Unsteady Surface Pressure Characterization of the Base Pressure Region of a Heavy Goods Vehicle

Abstract

This paper presents an experimental investigation into the time-dependent aerodynamics within the base region of a representative heavy goods vehicle. The work conduced is surface-based, and involved using multiple, customized dynamic pressure sensors for both aligned and mis-aligned flow configurations. Uniquely, the methodology adopted allowed high resolution, detailed interrogation of this region and the presentation of several new insights. Among the most significant are the detailed characterization and quantification of the degree of flow-misalignment necessary to prompt development of a complex vortex/wake structure reported previously. Once developed, this structure dominated the upper-windward quadrant of the base region with measured unsteady surface loads up to 2-3 times greater than that observed under nominal flow conditions. Presented spectral information also showed evidence of both Strouhal-based vortex shedding within the wider base-pressure region as well as more localized regions containing higher spectral contributions centered broadly at several multiples of the primary shedding frequency.