This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
A Holistic Approach to Aerodynamics of Intercity and Interurban Buses
Technical Paper
2014-01-0581
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
The aerodynamic drag of cars, trucks and buses have been closely examined over the years. Many of them focus on the front end and to some extent on rear end of the vehicles [1]. Of course these are the two surfaces that contribute to more than 85 % of the total drag. This is because these surfaces are almost normal to the direction of air flow and hence create enormous pressure differences and hence drag. A lot of optimization has also gone into these, by way of reducing the sharp corners at ‘A’ pillars, introducing aerodynamic dome and even ‘boat tail flap plates’ [2-3] for some trailers.
However, part of the vehicle that has not received sufficient attention in aerodynamic drag considerations is the ‘transverse outer profile’ of vehicle. This transverse outer profile is nothing but the cross sectional profile formed by the vehicle's sides, roof and their integration. This has a considerable impact on aerodynamic drag, especially in buses travelling on highways at considerably high speeds. In buses the roof and sides constitute 75 to 87% (considered for bus lengths of 7 to 12 meters) of the overall outer surface area of the vehicle.
This paper discusses the effect of this ‘transverse outer profile’ on the overall aerodynamic drag of the vehicle. CFD (Computational Fluid Dynamics) is used as a tool to understand the skin friction, vortices and hence drag, created by the transverse outer profile. Consequently ways of reducing this drag component, by optimizing the transverse outer profile is evaluated. The variables in this evaluation include - roof curvature, side panel profile and the cant rail cross-section. On the other hand the constraints include various regulatory and ergonomic requirements that define the boundaries of interior saloon space that is enveloped by the outer profile. Within this narrow space, various options of outer profile are tested in CFD, to arrive at the profile that has the lowest drag coefficient, popularly known as Cd.
Authors
Topic
Citation
Shekar, V., ThuraiMoni, A., Reddy, S., and Cherukuri, A., "A Holistic Approach to Aerodynamics of Intercity and Interurban Buses," SAE Technical Paper 2014-01-0581, 2014, https://doi.org/10.4271/2014-01-0581.Also In
References
- Fletcher C.A.J and Stewart G.D.H Bus Drag Reduction by the Trapped Vortex Concept for a Single bus and Two Buses in Tandem Journal of Wind Engg and Industrial Aerodynamics 143 168 1986
- Englar , R. Advanced Aerodynamic Devices to Improve the Performance, Economics, Handling and Safety of Heavy Vehicles SAE Technical Paper 2001-01-2072 2001 10.4271/2001-01-2072
- Hyams D.G. , Sreenivas , K. , Pankajakshan , R. et al. Computational simulation of model and full scale Class 8 trucks with drag reduction devices Computers & Fluids 27 40 2011
- Anderson , J. D. A History of Aerodynamics and its Impact on Flying machines Cambridge University Press New York 0-521-45435-2 1997
- Newton , I. Philosophiae Naturalis Principia Mathematica, Book II 1726
- Alam , F. , Watkins , S. , Zimmer , G. , and Humphris , C. Effects of Vehicle A-pillar Shape on Local Mean and Time-Varying Flow Properties SAE Technical Paper 2001-01-1086 2001 10.4271/2001-01-1086
- Venkat , S. and Rasmi , S. An Automated Shape Optimization Procedure for Drag Reduction of Ground Vehicles SAE Technical Paper 2005-26-321 2005 10.4271/2005-26-321