Fixed Boundary transition effect on transport aircraft aerodynamic characteristics under different Reynolds numbers

Abstract

Scale differences between test models and real aircraft result in Reynolds number effect, which made it impossible to simulate boundary layer conditions and obtain accurate aerodynamic characteristics of vehicles, especially of transport aircraft, by wind tunnel tests. Normally, laminar flow would exit over super critical wing during wind tunnel tests. Fixed transition effect on super critical wing aerodynamics characteristics was investigated in traditional wind tunnels. The relative experiments were conducted in a transonic wind tunnel. Force/moment and surface pressure distribution were measured with a full model and a half model respectively. Test Mach number ranged from 0.7 to 0.86, and Reynolds number ranged from 3.3 million to 16.5 million. Experiment results showed that surface pressure distribution would be changed significantly by fixed transition when shock wave and induced boundary layer separation appeared on upper surface. With the increasing of test Reynolds numbers, its effect became weakened, and the effect was ignorable when test Reynolds number exceeded 15 million. To obtain credible wind tunnel results, fixed boundary layer transition of super critical airfoil were recommended when test Reynolds numbers were less than 15 million.