Partially Submerged Riblets for Lower Pressure and Viscous Drag
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional riblets that protrude above the surface of objects increase drag by enhancing pressure drag due to increased wetted area, while smooth surfaces do not effectively reduce drag, leading to inefficiencies in energy consumption and range for vehicles moving through fluids.
Innovation Solution
The implementation of partially submerged periodic riblets, where each riblet's peak is above and valley is below the smooth surface plane, creating a constant cross-sectional area and reducing pressure drag by alternating smooth and riblet regions, thereby minimizing overall drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional riblets protrude above the surface, then viscous drag is reduced, but pressure drag increases due to increased wetted area
Solution Approach 1:
The patent applies local quality by creating riblets with non-uniform depth along the flow direction. The riblets have a first depth in a forward portion and a second depth in a rearward portion, with the second depth being less than the first depth. This gradual reduction in depth allows the riblets to maintain effectiveness in reducing viscous drag while minimizing the increase in pressure drag by reducing the wetted area compared to uniform-depth riblets.
2Object-generated harmful factors
If smooth surfaces are used, then pressure drag is minimized, but viscous drag is not effectively reduced
Solution Approach 1:
The patent combines smooth surface regions with riblet regions, where the smooth surface minimizes pressure drag and the riblet regions reduce viscous drag. The transition from smooth surface to riblets and back to smooth surface creates optimal flow conditions that address both drag components effectively.
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 approach reduces both pressure and viscous drag, leading to lower fuel consumption, increased range, and improved performance by maintaining a consistent cross-sectional area and delaying turbulent boundary layer separation.
Implementation Method 1
The use of partially submerged ribbed surfaces on physical objects reduces overall drag (which includes pressure and viscous drag) experienced by the physical object... partially submerged periodic riblets may reduce heat transfer on a hot or cold surface adjacent to a turbulent boundary layer... 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
AI summary
In one embodiment, a method for reducing drag includes forming a smooth surface on a first portion of a physical object. The method also includes forming periodic riblets on a second portion of the physical object. The method further includes generating a flow over the periodic riblets of the second portion of the physical object and over the smooth surface of the first portion of the physical object. The second portion of the physical object is adjacent to the first portion of the physical object. Each peak of each riblet of the periodic riblets of the second portion of the physical object is located above a plane of the smooth surface of the first portion of the physical object. Each valley between adjacent riblets of the periodic riblets of the second portion of the physical object is located below the plane of the smooth surface of the first portion of the physical object. A length of each riblet of the periodic riblets runs parallel to a direction of the flow.