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A full-scale investigative wind tunnel test was performed on a dirt track race car in the Langley Full Scale Tunnel (LFST). Lift and drag forces were measured and flow visualization studies performed for the purpose of quantifying the aerodynamic characteristics in order to assist designers and drivers of this class of vehicle. Results from the downforce measurements showed a rear axle biased aerodynamic balance. Flow visualization studies revealed large areas of separated flow on the forward portion of the side pods as well as over a large portion of the rear deck and spoiler behind the driver.

Application of a formally designed experiment to wind tunnel testing of a sportscar prototype was explored at the Langley Full Scale Tunnel. A two-level fractional factorial design with center points was used to determine the effect of front ride height, rear wing angle, gurney flap height, spoiler height, and yaw angle on the front downforce, rear downforce, drag, and lift-to-drag ratio of the racecar. Regression models were created for each of the responses to provide aerodynamic prediction and optimization capabilities. Prediction models provide an “aerodynamic mapping” that can be used for effective tuning of the car at the track as well as serve as a math model for numerical lap simulations.

This paper reviews the development of a new test capability for race cars at the Langley Full-Scale Tunnel. The existing external force balance of the Langley Full-Scale Tunnel, designed for use with full-scale aircraft, was reconfigured for automobile testing. Details of structural modifications relevant to supporting cars and force measurements are shown. A specialized automobile force balance, measuring vehicle drag and individual wheel downforce, was then designed, constructed and calibrated. The design was governed by simplicity and low cost and was tailored to the stock car racing community. The balance became fully operational in early 1998. The overall layout of the automobile balance and comparisons to reference data from another full-scale wind tunnel is presented.

External aerodynamics remains one of the major concerns in designing a new generation road vehicle. In the present study, the external aerodynamics of an Ahmed body at a scale and Reynolds number, that are representative of a car or light truck at highway speeds, is explored. An experimental model test was compared with a computational model using various back angles. In addition, the experiment allowed lift and drag to be measured at yaw angles up to ±15 degrees. Reynolds number effect on drag and lift coefficients was studied and wind averaged drag coefficients were calculated. The numerical calculations used a Reynolds-averaged, unsteady Navier-Stokes formulation. Both experimental and computational results are presented for back angles of 0-, 12.5-, and 25-degrees, then compared with each other and the data available in the literature.

Recently, there has been a strong emphasis on aerodynamic and aeroacoustic wind tunnel testing of automobiles. While significant level resources have been spent on investigating aerodynamics, the methodology has not changed appreciably since the beginning of aerodynamics as a science. Over the past decade, a number of global flow diagnostic techniques have been developed that drastically increase the quality and quantity of data from wind tunnel testing. One of these technologies is the use of pressure sensitive luminescent coatings, known as pressure-sensitive paint, a method which has matured considerably since its inception and is now used extensively in aerospace applications with good results. The goal of this research is to implement this technology in the full scale testing of high performance automotive vehicles. This paper discusses the details of a preliminary test, such as technique, paint formulation, camera and lighting hardware, and data reduction and analysis.

A road simulation system has been developed at the Langley Full-Scale Tunnel (LFST) to support the aerodynamic testing of NASCAR-class race cars. The leading edge of the existing ground board was recontoured to alleviate a separation bubble and an active suction boundary layer control system, incorporating a bleed slot and axial flow blower, has been implemented. Performance evaluations include boundary layer surveys at various locations in the vicinity of the car balance with the empty tunnel as well as force measurements with a representative vehicle both with and without the boundary layer control system operating.

A Design of Experiments (DOE) approach to wind tunnel testing of performance automobiles is being explored at the Langley Full-Scale Tunnel. Traditional methods for wind tunnel testing have focused on conventional “one factor at a time” (OFAT) methods which have difficulty in unearthing valuable interactive effects between variables. In an effort to better characterize a vehicle's aerodynamic behavior as a function of common variables, an exploratory study was completed using the DOE methodology for a common sedan racecar. A two-level factorial designed experiment with center points produced regression models for the lift, drag, and lift to drag ratio as a function of ride height, grille porosity, and yaw angle. In addition, model adequacy and uncertainty levels were described.