Search Results (252)

A rapid quasi-one-dimensional (quasi-1D) reacting-flow analysis code was developed for the preliminary assessment of rocket-based combined cycle engines over a broad flight envelope. The internal flow was modeled as steady and quasi-1D in a variable-area duct by solving the coupled conservation equations together with species transport, and finite-rate chemical kinetics were included to represent combustion-induced heat release and composition change. To incorporate configuration-dependent mixing effects that affect RBCC heat release evolution and thermal choking tendencies, a streamwise mixing efficiency distribution was extracted from non-reacting 3D CFD and prescribed as an input to the quasi-1D formulation to represent the progressive availability of reactable fuel along the flowpath. A mode-dependent solution strategy was established by separating the computation into scramjet mode and ramjet mode procedures with a switching criterion based on whether a sonic condition occurs within the combustor, allowing thermal choking and mode transition behavior to be addressed within a single framework. The numerical solver was implemented in Python 3.12.2 and integrated using a stiff ordinary differential equation (ODE) scheme to ensure robust convergence in the presence of reaction-induced stiffness. Verification against previously published hydrogen-fueled scramjet results reproduced the overall streamwise trends of key quantities including Mach number, pressure, temperature, and density. The developed code was then applied to an RBCC configuration under operating conditions representative of ERJ and ESJ regimes, and the quasi-1D predictions were compared with cross-section-averaged 3D RANS CFD results, showing consistent mode identification and comparable axial behavior at a level suitable for preliminary analysis with substantially reduced computational cost. Full article

This work presents an integrated experimental and numerical determination of the aerodynamic (lift) characteristics of an ogive forebody equipped with all moving canards. Experimental testing was conducted in the subsonic custom-made wind tunnel of the Vlatacom Institute at a nominal free stream velocity of 32 m/s (and Mach number M = 0.09). Aerodynamic loads on the canards were measured using a custom one-component force balance, while free stream flow properties were obtained via a calibrated Pitot–Prandtl probe on the full-scale geometry model. On the numerical side, RANS simulations were performed in ANSYS Fluent using the k-ω SST turbulence model. Two geometric representations were considered: (a) a high-fidelity configuration explicitly resolving the physical gap between the canard and ogive, and (b) a simplified configuration with the gap removed. Boundary conditions, Reynolds number, and operating parameters were matched to the wind tunnel conditions to enable a strict one-to-one comparison. Particular emphasis was placed on examining the effect of geometric simplification on the predicted lift characteristics. The gap-resolved configuration reproduces the experimentally measured lift curve within approximately 10% across the investigated angle-of-attack range, satisfying conventional aerodynamic validation criteria. The results confirm both the robustness of the applied RANS approach for highly three-dimensional separated flows often found in engineering applications, as well as the reliability of the experimental measurement system. Full article

The safe release of external stores from aircraft is a complex aerodynamic problem governed by strong interactions between the store and the carrier. During separation, the store is subjected to rapidly varying pressure fields, strong aerodynamic interference, and inertial effects that collectively determine the trajectory and stability of the body in the critical milliseconds following release. This study presents a numerical investigation of the separation of an external store from the high-wing configuration aircraft. Both gravitational and impulse-based release mechanisms are examined across multiple suspension stations and a wide range of flight conditions. Computational fluid dynamics (CFD) methods were employed using a density-based, compressible solver with SST k–ω turbulence modeling, combined with a fully coupled six-degree-of-freedom (6DOF) solver and dynamic mesh deformation techniques. The study considers a wide range of Mach numbers from 0.6 to 0.9 and angles-of-attack between −2° and 4°, and three different suspension stations located at the inner wing pylon, outer wing pylon, and fuselage centerline. These conditions strongly influence the aerodynamic environment around the store and therefore affect its initial motion after release and flight path. The impulse ejection forces used in the analysis come from experimental data and are applied through a user-defined function (UDF) at each time step, allowing the simulation to reproduce the ejection event as realistically as possible. Numerical results confirm that the flight paths of external store are highly non-symmetrical, requiring the employment of complex computational models for their successful resolution, and that they gravely depend on the operating conditions, carrier geometry as well as the suspension location. Full article

