This study investigates the application of the Co-Flow Jet (CFJ) active flow-control methodology to an automotive rear wing through a combined CFD and experimental campaign conducted on a modified McLaren 765LT. The work evaluates the aerodynamic response, energy performance, and practical integration of embedded Co-Flow systems under representative on-track conditions. An extensive CFD design campaign assessed multiple Co-Flow architectures, from which three representative configurations incorporating embedded ducted axial fans were selected for experimental testing. The results indicate that aerodynamic performance is strongly influenced by the interaction between momentum injection, vehicle conditions, and duct architecture. The most effective configuration achieved drag reductions of up to 9% together with downforce increases of approximately 15% under highly loaded conditions, significantly exceeding the repeatability levels of the measurements. The efficiency analysis further showed that, under selected operating conditions, the aerodynamic benefits obtained from the Co-Flow system can exceed the electrical power required by the actuation system. However, increased mass-flow capability alone was not found to guarantee improved aerodynamic performance or efficiency. The results demonstrate the successful integration and operation of a fan-driven Co-Flow system on a production-based vehicle and highlight the importance of momentum injection level and duct design. The findings should be interpreted within the scope of the investigated vehicle and operating envelope. Due to confidentiality constraints, part of the absolute aerodynamic data could not be disclosed, and the results are therefore presented primarily as relative variations.

The paper presents a multi-temperature model for H2/He mixture derived from the state-to-state kinetics. Electronically excited states have been included in the model as separate pseudo-species. The theoretical approach on the reduction of a state-specific model to multi-temperature kinetic is described in detail in the Supplementary Material, reporting also analytical fits. The model has been verified against state-to-state calculations in 0D approximation, demonstrating a good degree of accuracy. The verification has also been performed investigating the hypersonic flow past a two-dimensional capsule entering in Uranus atmosphere.

A multi-internal-temperature approach for hypersonic air kinetics has been consistently derived from the state-specific vibrational kinetics. Vibrational levels have been grouped in a limited number of subsets (one to five), each one characterized by its own concentration and temperature, approximating the entire distribution as a piecewise Boltzmann. The capability of the reduced-order model in terms of accuracy and computational savings has been tested comparing the results with those obtained using the state-to-state approach. Firstly, a 0D heat bath evolution in thermochemical non-equilibrium is considered. Then, the proposed model has been implemented in a finite volume solver for the solution of the Euler equations, employing a Flux Vector Splitting scheme with MUSCL reconstruction, and used to solve an axisymmetric hypersonic flow pasta sphere.

In the current emerging of New Space Economy, space exploration is becoming a priority for the scientific community, for Space Agencies, and for industries. In this field, while gas giants (Jupiter and Saturn) have been explored thanks to NASA space missions, the study of ice giants (Uranus and Neptune) remains an open issue. ESA and NASA are carrying out extensive researches to devise affordable strategies in order to reach these planets in a reasonable time. Specifically, a critical issue in planet exploration is the atmospheric entry phase, due to the extremely challenging flight conditions experienced by the space vehicle. This paper illustrates a numerical investigation of entry and aerocapture maneuvers for ice giant orbit insertion. A comparison between the full State-to-State kinetic model and the proposed hybrid macroscopic model, coherently derived from state-specific dynamical data, is presented in detail. Two different flow regimes are analyzed: a low enthalpy flow, characterized by molecular dissociation, and a high enthalpy flow, where ionization and radiation become relevant.

This study explores the turbulent breakdown of high-enthalpy hypersonic boundary layers under adiabatic wall conditions using direct numerical simulations, with a focus on finite-rate chemistry effects. By subjecting a Mach 10 boundary layer to controlled perturbations via suction and blowing, the investigation shows the evolution from laminar to fully turbulent regime, via second-mode transition. In contrast to conventional understanding, this work identifies subharmonic breakdown scenario as significant contributor to turbulent transition, with energy transfer to secondary disturbances driving the process. The influence of finite-rate chemistry on growth rates is analyzed, revealing that chemical non-equilibrium has a stabilizing effect on secondary instabilities. Dynamic mode decomposition analysis further elucidates the modes predominantly involved in turbulent breakdown.

