluid flows during use. A frictional resistance acting on a surface region along a flow direction during a flow around the object in the fluid is calculated and added up to a cumulative frictional resistance over a length of the surface region in the flow direction, after which the riblets are provided on and/or in a partial region of the surface in which an increase in the cumulative frictional resistance is at least 0.9, in particular greater than 1.0 to 0.9. Moreover, a method is provided for modifying a surface of an object around which a fluid flows during use, such as a foil. A structure having riblets is created on and/or in the surface, which structure reduces flow resistance of the object. Furthermore, a fluid flows around an object during use.