Search Results (118)

Corner separation at the junction of blade surfaces and end walls remains a significant challenge in compressor cascade performance. This study proposes a passive flow control strategy inspired by the geometric arrangement of biological fish scales to address this issue. A fish scale-like surface structure was applied to the suction side of a cascade blade to reduce viscous drag and modulate secondary flow behavior. Wind tunnel experiments and numerical simulations were conducted to evaluate its aerodynamic effects. The results show that the fish scale-inspired configuration induced climbing vortices that energized low-momentum fluid near the end wall, effectively suppressing both passage and corner vortices. This led to a reduction in spanwise flow penetration and a decrease in total pressure loss of up to 5.69%. The enhanced control of secondary flows also contributed to improved flow uniformity in the end-wall region. These findings highlight the potential of biologically inspired surface designs for corner vortex suppression and aerodynamic efficiency improvement in turbomachinery systems. Full article

To establish a theoretical foundation for assessing the dynamic performance of high-speed train catenary systems in wind-prone regions, this study develops a coupled pantograph–catenary model using ANSYS(2022R1) APDL. The dynamic responses of conventional high-speed pantographs traversing both mainline and transition sections are analyzed under varying operational conditions. The key findings reveal that an elevated rated tension in the contact wire and messenger wire reduces the pantograph lift in wind areas with no crosswind compared to non-wind areas, with an average lift reduction of 8.52% and diminished standard deviation, indicating enhanced system stability. Under a 20 m/s crosswind, both tested pantograph designs maintain contact force and dynamic lift within permissible thresholds, while significant catenary undulations predominantly occur at mid-span locations. Active control strategies preserve the static lift force but induce pantograph flattening under compression, reducing aerodynamic drag and resulting in smaller contact force fluctuations relative to normal-speed sections. In contrast, passive control increases static lift, thereby causing greater fluctuations in contact force compared to baseline conditions. The superior performance of active control is attributed to its avoidance of static lift amplification, which dominates the dynamic response in passive systems. Full article

An aircraft that has been carefully optimized for a single flight condition will tend to perform poorly at other flight conditions. For aircraft such as long-haul airliners, this is not necessarily a problem, since the cruise condition so heavily dominates a typical mission. However, other aircraft, such as Unmanned Aerial Vehicles (UAVs), may be expected to perform well at a wide range of flight conditions. Morphing systems may be a solution to this problem, as they allow the aircraft to adapt its shape to produce optimum performance at each flight condition. This study proposes an aerodynamic optimization framework for morphing airfoils by integrating Principal Component Analysis (PCA) for geometric dimensionality reduction and deep learning (DL) for surrogate modeling, alongside an optimization-guided data augmentation strategy. By employing PCA, the geometric dimensionality of airfoil surfaces is reduced from 24 to 18 design variables while preserving 100% shape fidelity, thus establishing a compressed morphing parameterization space. A Multi-Island Genetic Algorithm (MIGA) efficiently explores the reduced design space, while iterative retraining of the surrogate model enhances prediction accuracy, particularly in high-performance regions. Additionally, Shapley Additive Explanation (SHAP) analysis reveals interpretable correlations between principal component modes and aerodynamic performances. Experimental results show that the optimized airfoil achieves a 54.66% increase in low-speed cruise lift-to-drag ratio and 10.90% higher climb lift compared to the baseline. Overall, the proposed framework not only enhances the adaptability of morphing airfoils across various low-speed flight conditions but also facilitates targeted surrogate refinement and efficient data acquisition in high-performance regions. Full article

This work studies the feasibility of integrating a hydrogen-powered propulsion system in a regional aircraft at the conceptual design level. The developed system consists of fuel cells, which will be studied at three technological levels, and batteries, also studied for four hybridization factors (X = 0, 0.05, 0.10, 0.20). Hydrogen can absorb great thermal loads since it is stored in the tank at cryogenic temperatures and is used as fuel in the fuel cells at around 80 °C. Taking advantage of this characteristic, two thermal management system (TMS) architectures were developed to ensure the proper functioning of the aircraft during the designated mission: A1, which includes a vapor compression system (VCS), and A2, which omits it for a simpler design. The models were developed in MATLAB^® and consist of different components and technologies commonly used in such systems. The analysis reveals that A2, due to the exclusion of the VCS, outperformed A1 in weight (10–23% reduction), energy consumption, and drag. A1’s TMS required significantly more energy due to the VCS compressor. Hybridization with batteries increased system weight substantially (up to 37% in A2) and had a greater impact on energy consumption in A2 due to additional fan work. Hydrogen’s heat sink capacity remained underutilized, and the hydrogen tank was deemed suitable for a non-integral fuselage design. A2 had the lowest emissions (10–20% lower than A1 for X = 0), but hybridization negated these benefits, significantly increasing emissions in pessimistic scenarios. Full article