A high-order shock-capturing central finite-difference scheme is evaluated for numerical simulations of hypersonic high-enthalpy flows out of thermochemical equilibrium. The scheme is an extension to thermochemical out-of-equilibrium flows of the technique presented in Sciacovelli et al. (2021) for high-speed flows in chemical nonequilibrium. It relies on a standard tenth-order accurate central-difference approximation of the inviscid fluxes, supplemented with a high-order accurate nonlinear artificial dissipation term of ninth-order accuracy in smooth flow regions. Close to flow discontinuities, a shock-capturing low-order term is activated based on a highly selective shock sensor. To enable robust and non oscillatory solutions in regions of strong discontinuities of the thermodynamic variables, including the vibrational temperature, a shock detector consisting of a combination of a pressure-based term and Ducros’ vorticity/dilatation sensor is applied to all conservation equations except that of vibrational energy. For the latter, a shock sensor based on the vibrational temperature itself is adopted instead, to account for the loose coupling between vibrational energy and pressure. The accuracy and robustness of the proposed approach is demonstrated for a variety of thermochemical non-equilibrium configurations, ranging from one-dimensional benchmarks to three-dimensional turbulent flows, for which the ILES capabilities of the selective high-order numerical dissipation are also showcased.

Abstract The goal of this paper is to create a solid and efficient design method leveraging a fuzzy logic algorithm. This fuzzy logic system presents a non-analytical structure, facilitating the management of numerical mappings and data obtained by measurements and analytical relations, while also utilising the knowledge distributed in previous projects. Employing this information, the fuzzy logic algorithm can quickly generate an initial design, serving as a solid foundation for further optimisation. This first-glance solution can be leveraged to generate a few other designs in its neighbourhood that will then constitute the Fuzzy Logic Base of rules for further optimisation. The proposed method’s effectiveness and efficiency are demonstrated through the design of a nozzle for both subsonic and transonic flow conditions.

In the era of space exploration, the scientific community is strongly focusing on the analysis of hypersonic flows in the presence of shock wave/boundary layer interaction. In these conditions, the flow field presents a complex shock structure due to the interaction of different shock waves with the boundary layer. The strong adverse pressure gradient makes the boundary layer separate, giving rise to a separation bubble. In the reattachment zone, the temperature can reach very high values, inducing thermochemical non-equilibrium effects. This research field is recently achieving more and more relevance in aerospace research, as the analysis of turbulent shock wave/boundary layer interaction so far has been mainly focused on perfect gas flows. In this manuscript, a Reynolds averaged Navier–Stokes (RANS) approach is considered, the shear stress transport (SST) model being coupled with the multitemperature approach proposed by Park to investigate thermochemical non-equilibrium effects in hypersonic turbulent shock wave/boundary layer interaction. The first part of the manuscript is devoted to the validation of the solver, and results for low enthalpy flat plate and compression ramp flows are presented. The numerical results are shown to be in good agreement with numerical solutions and experimental measurements. Afterward, the free stream conditions are modulated to make non-equilibrium relevant and analyze a reacting flow.

In this paper, the manufacturing challenges and related technological solutions concerning the prototyping of microwave ablation (MWA) probes are addressed. In particular, the intertwined aspects pertaining probe design, fabrication and target performance are tackled. The development of a 14G MWA probe prototype, working at a frequency of 2.45 GHz, is proposed as a case study, describing design efforts and the use of rapid prototyping technologies combined with other manufacturing processes. A specific focus is dedicated to the insulating part of the probe radiating section, featuring high aspect ratio and complex shape, which was fabricated by means of Digital Light Processing (DLP) and by using a biocompatible material, the EnvisionTEC E-Shell® 300. Furthermore, the probe handling, properly designed to arrange cables and tubes routing, was fabricated by means of Fused Deposition Modeling (FDM) technology. Finally, ex vivo experiments conducted on bovine liver showed satisfactory treatment performance and structural reliability of the 14G MWA probe prototype. Besides being characterized by a good impedance matching ( S11 = −25 dB), prototype performance were also in good agreement with design simulations and even satisfying if compared to other results available in literature as, with an input radiation power of 40 W, the ablated zone after a 10 min treatment exhibited a ratio of the radial and longitudinal axis of 0.66.