As an important aerodynamic configuration of the new-generation UAV, the dorsal S-shaped inlet’s performance is affected by the complex coupling of inflow conditions and the boundary layer ingestion effect. To investigate the influence mechanisms of these factors on inlet performance, CFD based on the scale-adaptive simulation (SAS) turbulence model is used to systematically analyze the flow field and performance of a UAV dorsal S-shaped inlet within a typical flight envelope. It is found that with increasing Mach number (0.6–0.9), the exit total pressure recovery decreases significantly, while the circumferential distortion coefficient almost doubles. As the angle of attack varies from −10° to 10°, a slight decrease in total pressure recovery is observed, but distortion improves due to a relatively stable separation region. Changes in sideslip angle have minimal impact on overall performance but notably alter the symmetry of the vortex system, resulting in a decrease in distortion coefficient. Additionally, at a specific Mach number, back pressure correlates positively with inlet performance. The increase in back pressure can effectively inhibit the flow separation and enhance the total pressure recovery, while the distortion coefficient decreases. The research results provide an important theoretical basis for the design optimization of the new-generation UAV. Full article

Whether the inlet can start successfully is a prerequisite for the propulsion system to provide normal power to an aircraft. To address the starting difficulty of a high-contraction-ratio TBCC inlet lacking self-starting capability, this study proposes a forced-starting strategy via cowl-lip axial translation and validates its feasibility through wind tunnel tests. This research focuses on an axisymmetric mixed-compression inlet designed for a cruise Mach number of 4.0, operating across a Mach number range of 0–4. To overcome the starting challenges induced by a high internal contraction ratio, cowl-lip translation was employed as the primary geometric adjustment mechanism, enabling the inlet to start at a lower contraction ratio before transitioning to its high-performance design configuration. Experiments were conducted in the FL-23 wind tunnel at inflow conditions of Mach 3.5 and Mach 4.0, comparing the inlet’s starting characteristics with and without the cowl-lip adjustment. The experimental results indicate that without active regulation, the inlet failed to self-start under both test conditions. However, with the implementation of the cowl-lip translation strategy, the inlet successfully achieved a started flow field. Furthermore, the inlet maintained a stable started state even after the cowl was translated back to its high-contraction-ratio design position. This study validates the effectiveness of using cowl-lip geometric translation as a forced-starting method for inlets. In summary, this approach resolves the starting issues of high-contraction-ratio inlets at critical Mach numbers and provides a valuable technical reference for variable-geometry inlets aiming to achieve both high performance and reliable starting across a wide Mach number range. Full article

As hypersonic aircraft applications become increasingly extreme, traditional regenerative cooling channels primarily using high-temperature alloys as wall materials can no longer simultaneously meet the dual requirements of thermal protection and lightweight design. This study, based on hypersonic environments with Mach numbers exceeding 8, selects five materials with significant advantages from metals, ceramics, and C/SiC composite materials to conduct a coupled design of wall materials for the flow and heat transfer characteristics of n-decane under 3 MPa pressure. The results show that the heat transfer ability of different material combination schemes is closely related to the thermal–physical properties of the materials, and the materials with obvious advantages in specific thermal–physical properties are dominant. Under a heat flux of 1.5 MW/m², the GH3128 + Cu composite scheme demonstrates a 17.5% increase in Nusselt number and a 17.6% improvement in comprehensive heat transfer coefficient compared to the traditional high-temperature alloy scheme. When the heat flux triples to 4.5 MW/m², the temperature variation of the GH3128 + Cu composite scheme is only 50% of that of the steel + C/SiC composite scheme. This indicates that multi-material coupling exerts both synergistic effects and inhibitory effects on flow and heat transfer characteristics, highlighting the importance of flexible material selection tailored to different tactical and technical requirements. Full article

