Parametric investigation of nonadiabatic compressible flow around airfoils

Abstract

The compressible flow of a mixture of dry air (an inert carrier gas) and water vapor with nonequilibrium and homogeneous condensation around thin airfoils is examined. The investigation is based on a recent transonic small-disturbance (TSD) theory. The theory provides the governing similarity parameters of the flow and condensation process. The parameters give the relationship between the flow properties, the amount of water vapor mass in the air, and the airfoil’s chord and thickness ratio. The results of varying the similarity parameters are demonstrated by numerical simulations. It is found that heat addition as a result of condensation causes significant changes in the compressible flow behavior and affects the aerodynamic performance of airfoils. Increasing the free-stream frozen Mach number or the airfoil’s chord (with fixed free-stream temperature, pressure, and amount of water vapor) augments the condensation region and the amount of heat transfer to the flow. The heat transfer to the flow also results in the appearance of a compression wave in addition to a regular shock wave. Also, decreasing the free-stream temperature with a fixed amount of water vapor in the air or increasing the free-stream temperature with a fixed free-stream supersaturation ratio enlarges the condensation region and reduces the shock wave strength. These results demonstrate the possible use of condensation phenomena to control aerodynamic characteristics of airfoils operating in internal flow systems.