Convexo-Concave Drag Reduction Structure for Flow Separation Suppression
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Solution Overview
Problem
Existing drag reduction technologies face challenges in effectively forming convexo-concave structures at the millimeter scale and lack specific details on surface configurations for optimal drag reduction, particularly in suppressing flow separation and reducing pressure resistance in moving objects.
Innovation Solution
A drag reduction structure featuring a convexo-concave design with specific dimensions (10 μm to 1000 μm height, 30 mm to 1000 mm length, and 0.2 mm to 50 mm width) is implemented, utilizing a combination of convex and concave portions to generate vortices at the boundary with a flat surface, reducing pressure resistance while minimizing frictional resistance increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If convexo-concave structures such as riblets and dimples are provided on the surface to reduce drag, then fluid resistance is reduced, but it becomes difficult to form them when their size is in the millimeter order depending on the form of the drag reduction structure
Solution Approach 1:
The patent changes the size parameter of the convexo-concave structure from millimeter order to micrometer order (10-1000 μm height), making the structure formable on film-shaped drag reduction structures while maintaining drag reduction effectiveness. This parameter change resolves the contradiction between achieving drag reduction and ensuring manufacturability.
2Object-affected harmful factors
If a rough surface and smooth surface are arranged to generate vertical vortex at the boundary to suppress flow separation, then pressure resistance is reduced, but specific shapes and configurations are not disclosed
Solution Approach 1:
The patent applies local quality by creating a drag reduction structure with spatially varying properties: a first portion with convexo-concave structures (rough surface) and a second portion without such structures (smooth surface). The specific configuration includes the first portion having a length of 30 mm or more in the second direction and widths of 0.2-50 mm, with the convexo-concave structures having heights of 10-1000 μm. This localized differentiation suppresses flow separation and reduces pressure resistance while providing manufacturable specifications.
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 suppresses flow separation and reduces drag, enhancing energy efficiency and carbon dioxide emission reduction in moving objects by optimizing the convexo-concave structure dimensions and placement.
Implementation Method 1
arranging a rough surface and a smooth surface to generate a vertical vortex at the boundary between the rough surface and the smooth surface to suppress the flow separation
Implementation Method 2
generate a vertical vortex at the boundary between the rough surface and the smooth surface to suppress the flow separation
Implementation Method 3
a dimple has been known as a method to reduce pressure resistance
Implementation Method 4
a riblet has been known as a method to reduce frictional resistance among fluid resistances
Data Source
AI summary
A drag reduction structure wherein a first portion including a plurality of convex portions and concave portions, and a second portion are placed on a first surface; a height from a bottom portion of the concave portion to a top portion of the convex portion, of the first portion, is 10 μm or more and 1000 μm or less; a length of the first portion in a second direction is 30 mm or more; and a width of the first portion and a width of the second portion, in a first direction crossing the second direction, is 0.2 mm or more and 50 mm or less.