Bluff body aerodynamics

Motivation
Turbulent flows past bluff bodies have diverse geophysical and engineering applications such as flow around unmanned aerial vehicles (UAV), wind turbines, buildings, automobiles, offshore structures, and tube bundles in heat exchangers. In these applications, the flow past the bluff body is highly three-dimensional (3D) and induces complex flow phenomena such as separation and reattachment, vortex shedding, and unsteady wake dynamics downstream, which affect momentum, energy, and mass transport processes in the flow around the body. The vortex shedding may lead to significant increases in unsteady aerodynamic loads which can cause flow-induced vibrations, acoustic noise and resonance, and fatigue damage or failure.

In the transportation industry, the aerodynamic drag experienced by airplanes and ground vehicles has a huge impact on fuel consumption and its associated GHG emissions. For example, in highway driving conditions, aerodynamic drag accounts for 30%-70% of fuel consumption for heavy trucks and buses and over 50% for passenger cars. GHG reduction has pushed the rapid shift from internal combustion engine vehicles to green vehicles, e.g., electric and hydrogen vehicles. However, the challenge has been range limits due to the effects of aerodynamic drag and wider market acceptance because of range anxiety. 

To address these issues, there is an urgent need to improve our physical understanding of the generation mechanisms of aerodynamic drag on bluff bodies to develop cost-effective flow control strategies to improve their energy efficiency in fluid-thermal applications.