Search Results (917)

Contaminated gas flows are encountered in most industrial processes and require efficient removal of fine dispersed particles of various types and characteristics. Conventional cyclones are widely used under harsh operating conditions; however, their separation efficiency for fine particulate fractions remains relatively low. In this study, next-generation cyclones with a multichannel design featuring cylindrical and spiral casings are investigated, enabling particle collection efficiencies of approximately 90% for particles with a diameter of 2 µm. Under harsh microclimatic conditions—particularly at high humidity levels of 70% or higher and elevated temperatures of 50 to 200 °C—such technology is prone to clogging, necessitating complex regeneration procedures. Recent research has focused on improved channel geometries incorporating secondary peripheral flows, adapted for gas cleaning in harsh environments. Experimental results demonstrate effective removal of fine-dispersed glass and clay particles up to 20 µm in size at initial concentrations of 0.5–15 g/m³. The theoretical assessment of the influence of harsh gas flow conditions includes analyses of critical flow characteristics and the mechanical forces acting on fine particles under varying temperature and humidity conditions. The results indicate a maximum purification efficiency of up to 87.3% with an aerodynamic pressure drop of 440 Pa. The impact of harsh microclimatic conditions is most pronounced in the magnitudes of the centrifugal and drag forces: with an increase in the gas flow temperature by every 50 °C within the range from 0 to 200 °C, these forces increase by factors of 7.3–32.7 and 4–6.3, respectively. Full article

To enhance the aerodynamic performance of Ti6Al4V functional components, this paper systematically investigated the femtosecond laser processing technology for surface drag-reduction microstructures, aiming to fabricate high-performance microstructures. (1) V-shaped, U-shaped, and rectangular micro-grooves were designed based on the boundary layer theory, and their drag-reduction mechanisms were elucidated through CFD numerical simulations. The results indicate that the V-shaped groove achieves a peak drag-reduction rate of 13.1% at a dimensionless depth of h⁺ = 15 and an aspect ratio of 1, primarily due to the formation of a low-velocity zone and the suppression of turbulent bursts by secondary vortices. (2) Through single-factor experiments, the influence laws of femtosecond laser process parameters on the V-shaped groove were explored. (3) Regression prediction models for groove dimensions were established using the Response Surface Methodology (RSM) to optimize the processing parameters. Under the optimized conditions, high-quality V-shaped groove arrays with a width of 55.9 μm and a depth of 55.5 μm were successfully fabricated on the Ti6Al4V surface, characterized by high consistency and a minimal heat-affected zone. This research provides an effective technical solution for the precision manufacturing of high-performance drag-reduction structures on titanium alloy surfaces. Full article

Surface orientation can influence the aerodynamic response of modern soccer balls, particularly in the drag crisis regime. This study quantified the orientation-dependent aerodynamic characteristics of the FIFA World Cup match ball Trionda using a single specimen and examined how these differences affect simulated flight at sea level and 1500 m altitude. Two reproducible reference orientations were defined: a red-panel-centered orientation (Series A) and a seam-junction-centered orientation (Series B). Each reference orientation was rotated by 0°, 90°, and 180°, resulting in six fixed-orientation conditions. Wind tunnel measurements were repeated three times per condition to obtain drag, lift, and side-force coefficients, and two-dimensional non-spinning flight simulations were performed for representative long-kick and free-kick conditions. All six orientations exhibited drag crisis behavior, but the transition response magnitude, subcritical drag level, and supercritical drag state differed among conditions. The representative transition region occurred at approximately Re = 2.0 × 10⁵ to 2.5 × 10⁵. Among the tested conditions, B-90 showed the lowest full-range mean drag coefficient (0.231), whereas A-90 showed the highest (0.266). In the simulations, lower drag orientations consistently produced longer flight ranges, and the B-90 > A-90 ordering was preserved across representative launch conditions and the expanded parametric comparison. These findings indicate that the aerodynamic response of Trionda cannot be represented adequately by a single mean drag coefficient and that surface orientation should be considered in aerodynamic characterization and flight prediction. Full article

