Study on the Effects of Surface Roughness on the Aerodynamic Characteristics of the CHN-T2 Wide-Body Aircraft Standard Model

Under actual flight conditions, the surface of civil aircraft is subject to prolonged erosion from wind, frost, rain, snow, sand, dust, and insect debris. This cumulative surface degradation significantly alters the skin microtopography, leading to progressive increases in surface roughness over flight time and consequently modifying the aircraft's aerodynamic characteristics. Similarly, in wind tunnel testing, particulate dust and organic impurities within the test section, accelerated by high-speed airflow, induce erosive wear and scratches on model surfaces. This progressive increase in surface roughness inevitably affects surface flow field characteristics, ultimately causing systematic deviations in aerodynamic performance evaluations. To address the impact of surface roughness on aerodynamic characteristics, this study combines wind tunnel experiments and numerical simulations to analyze the fundamental aerodynamic force characteristics of the wide-body aircraft standard model CHN-T2 under varying surface roughness levels. The research further investigates the influence of roughness on aerodynamic performance and transition characteristics at different angles of attack. Building on this, the study delves into the micromechanisms of surface roughness effects across a wide Reynolds number range. Results indicate that increased roughness elevates the total drag coefficient, advances the transition location from laminar to turbulent flow on wing surfaces, and enhances friction drag. The impact of roughness intensifies with increasing Reynolds number initially, subsequently stabilizing at higher values. Specifically, at low Reynolds numbers (3.3 million to 8 million), shock wave-induced transition dominates the outer wing region, with roughness increases causing forward movement of both shock wave and transition locations. At moderate Reynolds numbers (10 million to 15 million), roughness effects amplify: the laminar flow region diminishes on the inner wing, while TS (Tollmien-Schlichting)/CF (crossflow) instability-driven transition predominates in the outer wing, with roughness exacerbating laminar region reduction. When Reynolds numbers rise further (15 million to 45 million), roughness effects stabilize. The study also reveals roughness-induced alterations in boundary layer displacement thickness, momentum thickness, and velocity profiles. These findings provide critical guidance for improving wind tunnel test data reliability at high Reynolds numbers and optimizing aircraft surface treatment design.