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The flow conditions in a closed test section wind tunnel are not the same as in freestream due in part to the constraints imposed by the wind tunnel walls. Boundary correction methods can be applied to wind tunnel results to estimate the effects of wind tunnel wall constraints. One such scheme, the two-variable method, which is a measurement based scheme used to estimate a particular class of wind tunnel wall constraints known as solid and wake blockage, is described herein. The Glenn L. Martin Wind Tunnel (GLMWT) has implemented the two-variable method and has applied it previously for large models in a variety of applications, primarily in the evaluation of yacht’s offwind sail performance. This paper describes the application of the two-variable method to simplified fastback style three-dimensional automobile shapes at zero yaw angle. Models ranged in size from 2.75% to 5.53% of the tunnel’s cross-sectional area.

Effects of boundary conditions on the computational simulation of time dependent flows is studied. In particular, the effect of various boundary conditions for the flow over a half circular cylinder which is known to exhibit periodic shedding under certain conditions is investigated. A type of convection boundary condition called the radiation boundary condition is demonstrated to eliminate the secondary frequency which contaminates the solution due to the partial reflection of the fluid structures at the exit plane. However, the boundary condition implementation comes at the additional cost of storing results corresponding to three time levels.

Reynolds Averaged Navier-Stokes equations (RANS) were solved for three cases, namely, flow over a half cylinder in a uniform stream, near a stationary wall and near a moving wall. Time accurate, incompressible computations were performed for a Reynolds number of half-a-million. Computed time histories of force coefficients exhibit a strong tonal nature representative of regular periodic shedding. The effect of the ground on the periodic shedding was studied and the computational results were compared with experiments for the free stream and stationary wall cases. Strouhal number computed from the computational simulations agrees well with the experimental results. Time averaged pressure distribution on the body and wall show reasonable agreement with experimental data.

A critical aspect of the performance of the front wing of a Formula One or Indy race car is studied by idealizing them as a symmetric two-dimensional airfoil operating in ground effect. When such an airfoil operates at heights roughly equal to the airfoil thickness and lower, measurable amounts of negative force are generated. As the height continues to decrease, there is an expected force reversal. There are two objectives of the study reported in this paper. The first is the adequate verification of the Finite-Analytic Navier-Stokes computational approach by comparing computational results for the case of a stationary airfoil at various heights above ground to experimental results. The second is to elucidate the force reversal phenomena for the specific case of a NACA 0015 airfoil traveling at high Reynolds number above stationary ground in still air by utilizing the validated code.