Distributed Electric Propulsion aircraft have gained significant attention for advancing green aviation. However, their application is constrained by the limited energy density of batteries, resulting in weight compensation and flight range limitation. Current research on DEP energy management predominantly focuses on thrust allocation during the cruise phase while largely neglecting the energy regeneration potential during the descent phase. Conventional all-motors active energy recovery strategies force the multi-motor array to operate within a low-efficiency region, since the required drag torque is small under low aerodynamic drag conditions. To solve this issue, this paper proposes an energy recovery strategy that dynamically adjusts the number of activated motors during the descent phase of aircraft. The proposed N-Active strategy can adaptively regulate the number of operating motors, shifting motor operating points from the low-efficiency region to the high-efficiency region, which effectively decouples energy regulation within the longitudinal symmetry plane and maximizes energy recovery benefits. In this study, a high-fidelity simulation platform is established, including nonlinear aerodynamic characteristics and propeller windmilling motor efficiency models. Moreover, the optimal performance of the N-Active multi-motor cooperative energy recovery optimization strategy is verified based on the constructed platform. Simulation results demonstrate that compared with the traditional all motors active strategy, the proposed method improves battery state of charge by 11.96% and reduces virtual weight of battery. This method can effectively alleviate the weight compensation effect of distributed electric propulsion aircraft without additional physical weight increment, thereby enhancing the loading capacity of aircraft. Full article

Boundary layer suction is a critical technique in hybrid laminar flow control (HLFC) for delaying transition and reducing drag. While the effectiveness of suction is well-established, systematic studies on the parametric optimization of suction hole diameter, location, and coefficient for two-dimensional airfoils remain scarce. This study addresses this gap through numerical investigations using the validated γ-${\widetilde{Re}}_{\theta t}$ transition model. The research systematically analyzes the synergistic effects of suction coefficient (C_q), location (5%, 10%, and 15% chord), and suction hole diameter (0.2 mm, 0.6 mm, and 1.0 mm) on transition characteristics and aerodynamic performance. The results reveal that suction location predominantly governs the viscous drag coefficient (C_Dv), whereas suction hole diameter primarily influences the pressure drag coefficient (C_Dp). Consequently, suction location selection proves more critical for drag reduction than suction hole diameter. The maximum drag reduction (11.9% decrease in C_D) and optimal transition delay (11.8% chord shift) are achieved using a small suction hole (0.2 mm) located at an aft position (15% chord) with a high suction coefficient. Furthermore, an optimal matching range exists between suction location and coefficient, which widens with decreasing suction hole diameter. Based on these findings, this study proposes an energy-efficient design strategy: employing small apertures across the suction region while gradually increasing suction rates toward the trailing edge to achieve significant drag reduction with minimal energy penalty. Full article

This study investigates whether aerodynamic interaction effects in an interlocked (negative-gap) counter-rotating dual Savonius rotor configuration can improve the efficiency of drag-based vertical-axis wind turbines in urban wind conditions. Two-dimensional Computational Fluid Dynamics (CFD) simulations were performed in ANSYS Fluent 2025 R2 using both steady and unsteady RANS approaches, including dynamic meshing to enable collision-free rotation in the interlocked overlap region. The numerical setup was first validated for a single two-bucket reference rotor against published experimental data of torque and power coefficients and subsequently applied to dual-rotor configurations with negative gap distances. The results show that the dual-rotor arrangement redistributes torque production over the azimuth angle and yields a smoother and consistently positive mean static torque coefficient, indicating improved self-starting behavior compared to the single rotor. Under transient operation, the dual-rotor configuration yields higher power coefficient values across the entire investigated tip-speed ratio range. The highest performance gain is observed at a tip-speed ratio of $\lambda \approx 1.0$, where the peak power coefficient increases from $c_p\approx 0.25$ (single-rotor) to $c_p\approx 0.32$ (dual-rotor), corresponding to an improvement of the power coefficient of about $\mathsf{\Delta }{c}_p/c_{p0}\approx 28\%$. Full article

High-speed train aerodynamics have mainly been improved by passive design methods, such as streamlined noses, local fairings, and surface smoothing. These methods have achieved clear benefits, but several important aerodynamic problems remain difficult to solve by geometry optimization alone. Open-air drag is still affected by tail flow separation, base-pressure recovery, and disturbances around bogies and the underbody; crosswind safety is influenced by unsteady leeward-side separation and wake asymmetry; slipstream behavior depends on wake vortices, boundary-layer development, and complex near-ground underbody flow; and tunnel-related pressure transients arise from compression-wave generation, propagation, and reflection. These coupled effects mean that one fixed train shape cannot perform optimally in all operating conditions. For this reason, this review proposes that active flow control (AFC) should not be regarded only as a drag-reduction or stability-improvement technique for high-speed trains. Instead, it should be understood as a mission-adaptive aerodynamic control framework, in which different control actions are used for different operating scenarios. This paper first clarifies that passive optimization is increasingly subject to diminishing returns under multi-objective and engineering constraints. It then reviews AFC studies on drag reduction, base-pressure recovery, wake and slipstream control, underbody flow conditioning, crosswind mitigation, and tunnel pressure-wave suppression. Related AFC studies on bluff bodies, road vehicles, and other separated flows are included only when their physical relevance to trains is clear. The review further distinguishes gross aerodynamic improvement from net energy gain and identifies actuator power, durability, maintainability, acoustic impact, validation level, and full-scale transferability as decisive feasibility factors. Current research is still dominated by open-loop numerical studies with simplified actuation. Future work should therefore move toward multi-objective, closed-loop, energy-aware, sensor–actuator-integrated, and explainable machine-learning-assisted AFC. The main message is that the next step in train aerodynamics is not simply a better fixed shape, but a control-enabled train that can selectively redistribute aerodynamic authority across its mission profile. Full article

