Effect of heterogeneous non-equilibrium condensation of moist air on the airfoil performance based on a blend model

In transonic and supersonic flows, moist air can undergo non-equilibrium condensation, which significantly influences the aerodynamic characteristics around airfoils. Therefore, it is essential to conduct an in-depth investigation into the flow mechanisms of transonic heterogeneous non-equilibrium condensation. In this study, a blend condensation framework incorporating multiple classical droplet growth laws is employed to describe heterogeneous non-equilibrium condensation in moist air. The framework accounts for different droplet growth regimes across the full Knudsen-number range, enabling a comprehensive representation of condensation behavior over a wide spectrum of droplet sizes. Based on this framework, numerical simulations were conducted to examine how variations in relative humidity and angle of attack influence transonic flow over the asymmetric RAE-2822 airfoil. The study emphasizes the impact of condensation on pressure coefficient distribution, aerodynamic forces, nucleation behavior, and subcooling intensity. Quantitative results demonstrate that latent heat release from condensation profoundly alters the pressure distribution, shifting the shock wave position upstream by 8.85% of the chord length when relative humidity increases from 30% to 70%. Furthermore, foreign nucleation induced by particles initiates the condensation process earlier, reducing the maximum supercooling degree by approximately 13 K compared to pure homogeneous nucleation. Aerodynamically, this non-equilibrium phase change leads to a maximum lift coefficient reduction of 41.7% and a drag coefficient increase of 74.2% under the tested conditions. These quantitative findings provide critical insights into the aerodynamic penalties of moist air condensation, offering a robust theoretical framework for transonic airfoil design and optimization in realistic atmospheric environments.