Title: A wind tunnel investigation into the effects of roof curvature on the aerodynamic drag experienced by a light goods vehicle

Authors: Jenny Holt; Kevin Garry; Stefan Velikov

Addresses: Applied Aerodynamics, Centre for Aeronautics, Cranfield University, BEDS, MK43 0AL, UK ' Applied Aerodynamics, Centre for Aeronautics, Cranfield University, BEDS, MK43 0AL, UK ' Applied Aerodynamics, Centre for Aeronautics, Cranfield University, BEDS, MK43 0AL, UK

Abstract: Roof curvature is used to increase ground vehicle camber and enhance rear-body boat-tailing to reduce aerodynamic drag. Little aerodynamic data is published for light goods vehicles (LGVs) which account for a significant proportion of annual UK licensed vehicle miles. This paper details scale wind tunnel measurements at Re = 1.6 × 10⁶ of a generic LGV utilising interchangeable roof panels to investigate the effects of curved roof profile on aerodynamic drag at simulated crosswinds between −6° and 16°. Optimum magnitudes of roof profile depth and axial location are suggested and the limited dataset indicates that increasing roof curvature is effective in reducing drag over a large yaw range, compared to a flat roof profile. This is primarily due to increased base pressure, possibly from enhanced mixing of longitudinal vortices shed from the rear-body upper side edges and increased turbulent mixing in the near-wake due to the increased effective boat-tail angle.

Keywords: aerodynamic drag reduction; roof curvature; wind tunnels; LGV; light goods vehicles; wind averaged drag; yaw; boat tail angle; simulation; crosswinds; roof profile depth; axial location; longitudinal vortices; turbulent mixing.

DOI: 10.1504/IJVD.2015.066478

International Journal of Vehicle Design, 2015 Vol.67 No.1, pp.45 - 62

Received: 05 Nov 2013
Accepted: 15 May 2014
Published online: 22 Dec 2014 *

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