American Institute of Aeronautics and Astronautics 1 Preliminary RANS Simulations and Experimental Study of a Simplified Tractor/Trailer Geometry Subrahmanya P Veluri * and Christopher J. Roy † Auburn University, Auburn, Alabama, Zip 36830 Anwar Ahmed ‡ and Rifki Rifki § Auburn University, Auburn, Alabama, Zip 36830 Abstract Preliminary results are presented for Steady-state Reynolds-Averaged Navier-Stokes (RANS) simulations of the flow in the empty wind tunnel. Also presented are the experimental results of flow visualization over the simplified tractor/trailer geometry conducted at Auburn University. The simulations of the empty wind tunnel are carried out to determine the position of the simplified tractor/trailer geometry in the test section of the wind tunnel relative to the test section floor. It is observed from the computational simulations that the boundary layer thickness on the test section floor at the beginning of the test section is 0.3 inches and at the position where the trailer ends is 0.9 inches. The computational results of the empty wind tunnel are compared with the experimental data for validation. The comparisons include the boundary layer properties on the test section floor and the flow angularity calculations at the beginning of the test section. Some preliminary experiments were conducted on the simplified tractor/trailer geometry placed in the wind tunnel. A symmetric flow pattern moving outward from the center of the model is observed on the front side of the tractor. As the flow accelerated past the corner, it is observed that the flow undergoes laminar separation followed by a turbulent reattachment. Flow on the top of the tractor and also the trailer was observed to be smooth. Nomenclature C D = drag coefficient D = drag force S = cross-sectional area of the truck k = turbulent kinetic energy ω = specific dissipation rate δ = boundary layer thickness δ* = displacement thickness θ = momentum thickness ρ = density I. Introduction HE trucking industry is the backbone of the freight transportation system in the United States. According to 2003 data collected by the U.S. Department of Energy, 1 there are approximately 2.2 million tractor-trailers operating on U.S. highways. These vehicles average 62,900 miles traveled per year at a fuel consumption rate of 5.2 * Research Assistant, Aerospace Engineering Dept., 211 Aerospace Engineering Bldg., Student Member AIAA. † Assistant Professor, Aerospace Engineering Dept., 211 Aerospace Engineering Bldg., Senior Member AIAA. ‡ Associate Professor, Aerospace Engineering Dept., 211 Aerospace Engineering Bldg., Senior Member AIAA. § Research Assistant, Aerospace Engineering Dept., 211 Aerospace Engineering Bldg., Student Member AIAA. T 24th Applied Aerodynamics Conference 5 - 8 June 2006, San Francisco, California AIAA 2006-3857 This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.