Search Results (344)

The vertical tail plays a crucial role in aircraft directional stability and lateral control, especially during low-speed operations such as takeoff and landing. This study examines the effect of aircraft mass on vertical tail geometry through a statistical analysis of 65 design parameters from civil jet aircraft. Aerodynamic performance of a sub-scale Boeing 777-200 vertical tail model was further investigated in a low-speed wind tunnel under rudder deflections and sideslip angles. Experiments were conducted at freestream speeds of 20 and 30 m/s, corresponding to Reynolds numbers of 5 × 10⁵ and 7.5 × 10⁵, with model blockage ratios below 2% in all configurations. Side force and drag coefficients were measured for rudder deflections from −30° to +30° and sideslip angles from −7.5° to +7.5°. Results show a nearly linear variation of side force with rudder deflection, while drag exhibits noticeable nonlinearity at higher deflections. At zero sideslip, increasing rudder deflection from 0° to 30° raised the side force coefficient from 0 to 0.65, with a maximum uncertainty of ±0.011, while drag coefficient uncertainty remained below ±0.0055. Furthermore, the application of positive or negative sideslip resulted in substantial variations in the side force coefficient, reaching values of up to ±1.1 depending on the direction. By integrating experimental data with statistical analysis of real aircraft geometries, this study provides reliable quantitative benchmarks and highlights the vertical tail’s aerodynamic importance. Full article

Enhancing ride comfort and vibration control performance is a critical requirement for fuel cell commercial vehicles (FCCVs). This study develops a semi-active seat suspension control strategy that integrates a fuzzy logic controller with a Modified Fireworks Algorithm (MFWA) to systematically optimize fuzzy parameters. A seven-degree-of-freedom (7-DOF) half-vehicle model, including the magnetorheological damper (MRD)-based seat suspension system, is established in MATLAB/Simulink to evaluate the methodology under both random and bump road excitations. In addition, a hardware-in-the-loop (HIL) experimental validation was conducted, confirming the real-time feasibility and effectiveness of the proposed controller. Comparative simulations are conducted against passive suspension (comprising elastic and damping elements) and conventional PID control. Results show that the proposed MFWA-FL approach significantly improves ride comfort, reducing vertical acceleration of the human body by up to 49.29% and seat suspension dynamic deflection by 12.50% under C-Class road excitation compared with the passive system. Under bump excitations, vertical acceleration is reduced by 43.03% and suspension deflection by 11.76%. These improvements effectively suppress vertical vibrations, minimize the risk of suspension bottoming, and highlight the potential of intelligent optimization-based control for enhancing FCCV reliability and passenger comfort. Full article

Submarine rift systems represent critical tectonic features whose accurate bathymetric characterization remains challenging yet essential for understanding plate boundary dynamics. However, traditional bathymetric inversion methods based on altimetric gravity data exhibit poor performance in resolving rift and steep-slope terrains. To address this limitation and enhance accuracy in complex topographic regions, we propose a multi-gravity-component fusion framework based on an improved DenseNet architecture. By integrating shipborne bathymetry, gravity anomaly (GA), vertical gravity gradient (VGG), vertical deflection components (meridian component ξ and prime vertical component η), and GEBCO_2024, we construct a 16 × 16 × 9 input tensor. The model incorporates adaptive transition layers to preserve fine-scale tectonic features and curvature-based stratification to balance learning across diverse terrains. Validation using 43,035 independent points yields an RMSE of 84.75 m, representing a 47.6% reduction relative to GEBCO_2024. Crucially, in the identified rift targets, errors decreased by 69.3–87.1%. Ablation studies reveal that vertical deflection components (ξ, η) dominate the physical constraints, with their removal increasing the RMSE by 91.08 m (a 107.5% increase relative to the baseline error). Architectural innovations and stratification reduce steep-slope RMSE by 6.1%. These results validate the efficacy of directional gravity derivatives for tectonic feature inversion and demonstrate significant potential for application to mid-ocean ridge systems. Full article

This study addresses the challenges encountered in mechanized agricultural fields, particularly the soil disruption associated with conventional horizontal rotary straw cleaning equipment. To mitigate the inefficiency of straw cleaning observed in the current vertical rotary apparatus, this study introduces a vertical rotary fixed-angle straw cleaning device. The essential conditions for establishing the cutter tooth angle were identified through theoretical analysis. Analyzing the kinematics of the cutter tooth to direct the movement of the straw, we determined that the deflection angle of the cutter tooth group (DA) is a critical parameter for enhancing the effectiveness of straw cleaning. A multiphase interaction model encompassing soil, straw, and machinery components was developed utilizing a coupled simulation approach with RecurDyn and EDEM software. The Box–Behnken response surface methodology was employed to systematically investigate the interaction effects of three critical parameters on both the straw cleaning rate and the soil disturbance rate: operation speed (OS), rotation speed of the straw cleaning rotary table (RS), and the DA. For optimization experiments where the OS is set to 2.4 m/s, RS is 400 r/min, and DA is 48°, the straw cleaning rate reaches 94.1% and the soil disturbance rate is 27.2%. This device can efficiently create a localized clean seeding belt for no-till planters without significantly damaging the soil structure, providing an innovative solution for the development of low-disturbance, high-efficiency conservation tillage equipment. Full article