The dynamics of a shock wave impinging on a transitional high-enthalpy boundary layer out of thermochemical equilibrium is investigated for the first time by means of a direct numerical simulation. The freestream Mach number is equal to 9 and the oblique shock impinges with a cooled flat-plate boundary layer with an angle of 10{\deg}, generating a reversal flow region. In conjunction with freestream disturbances, the shock impingement triggers a transition to a fully turbulent regime shortly downstream of the interaction region. Accordingly, wall properties emphasize the presence of a laminar region, a recirculation bubble, a transitional zone and fully turbulent region. The breakdown to turbulence is characterized by an anomalous increase of skin friction and wall heat flux, due to the particular shock pattern. At the considered thermodynamic conditions the flow is found to be in a state of thermal non-equilibrium throughout, with non-equilibrium effects enhanced and sustained by the shock-induced laminar/turbulent transition, while chemical activity is almost negligible due to wall cooling. In the interaction region, relaxation towards thermal equilibrium is delayed and the fluctuating values of the rototranslational and the vibrational temperatures strongly differ, despite the strong wall-cooling. The fully turbulent portion exhibits evolutions of streamwise velocity, Reynolds stresses and turbulent Mach number in good accordance with previous results for highly-compressible cooled-wall boundary layers in thermal nonequilibrium, with turbulent motions sustaining thermal nonequilibrium. Nevertheless, the vibrational energy is found to contribute little to the total wall heat flux.

In the era of space exploration, one of the fundamental goals is the investigation of the atmospheric re-entry of a space vehicle, which undergoes tremendous heat load due to the shock waves forming in front of its thermal shield. In the view of heat mitigation, ablative materials are employed for the design of the Thermal Protection System (TPS) of most of the modern vehicles. Such materials essentially modify the nature of the gas in the boundary layer due to the interaction of the solid and gas phases. Thanks to the material consumption, heat load is mitigated at the expense of ablated species which significantly contaminate the boundary layer gas mixture. In this context, this work aims at characterizing the aerothermodynamics environment around a bluff body in the presence of ablation and thermochemical non-equilibrium. Specifically, a five species neutral air mixture (N2, O2, NO, N, O) is combined with a six ablated species mixture (CO, CN, CO2, C, C2, C3). Two test cases are considered. Firstly, a subsonic pure nitrogen flow past an ablative sample is simulated, which is used as verification study by direct comparison with numerical results. For this reason, a classic multitemperature (mT) approach is employed to handle non-equilibrium. The second test case is a well-known hypersonic air flow past a spherical body used as a benchmark to assess the influence of ablation. In this case, two different kinetics models are used, namely the classical multitemperature and the more sophisticated State-to-State (StS) approach.

In this paper, the dynamic of inertial capsules into microfluidic bifurcations is studied. The fluid evolution is based on the solution of the BGK - lattice Boltzmann scheme including a forcing term accounting for immersed geometries. The dynamic-Immersed Boundary forc-ing strategy is adopted for imposing no-slip boundary conditions on moving deformable or rigid structures, while, on fixed immersed geometries the Bouzidi-Firdaouss-Lallemand second-order bounce back technique is implemented. The proposed computational frame -work is employed to detail dynamics and deformation of rigid and deformable capsules traveling into a branching duct. This journey is characterized in terms of i) the cap-sule/bifurcation interaction depending on the sharpness of the branching channels junc-tion; ii) daughter branches aperture angle; iii) occlusion ratio, the ratio between capsule size and main channel diameter; iv) flowing capsules stiffness; v) number of flowing par-ticles.(c) 2022 Elsevier Inc. All rights reserved.

This paper describes the most advanced results obtained in the context of fluid dynamic simulations of high-enthalpy flows using detailed state-to-state air kinetics. Thermochemical non-equilibrium, typical of supersonic and hypersonic flows, was modeled by using both the accurate state-to-state approach and the multi-temperature model proposed by Park. The accuracy of the two thermochemical non-equilibrium models was assessed by comparing the results with experimental findings, showing better predictions provided by the state-to-state approach. To overcome the huge computational cost of the state-to-state model, a multiple-nodes GPU implementation, based on an MPI-CUDA approach, was employed and a comprehensive code performance analysis is presented. Both the pure MPI-CPU and the MPI-CUDA implementations exhibit excellent scalability performance. GPUs outperform CPUs computing especially when the state-to-state approach is employed, showing speed-ups, of the single GPU with respect to the single-core CPU, larger than 100 in both the case of one MPI process and multiple MPI process. (C) 2017 Elsevier B.V. All rights reserved.

