Angle Of Attack vs. Drag
Reynolds Composites Studio engineers analyzed rim sections using an analytical
Computational Fluid Dynamics (CFD) program.
Results of the analysis of the rim sections can be used to determine design trends and modifications that are beneficial to rim performance. This is the foundation Reynolds Composites Studio engineers apply during initial design to optimize rim section contour. CFD analysis enables our engineers to make design decisions about the contour and dimensions of a rim in the computer before building the physical model. While wind tunnel testing for validation is important, utilization of CFD analysis takes the guesswork out of aerodynamic design. All CFD analysis models were run at sea level under conditions accepted by N.A.C.A. as “standard conditions.”
The primary point of interest for the cyclist (as opposed to the engineer) is drag value. Comparison of the drag values of various shapes can indicate trends useful for optimizing rim contour, and dimension. The engineer can use additional data to determine more sophisticated variables required to improve rim performance as a low drag shape.
This chart represents Drag in Pounds associated with a specific Angle of Attack (AOA). The graph data correlates the drag of each individual rim section analyzed at every incremental AOA between 1° and 20°. The numerical values represented by Drag in Pounds and AOA correlate the values of the specific data to a Cartesian coordinate on the graph. The data on the graph represents the performance of the RZR 46 T to consistently perform with the lowest drag at every angle of attack between 1° and 20°. CFD analysis allowed Reynolds Composites Studio engineers to optimize the RZR 46T rim contour and dimensions to outperform competitor’ wheels.
Angle Of Attack = 20 Degrees
The graphic and data associated with Angle of Attack = 20° represent an air speed of 30.0 MPH with the prevailing wind coming from 20° off of a direct headwind. Analysis at angles of 25° - 90° can be useful for analysis, but they do not correlate to real world conditions because the forward velocity of the bicycle prohibits a resultant force vector of much greater than 20° to be a realistic model for analysis. The gradient scale can be used to reference high and low pressure. Red is the highest pressure, and blue is the lowest. The highest pressure is nearly identical to the speed of the wind. Low pressure is represented within the scale of yellow to blue, and is associated with higher air velocity than the wind speed. Low pressure (yellow-blue) is the region of the rim where lift is created. The top illustration and data represent the RZR 46T. The lower left illustration and data represents the Pro VT-1 rim section, and the lower center and right illustrations represent the rim section of a well-known competitor.
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