A Simplified Fourwall Interference Assessment Procedure for Airfoil Data Obtained in the Langley 0.3-Meter Transonic Cryogenic Tunnel

SUMMARY A simplified fourwall interference assessment method has been described, and a computer program developed to facilitate correction of the airfoil data obtained in the Langley 0.3-m Transonic Cryogenic Tunnel (TCT). The procedure adopted is to first apply a blockage correction due to sidewall boundary- layer effects by various methods. layer corrected data are then used to calculate the top and bottom wall interference effects by the method of Capallier, Chevallier and Bouinol, using the measured wall pressure distribution and the model force coefficients. The inter- ference corrections obtained by the present method have been compared with other methods and found to give good agreement for the experimental data obtained in the TCT with slotted top and bottom walls. The sidewall boundary- INTRODUCTION Wall interference is a problem of concern in testing of airfoils in wind tunnels, particularly at transonic speeds. This is largely due to the complex flow features at the ventilated walls introducing uncertainties in the boundary conditions. Therefore, modern wall interference calculation methods, in lieu of the classicaL boundary conditions, use experimentally measured values of the pressure and/or flow inclinations at the wall to correct the test data.