Recently, the United States unveiled a conceptual design of an unmanned high-speed vehicle, the SR-72, which boasts a maximum flight speed of Mach 6, enabling rapid airspace dominance and superior combat performance. To this end, this study conducted a comprehensive review of publicly available data and employed 3D modeling software to reconstruct the SR-72 configuration, utilizing the supersonic thin airfoil NACA 16006 for the wing design. Subsequently, a meticulously structured computational mesh was generated. Numerical simulations were conducted across subsonic, transonic, supersonic, and high-Mach-number flow regimes. The results reveal that the vehicle exhibits high maneuverability in subsonic conditions, with a stall angle of attack reaching 24°. In transonic conditions, significant wave drag is observed, while, in supersonic and high-Mach-number flow regimes at Mach 6, the vehicle demonstrates excellent wave-riding performance, enabling extended cruise durations and improved fuel efficiency. Furthermore, the initial airfoil was optimized using the CST (Class-Shape Transformation) parameterization method and the SLSQP (Sequential Least Squares Programming) algorithm. Under the given constraints, the drag coefficient was reduced by 40%, demonstrating a significant optimization effect. Full article

This investigation designs grilles of two configurations inside an S-shaped inlet for UAVs. The present work numerically investigates the effects of the configurations, numbers, diameters, and lengths of the grilles on the inlet aerodynamic performance under different flight conditions, such as airflow Mach number, angle of attack, and sideslip angle. The influences of the baseline configuration, Configuration 1, and Configuration 2 on the aerodynamic performance of the inlet are systematically compared. The numerical results show that after installing the grilles, the total pressure recovery decreases by an average of 5.42% for Configuration 1 and 3.46% for Configuration 2. In terms of the absolute circumferential total pressure distortion, which decreases by 1.26% for Configuration 1 and 2.34% for Configuration 2, the swirl distortion index of Configuration 2 approaches zero. It is found that a large sideslip angle significantly degrades the inlet performance, and Configuration 1 experiences the maximum decline of approximately 0.0124 in the total pressure recovery. Based on the optimized design of Configuration 1, the optimal parameters are determined as 5 grille rows, a grille diameter of 4 mm, and a grille length of 6 mm. This configuration achieves an optimal balance between flow regulation and resistance suppression, with a maximum total pressure recovery of 0.9884 and the absolute circumferential total pressure distortion controlled below 0.015. This study clarifies the optimization direction of key parameters for grilles and provides a theoretical basis and technical reference for the design of UAV S-shaped inlet and grille integrations. Full article

This paper presents a unified aerodynamic design and optimization framework for morphing Blended-Wing-Body (BWB) Unmanned Aerial Vehicles (UAVs) operating in subsonic and near-transonic regimes. The proposed framework integrates parametric CAD modeling, Computational Fluid Dynamics (CFD), and surrogate-based optimization using Response Surface Methodology (RSM) to establish a generalized approach for geometry-driven aerodynamic design under multi-Mach conditions. The study integrates classical aerodynamic principles with modern surrogate-based optimization to show that adaptive morphing geometries can maintain efficiency across varied flight conditions, establishing a scalable and physically grounded framework that advances real-time, high-performance aerodynamic adaptation for next-generation BWB UAVs. The methodology formulates the optimization problem as drag minimization under constant lift and wetted-area constraints, enabling systematic sensitivity analysis of key geometric parameters, including sweep, taper, and twist across varying flow regimes. Theoretical trends are established, showing that geometric twist and taper dominate lift variations at low Mach numbers, whereas sweep angle becomes increasingly significant as compressibility effects intensify. To validate the framework, a representative BWB UAV was optimized at Mach 0.2, 0.4, and 0.8 using a parametric ANSYS Workbench environment. Results demonstrated up to a 56% improvement in lift-to-drag ratio relative to an equivalent conventional UAV and confirmed the theoretical predictions regarding the Mach-dependent aerodynamic sensitivities. The framework provides a reusable foundation for conceptual design and optimization of morphing aircraft, offering practical guidelines for multi-regime performance enhancement and early-stage design integration. Full article

