Flow and Heat Transfer Characteristics of Aerothermodynamic Loading on a Double Cone at Mach 12

Abstract

Abstract Although a significant body of research exists on shock-wave shear layer interactions (SWSLI), the scientific literature is lean with respect to the physics underlying SWSLI at extreme Mach number regimes. It is well known that small perturbations can lead to significant fluid dynamic changes (e.g., transition and associated heat transfer characteristics) at high Mach numbers, especially when the flow is in thermal and chemical non-equilibrium. While experiments have investigated the physics of flow over compression ramps, the physio-thermo-chemical processes remain elusive at high enthalpy condition. The dynamics are further complicated in the presence of non-smooth surface (due to the impact of debris, uncertainties in manufacturing processes, etc.) that drastically enhances the near-wall interactions. This is of great importance to accurately predict the aerothermal performance and trajectory of high-speed vehicles operating with realistic material surfaces (e.g., roughness elements, cavities, or protrusions). To address this, this research aims to investigate the influence of thermochemical non-equilibrium flow over a smooth double cone, and the influence of concave cavity on a double cone on the resulting post-shock non-equilibrium high-speed aerodynamic flow, and the associated SWSLI and heat transfer characteristics. In the present work, the massively parallel computational fluid dynamic solver, Eilmer, is utilized to simulate compressible high-speed fluid dynamics and near-body flow physics. Eilmer is a structured/unstructured grid flow solver based on finite-volume discretization of the time-accurate compressible Navier-Stokes equations with validated turbulence models, finite-rate internal energy excitation, and chemical kinetics. The work first targets a validation case study conducted based on measurements at the CUBRC facility that investigated the high-speed flow over a 25/55-degree double cone at a Mach number of 11.9 on an idealized smooth surface. Next, an in-depth overview of the thermochemical non-equilibrium flow physics is presented for the 2D axisymmetric 25/55-degree double cone. From there, a series of 2D axisymmetric double cone computations are conducted with a semi-circular cavity on the 55-degree surface region with a radius ranging from L/R (length of the ramp/cavity radius) of 100 to 33. The evolution of near-surface phenomena of interest, such as shear layer mixing and heat transfer are quantified showing increased intensities due to the presence of the cavity. The results from this study provide much-needed insights into the underpinning behavior governing SWSLI in the presence of non-ideal surfaces, and the effect of thermochemical non-equilibrium in higher Mach number flows.