Airbrake CFD Analysis for Land Speed Record Vehicles

Abstract

The Wairua 2 land speed vehicle is a 500 mph streamliner that is being built as a successor to the Wairua 1, an already successful 300+ mph Bonneville land speed record holding vehicle. Wairua 2 will decelerate via airbrakes and redundant parachute systems. The studies here summarize the computational fluid dynamics (CFD) aerodynamic performance of five different airbrake designs mounted on the lower sides of the vehicle just aft of the driver cockpit. The airbrake designs range from simple flat plates, to more complex shapes with holes, serrated edges, and side flow fences. Drag values and the airbrake effects on the vehicles are presented, as well as downstream wake effects. Deceleration simulations predicting the speed decrease at the end of the course are also shown for each design. The buffeting from a perforated vs. unperforated design is compared using unsteady CFD analysis. The perforated design shows higher drag coefficients for both the steady and unsteady simulations. The perforated design exhibits reduced buffeting and lower force oscillation amplitudes for the fundamental frequency and harmonic frequencies, however it also exhibits a slight drag reduction due to its smaller frontal area. Designers must balance the structural capability, manufacturability, and the aerodynamic performance when selecting an airbrake design.