Undulating Bicycle Wheel Rim Aerodynamic Drag Reduction
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Solution Overview
Problem
Conventional bicycle wheel rims suffer from aerodynamic issues, resulting in increased drag and steering challenges due to the transverse resultant force caused by ambient air at non-zero yaw angles, which requires riders to apply significant steering input to maintain direction.
Innovation Solution
The introduction of an undulating configuration on the rim and spokes, with smooth transitions and varying radial heights, reduces drag and shifts the center of pressure closer to the hub, mitigating the steering challenges by improving aerodynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional straight extruded rim sections are used, then manufacturing is simple and cost-effective, but aerodynamic drag is high and steering stability is poor
Solution Approach 1:
The rim cross-section is changed from a straight extruded shape to an airfoil-shaped cross-section with curved upper and lower surfaces. The upper surface is convex and the lower surface is concave, creating a curved aerodynamic profile that reduces drag while maintaining structural integrity. This curvature principle directly addresses the aerodynamic drag issue while the extrusion process maintains manufacturing simplicity.
Solution Approach 2:
The rim geometry parameters are optimized by varying the depth of the rim section and the specific curvature profiles of the upper and lower surfaces. The airfoil cross-section parameters (depth, curvature radius, thickness distribution) are carefully selected to minimize aerodynamic drag at typical cycling speeds while ensuring the rim maintains sufficient strength and stiffness.
2Device complexity
If conventional constant depth rim sections are used, then structural simplicity is maintained, but center of pressure is far from hub causing steering instability
Solution Approach 1:
The airfoil-shaped cross-section with its specific curvature distribution shifts the aerodynamic center of pressure closer to the hub by creating a more streamlined flow pattern around the rim. The curved upper and lower surfaces guide air flow more efficiently, reducing the transverse force moment arm and improving steering stability without adding structural complexity.
Solution Approach 2:
By optimizing the depth and curvature parameters of the airfoil cross-section, the center of pressure position is adjusted to be closer to the hub. This parameter optimization achieves better steering stability while maintaining the relative simplicity of the rim structure through a single integrated airfoil profile rather than multiple components.
3Object-affected harmful factors
If undulating rim configuration is implemented, then aerodynamic drag is reduced and steering stability improves, but manufacturing complexity increases
Solution Approach 1:
The undulating configuration is achieved through the airfoil-shaped cross-section which inherently provides a streamlined, curved profile. This curvature design reduces aerodynamic drag by promoting smooth air flow separation and reducing turbulence, while the undulating pattern along the rim circumference further optimizes airflow without requiring complex multi-component construction.
Solution Approach 2:
The undulating rim configuration is realized by varying geometric parameters (depth, curvature radius, thickness) along the circumferential direction of the rim. These parameter variations create the aerodynamic profile that reduces drag and shifts the center of pressure, while the entire structure remains a single integrated component suitable for extrusion or composite manufacturing.
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
Computational Fluid Dynamics analysis shows reduced drag and a closer center of pressure to the hub in wheels with undulating rims, reducing the need for large steering inputs and enhancing overall cycling performance.
Implementation Method 1
Conventional wheel rim designs may result in a large amount of drag on the wheel, reducing the speed of the bicycle
Implementation Method 2
Computational Fluid Dynamics (CFD) analysis has been carried out which compares the drag produced at 15m/s on a wheel having a rim with an undulating configuration
Implementation Method 3
movement of ambient air, travelling at a non-zero yaw angle relative to the general direction in which the bicycle is travelling, may cause a transverse resultant force to be applied to the wheel
Implementation Method 4
The point of action of this force on the wheel is known as the centre of pressure
Data Source
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AI summary
A wheel (1) for use with a bicycle, the wheel (1) comprising a hub (4) about which the wheel (1) is mountable to a bicycle, a rim (2) about which a tyre (6) is mountable, and a plurality of spokes (3) that extend between the hub (4) and the rim (2), wherein the rim (2) and/or one or more of the spokes have a leading and/or trailing edge, at least part of which has an undulating configuration.