In high-enthalpy shock tunnels, gas molecules are excited to higher vibrational and chemical energy states. However, rapid expansion and acceleration through the nozzle leave insufficient time for vibrational deexcitation and recombination, leading to significant gas–surface interaction effects on wall heat transfer. This research utilizes computational fluid dynamics (CFD) to study the influence of vibrational accommodation and finite-rate catalysis on flow field structure and peak heat flux in hypersonic compression corner flows under thermochemical nonequilibrium free-stream conditions, characterized by low-to-medium Reynolds numbers and high Mach numbers. The results indicate that vibrational accommodation and finite-rate catalysis have a negligible influence on the structure of the flow separation bubble. However, both significantly affect the peak heat fluxes, which can be decomposed into three components: translational-rotational heat flux, vibrational heat flux, and catalytic heat flux. More importantly, a validated theoretical method is proposed to predict the peak heat flux by accounting for the effects of incomplete vibrational accommodation and finite-rate catalysis. Furthermore, the proposed theoretical framework suggests an equivalence relation between the vibrational accommodation coefficient and the catalytic coefficient, indicating a quantitative interplay between the two and their comparable influence on heat flux under certain flow conditions.
The energy transport and exchange processes among the mean kinetic energy (MKE), turbulent kinetic energy (TKE), mean internal energy and turbulent internal energy in a shock wave/turbulent boundary layer interaction (SBLI) are quantified using direct numerical simulations. By analyzing the transport budgets of mean and fluctuating energy modes, the primary mechanisms governing energy transfer cycles within the interaction region are identified. Results show that energy transfer is dominated by three key processes: turbulence production ( P_k ), which transfers energy from the mean flow to turbulence, mean pressure dilatation ( Φ^pm ), which mediates the compressibility-driven energy exchange between MKE and mean internal energy, and viscous dissipation ( ε ), which irreversibly converts TKE into mean internal energy. The effects of variable density and terms related to turbulent internal energy are found to be negligible. The present work clarifies the essential energy transfer pathways in SBLI, offering valuable insights for the development of improved turbulence closure models and the design of effective flow control strategies.
Abstract This paper presents a nonlinear spectral difference (SD) scheme with adaptive linear weights for solving hyperbolic conservation laws. The proposed scheme enhances the traditional SD method by incorporating a nonlinear weighting strategy that adaptively adjusts linear weights based on local solution smoothness. The scheme maintains fifth-order accuracy in smooth regions while effectively capturing discontinuities. The numerical framework is validated through a series of benchmark problems, and the results demonstrate the proposed nonlinear scheme’s high-order accuracy, robustness, and ability to resolve complex flow structures without spurious oscillations. The adaptive linear weighting strategy ensures stability and accuracy across a wide range of flow conditions, making the scheme suitable for high-resolution simulations in computational fluid dynamics.
Abstract Reacting flow simulations represent a formidable challenge in numerical analysis because they incorporate complex mechanisms from various reacting flows alongside high-velocity fluid dynamics. This intersection makes them among the most intricate types of computational analyses available. A comprehensive review of existing experimental models, critical input parameters, and the methodologies behind active simulation methods is essential for advancing the field. This review emphasizes the fundamental processes that consistently affect the accuracy and predicted flow properties of a hybrid-rocket combustion model. It discusses various turbulence models, chemical mechanisms, and dimensional analyses. The key features of these turbulence, chemistry and dimensional models are outlined, and it was found that the existing numerical models have limited applicability to a complete hybrid rocket engine configuration. The review identifies the lacuna in the numerical and experimental models of hybrid rocket engines. The study also surveys current and planned space missions that use hybrid propulsion, thereby providing market context. Additionally, the paper explores solutions to common errors, offering insights on how to avoid them to minimize inaccuracies and instabilities in simulations. It summarises crucial overlooked aspects and proposes steps to address these issues comprehensively. The research also proposes a method for evolving the numerical model of hybrid rocket engines so as to reduce computational cost and time.
Abstract The multi-objective optimization of a horizontal axis wind turbine blade is performed to optimize its aerodynamic and structural performance by coupling two-way fluid–structure interaction (FSI) with a multi-objective particle swarm optimization (MOPSO) algorithm. The design parameters include chord and twist distributions, tip speed ratio, and blade material, while modal frequencies, allowable stress, and tip deformation were set as design constraints. The objectives are to maximize aerodynamic performance and reduce blade mass while ensuring structurally safe operation. Blade deformation in the flapwise and edgewise directions induces oscillatory velocity and alters the twist distribution, thereby changing the apparent angle of attack. Variations in the relative wind speed and the angle of attack affect the blade’s aeroelastic performance. The reduced deformation of the optimized flexible blade results in a higher pressure coefficient and lower stress. Compared with the baseline blade, the optimized flexible blade demonstrates a 12.5% improvement in aerodynamic performance, a 7.15% reduction in weight, and a 22% reduction in blade displacement.
