Session: 10-03-02: CFD Applications - II

Paper Number: 94997

94997 - Simulating Aerodynamic Effects of Location and Orientation of Bicycles Mounted on Sedans 

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 many factors including cost, type of car, and ease of mounting. 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. The novel software Fluent-Meshing created an advanced computational grid that efficiently captures the various small components of the bike and the aerodynamic features of the sedan. The turbulent models were tested and results were compared. Three sets of simulations were done, one with just the car, one with a bike mounted on a roof rack of the car, and one with a bike mounted on a trunk rack of a car. After a mesh sensitivity analysis, determining an optimal mesh size, all 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. The results were also compared to similar simulations and the values of the actual car. The results showed that the car was the most aerodynamic with a drag coefficient of .34, drag force of 328 N, and assumed gas mileage of 29 mpg, followed by the car with the trunk rack with a drag coefficient of .37, drag force of 354 N, and gas mileage of 27 mpg, then the car with the roof rack with a drag coefficient of .37, drag force of 391 N, and gas mileage of 24.5 mpg. There was an increase in drag coefficient from adding the bike, but the difference in drag force between the two models with the bikes is due primarily to the difference in area. Overall, there seems to be a significant difference in the aerodynamic and environmental effects of the car depending on the location and orientation of mounting a bike. The present work shows an analysis that identifies the best configuration of mounted bike in vehicles. Also, the present work describes a path to generate advanced computational grids of complex 3D objects that contain small features to perform simulations of fluid dynamics. The illustrated techniques are useful in simulating of 3D stented aneurysms, airplane aerodynamics, and advanced fin heat exchangers.

Presenting Author: Isaac Perez-Raya Rochester Institute of Technology

Presenting Author Biography: I work in the field of mechanical engineering, conducting research with a diverse set of applications including electrochemical fuel cells, boiling heat transfer, and medical applications such as breast cancer and brain aneurysms. All of these varied areas require application of the same core principles. In each case, their modeling is based on the numerical solution of governing equations of flow transport (e.g. hydrogen transport in fuel cells; water and heat transport in boiling; blood and heat transport in breast cancer; and blood transport in aneurysms). Also, modeling of each of these scenarios is carried out based on the definition of source terms in the governing equations to account for chemical reactions or species generation/consumption (e.g. consumption of hydrogen in fuel cells; liquid evaporation at the interface in boiling flows; and tumor heat generation in breast cancer). Therefore, electrochemical fuel cells, boiling heat transfer, breast cancer, and aneurysms are not disparate endeavors.<br/><br/>By simulating non-conventional direct borohydride fuel cells, I described the electrochemical reactions with high electricity generation (with eight electrons per reaction instead of two electrons per reaction in conventional hydrogen fuel cells) and the effect of the components of the fuel cell on the performance at different operating conditions. Also, I proposed the OCASIMAT (One Cell Algorithm for Sharp Interfaces and MAss Transfer) method that accurately computes liquid evaporation and interfacial heat transfer at moving interfaces in boiling flows using commercial simulation software (ANSYS-Fluent). By applying OCASIMAT, I became the first researcher to customize commercial software in order to accurately simulate the changes in temperature and fluid velocities in simulations of boiling. I devised methods of breast cancer detection that rely on simulations that show changes on the breast surface temperature due to the heat generated by tumors. I published a highly cited paper discussing the use of infrared cameras to detect breast cancer. My paper also describes methods to improve the detection of breast cancer using infrared cameras and computer simulations/inverse models. In my postdoc, I developed patient-specific simulations of brain aneurysms by post-processing magnetic-resonance imaging data using artificial intelligence techniques.

Authors:

Sarah Goodrich Rochester Institute of Technology
Isaac Perez-Raya Rochester Institute of Technology