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This paper details the aerodynamic development of the University of Maryland's Pride of Maryland solar powered race car. This vehicle was built for the General Motors Sunrayce U.S.A., held in July of 1990. Two 3/8 scale models were built and tested in the university's wind tunnel. In addition, computational fluid dynamics and full scale testing were used to verify the design. Race experience further proved the worthiness of the design. Conclusions were drawn between the 3/8 scale model test results and the full scale results.

A critical aspect of the performance of the front wing of a Formula One or Indy race car is studied by idealizing it as a negatively cambered two-dimensional airfoil operating in ground effect and determining the fiowfield at various heights. When the airfoil operates at heights roughly equal to the airfoil thickness, significant negative lift is generated. As the height is decreased, there is an expected downforce reduction. The primary objective of this work is to elucidate the force reduction phenomena for the specific case of an inverted NACA 4412 airfoil traveling at high Reynolds number above ground in still air. This is the road condition. The secondary objective is to compare and contrast the fiowfield about this airfoil in road conditions and when operating in the wind tunnel environment, i.e. when the airfoil and the ground are not moving relative to each other.

There is little information in the technical literature about the dependence of drag coefficient, CD, on aspect ratio (height/width) for car and truck aerodynamics. Some of the information suggests that CD should increase with aspect ratio as the flow over the body becomes more two dimensional. Recent tests of candidate shapes for a commercial van with various roof heights suggested the opposite is true; the taller vans had lower drag coefficients. This report discusses the results of several experimental investigations to examine this relationship. Scale model and production drag measurements of commercial vans are presented along with drag measurements of simple shapes. The shapes consisted of eight radiused rectangular boxes of constant length and frontal area, but with different height/width ratios. The effects of underbody roughness and bumper presence were evaluated and are discussed.

Almost all published results of wake measurements for ground vehicles or similar shapes have included very limited information on streamwise development of wake structures. This is typically a result of the fact that the wake measurements have been conducted as parts of particular vehicle development efforts. So the focus has been on the incremental changes in the wakes associated with alternative geometries or buildup of various parts. The objectives are typically reached by limiting the surveys to a single streamwise plane. The present study, by contrast, is a study of wake development for a series of relatively simple rectangular shapes with radiused edges with a systematic variation in the ratio of height to width or “Aspect Ratio”.

The work presented here is a further step in a continuing effort by the authors to study and document the aerodynamic effect of varying aspect ratio, ground clearance, and underbody roughness for basic rectangular shapes with radiused edges in ground effect. Previous papers by the authors have presented extensive wake data for a range of aspect ratios and underbody roughness conditions. Force and moment data have been published for various aspect ratios, underbody roughness, and ground clearance. In this paper, additional wake data showing the effects of variation in ground clearance is presented. The focus of this paper is on analyses to make progress toward a rational correlation between body characteristics, the forces, and the measured wake properties. A parametric analysis is presented linking the effects of the parameters varied in the study to the changes in the aerodynamic forces and moments. Results show correlations between the wake flows and the force results.

Wind tunnel testing of reduced-scale models is a valuable tool for aerodynamic development during the early stages of a new vehicle program, when basic design themes are being evaluated. Both full-and reduced-scale testing have been conducted for many years at the General Motors Aerodynamics Laboratory (GMAL), but with increased emphasis on aerodynamic drag reduction, it was necessary to identify additional facilities to provide increased test capacity. With vehicle development distributed among engineering teams around the world, it was also necessary to identify facilities local to those teams, to support their work. This paper describes a cooperative effort to determine the correlation among five wind tunnels: GMAL, the Glenn L.