The reduction in aerodynamic drag remains a crucial pathway for enhancing turbomachinery efficiency. Riblet structures are a well-established passive technique to reduce viscous drag, but their application has been constrained by the challenge of adapting size and orientation to match the local flow conditions. This study presents a novel laser-based fabrication process developed at the Laserinstitut Hochschule Mittweida, which enables the production of continuously adapted riblets on complex curved surfaces. Numerical simulations were employed to design riblet patterns for the NACA0012 airfoil at zero angle of attack, followed by laser manufacturing and high-resolution surface characterization. Aerodynamic performance was evaluated through wake surveys in a Göttingen-type wind tunnel at the Jade University of Applied Sciences. The results validate the numerical design approach and show that tailored riblet structures provide a notable improvement in drag reduction compared to constant geometries, with relative gains of about $8\%$ for the one-sided and $16\%$ for the two-sided application. These findings underline the potential of advanced laser-based manufacturing processing to enable riblet integration in turbomachinery under industrially relevant conditions. Full article

Highway merging and platoon formation are critical scenarios in heavy-duty vehicle aerodynamics. This study presents a transient computational fluid dynamics (CFD) analysis of two trucks undergoing a merging maneuver and subsequent platoon formation. A three-dimensional unsteady Reynolds-Averaged Navier–Stokes (uRANS) approach with the SST k–ω turbulence model is employed under zero-crosswind and yawed inflow conditions. The present work provides a time-resolved characterization of truck–truck aerodynamic interactions during dynamic spacing evolution, enabling the capture of unsteady wake effects that are not accessible in steady-state formulations commonly used in cooperative driving studies. Unlike previous steady analyses, the approach resolves transient wake development, vortex shedding, and their direct impact on instantaneous aerodynamic loads. Results identify three interaction regimes: weak interaction, strong wake interaction during wake impingement, and wake recovery at larger spacing. Under zero-crosswind conditions, significant drag reduction is observed, confirming platooning benefits. However, crosswind conditions substantially reduce this benefit and increase lateral loads due to asymmetric pressure distribution and wake deflection. A non-linear spacing–drag relationship is observed, governed by wake evolution and shear-layer interaction. These findings provide quantitative insight into transient aerodynamic interactions and highlight the importance of accounting for unsteady and crosswind effects in platoon performance assessment. Full article

Ice accumulation on aircraft surfaces severely affects aerodynamic performance by increasing drag and reducing lift, leading to stall conditions. Conventional thermal and pneumatic anti-/de-icing systems, although widely used, have some disadvantages, including high cost, inefficiency, and environmental unsustainability. Hydrophobic and icephobic coatings have emerged as a promising alternative to reduce ice adhesion and delay ice formation. This paper reviews the use of silane agents in epoxy-based coatings, incorporating functional additives such as natural fibers, quantum dots, and nanoparticles, to enhance hydrophobicity. Results demonstrated that the combination of silanes and functional additives affects surface features and wettability, improving hydrophobicity. These case studies show the potential of this approach in the development of coatings for advanced aircraft ice-protection applications. Full article

Effective thermal management is crucial for the development of future electrified aircraft propulsion systems. One of the most challenging phases is the take-off phase, which imposes particularly high demands on cooling systems. In addition, the aerodynamic drag during cruise flight has to be kept to a minimum. This study introduces a novel experimental thermal management system using a test stand with a modular air duct (TMTmad), which is designed specifically to investigate different configurations of air supply and heat exchanger in fuel cell-based electrified propulsion systems. Given the versatility of nacelle-integrated electrified propulsion architectures, this approach offers high flexibility in the design and integration of thermal management systems. This includes aspects such as the location, orientation and geometry of an air-cooled heat exchanger (HEX), as well as the inlet and outlet configurations. Moreover, the optimization of the uniform flow guidance of the duct flow within the nacelle and the integration of additional fans to ensure airflow under critical conditions can be studied. The main heat source delivers up to 6 $\mathrm{k}\mathrm{W}$ of heating power with a temperature range from −20 °C to 200 °C. The study measures the heat flux and pressure losses within these systems and includes a thorough fluid flow analysis. Furthermore, the experimental data serves as a valuable resource for validating numerical models of cooling ducts, enhancing the accuracy and reliability of future design iterations. Full article

