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

Paper #:
  • 2017-01-1538

  • 2017-03-28
This paper conducts numerical simulation and wind tunnel testing to study the passive jet boat tail(JBT) drag reduction flow control 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 70miles/h, zero yaw angle and Reynolds number of 4.97x105 . The wind tunnel testing measured a drag reduction of 12% due to the JBT configuration, but the 3D CFD over-predicts it with a drag reduction of 19.7%. For the CFD, the in house CFD code of FASIP is used. The unsteady Reynolds averaged Navier-Stokes (URANS) equations are solved with one-equation Spalart-Allmaras turbulence model. A low diffusion E-CUSP approximate Riemann solver with 3rd order MUSCL scheme for inviscid fluxes and a second order central differencing scheme are used for the viscous terms. More CFD simulation and detailed results at different yaw angles will be simulated and presented in the full paper.
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