Large-Eddy Simulations of Wind Shear from Passing Vehicles Under a Freeway Overpass

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Large-Eddy Simulations of Wind Shear from Passing Vehicles Under a Freeway Overpass


California is moving toward a 100% clean energy future, and expanded wind energy will be a major component of the state’s future energy portfolio. Innovations in wind energy resources will move California closer to achieving its goal. To gain a better understanding of transient pressure and the wind shear generated at the bridge poles from passing vehicles, this study performed large-eddy simulations of a vehicle (also called an Ahmed body) moving under a freeway overpass at a distance of 0.75 w (width) from the bridge poles. Results include transient contours of mean velocity, turbulent kinetic energy, vorticity, and pressure around the vehicle and at the bridge poles at different time steps. Additionally, results indicate the vehicle’s base pressure changes with time, indicating the impact of the poles' constraints on the vehicle's drag. On the bridge poles, the location of the stagnation point changes with the passing of the vehicle, and the poles experience a transient load, with the peak load associated with the passage of the vehicle's leading edge. The transient wind generated between the poles is mostly due to the vehicle’s front and decreases with the passing of the vehicle. The pressure at this location oscillates between a peak positive and a peak negative, generating a force potential for possible electric power generation. This data indicates the potential of capturing vehicle-generated wind energy for electric power generation, which could help California meet its clean energy goals and mitigate the negative impacts of climate change. 



Dr. Rahai is a Professor in the Departments of Mechanical and Aerospace Engineering & Biomedical Engineering and Associate Dean for Research and Graduate Studies in the College of Engineering at California State University, Long Beach (CSULB). He has supervised over 70 Master’s theses, projects, and PhD dissertations and published more than 90 technical papers. He has received over $11 million in grants and contracts from the National Science Foundation, Federal Highway Administration, California Energy Commission, California Air Resources Board, Port of Los Angeles, California Department of Transportation (Caltrans), The Boeing Company, Southern California Edison, Long Beach Airport, and Long Beach Transit, among others. He has been granted patents for a high-efficiency vertical axis wind turbine (VAWT) and wind turbine apparatus and for reducing NOx emission of Cargo Handling Equipment using a Humid Air System. He also has pending patents related to a new conformal vortex generator tape for reducing wing-tip vortices, and environmental artificial trees for reducing ambient NOx. For the past 26 years, he has been a consultant to the local energy and aerospace industries. Dr. Rahai is the recipient of several scholarly and creative activities awards (RSCA), including the 2012 CSULB Impact Accomplishment of the Year in RSCA Award, the 2002–2003 CSULB Distinguished Faculty RSCA Award, and the 2004 Northrop Grumman Excellence in Teaching Award. Dr. Rahai received the Outstanding Engineering Educator Award from the Orange County Engineering Council in California in 2014, and in 2019, he was inducted as a senior member of the National Academy of Inventors (NAI). 


Assma is a graduate student in the joint Ph.D. program in Engineering and Computational Mathematics between CSULB’s College of Engineering and the Claremont Graduate University (CGU) and a research assistant at the Center for Energy and Environmental Research & Services (CEERS) in the College of Engineering at CSULB. She has been involved in various projects at CEERS related to the aerodynamics of rotating cylinders and wind shears from passing vehicles. Assma is the author and co-author of two technical conference papers and one journal paper. 

October 2022
Large-eddy simulation
Turbulent shear
Vehicle's drag
Fluid-structure interaction



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