Entropy losses in transonic shock-boundary-layer interaction

Wall-resolved large-eddy simulations are conducted to examine a Mach 1.1 normal shock-turbulent boundary layer interaction (SBLI) under systematically varied wall-to-recovery temperature ratios. A second-law thermodynamic analysis is employed to characterize the underlying mechanisms of entropy generation. Three distinct regimes are identified: a cooling-dominated regime, in which wall cooling substantially reduces total entropy production; a friction-dominated regime, where viscous dissipation is the primary source of irreversibility; and an intermediate entropy-balanced regime, where contributions from both shock-induced and wall-related mechanisms become comparable. Entropy generation due to viscous effects and heat conduction is quantified using newly defined, non-dimensional entropy dissipation coefficients. These coefficients exhibit robust self-similar scaling with the boundary-layer momentum-thickness Reynolds number, providing a generalized framework for assessing thermodynamic losses in wall flows and SBLI arrangements. Thus, the results offer a comprehensive entropy-based characterization of SBLI under variable thermal boundary conditions, yielding new insight into the coupled effects of aerodynamic heating, wall cooling, and shock dynamics in transonic flows. The proposed framework contributes to the development of physically grounded loss metrics, with implications for the design and optimization of high-speed propulsion and turbomachinery systems.