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Improved CFD Methodology for Class 8 Tractor-Trailer Coastdown Correlation
ISSN: 0148-7191, e-ISSN: 2688-3627
Published September 24, 2013 by SAE International in United States
Annotation ability available
Recent regulations on greenhouse gas (GHG) emission standards for heavy duty vehicles have prompted government agencies to standardize procedures to assess aerodynamic performance of Class 8 tractor-trailers. The coastdown test procedure is the primary reference method to assess vehicle drag and other valid alternatives include wind tunnel testing and computational fluid dynamics (CFD) simulations.
While there have been many published studies comparing results between simulations and wind tunnel testing, it is less well understood how to compare results with coastdown testing. Both the wind tunnel and simulation directly measure aerodynamic drag forces in controlled conditions, while coastdown testing is conducted in an open road environment, aerodynamic forces are calculated from a road load equation, and variable wind and vehicle speed introduce additional complexity.
In this paper we evaluate different methods to improve the correlation of absolute drag values between simulation and coastdown testing. Coastdown tests were performed on a 2010 ProStar Long Sleeper with a standard 53-foot dry-box trailer at Ford Proving Ground in Arizona per EPA's modified J1263 & J2263 procedure. The CFD simulations use a Lattice Boltzmann based method on a high fidelity geometric model. The first drag results are established by using validated best-practice CFD methodology. Subsequently, we improve the comparison to coastdown test results by accounting for the aerodynamic torque on the wheels, the detailed shape of the tires, and the impact of different surface roughness values on the tractor-trailer surfaces. Finally, we discuss the impact of the variable vehicle speed and wind conditions during the testing.
CitationGolsch, K., Duncan, B., and Kandasamy, S., "Improved CFD Methodology for Class 8 Tractor-Trailer Coastdown Correlation," SAE Technical Paper 2013-01-2412, 2013, https://doi.org/10.4271/2013-01-2412.
- Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles Federal Register 76 179 57106 57513 September 15 2011
- Howell , J. , Sherwin , C. , Passmore , M. , and Le Good , G. Aerodynamic Drag of a Compact SUV as Measured On-Road and in the Wind Tunnel SAE Technical Paper 2002-01-0529 2002 10.4271/2002-01-0529
- Le Good , G. , Howell , J. , Passmore , M. , and Cogotti , A. A Comparison of On-Road Aerodynamic Drag Measurements with Wind Tunnel Data from Pininfarina and MIRA SAE Technical Paper 980394 1998 10.4271/980394
- Walter , J. , Pruess , D. , and Romberg , G. Coastdown/Wind Tunnel Drag Correlation and Uncertainty Analysis SAE Technical Paper 2001-01-0630 2001 10.4271/2001-01-0630
- Buckley , F. ABCD - An Improved Coast Down Test and Analysis Method SAE Technical Paper 950626 1995 10.4271/950626
- Duncan , B. , Kandasamy , S. , Sbeih , K. , Lounsberry , T. et al. Further CFD Studies for Detailed Tires using Aerodynamics Simulation with Rolling Road Conditions SAE Technical Paper 2010-01-0756 2010 10.4271/2010-01-0756
- Buckley , F. , Marks , C. , and Walston , W. Analysis of Coast-Down Data to Assess Aerodynamic Drag Reduction on Full-Scale Tractor-Trailer Trucks in Windy Environments SAE Technical Paper 760850 1976 10.4271/760850
- D'Hooge , A. , Palin , R. , Johnson , S. , Duncan , B. et al. The Aerodynamic Development of the Tesla Model S - Part 2: Wheel Design Optimization SAE Technical Paper 2012-01-0178 2012 10.4271/2012-01-0178
- Wickern , G. , Zwicker , K. , and Pfadenhauer , M. Rotating Wheels - Their Impact on Wind Tunnel Test Techniques and on Vehicle Drag Results SAE Technical Paper 970133 1997 10.4271/970133
- Modlinger , F. , Adams , N. New Directions in the Optimization of the Flow around Wheels and Wheel Arches 7th MIRA International Conference on Vehicle Aerodynamics 22 23 October 2008 978 1 906400 05
- SAE International Surface Vehicle Recommended Practice Road Load Measurement Using Onboard Anemometry and Coastdown Techniques SAE Standard J2263 Dec. 2008
- Overview of Coastdown Procedures Federal Regulations for Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium and Heavy Duty Engines and Vehicles, 40 CFR Part 1066.301 of the Federal Register 76 179 September 15 2011
- SAE International Surface Vehicle Recommended Practice Road Load Measurement and Dynamometer Simulation Using Coastdown Techniques SAE Standard J1263 March 2010
- Ranganathan , A. Adaptation of Linux and *BSD in Automotive Embedded Software SAE Technical Paper 2007-26-057 2007 10.4271/2007-26-057
- Kandasamy , S. , Duncan , B. , Gau , H. , Maroy , F. et al. Aerodynamic Performance Assessment of BMW Validation Models using Computational Fluid Dynamics SAE Technical Paper 2012-01-0297 2012 10.4271/2012-01-0297
- Duncan , B.D. , Fischer , A. , and Kandasamy , S. Validation of Lattice-Boltzmann Aerodynamics Simulation for Vehicle Lift Prediction ASME Conf. Proc. 2010, 2705 (2010), ASME Paper No. FEDSM-ICNMM2010-30891
- Cyr , S. , Ih , K. , and Park , S. Accurate Reproduction of Wind-Tunnel Results with CFD SAE Technical Paper 2011-01-0158 2011 10.4271/2011-01-0158
- Lounsberry , T. , Gleason , M. , Kandasamy , S. , Sbeih , K. et al. The Effects of Detailed Tire Geometry on Automobile Aerodynamics - a CFD Correlation Study in Static Conditions SAE Int. J. Passeng. Cars - Mech. Syst. 2 1 849 860 2009 10.4271/2009-01-0777
- Horrigan , K. , Duncan , B. , Keating , A. , Gupta , A. et al. Aerodynamic Simulations of a Generic Tractor-Trailer: Validation and Analysis of Unsteady Aerodynamics SAE Technical Paper 2008-01-2612 2008 10.4271/2008-01-2612
- Fischer , O. , Kuthada , T. , Widdecke , N. , and Wiedemann , J. CFD Investigations of Wind Tunnel Interference Effects SAE Technical Paper 2007-01-1045 2007 10.4271/2007-01-1045
- Fischer , O. , Kuthada , T. , Wiedemann , J. CFD Validation Project on Vehicle Scale Models under the Constraint of an Open Jet Wind Tunnel EUROMECH Colloquium 509 Vehicle Aerodynamics Berlin 2009
- Fischer , O. , Kuthada , T. , Mercker , E. , Wiedemann , J. et al. CFD Approach to Evaluate Wind-Tunnel and Model Setup Effects on Aerodynamic Drag and Lift for Detailed Vehicles SAE Technical Paper 2010-01-0760 2010 10.4271/2010-01-0760
- Fischer , O. , Kuthada , T. , Wiedemann , J. , Dethioux , P. et al. CFD Validation Study for a Sedan Scale Model in an Open Jet Wind Tunnel SAE Technical Paper 2008-01-0325 2008 10.4271/2008-01-0325
- SAE International Surface Vehicle Recommended Practice SAE Wind Tunnel Test Procedure for Trucks and Buses SAE Standard J1252 July 1981