Turbulent Triggers and the Model Quality Influence on Aerodynamic Characteristics of the Laminar Aerofoil in Transonic Flow Regime

Abstract

The test with a roughness application on the laminar aerofoil has been conducted in the N-3 trisonic wind tunnel of the Institute of Aviation in Warsaw. The main goal of tests was to investigate the influence of the boundary layer transition triggers on a laminar profile aerodynamic characteristic. For baseline configuration, the natural transition was applied. As a local roughness on the upper model surface, the carborundum strips with different heights were applied. These were positioned on the upper model surface in the front of the shock position occurrence. The Mach number during test was equal Ma = 0.7 and Reynolds number was about 2.85·106. Tests have been conducted for different model incidence in range 0°-7°. Current article refers partially to the previous study, where aerofoil model with lower quality of surface had been tested. Investigation results from previous work indicated that some of transition positions improved an aerodynamic characteristic by reducing the drag coefficient value and decreasing shock wave unsteadiness in the transonic regime. However, current article indicates that beneficial effects in respect to the baseline configuration are also strictly dependent on the model quality and turbulent triggers size. Improved surface quality of the laminar aerofoil model affected on aerodynamic characteristics with and without turbulent triggers. Resultant aerodynamic coefficients of all tested cases i.e. drag, lift and lift to drag ratio were compared.

Direct Numerical Simulations of Transonic Flow Around an Airfoil at Moderate Reynolds Numbers

“…Since the non-dimensional temperature at the isothermal airfoil surface is constant and equal to unity, the wall pressure is proportional to the wall density according to quality and polished surface, respectively. Assuming similar viscosity for both experiments, the Strouhal numbers of buffet phenomena in [41] are St ≈ 0.09 − 0.14. Even though the experiments were carried out at significantly higher Reynolds numbers showing permanent shock waves, the suggested buffet frequencies agree well with the low-frequency phenomenon at St ≈ 0.12 in the current work.…”