The Reynolds number effect is one of the key factors for predicting the aerodynamic characteristics of advanced aircraft since it affects flight performance and development costs. This paper provides a comprehensive discussion of three major aspects of the Reynolds number effects of aircraft. Firstly, the advantages and limitations of different research methods in exploring the Reynolds number effect are introduced, with particular emphasis on large low-temperature wind tunnels as an effective way to obtain the aerodynamic characteristics of real flight Reynolds numbers. Secondly, the nonlinearity and complexity of high-Reynolds-number flow fields and their effects on aerodynamic characteristics are thoroughly analyzed. This analysis encompass diverse scenarios including slot flows around multi-element airfoils, shock-wave/boundary layer interaction over supercritical airfoils, high-angle-of-attack fighters, and inlet performance of flying wing configurations. Finally, correction methods for the Reynolds number effects are discussed, underscoring the importance of integrating wind tunnel experiments, numerical simulations, and flight tests. Based on a rigorous analysis of existing correction models' performance, insights are provided for developing more precise correction frameworks. In summary, the overview presented in this paper serves as a valuable reference for deepening our understanding of high Reynolds number effects, advancing the development of efficient simulation methods, enhancing aircraft design levels, and provides technical guidance for advanced aircraft development.

To investigate the drag reduction laws and the Reynolds number effects of porous media under cryogenic and high Reynolds number conditions, this study conducted skin-friction measurements and drag reduction experiments in a 0.3 m transonic cryogenic wind tunnel. Pressure sensors and oil flow devices were installed downstream of the smooth plate and porous media region respectively, to measure the power spectra of fluctuating pressure and the global skin friction. It is shown that the skin friction coefficient decreases with the increase of Reynolds number. With the increase of Reynolds number (increasing the Mach number or decreasing the total temperature of the incoming flow), the porous media drag reduction ratio shows a non-uniform decreasing trend. Besides, the introduction of porous media, the low-frequency signal strength of the downstream pulsating pressure increases, and the intensity of the high-frequency signal is weakened. Under the typical condition that Mach number Ma = 0.300, Reynolds number Re = 7.51×10⁶ and the total temperature of the incoming flow T₀ = 140 K, the drag reduction ratio of porous media is 11.4%, which initially verifies the feasibility of the drag reduction control strategy under low temperature and high Reynolds number conditions.