Truck Rear View Mirror Drag Reduction Using Passive Jet Boat Tail Flow Control

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. The condition selected for CFD (computational fluid dynamics) simulation is at high way speed of 70 miles/h, zero yaw angle and Reynolds number of 4.8x10⁵. The wind tunnel testing measured a drag reduction of 10.1% due to the JBT configuration. The 3D CFD based on RANS model predicts the drag reduction of 11.0%, an excellent agreement. This study confirms that the JBT device is very effective for heavy duty truck mirror drag reduction from both numerical simulation and wind tunnel experiment.