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Aerodynamic Comparison of Dimpled vs. Smooth Bicycle Frame Tubes

This research study compares the aerodynamic efficiency of dimpled and smooth bicycle frame tubes at a speed of 11 m/s. Findings reveal a reduction in drag with dimpled tubes, positioning them closely to Kamm Tail designs in aerodynamics. The study emphasizes the suitability of dimpled tubes in various wind conditions compared to airfoil and Kamm Tail shapes.

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Aerodynamic Comparison of Dimpled vs. Smooth Bicycle Frame Tubes

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  1. Neal E. Joslyn Christopher W. Roberson

  2.  Current State: Little is known about the effects of dimplesonthe aerodynamics ofbicycle frame tubes  Research Question: Determine whether a dimpled bicycle frame is more aerodynamic then a smooth one.  Rationale: Traditional round frame tubes have superior ride characteristics to airfoils, but suffer from aerodynamic drag. Our goal is to engineer a design that takes the best of both worlds.

  3.  This is the smooth mesh cylinder that is representing the part of the down tube of a bicycle. This is where racing designforbicycles is today.

  4.  This test was conducted at 11 m/s, a typical average speed for bicycle races. This study shows that there is a turbulent region at the back of the tube. This is greatly increases the pressure difference, increasing totaldrag.

  5.  This is the dimpled mesh cylinder that is representing the downtube that we propose to bemoreaerodynamic.

  6.  This test was also conducted at 11 m/s. Compared to the smooth frame analysis, there is a great reduction in turbulencebehind the tube,reducingtotal drag.

  7.  Kamm Tail  This shape is growing in popularity because it feels like an airfoil (aerodynamically), but is a better ride  Airfoil  This shape is the shape of choice by professionals when it comes to time trials. It has the least amount of drag and therefore more aerodynamic than the other shapes.

  8.  The benefit of having a Kamm Tail is most of the aerodynamic capabilities of a Airfoil without the harshness of the ride. The shape allows for flexibility where it is needed and rigidity where it is needed.

  9.  Without a doubt the airfoil shape outperforms the other shapes when it comes to aerodynamics. There is little to no pressure build- up behind the airfoil when the flow of fluid has a yaw angle of zero degrees.

  10. Although the airfoil outperformed the other shapes it comes with concerns. In any sort of cross wind the ride becomes much tougher and the bike itself is not a comfortable ride.  0.3000 Viscous Drag 0.2500 Pressure Drag The Kamm Tail provides almost as much of a reduction in drag force and it is a much smoother ride providing flexibility whereit is needed.  0.2000 **Important** -The point of thisproject was to see the affects of dimples. The dimpled tube was more aerodynamic than the smooth tube which proves out hypothesis. Surprisingly the dimpled tube was not far behind the Kamm Tail design as far as aerodynamics is concerned.  0.1500 0.1000 0.0500 Another important point is that the dimpled tube will perform the same on any wind conditions. The airfoil and Kamm Tail will experience harder riding conditions oncrosswinds.  0.0000 Smooth Tube Dimpled Tube Airfoil Kamm Tail

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