The complex jet-ground interactions of Short Take-off and Vertical Landing (STOVL) aircraft are critical to flight safety and performance, yet studying them with traditional full-scale wind tunnel tests is prohibitively expensive and time-consuming, hindering design optimization. This study addresses this challenge by developing and numerically verifying a “pressure ratio–momentum–geometry” multi-dimensional similarity framework, enabling accurate and efficient scaled-model analysis. Systematic simulations of an F-35B-like configuration demonstrate the framework’s high fidelity. For a representative curved nozzle configuration (e.g., the F-35B three-bearing swivel duct nozzle, 3BSD), across scale factors ranging from 1:1 to 1:15, the plume deflection angle remains stable at 12° ± 1°. Concurrently, axial force (F) and mass flow rate (Q) strictly follow the square scaling relationship ($F\propto 1/n^2, Q\propto 1/n^2)$, with deviations from theory remaining below 0.15% and 0.58%, respectively, even at the 1:15 scale, confirming high-fidelity momentum similarity, particularly in the near-field flow direction. Second, a 1:13.25 scale aircraft model, constructed using Froude similarity principles, exhibits critical parameter agreement (intake total pressure and total temperature) of the prototype-including vertical axial force, lift fan mass flow, and intake total temperature—all less than 1.5%, while the critical intake total pressure error is only 2.2%. Fountain flow structures and ground temperature distributions show high consistency with the full-scale aircraft, validating the reliability of the proposed “pressure ratio–momentum–geometry” multi-dimensional similarity criterion. The framework developed herein has the potential to reduce wind tunnel testing costs and shorten development cycles, offering an efficient experimental strategy for STOVL aircraft research and development. Full article

In winter, stay cable sheaths are prone to icing, which increases cable loads and poses a falling-ice hazard upon thawing. While manual and chemical de-icing are common methods, their safety and cost drawbacks make robotic de-icing a promising alternative. Robotic de-icing offers a promising alternative. However, to protect the sheath from damage, the de-icing blade is designed to minimize contact with its surface. Consequently, a thin layer of residual ice is often left behind, which reduces the surface friction coefficient and complicates the climbing process. This study evaluates the climbing performance of a self-manufactured cable-climbing mechanism through laboratory tests and dynamic simulations (ADAMS). A physical prototype was built, and dynamic simulations of the cable-climbing mechanism were conducted using Automated Dynamic Analysis of Mechanical Systems (ADAMS) software. The preliminary validation results demonstrate that the mechanism is capable of maintaining stable climbing under extreme conditions, including a friction coefficient of 0.12 to reflect thin-ice variability and indicated stable climbing even at μ = 0.12), a vertical inclination of 90°, and a load of 12 kg, confirming the design’s validity. Furthermore, we analyzed key parameters. A lower friction coefficient requires a higher clamping force and adversely affects the climbing speed due to increased slip. Similarly, an increased payload elevates the mechanism’s deflection angle, spring force, and wheel torque, which in turn reduces the climbing speed. Cable inclination has a complex effect: deflection decreases with slope, yet clamping force peaks near 70°, showing a bell-shaped trend. This peak requirement dictated the damping spring selection, which was given a safety margin. This ensures safe operation and acceleration at all other angles. Limitations: The present results constitute a feasibility validation under controlled laboratory conditions and rigid-support simulations. The long-term effects of residual ice and field performance remain to be confirmed in planned field trials. Full article