Aiming at the problem that conventional friction reducers used in fracturing cannot simultaneously possess properties such as temperature resistance, salt resistance, shear resistance, rapid dissolution, and low damage. Under the design concept of “medium-low molecular weight, salt-resistant functional monomer, supramolecular physical crosslinking aggregation, and enhanced chain mechanical strength”, acrylamide, sulfonic acid salt-resistant monomer 2-acrylamide-2-methylpropanesulfonic acid, hydrophobic association monomer, and rigid skeleton functional monomer acryloyl morpholine were introduced into the friction reducer molecular chain by free radical polymerization, and combined with the compound suspension technology to develop a new type of multi-functional viscous friction reducer suspension (SAMD), the comprehensive performance of SAMD was investigated. The results indicated that the critical micelle concentration of SAMD was 0.33 wt%, SAMD could be dissolved in 80,000 mg/L brine within 3.0 min, and the viscosity loss of 0.5 wt% SAMD solution was 24.1% after 10 min of dissolution in 80,000 mg/L brine compared with that in deionized water, the drag reduction rate of 0.1 wt% SAMD solution could exceed 70% at 120 °C and still maintained good drag reduction performance in brine with a salinity of 100,000 mg/L. After three cycles of 170 s⁻¹ and 1022 s⁻¹ variable shear, the SAMD solution restored viscosity quickly and exhibited good shear resistance. The Tan δ (a parameter characterizing the viscoelasticity of the system) of 1.0 wt% SAMD solution was 0.52, which showed a good sand-carrying capacity, and the proppant settling velocity in it could be as low as 0.147 mm/s at 120 °C, achieving the function of high drag reduction at low concentrations and strong sand transportation at high concentrations. The viscosity of 1.4 wt% SAMD was 95.5 mPa s after shearing for 120 min at 140 °C and at 170 s⁻¹. After breaking a gel, the SAMD solution system had a core permeability harm rate of less than 15%, while the SAMD solution also possessed the performance of enhancing oil recovery. Compared with common friction reducers, SAMD simultaneously possessed the properties of temperature resistance, salt resistance, shear resistance, rapid dissolution, low damage, and enhanced oil recovery. Therefore, the use of this multi-effect friction reducer is suitable for the development of unconventional oil reservoirs with a temperature lower than 140 °C and a salinity of less than 100,000 mg/L. Full article

The design of heat and drag reduction systems for hypersonic vehicles has garnered widespread global attention. In this study, the Navier–Stokes equations and the SST k-ω turbulence model are employed to establish a simulation model for heat and drag reduction induced by a forward-facing cavity. The numerical methods are validated using existing experimental results. The oscillation characteristics of the bow shock wave at the head and the shock inside the cavity in hypersonic flows are investigated. The heat and drag reduction mechanisms of the forward-facing cavity are discussed. The effects of the diameter and depth of the cavity on drag and heat reduction are comprehensively analyzed. The obtained results show that a reduction in drag and heat is achieved when a forward-facing cavity is added to the vehicle. The main reasons for this heat reduction are the cold ring mechanism and the energy conversion mechanism. The size of the cold ring is significantly affected by the cavity diameter, whereas the energy conversion mechanism is more sensitive to variations in diameter. The maximum reduction in heat load is 2.2%, and the maximum reduction in the Stanton number is 25.3%. Increases in both diameter and depth enhance drag reduction, achieving an average drag reduction of approximately 1.65%. Full article

By changing the aerodynamic shape of the trailing edge of its wing, an aircraft can achieve lift and drag reduction during takeoff and landing and continuously achieve better aerodynamic efficiency while cruising, which plays an important role in the whole flight process and has always been a research hotspot in the field of aviation structure. Firstly, the principle scheme of wing trailing edge deformation based on a two-stage multi-link mechanism was designed and realized, and then the mechanical structure was designed in a way that ensured the machining feasibility of the prototype. Secondly, a control system scheme was designed to realize synchronous and differential deformation movement of single and double mechanisms. Finally, power drive device selection and prototype manufacturing verification were carried out. The experiments show that the designed and manufactured variable camber wing trailing edge prototype can achieve two modes of wing trailing edge deformation, namely the overall deflection of the variable camber wing trailing edge +5°~−20° and the wing tip deflection +10°~−10°. The deformation error is measured within 5%. Full article

