Partially Submerged Riblets for Boundary-Layer Drag Reduction
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Solution Overview
Problem
Existing surfaces with smooth or protruding riblet patterns experience significant drag forces when moving through fluids, leading to increased energy consumption and reduced performance in vehicles and other objects.
Innovation Solution
The use of partially submerged periodic riblets, which are grooves or channels partially depressed below a smooth surface, alternated with smooth regions to reduce drag by minimizing the wetted area and pressure drag penalties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If riblets extend far below the surface, then viscous drag reduction improves, but manufacturing complexity and structural integrity worsen
Solution Approach 1:
Instead of extending riblets deeply below the surface, this invention uses partial action by positioning riblets at an optimal depth within the boundary layer. This provides sufficient viscous drag reduction while avoiding the manufacturing complexity and structural issues associated with deep recesses.
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
This solution effectively reduces overall drag, including pressure and viscous drag, allowing for increased range, reduced fuel costs, and improved performance in vehicles by delaying flow separation and maintaining a constant cross-sectional area.
Implementation Method 1
The use of partially submerged periodic riblets may delay or prevent the separation of the flow in a turbulent boundary layer from the surface
Implementation Method 2
The use of partially submerged periodic riblets may delay or prevent the separation of the flow in a turbulent boundary layer from the surface
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
In one embodiment, a method for reducing drag includes forming a smooth surface (130) on a first portion (120) of a physical object (100). The method also includes forming periodic riblets (110) on a second portion (130) of the physical object (100). The method further includes generating a flow over the periodic riblets (110) of the second portion (130) of the physical object (100) and over the smooth surface (130) of the first portion (120) of the physical object (100). The second portion (130) of the physical object (100) is adjacent to the first portion (120) of the physical object (100). Each peak of each riblet (110) of the periodic riblets (110) of the second portion (130) of the physical object (100) is located above a plane of the smooth surface (130) of the first portion (120) of the physical object (100). Each valley between adjacent riblets of the periodic riblets (110) of the second portion (130) of the physical object (100) is located below the plane of the smooth surface (130) of the first portion (120) of the physical object (100). A length of each riblet (110) of the periodic riblets (110) runs parallel to a direction of the flow.