This study presents an experimental investigation of oxygen-assisted atomization as a novel strategy for supersonic combustion control, benchmarked against air-assisted atomization. Experiments were conducted in a Mach 2.5 flow with liquid kerosene injection with a 1580 K total temperature and 0.93 MPa total pressure at an equivalence ratio of 0.6, varying gas-to-liquid mass flow rate ratios (GLRs). CH* chemiluminescence was employed to identify combustion zones. Increasing GLR enhances combustion performance and regulates flame stabilization modes. At low-to-moderate GLRs (10–14%), cavity-shear-layer-driven combustion manifests as flame oscillations (265–278 Hz) between cavity and jet wake regions. Transitioning to high GLR (20%) stabilizes combustion in jet wakes, suppressing low-frequency oscillations but inducing broadband fluctuations. Furthermore, oxygen-assisted atomization demonstrates synergistic physicochemical enhancement at GLR=10%: improved atomization quality strengthens fuel–air mixing (physical effect), while localized oxygen enrichment accelerates reaction kinetics (chemical effect). This dual mechanism shifts the flame upstream and expands the reaction zone, yielding a peak static pressure increase exceeding 10% and a 23.7% improvement in thrust augmentation compared to air-assisted cases. However, in the local low-temperature region, oxygen tends to combine with H and OH radicals to form HO2, inhibiting the reactivity of the chain reaction.

Buzz is a critical concern in aeroelasticity in modern aircraft design. It stems from the coupling of flow and structural modes, causing structural instability. As wings grow larger, aeroelastic effects gain more significance, especially the influence of the structural mode of the main wing with higher flexibility on the buzz characteristics. Based on two-dimensional three-degree-of-freedom airfoils, this paper delves into how the plunge and pitch modes affect flap buzz in buffeting flows. Using an aeroelastic model based on a reduced-order model (ROM) and CFD/CSD time-domain simulations, the study shows that airfoil structural modes notably impact flap buzz. The plunge-flap deflection coupling is weak, yet the plunge mode enlarges the instability range of the flap deflection mode. Conversely, the pitch-flap deflection coupling is strong, and the pitch mode shrinks the instability range of the flap deflection mode. Notably, the ratio of flap deflection frequency to plunge frequency has negligible effects on the instability of the flap deflection mode, while the ratio of flap deflection frequency to pitch frequency has significant impacts on it. Adjusting the ratio between the structural frequency and the flap deflection frequency can be an effective strategy for avoiding buzz.

This article proposes a variational quantum algorithm to solve linear and nonlinear thermofluid dynamic transport equations. The hybrid classical-quantum framework is applied to problems governed by the heat, wave, and Burgers’ equations in combination with different engineering boundary conditions. Topics covered include the encoding of band matrices, as in the consideration of nonconstant material properties and upwind-biased first- and higher-order approximations, widely used in engineering computational fluid dynamics, by the use of a mask function. Verification examples demonstrate high predictive agreement with classical methods. Furthermore, the scalability analysis shows a polylog scaling of the number of quantum gates with the number of qubits. Remaining challenges refer to the implicit construction of upwind schemes and the identification of an appropriate parameterization strategy of the quantum ansatz.

Understanding the spatiotemporal evolution and vortex–particle coupling mechanisms of polydisperse microparticles in supersonic transverse jets is a fundamental challenge in aerospace propulsion systems. This study uses a Mach 2.6 supersonic direct-connect experimental platform with a total temperature of 1550 K and a velocity of ∼1392 m/s. This platform is integrated with high-speed planar laser scattering and high-speed shadowgraph imaging. This setup is used to elucidate the dynamic behaviors of polydisperse microparticles (ranging in size from 0.1 to 150 μm) in supersonic transverse jets. Experimental results show that the particle clusters form three quasi-coherent distribution patterns sequentially along the jet trajectory: a fluctuating distribution on the windward side, a trailing distribution on the leeward side, and a roller-type distribution near the injection wall. Analysis based on proper orthogonal decomposition shows that shear layer instability dominates the particle dispersion process, exhibiting multiscale transfer characteristics. The study points out that the particle distribution pattern is essentially a spatiotemporal representation of their clustering behavior during the dynamic evolution of the large-scale roller-type vortex. The degree to which the particle response time matches the vortex timescale (i.e., the Stokes number) determines the clustering pattern. These findings provide critical experimental insights into particle-laden dynamics within supersonic multiphase flows.

Under high-enthalpy conditions, the calculation of transport properties such as viscosity and thermal conductivity needs to account for nonequilibrium effects, including vibrational nonequilibrium and the dissociation of molecules. Current models require computationally intensive mixing rules and are limited to certain temperature ranges. With scale-resolving simulation becoming more commonplace, there is a need for efficient formulations that can cover a wide range of temperatures. In this contribution, a simplified formulation is proposed for the viscosity and thermal conductivity of air in the temperature range 100–9000 K. Thermal conductivity is decomposed into ro-translational and vibrational contributions for molecular species. The predictions are applicable to both equilibrium and nonequilibrium conditions. For equilibrium air, the predictions are typically within a few percent of reference data. An application to a transitional mixing layer, starting with partially dissociated air at a temperature of 6000 K, is presented. The mixing layer is simulated with a high-order finite difference method and undergoes inflectional instability and transition to turbulence. With the new method the transport properties are within 2.2% of reference values, while the reduced complexity means that the simulations are substantially faster.