This work presents a detailed analysis of the shock wave/boundary layer interaction in hypersonic flows around a double-cone. Numerical simulations have been carried out by solving the axisymmetric Navier- Stokes equations for an oxygen mixture. Thermochemical non-equilibrium is taken into account by employing the multi-temperature model (mT) proposed by Park and the State-to-State model (StS). The occurrence of surface processes is also analyzed considering both non-catalytic and fully-catalytic wall models. It is shown that the evaluation of correct free stream conditions is fundamental for the prediction of the separation extent and the corresponding heat transfer in high enthalpy conditions.

: A high-order shock-capturing finite-difference scheme for scale-resolving numerical simulations of hypersonic high-enthalpy flows, involving thermal non-equilibrium effects, is presented. The suitability of the numerical strategy for such challenging configurations is assessed in terms of accuracy and robustness, with special focus on shock-capturing capabilities. The approach is demonstrated for a variety of thermochemical non-equilibrium configurations.

The paper presents highly detailed two-dimensional numerical simulations of hypersonic nitrogen and air flows around a double wedge, characterized by a complex shock wave/boundary layer interaction (SWBLI). The aim of the study is on one hand to investigate the unsteady behavior of such an interaction and on the other to evaluate thermo-chemical non-equilibrium effects. Two different thermo-physical models have been considered, the classical multi-temperature, or mode approximation, and the state-to-state vibrational kinetics. It is shown that for the geometric configuration under investigation, the occurrence of unsteady periodic behavior depends on the flow conditions and is inhibited in the high enthalpy case. Furthermore, non-equilibrium effects become relevant in the case of high enthalpy flows and discrepancies between the results obtained with the two models are observed.

A hypersonic, spatially evolving turbulent boundary layer at Mach 12.48 with a cooled wall is analysed by means of direct numerical simulations. At the selected conditions, massive kinetic-to-internal energy conversion triggers thermal and chemical non-equilibrium phenomena. Air is assumed to behave as a five-species reacting mixture, and a two-temperature model is adopted to account for vibrational non-equilibrium. Wall cooling partly counteracts the effects of friction heating, and the temperature rise in the boundary layer excites vibrational energy modes while inducing mild chemical dissociation of oxygen. Vibrational non-equilibrium is mostly driven by molecular nitrogen, characterized by slower relaxation rates than the other molecules in the mixture. The results reveal that thermal non-equilibrium is sustained by turbulent mixing: sweep and ejection events efficiently redistribute the gas, contributing to the generation of a vibrationally under-excited state close to the wall, and an over-excited state in the outer region of the boundary layer. The tight coupling between turbulence and thermal effects is quantified by defining an interaction indicator. A modelling strategy for the vibrational energy turbulent flux is proposed, based on the definition of a vibrational turbulent Prandtl number. The validity of the strong Reynolds analogy under thermal non-equilibrium is also evaluated. Strong compressibility effects promote the translational–vibrational energy exchange, but no preferential correlation was detected between expansions/compressions and vibrational over-/under-excitation, as opposed to what has been observed for unconfined turbulent configurations.

During atmospheric entry, the flow environment around capsules or space debris is characterized by complex fluid thermochemistry and gas-surface interactions (GSI). Computational fluid dynamics (CFD) simulations of these conditions are crucial in the design process of such objects. A promising approach for the simulation of complex geometries is the use of immersed boundary methods (IBM) and adaptive mesh refinement techniques (AMR). These methods offer reliable and efficient mesh generation and adaptation with minimal user intervention. To that end, this paper presents the recent developments of two IBM-AMR solvers coupled with the same external thermochemistry library for the accurate modelling of such complex flows including GSI. Several verification and validation cases are presented, which demonstrate the performance of the solvers. Results are analyzed in comparison with a body-conforming solver that uses the same thermochemistry library to achieve a consistent assessment of the underlying numerical methods. A good agreement between all the solvers is indicated with certain discrepancies arising due to the differences in surface treatments.