Optimised Tube Profile
As a frame cuts through the wind, the airflow varies dramatically along every tube, joint and transition, e.g. the airflow upstream of the upper 1/3 of down tube is already turbulent due to the front wheel, however in the lower 1/3 of the down tube upstream airflow is near laminar.
The complex interaction of frame and forks, with wheels and components, at a variety of wind yaw angles, and most importantly incorporating the rider, necessitates the airflow to be managed specific to the aerodynamic characteristics of each element.
The design of the Alize achieves this through the complex morphing of every tube profile and joint. We couldn't just settle for the cookie-cutter approach of using a standard aerofoil profile along the length of every tube. If only bike aerodynamics were that simple.
But where do you start? With some guys who know a thing or two about the wind… and Computational Fluid Dynamics… or a virtual wind tunnel to you and me.
The design of the Alize achieves this through the complex morphing of every tube profile and joint. We couldn't just settle for the cookie-cutter approach of using a standard aerofoil profile along the length of every tube. If only bike aerodynamics were that simple.
But where do you start? With some guys who know a thing or two about the wind… and Computational Fluid Dynamics… or a virtual wind tunnel to you and me.
Extended Kammtail Design
Achieving a balance between optimised aerodynamics and cycling performance is a complex challenge, with the stiffness and weight requirements of a bike creating additional constraints.
Traditional high aspect ratio aerofoils are significantly less efficient when designing an aerodynamic road bike frameset, as lateral and torsional stiffness requirements, and the ride and handling performance are more critical than in TT or triathlon bike designs.
Firstly, incorporating a progressive Kamm back aerofoil profile in the lower 1/3 of the down tube, with the extended trailing edge becoming truncated and morphing into a squared-off surface, enabled a significantly more efficient transition from the down tube to seat tube.
But we didn't stop there. Through computational fluid dynamic modeling and extensive wind tunnel testing (which is much more fun that sitting in front of
a computer) our aerodynamicists developed a revolutionary design that "tricks" the traditional Kammtail behind the lower down tube to extend further.
The specific proportions of the down tube and seat tube profiles force the airflow to remain laminar around the down tube and seat tube, and rear wheel. The static air above the bottom bracket results in little turbulent energy dissipation in this area.
The specific proportions of the down tube and seat tube profiles force the airflow to remain laminar around the down tube and seat tube, and rear wheel. The static air above the bottom bracket results in little turbulent energy dissipation in this area.
Wind Tunnel Testing of Alize Prototype R02:V04
Computational Fluid Dynamics analysis of Alize Prototype R02:V01
Traditional airfoil shape of head tube maintains laminar airflow
Extended Kammtail effect in lower section of download and seat tube
Extended Kammtail effect in lower section of download and seat tube
Airfoil profile with blunted leading edge and extended trailing edge manages and cleans-up the turbulent airflow coming off the front wheel Extended Kammtail in bottom bracket