In the present work, off-design operating condition is considered to be the ability of the turbine to operate down to 50% to 20% of its nominal intake air flow rate. An important consequence of these off-design points is the change in the inlet incidence angle, which varied from nominal to −20°. Tests were performed on a seven-blade rotor cascade with platform cooling through an upstream slot simulating the stator-to-rotor interface gap. To model the impact of rotation on purge flow injection, a set of fins were installed inside the slot to give the coolant flow a tangential direction. Different cascades’ off-design operating conditions were tested, covering downstream velocity values up to Ma_2is = 0.55, with two inlet turbulence intensity levels of 0.6% a and 7%. A thermal measurement campaign was conducted with the Thermochromic Liquid Crystal technique to measure the adiabatic film cooling effectiveness at various coolant-to-main-flow mass flow ratios, different incidence angles, mainstream Mach numbers, and turbulence levels. The results describe the complexity of the turbine operating under off-design operating conditions, relating the improvement in the platform thermal protection to the reduced secondary-flows activity induced by negative incidence. Full article

The airflow velocity at the solid–air interface is directly proportional to the generated drag and heat. Therefore, reducing drag and heat at such interfaces under extreme operating conditions (e.g., supersonic flight) is particularly important. In contrast to the passive drag-reduction technique, which cannot significantly reduce drag and heat, in this study, an active interface drag- and heat-reduction technique based on a windward concave cavity (reverse jet) is presented. The effect of the number of jet holes, their relative position, size, and other parameters on the drag and heat at 6.5 Mach is investigated using the FLOEFD simulation software. The results show that a five-hole cross-distributed jet achieves the best thermal protection: the total surface static pressure, drag, and surface temperature are reduced by 51.7%, 33.9%, and 31.2%, respectively, compared with the case without a reverse jet. This study provides guidance for the structural design of thermal protection and drag-reduction systems. Full article

Transonic shock buffet, characterized by large-amplitude self-sustained shock oscillations arising from shock wave/boundary layer interactions, poses significant challenges to aircraft handling quality and structural integrity. Conventional control strategies for buffet suppression typically require prior knowledge of unstable steady-state solutions or time-averaged flow fields and are only applicable to fixed-flow conditions, rendering them inadequate for realistic flight scenarios involving time-varying parameters. This study proposes a data-driven adaptive control framework for transonic buffet suppression utilizing localized morphing skin as the actuation mechanism. The control system employs a Multi-Layer Perceptron neural network that dynamically adjusts the local skin height based on lift coefficient feedback, with the target lift coefficient determined through a moving average method. Numerical simulations on the NACA0012 airfoil demonstrate that the optimal actuator configuration—a skin length of 0.2c with maximum deformation positioned at 0.65c—achieves effective buffet suppression with minimal settling time. Beyond this baseline case, the proposed method exhibits robust performance across different flow conditions. Furthermore, the controller successfully suppresses buffet under time-varying flow conditions, including simultaneous variations in Mach number and angle of attack. These results demonstrate the potential of the proposed framework for practical aerospace applications. Full article

