Practical Application of the Two-Variable Blockage Correction Method to Automobile Shapes

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. The results obtained using this method are compared to the results obtained when using two other commonly applied blockage correction schemes, namely the continuity method and the area ratio method.