This study addresses numerical challenges in simulating pressureless air-mixed droplet flows under atmospheric icing conditions. The governing equations, commonly referred to as the Eulerian droplet equations, comprise a combination of the pressureless gas dynamic (PGD) equations and source terms that account for drag and gravitational effects. Within this framework, three fundamental challenges are identified: 1) the need for a relaxation model to handle the advection terms, 2) numerical instabilities induced by stiff source terms, and 3) the formulation of suitable boundary conditions on solid surfaces. For these challenges, we propose novel numerical strategies. First, we introduce a relaxation model that retains mathematical equivalence with the PGD equations, facilitating the implementation of a Godunov-type upwind scheme for spatial flux computation. Second, we employ a time integration scheme for the source terms based on ordinary differential equation solvers, enhancing numerical stability through the introduction of a Courant–Friedrichs–Lewy (CFL)-like parameter. Third, we present characteristic equation-based boundary conditions to accurately capture droplet impingement behavior and reduce spurious peaks in collection efficiency near stagnation points. In addition, a positivity-preserving intercell flux formulation is implemented to ensure non-negative liquid water content in shadow regions. Validation results demonstrate that the proposed approaches improve both the accuracy and stability of numerical simulations of pressureless air-mixed droplet flows in icing environments.

Analyzing and predicting unsteady flowfields is a complex and critical challenge in fluid mechanics. It significantly impacts researchers' understanding of intricate flow behaviors and often requires substantial time to collect valuable data for guiding relevant designs and controls. In this study, we propose a new frequency proper orthogonal decomposition–gated recurrent unit (FPOD-GRU) framework to enhance the efficiency of flowfield analysis and prediction. First, we refine the original FPOD model to effectively represent the low-dimensional intrinsic structure of flowfields both concisely and rapidly. Additionally, we enhance the classical gated recurrent unit (GRU) deep neural network framework by introducing a time-feature dimension conversion mechanism. This innovation allows our framework to reproduce flowfields more quickly and accurately. We then apply the new framework to analyze and predict the static stall flowfield of the NACA0012 airfoil. The results of our analysis explain the evolving characteristics of the flowfield, which align with the vorticity contour, and reveal certain macroscopic mechanical properties. Furthermore, compared to the classical dynamic mode decomposition (DMD) method, the FPOD-GRU framework demonstrates higher predictive precision for the flowfield, particularly in the region near the airfoil wall.

Prior work from the authors presented a new method for addressing the computational and organizational challenges of wing aerostructural optimization at the preliminary design stage. This new method employed a one-shot surrogate model of a structural suboptimization embedded in a coupled-adjoint formulation and is herein referred to as asymmetric coupled-adjoint optimization using a structural surrogate (ACOSS). However, this earlier work only investigated the method under a single cruise condition, and it is of interest to consider separate multidisciplinary analyses (MDAs) for both the sizing and cruise conditions as a further development of the methodology. As shown herein, the cruise MDA is dependent on the sizing MDA since the surrogate model represents a structural sizing process. This dependence is also characteristic of other architectures that include a structural suboptimization. To capture this dependence, an expanded coupled-adjoint formulation for ACOSS is presented in this work. The methodology is demonstrated on an aerostructural optimization of the NASA Common Research Model wing. The ACOSS architecture and adjoint methodology are also further generalized to cases with multiple sizing load cases and multiple cruise cases.

Fluidic thrust vectoring control is an essential technology for the next-generation high-stealth and large-maneuverability aircraft. A novel tertiary-flow thrust vectoring scheme based on dual synthetic jets (DSJs) was first proposed in our previous research. Dual synthetic jet actuators are the tertiary-flow actuators, which can significantly enhance the mixing between the primary jet and the secondary jet and activate the Kelvin–Helmholtz instability of the shear layer, thus rapidly constructing the local low-pressure area and then achieving thrust vectoring control. In this research, ground and flight tests at subsonic speeds are further conducted. Vectoring deflection angle increases with the momentum coefficient of DSJ, and its changing process can be divided into a linear control phase and a saturation phase. The pressure along the Coanda surface emerges as two peaks, respectively, induced by DSJ’s entrainment effect and the Coanda attachment of the primary jet. The achievable deflection response time, return-to-center response time, and deflection angular velocity are separately 111.5 ms, 67.6 ms, and 320°/s, indicating a significantly improved rapid response characteristic compared to classical secondary flow nozzles. Flight test results show that this novel thrust vectoring nozzle achieves the pitch control with the maximum pitch angular velocity of 6.22°/s. Moreover, the response time of pitch angular velocity is only 12 ms, further revealing the advantage of rapid response.

This article uses refined higher-order shell theories to generate higher-order closed-form solutions for the static and vibration analysis of laminated sandwich hyperbolic and elliptical paraboloids, which are scarcely addressed in existing literature. A generalized theory is employed to formulate several equivalent single-layer shell models. Most refined and classical shell theories can be theoretically unified because a theory is independent of the selection of the shearing stress function. The theory generates an appropriate distribution of transverse shear stresses through the thickness of the shell and does not require a problem-dependent shear correction factor. The governing equations of motion and associated boundary conditions are derived using Hamilton’s principle. Higher-order Navier-type closed-form solutions are obtained for simply supported boundary conditions. For laminated composite and sandwich paraboloids, nondimensional results are presented in tabular and graphical forms. The study emphasizes the impact of shell curvature, thickness ratio, and layups on the deflection, stresses, and natural frequencies of laminated and sandwich paraboloids. A comparison is made between the results of several refined shell theories and, if available, with results from previous publications. A major highlight of the present research is the first-time presentation of numerical results for laminated and sandwich paraboloids, establishing new benchmarks.