Effects of multiple cavities on rarefied hypersonic flows

Cavity structures on hypersonic vehicle surfaces alter aerodynamic heat flux and force (pressure) compared to flat surfaces. In this study, an investigation explores the aerodynamic effects of multiple cavities on rarefied hypersonic flows, utilizing the Direct Simulation Monte Carlo method to assess the impact on hypersonic vehicle surfaces. While previous research predominantly concentrated on the implications of a single cavity, this study extends the investigation to multiple cavity configurations under rarefied flow conditions, which are less understood but critical due to the potential for significant impacts on vehicle performance and structural integrity. The research examines how variations in the number of cavities, as well as their geometric arrangement (distance and length-to-depth ratio), influence key aerodynamic parameters, including pressure, skin friction, and heat transfer coefficients. The study's findings reveal that in the rarefied hypersonic flow at Mach 25 at 70 km, each cavity independently influences the flow field and the aerodynamic surface properties, largely determined by its geometric characteristics, irrespective of adjacent cavity presence. The study underscores that the macroscopic aerodynamic force escalates with an increase in the number of cavities and their length-to-depth ratio, while it diminishes with inter-cavity distance. These insights are crucial to optimizing the design of hypersonic vehicles, contributing to improved performance and stability by managing aerodynamic forces more effectively. The comprehensive data and analyses provided support the development of more accurate models to predict and control the behavior of hypersonic vehicles with multiple cavities.