This study presents a numerical investigation of fluid flow around a heated rectangular cylinder controlled by an inclined partition, aiming to suppress vortex shedding, reduce aerodynamic drag, and enhance thermal exchange. The double multiple relaxation time lattice Boltzmann method (DMRT-LBM) is employed to investigate the influence of Reynolds number variations and partition positions on the aerodynamic and thermal characteristics of the system. The results reveal the presence of three distinct thermal regimes depending on the Reynolds number. Increasing the Reynolds number intensifies thermal vortex shedding, thereby improving heat exchange efficiency. Moreover, a higher Reynolds number leads to a greater reduction in the drag coefficient, reaching $125.41\%$ for $Re=250$. Additionally, improvements in thermal performance were quantified, with Nusselt number enhancements of $29.47\%$ for $Re=100$, $55.55\%$ for $Re=150, 74.78\%$ for $Re=200$, and $82.87\%$ for $Re=250$. The influence of partition positioning g on the aerodynamic performance was also examined at $Re=150$, revealing that increasing the spacing g generally leads to a rise in the drag coefficient, thereby reducing the percentage of drag reduction. However, the optimal configuration was identified at $g=2d$, where the maximum drag coefficient reduction reached $130.97\%$. In contrast, the impact of g on the thermal performance was examined for $Re=100, 150,$ and $200$, revealing a significant heat transfer improvements on the top and bottom faces: reaching up to $99.47\%$ on the top face for $Re=200$ at $g=3d$. Nevertheless, for all Reynolds numbers and partition placements, a decrease in heat transfer was observed on the front face due to the partition shielding it from the incoming flow. These findings underscore the effectiveness of an inclined partition in enhancing both the thermal and aerodynamic performance of a rectangular component. This approach holds strong potential for various industrial applications, particularly in aeronautics, where similar control surfaces are used to minimize drag, as well as in heat exchangers and electronic cooling systems where optimizing heat dissipation is crucial for performance and energy efficiency. Full article

This paper provides a detailed review of the evolution and development of corrugated wings, a biomimetic concept that is very effective under low Reynolds number flights. We will highlight, through reviewing experimental and numerical studies, the emphasis on its aerodynamic performance for lift enhancement, flow separation delay, and drag reduction in the aerodynamics of corrugated wings. Furthermore, we focus on topics such as fluid–structure interaction and aeroacoustics, presenting the possibility of morphing wing technologies in tandem and its effects on an angle of attack at various flight modes. This review outlines durability issues, materials selection, and experimental testing complemented by numerical models while determining the importance of interdisciplinary developments within corrugated wing aerodynamics using potential AI-assisted design. Our review envisions the application of aerodynamics of corrugated wings in the development of UAVs, MAVs, and future advanced aviation systems by integrating the principles from biology to engineering. Full article

Annular flow channels, which are distinct from circular pipes, represent a complex flow structure widely applied in fields such as food engineering and petroleum engineering. Discovering the internal flow patterns is conducive to the study of heat and mass transfer laws, thereby playing a crucial role in optimizing flow processes and selecting equipment. However, the mechanism underlying the influence of annular turbulent flow on macro-pressure drop remains to be further investigated. This paper focuses on the roughness of both inner and outer pipes, as well as positive and negative eccentricities. Numerical simulation is employed to study the microscopic characteristics of the flow field, and the numerical model is validated through indoor experimental measurements of pressure drop laws. Further numerical simulations are conducted to explore the microscopic variations in the flow field, analyzed from the perspectives of wall shear force and turbulence characteristics. The results indicate that an increase in inner pipe roughness significantly enhances the wall shear force on both the inner and outer pipes, and vice versa. In the concentric case, wall shear force and turbulence characteristics exhibit central symmetry. Eccentricity leads to uneven distributions of velocity, turbulence intensity, and shear force, with such unevenness presenting axial symmetry under both positive and negative eccentricities. Additionally, eccentricity demonstrates turbulence drag reduction characteristics. This study enhances our understanding of the mechanism by which annular turbulent flow influences pressure drop. Furthermore, it offers theoretical backing for the design and optimization of annular space piping, thereby aiding in the enhancement of the performance and stability of associated industrial systems. Full article

