Bicycle Frame Tubercles Delay Flow Separation at Low Yaw Angles
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Solution Overview
Problem
Bicycle frames, particularly the front forks, frame, and seat post, contribute significantly to aerodynamic drag due to boundary layer separation at low yaw angles, leading to increased drag and reduced cycling performance.
Innovation Solution
The introduction of elongate structural members with a lengthwise extending leading edge featuring a series of forwardly extending protrusions, or tubercles, spaced apart to form chordwise extending ribs, which delay flow separation and maintain low drag even at varying yaw angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cross-sectional shapes are used for bicycle frame components, then the structure is simple and easy to manufacture, but boundary layer separation occurs at low yaw angles resulting in increased drag
Solution Approach 1:
The patent applies local quality by adding protrusions only to the leading edge of frame components rather than redesigning the entire cross-section. This localized modification delays boundary layer separation at the critical leading edge region while preserving the overall simple cross-sectional shape and ease of manufacture of the frame components.
Solution Approach 2:
The protrusions on the leading edge introduce curved surfaces that modify the airflow pattern. The curved geometry of the protrusions helps to keep the boundary layer attached at higher yaw angles compared to conventional flat or simple curved leading edges, thereby reducing drag without requiring complex cross-sectional redesigns.
2Object-affected harmful factors
If narrow cross-sections resembling thick aerofoils are used to reduce drag, then aerodynamic performance improves, but the chord-to-thickness ratio is restricted by UCI rules and the structure becomes more complex
Solution Approach 1:
The leading edge is segmented into multiple sections by adding spaced protrusions along its length. This segmentation creates a series of smaller curved surfaces that collectively delay separation across the entire leading edge, achieving better aerodynamic performance than a single smooth leading edge while maintaining regulatory compliance and manageable structural complexity.
3Ease of manufacture
If conventional smooth leading edges are used, then manufacturing is easier, but flow separation occurs at yaw angles as low as 5 degrees increasing drag
Solution Approach 1:
The patent changes the geometric parameters of the leading edge by adding protrusions with specific dimensions and spacing. This parameter modification transforms the leading edge from a simple smooth surface to one with controlled irregularities that promote flow attachment, improving reliability of flow attachment stability across varying yaw angles while remaining manufacturable.
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 design reduces drag by maintaining flow attachment, resulting in a power saving of 5.34 Watts at 54 kph, equivalent to a 1-1.5% drag reduction for the rider/bicycle combination, and maintains low aerodynamic drag across a wide range of yaw angles.
Implementation Method 1
the Reynolds numbers of the front forks, frame and seat post of a bicycle are sufficiently low that under normal riding conditions the boundary layers are laminar, and this results in boundary layer separation at yaw angles as low as 5 degrees
Implementation Method 2
When boundary layer separation occurs, the flow is described as separated or stalled, and the drag is increased
Data Source
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AI summary
The present disclosure relates to a bicycle frame and associated bicycle components, and to reducing the aerodynamic drag of these. In one aspect, there is provided an elongate structural member of a bicycle frame, the member comprising a lengthwise extending leading edge, the leading edge comprising at least a pair of forwardly extending protrusions spaced apart lengthwise therealong. In one form, the protrusions comprise tubercles, a series of which are spaced apart lengthwise along the leading edge, and which further extend to at least one side of the leading edge so as to transition into a chordwise extending rib.