Evaluation of Wall-Interference Correction Method Using Numerical Analysis and Porous Wall Model

Abstract

Evaluation of the conventional linear wall-interference correction method is conducted using flows around a two-dimensional airfoil in a wind tunnel computed by computational fluid dynamics and a porous wall model. First, the computational results are validated by comparison with wind-tunnel test measurements. Then, the wall-interference effect is discussed using these results. Porous walls are effective for reducing blockage, which change the Mach number around the airfoil. However, high wall porosity causes large downwash, which changes the flow angle. In this paper, Mokry’s method, which is one of the linear wall-interference correction methods, is evaluated quantitatively using computational fluid dynamics. Computational result with wind-tunnel walls are corrected by Mokry’s method, and the corrected result is compared with the one without wind-tunnel walls. Mokry’s method shows high accuracy in subsonic and no-stall conditions, which satisfy the requirement of the small-perturbation potential equation. Its accuracy is also high even if the model is large relative to the wind-tunnel size. However, an error of about 10 drag counts is caused due to a shock wave in transonic flow conditions, and accuracy rapidly degrades around the stall condition, where an error exceeding 100 counts is caused by flow separation.