Floating offshore wind turbine (FOWT) platforms are subject to a wide range of hydrodynamic loading and dynamic movement, making hydrodynamic force evaluation difficult. Amongst various floating platforms, submersible platforms are structurally complex, with multiple members held together by cross-braces. The influence of these members on hydrodynamic loading is poorly understood. An investigation of the effect of these members on loads is essential to optimise the design of FOWT platforms, mooring systems, and protective coatings, leading to a reduction in construction and maintenance costs. This paper numerically investigates the effect of structural members on the forces acting on a static semi-submersible platform in a unidirectional current flow of Reynolds number ($Re$) ranging from 2000 to 200,000, based on structural diameter and tidal velocity. The OC4 semi-submersible is chosen as the baseline platform. For each $Re$, this study is divided into three stages, such that in each stage, the number of members increased. These stages are as follows: (1) a finite cylinder (FC), (2) a finite cylinder with a heave plate (FCHP), (3) three cylinders with heave plates (TCHP) in an equilateral triangle arrangement, and (4) the OC4 semi-sub. The drag coefficient (${\overline{C}}_d$) increases with increasing structural members and weakly varies with increasing $Re$. However, the viscous drag coefficient (${\overline{C}}_f$) decreases with increasing $Re$, and a reverse trend is seen in the case of the pressure drag coefficient (${\overline{C}}_p$), with pressure drag dominating over friction drag. Further, the contribution of individual members is observed to vary with $Re$. The contribution of cylinders towards ${\overline{C}}_d$ is higher than heave plates, showing that contributions directly depend on the aspect ratio of members. In the case of TCHP and OC4, the contribution of the rear members is higher than that of the leading members due to the strong wake effect of the former. Also, the braces and pontoons of OC4 have contributed substantially towards total ${\overline{C}}_d$, unlike the central cylinder, which has experienced low drag due to the wake effect of the front cylinder and heave plate. Also, flow visualisation has shown vortex cores, and recirculating flows in the near wake of the cylinders and under the heave plates. Recirculation zones under the heave plates lead to vertical pressure on the structures. This vertical pressure increases with the number of structural members and the vertical pressure coefficient (${\overline{C}}_v$), varying with $Re$ due to three-dimensionality in the wake. Further, this pressure varies across the bottom surfaces of structures. Analyses of the streamwise pressure coefficient have shown it is highest on the front surfaces of cylinders. The highest friction is on the top and sides of the heave plates, and there is considerable friction on the sides of the cylinder. Full article

Flow around clustered cylinders is widely encountered in engineering applications such as wind energy systems, pipeline transport, and marine engineering. To investigate the hydrodynamic performance and vortex dynamics of multiple cylinders under forced vibration at low Reynolds numbers, with a focus on understanding the interference characteristics in various configurations, this study is based on a self-developed radial basis function iso-surface ghost cell computing platform, which improves the implicit iso-surface interface representation method to track the moving boundaries of multiple cylinders, and employs a self-constructed CPU/GPU heterogeneous parallel acceleration technique for efficient numerical simulations. This study systematically investigates the interference characteristics of multiple cylinder configurations across various parameter domains, including spacing ratios, geometric arrangements, and oscillation modes. A quantitative analysis of key parameters, such as aerodynamic coefficients, dimensionless frequency characteristics, and vorticity field evolution, is performed. This study reveals that, for a dual-cylinder system, there exists a critical gap ratio between X/D = 2.5 and 3, which leads to an increase in the lift and drag coefficients of both cylinders, a reduction in the vortex shedding periodicity, and a disruption of the wake structure. For a three-cylinder system, the lift and drag coefficients of the two upstream cylinders decrease with increasing spacing. On the other hand, this increased spacing results in a rise in the drag of the downstream cylinder. In the case of a four-cylinder system, the drag coefficients of the cylinders located on either side of the flow direction are relatively high. A significant increase in the lift coefficient occurs when the spacing ratio is less than 2.0, while the drag coefficient of the downstream cylinder is minimized. The findings establish a comprehensive theoretical framework for the optimal configuration design and structural optimization of multicylinder systems, while also providing practical guidelines for engineering applications. Full article

Meta-aircraft, in High-Altitude, Long-Endurance (HALE) unmanned aerial vehicle (UAV) applications, utilize a strategy of formation flying in the stratosphere and aerial docking in the troposphere to enhance flight range and gust resistance. This paper explores an aerial docking strategy for unmanned meta-aircraft using a surrogate model based on aerodynamic data. The study begins with an analysis of the aerodynamic characteristics and the establishment of a dynamic model, followed by the development of a surrogate model using the vortex lattice method and a BP neural network. This model accurately simulates aerodynamic changes near the wingtip. Optimization of the docking process, focusing on impulse and moment of impulse, is achieved using a greedy algorithm. The results show a reduction in drag impulse and rolling moment by 10.89% and 15.76%, respectively, thereby easing the burden on the control system of UAVs. Full article

It is increasingly common for simulation and AI tools to aid in the vehicle design process. The IPG CarMaker uses a multibody vehicle model and a learning algorithm for the virtual driver. The goal is to discover the behavior of the learning algorithm from the point of view of reliability and convergence. Simulations demonstrate that the lap time converges reliably. We also report that small changes in the vehicle parameters induce small changes in the simulated lap time, i.e., the lap time is a differentiable function of the vehicle parameters. Part 2 of this paper explains the aerodynamics and Drag Reduction System optimization. Full article

Part 1 of this paper summarizes the application of the IPG CarMaker 11.0 software for lap-time simulation and optimization. The goal is to use the IPG CarMaker on a given track for the optimization of the aerodynamics package parameters and the drag reduction system (DRS). The optimal aerodynamic downforce coefficient is determined for a given vehicle. The simulations clearly suggest that the application of the DRS pays off for a Formula Student car, if the DRS activation and deactivation times are chosen carefully. As IPG CarMaker seems to be a powerful tool, the Arrabona Racing Team decided to extend its application. Full article