This study presents a high-fidelity CFD-based optimization of a combined sacrificial-pile and collar (SPC) system designed to suppress local scour at circular bridge piers. Following rigorous validation against benchmark flume experiments (scour depth error < 3%), a systematic parametric study was conducted to quantify the influence of pile-to-pier spacing (d_p/D = 4–6) and collar elevation (h_c/D = 0–0.3). The optimal layout is found to be a sacrificial pile at d_p/D = 5 and a collar at h_c/D, which yields a 51.2% scour reduction relative to the unprotected case. Flow field analysis reveals that the pile wake deflects the lower approach flow, while the collar vertically displaces the horseshoe vortex; together, these mechanisms redistribute bed shear stress and prevent secondary undermining. Consequently, the upstream conical pit is virtually eliminated, lateral scour is broadened but markedly shallower, and the downstream dune tail bifurcates into two symmetrical ridges. To the best of the authors’ knowledge, this study presents the first high-fidelity CFD-based optimization of a combined sacrificial-pile and collar (SPC) system with a fully coupled hydrodynamic-morphodynamic model. The optimized layout yields a 51.2% scour reduction relative to the unprotected case and, more importantly, demonstrates a positive non-linear synergy that exceeds the linear sum of individual device efficiencies by 7.5%. The findings offer practical design guidance for enhancing bridge foundation resilience against scour-induced hydraulic failure. Full article

In this paper, we present a novel iterative method that minimizes the weight of an all-steel arch bridge during the in-plane preliminary design stage. The behavior of the bridge is assumed to be contained within the plane of the arch. The preliminary design is assumed to be governed by the maximum allowable static deflection at a given checkpoint at the deck under a simplified load combination selected by the designer. The designer can select variables commonly used in preliminary design, such as the web slenderness of the cross-sections of both the arch and the deck and their relative flexural stiffness levels. Moreover, the general method is particularized for tied-arch bridges with vertical hangers: its iterative flowchart is adapted, an approximate analytical formulation that allows manual calculations is provided, and a parametric study that illustrates the effect of the main variables on the weight of the bridge is carried out. The main design recommendations drawn from this research for minimizing the weight of a bridge are as follows: a rise/span ratio between 1/5 and 1/7; cross-sections with significantly different stiffnesses in the arch and deck, ideally with highly flexible arches; and cross-sections with the thinnest possible webs. Full article

Ultra-fast fire, characterized by rapid heat release and associated overpressure, poses serious challenges to structural safety in industrial facilities. This study presents the design and evaluation of a protective block capable of resisting both the thermal and mechanical effects of ultra-fast fires. The study combined material- and component-level fire tests with structural simulations. The fire scenario was defined as reaching 1 MW within 60 s with a peak overpressure of 5 bar, comparable to dust fire conditions. Fire resistance was achieved with a layered system comprising a 1 mm perforated steel plate to prevent coating detachment, a 5 mm fire-resistant coating, a 2 mm front steel plate, 25 mm glass wool, and a 2 mm back steel plate. Structural analysis confirmed that a frame system with 200 mm × 200 mm H-beams (vertical) and 150 mm steel plates (horizontal) limited deflection to about 50 mm under 5 bar overpressure. These results demonstrate the feasibility of integrating material-level fire resistance with structural optimization, providing a practical basis for protective block design in ultra-fast fire scenarios. Full article

In recent years, tail-sitter unmanned aerial vehicles (UAVs), capable of vertical take-off and landing (VTOL) and long-range flight, have garnered extensive attention. However, the challenge of yaw control, particularly for large-scale UAVs, has become a significant obstacle. It is challenging to generate sufficient yaw moments by motor differential thrust without compromising control authority in other channels or increasing mechanical complexity. Therefore, this paper proposes the concept of blown yaw, which utilizes the high-velocity airflow over rudders, induced by the propellers slipstream, to enhance the yaw control torque actively. An over-actuated, hundred-kilogram-class, tail-sitter UAV is designed to validate the effectiveness of the proposed method. To address the control allocation problem introduced by the implementation of blown yaw, an optimization-based control allocation module is developed, capable of precisely mapping the required forces and torques to all actuators. The proposed method, combined with computational fluid dynamics (CFD) simulations, accounts for the propeller model and the significant differences in actuator effectiveness across various flight conditions. Simulation results demonstrate that the proposed blown-yaw method significantly enhances the yaw control performance, achieving an overall energy savings of approximately 8.0% and a 60% reduction in the mean-squared error. Furthermore, the method exhibits robust performance against variations in control parameters and external disturbances. Full article

To address the dynamic characteristics of vehicle semi-active suspension systems under special operating conditions and multi-source excitations, this paper proposes a fuzzy adaptive proportional–integral–derivative model predictive control (PID-MPC) strategy aimed at enhancing ride comfort during vehicle operation. The proposed approach employs MPC as the primary controller to optimize suspension performance, incorporating a fuzzy adaptive PID compensation mechanism for real-time adjustment of PID parameters, thereby improving control efficacy. A half-car semi-active suspension model was established on the MATLAB/Simulink (2020b) platform, with simulation validation conducted across diverse road profiles, including speed bump road surface, Class B road surface, and Class C road surface. Simulation results demonstrate that the proposed strategy achieves a significant reduction in both vehicle vertical acceleration and vehicle pitch angle acceleration while maintaining appropriate suspension deflection and tire dynamic loads, effectively elevating occupant ride comfort. Research demonstrates that the fuzzy adaptive PID-MPC control strategy exhibits commendable performance under typical road operating conditions, possessing notable potential for practical engineering implementation. Full article

