Simulating Aerodynamic Effects of Location and Orientation of Bicycles Mounted on Sedans

Abstract

Biking is a common activity, and many people want or need to drive their bike to different locations, necessitating a bike rack to easily transport it. Choosing a bike rack relies on cost, car type, and mounting ease. One of the aspects of choosing a rack that is less studied is the aerodynamics and effect on gas mileage and pollution. This paper describes the methods and results of simulations in ANSYS-Fluent, comparing the aerodynamics of different racks and bike positions on a car. Three simulations were done, one with just the car, one with a bike mounted on a roof rack, and one with a bike mounted on a trunk rack. After a mesh sensitivity analysis, determining a minimum mesh size, the three simulations were run with the same mesh and simulation settings to keep everything as similar as possible, with the geometries being the main difference between the simulations. Results were compared to similar simulations and values of the actual car. Results showed the car without bike as the most aerodynamic with a drag coefficient of 0.35, drag force of 335.8 N, and a gas mileage of 29 mpg, followed by the vehicle with the trunk rack with a drag coefficient of 0.37, drag force of 353 N, and gas mileage of 27.8 mpg, then the car with the roof rack with a drag coefficient of 0.40, drag force of 423 N, and gas mileage of 22.97 mpg. Overall, results show significant differences in the aerodynamic and environmental effects depending on the location and orientation of mounting a bike.