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This paper conducts numerical simulation and wind tunnel testing to demonstrate the passive flow control jet boat tail (JBT) drag reduction technique for a heavy duty truck rear view mirror. The JBT passive flow control technique is to introduce a flow jet by opening an inlet in the front of a bluff body, accelerate the jet via a converging duct and eject the jet at an angle toward the center of the base surface. The high speed jet flow entrains the free stream flow to energize the base flow, increase the base pressure, reduces the wake size, and thus reduce the drag. A baseline heavy duty truck rear view mirror is used as reference. The mirror is then redesigned to include the JBT feature without violating any of the variable mirror position geometric constraints and internal control system volume requirement. The wind tunnel testing was conducted at various flow speed and yaw angles.

Development of new, competitive vehicles in the context of stricter regulations to reduce greenhouse gas emissions and increase fuel economy is driving OEM of commercial vehicles to further explore options for reducing aerodynamic drag in a real-world setting. To facilitate this in regards to the aerodynamics of a vehicle, virtual design methods such as CFD are often used to compliment experiments to help reduce physical testing time and costs. Once validated against experiments, CFD models can then act as predictive models to help speed development. In this paper, a wind tunnel experiment of a Class 8 truck is compared to a CFD simulation which replicates said experiment, validating the CFD model as a predictive tool in this instance. CFD is then used to evaluate the drag and flow around the vehicle in an open road scenario, and the results between the open road and wind tunnel scenarios are compared.