This study simplifies the local model of the orthotropic steel bridge deck pavement into a two-dimensional composite continuous beam. Based on the Modal Superposition Method and Duhamel Integration, an analytical solution for the dynamic response of the composite continuous beam under moving harmonic loads is derived. Using the UHPC (Ultra-High Performance Concrete)-SMA (Stone Mastic Asphalt) composite pavement as an example, the influence of structural parameters on the analytical results is investigated. The results demonstrate that the natural frequencies of the three-span continuous composite beam obtained from the analytical method exhibit a relative error of less than 10% compared to finite element modal analysis, indicating high consistency. Furthermore, the analytical solutions for four key indicators—deflection, bending stress, interlayer shear stress, and interlayer vertical tensile stress—closely align with finite element simulation results, confirming the reliability of the derived formula. Additionally, increasing the thickness of the steel plate, UHPC layer, or asphalt mixture pavement layer effectively reduces the peak values of all dynamic response indicators. Full article

This article presents a numerical study of the influence of applied nonlinearities on the response of a flat slab–column structure under progressive collapse conditions. A key aspect of the work is the extension of nonlinear static analysis by considering cases of material nonlinearity combined with both linear and nonlinear geometry, using a corotational formulation and a damage-based elasto-plastic concrete model. A multi-layer shell element implemented in the OpenSees platform is used to distinguish between the strength characteristics of the concrete and reinforcement, with particular attention given to the modeling of the slab–column connection in nonlinear analyzes involving both shell and beam elements. The applied vertical pushover analysis enabled the derivation of load–displacement curves and the identification of the sequence in which plastic hinges can be formed. The development of membrane action resistance, expressed through the formation of compressive and tensile rings, is observed numerically when both material and geometric nonlinearities are simultaneously considered. Moreover, the transition from compressive membrane action to tensile membrane action occurs once the deflections reach the value equal to the effective depth of the slab. This insight may serve as an important guideline for the development of future revisions to design standards related to progressive collapse. Full article

This study used reanalysis and lidar observations to investigate nocturnal downslope wind events in the Taklimakan desert, revealing their vertical structure, influencing factors, climatology, and impacts on boundary layer dynamics and dust emissions. 125 events were detected along the northern slope of the Kunlun Mountains, impacting Minfeng. Due to its weakness after onset, downslope flow is deflected horizontally when it encounters the opposing synoptic winds. The continued radiative cooling, dense air drainage, and adiabatic warming intensify downslope flow as the night progresses, causing it to gradually sink and overcome the opposing synoptic winds. Downslope wind events typically occur between an hour before and two hours after sunset, with the strongest occurring at or before sunset due to the longer period of radiative cooling and the coincidence with early evening instability conditions. Strong events occur under weak stability conditions as a stable atmosphere with a strong inversion layer can inhibit sinking motion. Most events, even the strongest ones, occur under dry conditions due to enhanced radiative cooling. Mechanical turbulence occurs when downslope flow hits the surface, whereas thermal turbulence occurs when warmer, downslope air weakens the lower atmosphere’s temperature inversion. Downslope wind events significantly raise dust emissions in the Taklimakan desert. Full article

The existing analytical methods lack a reasonable explanation for the cracking and deformation response mechanism of two-way reinforced concrete (RC) slabs under combined horizontal and vertical loads during a fire. In addition, there is a lack of comparative studies on different boundary conditions. Therefore, solid finite-element models were established using ABAQUS 6.14 software to simulate the behavior of two-way RC slabs under combined horizontal and vertical loads in fire. The models considered two different support conditions: four edges simply supported (FSS) and adjacent edges simply supported and adjacent edges quasi-fixed (ASSAQF). Based on experimental model verification, mechanical and parametric analyses were performed to further investigate the deflection, stress variation characteristics, and mechanical response of a concrete slab and reinforcements. The results show that (1) The stress redistribution process of two-way RC slabs under combined horizontal and vertical loads with these two support conditions (FSS and ASSAQF) during fire undergoes four stages: elastic, elastic–plastic, plastic, and tensile cracking. (2) Increasing the horizontal load, vertical load level, and length–width ratio and decreasing the slab thickness all shorten the fire resistance to a certain extent. (3) Compared to slabs with FSS, the stronger support condition of slabs with ASSAQF significantly prolongs the duration of the inverted arch effect stage, resulting in a superior fire resistance, with the fire resistance performance improved by 11–59%. Full article