Numerical Techniques Applied To the Assessment of Sidewall Boundary Layer Interference in 2-D Wind Tunnel Testing of Airfoils

摘要

The effect of sidewall boundary layers in wind tunnel testing is analyzed using an invisicd wing code coupled with a small crossflow boundary layer method to compute the sidewall boundary layer. The method is used to predict effects on the so called A4 supercritical airfoil in the IAR 1.5x1.5m wind tunnel. This can be operated in a 2-D mode with a 0.38m wide insert in the working section giving usually a width to chord ratio of about 1.5. Although sidewall boundary layer effects are alleviated to some extent by allowing for controlled suction on the walls surrounding the airfoil, it is shown in he present paper that a residual effect is ~direct C still experienced in such a narrow facility. Also analysis is made for the A4 airfoil tested in the full span 1.5m wind tunnel facility at IAR for which the width to chord ratio was 4.5. A second numerical method using a 3-D Navier-Stokes code is also presented for comparison. Finally results of the analysis are compared vis-a-vis wind tunnel data obtained for the A4 airfoil in both the narrow span and large span IAR facilities.