Despite substantial advances in turbofan engineering, a crucial gap persists: there remains the need for an all-inclusive comparative analysis that includes real-world operational data and evaluates the performance of modern turbofans used in aviation. Specifically, systematic investigations that examine the exergy and efficiency of turbofan engines for takeoff and cruise remain scarce. Further, the current literature needs to address rigorous performance assessments that include simultaneous consideration of the combined effects of ambient conditions (e.g., temperature, density, relative humidity), Mach number, and turbine inlet temperature on high-bypass turbofan engines used in modern, commercial aircraft. Energetic and exergetic analyses were conducted on five commercial high-bypass turbofan engines with different configurations for both takeoff and cruise flight modes. The computational thermodynamic models developed showed strong correlation with manufacturers’ specifications. Performance evaluations included variations in ambient conditions, altitude, Mach number, and turbine inlet temperature. Results demonstrate that three-spool engine architecture exhibits 70–71% reduction in exergy destruction between flight phases compared to 62.5% for two-spool designs, indicating greater operational adaptability. The combustion chamber emerged as the dominant contributor to irreversibilities, representing approximately 55–58% of overall exergy destruction during takeoff operations. Results demonstrate that increased ambient temperature and/or humidity increase both degraded exergetic efficiency and thrust-specific fuel consumption, and that Mach number and altitude influenced efficiency metrics through ram compression and density effects, while higher turbine inlet temperatures enhanced exhaust kinetic energy via increased thermal input. We show that cruise operations demonstrated superior exergetic efficiency (68–74%) compared with takeoff (47–60%) across all engine configurations. Our results confirm the fundamental trade-off in turbofan design: for long-range applications, high-bypass engines prioritize propulsive efficiency, while for power-intensive operations, moderate-bypass configurations deliver higher specific thrust. Full article

Exposure of propulsion gas turbines to inlet flow contaminated with dust, sand, or ash particulates can lead to a myriad of complex and interrelated damage modes that reduce engine operational life, increase maintenance costs, and pose a safety risk to passengers and hardware assets. Experimental and computational research is ongoing to better understand the fundamental physics underlying this phenomenon, but data from full-scale engine tests with particles are needed for anchoring and validation under fully representative conditions. In this study, compressor blade/particle interactions are investigated at field-relevant conditions using Rolls-Royce/Allison M250-C20C turboshaft engines in an instrumented engine test cell. A novel experimental dataset was produced, yielding a qualitative visualization of particle impact regions on blades and vanes of an on-engine full six-stage axial compressor at transonic tip speeds for two particle compositions and two inlet particle delivery configurations. This investigation contributes the first experimental dataset of its kind for a rotating frame at transonic blade tip speeds (nominal Mach 1.0). By comparing the resulting impact patterns produced in this work to those of fielded hardware, it is shown that for field-relevant high-Stokes number particle conditions at the first-stage rotor, particle/engine dynamics simplify significantly due to ballistic inertial particle behavior. In addition, the spatial distribution of particle concentration and particle velocities across the compressor inlet plane was found to have only minor effects on the resulting particle/blade impact patterns for the two dust injection configurations tested. Full article

A two-dimensional D2Q9 lattice Boltzmann (LBM) model with a sinusoidal pressure inlet boundary condition is implemented to study pulsatile flow through pseudo-periodic porous channels. Simulations in MATLAB are performed for geometries containing periodically arranged rectangular, circular, and elliptic obstacles to represent simplified porous media. Grid- and time-step-independence tests, together with the verification of small pressure and density variations, ensure low-Mach-number, weakly compressible flow and numerical stability. The study focuses on the coupling between the oscillation frequency and spatial periodicity of the structure. The results reveal distinct resonance effects, where the cycle-averaged flow rate exceeds the steady-state value by up to 40–50% at optimal frequencies. A dimensionless response function, $R\left(\omega \right)={\bar{Q}}_{\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{s}}/Q_{\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{a}\mathrm{d}\mathrm{y}}$, is introduced to quantify flow enhancement. The response amplitude and bandwidth depend strongly on obstacle shape and porosity—circular and elliptical obstacles produce the largest enhancement due to smoother streamline transitions, whereas rectangular and triangular ones show weaker responses. The frequency dependence of $R\left(\omega \right)$ follows a resonance-type trend consistent with Womersley theory, reflecting the interaction between temporal forcing and spatial periodicity. These findings provide quantitative insights into pulsation-induced flow enhancement and establish physically grounded boundary and outlet conditions for reliable LBM modeling of unsteady transport in microfluidic, biological, and enhanced oil recovery systems. Full article