Liquid Hydrogen (LH2) as an energy carrier for passenger aircraft has the potential to combine low climate impact and high lifecycle energy efficiency. Due to its significantly different physical properties compared to kerosene, the integration of LH2 fuel storage and distribution systems interacts with the general configuration of the aircraft. In order to assess promising configuration combinations quantitatively, an aircraft design and assessment framework is further developed. These additions are aimed at capturing the interdependencies originating from the fuel system integration choices at the aircraft level and quantifying the effect of trim drag. The framework is applied to a selection of LH2 mid-to-long-range aircraft designs. A comparison of the mass breakdown, aerodynamics breakdown and performance indicators such as specific energy consumption is carried out for the framework-generated aircraft models. A trim drag induced block fuel penalty is quantified for the aircraft selection as well as a mitigation strategy based on operational constraints. Full article

In this paper, the design of a novel deployable scissor-structural mechanism (SSM) for the morphing of a generic missile nose cone is presented. The aim of the study is to explore a geometric transformation specially designed for the missile’s flight envelope, ensuring optimal aerodynamic performance and decreasing the aerodynamic drag coefficient across different flight conditions, then to apply it. For the geometric transformation the proposed mechanism is composed of multiple scissor-like elements (SLEs), providing a reconfigurable structure capable of adjusting the nose cone shape dynamically. To achieve a continuous and smooth missile nose cone surface the study incorporates a superelastic alloy (SEA) skin, which can deform compatibly with the SLE movements. A computational routine provides the study with an optimum SSM configuration which makes the geometric transformation the best. The computational routine minimizes the structural error between deformed nose cone shape and target nose cone shape. Full article

This study focuses on the aerodynamic performance optimization of the SG6043 airfoil for application in small horizontal axis wind turbines (HAWTs) operating under low-Reynolds-number conditions. Recognizing the critical role of lift-to-drag ratio (Cl/Cd) in maximizing turbine power output, the research investigates the performance of SG6043 through design modifications and computational analysis. Initially, the baseline airfoil’s aerodynamic characteristics were verified using simulation tools like QBlade v0.96.3 software, confirming its previously reported performance. Subsequently, the airfoil was systematically modified by varying key parameters including thickness-to-camber ratio and angle of attack (AOA), operating at different Reynolds numbers. Among the modified versions, SG6043M5-7, SG6043M5-8, and SG6043M5-9 showed significant aerodynamic performance improvement, with SG6042M5-9 achieving the highest Cl/Cd ratio of 193.44 at Re = 6 × 10⁵ and AOA = 3.5°. The results demonstrated that a reduced thickness (5%) combined with moderate to high camber (7–9%) enhances the aerodynamic performance. Full article

This study presents a flight-envelope-based methodology for aerodynamic load assessment and composite material selection applied to a hybrid fixed-wing tri-rotor VTOL (Vertical Take-Off and Landing) unmanned aerial vehicle (UAV). A certification-oriented maneuver and gust envelope was established to define the critical load cases. Reynolds-averaged Navier–Stokes (RANS) simulations of the full aircraft at nominal cruise were performed to determine global aerodynamic coefficients and distributed pressure fields, including interference effects from the fuselage and externally mounted VTOL system. A complementary wing-only angle-of-attack study was used to characterize lift, drag, and chordwise pressure distributions over the relevant incidence range. Critical envelope points were mapped to equivalent aerodynamic states in terms of lift coefficient and angle of attack, enabling a quasi-steady correlation between certification loads and CFD (Computational Fluid Dynamics) results. In parallel, carbon fiber-reinforced polymer (CFRP) laminates were experimentally evaluated under tensile, open-hole tensile, and flexural loading. The results indicate that, within the two investigated laminate configurations, the [0°/90°] CFRP laminate provides the more suitable strength and stiffness for primary wing structures, while off-axis laminates are better suited for secondary regions. The proposed workflow links flight-envelope definition, aerodynamic analysis, and material selection, providing a basis for preliminary structural design. Full article