Search Results (742)

Reservoir landslides undergo saturated–unsaturated transitions under hydrological variations. Matric suction significantly influences slip-zone soil strength. Existing studies lack analysis of suction–rate–strength coupling, while Amontons’ model fails for cohesive soils. This study investigated Huangtupo landslide slip-zone soil in the upper reaches of the Yangtze River using pressure plate and saturated salt solution methods to determine the soil–water characteristic curve. Suction-controlled ring shear tests were conducted under three matric suction levels ($\Psi$ = 0, 200, and 700 kPa) across net normal stresses (${\sigma }_{net}$ = 100–800 kPa) and shear rates ($\dot{\gamma }$ = 0.05–200 mm/min). Key findings revealed the following: (1) significant suction–rate coupling effects were shown, with 700 kPa suction yielding 30% higher residual strength than saturated conditions, validating matric suction’s role in enhancing effective stress and particle contact strength; (2) residual cohesion showed strong logarithmic correlation with shear rate, with the fastest growth below 10 mm/min, while the residual friction angle varied minimally (0.68°), contributing little to overall strength; (3) a bivariate model relating residual cohesion to $\dot{\gamma }$ and $\Psi$ was established, overcoming traditional single-factor limitations. The study demonstrates that dual-parameter Coulomb modeling effectively captures multi-field coupling mechanisms in unsaturated slip-zone soils, providing theoretical foundations for landslide deformation prediction and engineering design under dynamic hydrological conditions. Full article

This work deals with the preparation and characterization of TiAlV/ZnAlCu composite materials. The aim is to create a model for biomaterial with good biocompatibility and acceptable mechanical properties. Infiltrating zinc into the reinforcement made of the titanium alloy could significantly improve the osseointegration of the bioimplant made from this material. The investigated reinforcements of three different geometries made from Ti-6Al-4V prepared by the SLM method (selective laser melting) were infiltrated with molten zinc or the Zn-based alloy. Two infiltration approaches were used—suction of the melt using a vacuum pump and centrifugal casting. By these procedures, different infiltration rates were achieved. Furthermore, the mechanical properties of the prepared composite materials were characterized by compression tests. The results were compared with the mechanical properties of the Ti-6Al-4V alloy reinforcement. Full article

Biopolymers have recently been introduced as eco-friendly alternatives to other chemical cementitious additives for sandy soil stabilization, especially in pavement construction. The resilient modulus (M_R) is a key metric considered in the mechanistic design of pavement layers that ensures a safe and economic design based on guaranteed accurate values. This study investigated the effects of dehydration on the M_R of biopolymer-treated sand. Prepared specimens were subjected to two different curing conditions. The first set underwent closed-system curing (CSC) for periods of 7, 14, and 28 days. The second set of specimens was cured at different levels of suction by controlling relative humidity (RH) using different salt solutions (0.27, 1.0, 9.7, 21.0, 54.6, 113.7, and 294 MPa), referred to as dehydration curing (DC). The soil water retention curve (SWRC) was measured over the entire suction range to evaluate the dehydration curing and to link the results of suction levels and dehydration regime. M_R tests were conducted on both sets of specimens using a dynamic triaxial system to simulate different confining, traffic, and dynamic stresses. The results showed a significant increase in M_R (i.e., up to eight times) for specimens cured under DC conditions that was proportional to the suction level across different zones of the SWRC. Scanning electron microscopy revealed a phase change from hydrogel to film, which enhanced cementation and bonding between particles. in addition, CSC treatment resulted in a 10–30% reduction in M_R. A new regression model is proposed to predict the M_R of biopolymer-treated sand as a function of confining stresses, dynamic stresses, and suction. These findings will assist pavement engineers and designers in achieving safe, sustainable, and economic designs. Full article

As aviation operations extend into complex natural environments, dust particles present significant challenges to flight stability and safety, particularly in dust-prone regions like southern Xinjiang. This study employs high-fidelity computational fluid dynamics (CFD) simulations, combined with the SST turbulence model and the Lagrangian discrete phase model, to analyze the aerodynamic response of the NACA 0012 airfoil at varying wind speeds (5, 15, and 30 m/s) and angles of attack (3°, 8°, and 12°). The results indicate that, at low speeds and moderate to high angles of attack, dust particles reduce lift by over 70%, primarily due to boundary layer instability, weakened suction-side pressure, and premature flow separation. Higher wind speeds slightly delay flow separation, but cannot counteract the disturbances caused by the particles. At higher angles of attack, drag increases by more than 60%, driven by wake expansion, shear dissipation, and delayed pressure recovery. Pitching moment frequently reverses from negative to positive, reflecting a forward shift in the aerodynamic center and a loss of pitching stability. An increase in dust concentration amplifies these effects, leading to earlier moment reversal and more abrupt stall behavior. These findings underscore the urgent need to improve aircraft design, control, and safety strategies for operations in dusty environments. Full article

Stable adhesion on non-magnetic, steep, and irregular underwater surfaces (e.g., concrete dams with cracks or biofilms) remains a challenge for inspection robots. This study develops a novel adsorption mechanism based on the synergistic operation of a Venturi-ejector and a composite suction cup. The mechanism utilizes the Venturi effect to generate stable negative pressure via hydrodynamic entrainment and innovatively adopts a composite suction cup—comprising a rigid base and a dual-layer EPDM sponge (closed-cell + open-cell)—to achieve adaptive sealing, thereby reliably applying the efficient negative-pressure generation capability to rough underwater surfaces. Theoretical modeling established the quantitative relationship between adsorption force (F) and key parameters (nozzle/throat diameters, suction cup radius). CFD simulations revealed optimal adsorption at a nozzle diameter of 4.4 mm and throat diameter of 5.8 mm, achieving a peak simulated F of 520 N. Experiments demonstrated a maximum F of 417.9 N at 88.9 W power. The composite seal significantly reduced leakage on high-roughness surfaces (Ra ≥ 6 mm) compared to single-layer designs. Integrated into an inspection robot, the system provided stable adhesion (>600 N per single adsorption device) on vertical walls and reliable operation under real-world conditions at Balnetan Dam, enabling mechanical-arm-assisted maintenance. Full article

The reverse circulation drill bit is the key component for the efficient and smooth implementation of the pneumatic hollow-through down-the-hole (DTH) hammer reverse circulation continuous coring (sampling) technology. To obtain the structural form of a reverse circulation drill bit with better reverse circulation performance, revealing its local flow fields by computational fluid dynamics (CFD) simulation is an effective approach. Taking the inner jet holes-type reverse circulation drill bit as the research object, three kinds of symmetrical and asymmetrical structures of inner jet holes were proposed. The CFD simulation results show that increasing the air volume supply and the number of inner jet holes leads to an increase in the velocity of air flow jet within the inner jet holes, an increase in the negative pressure formed in the central through channel below the inner jet holes, an enhancement of the reverse circulation performance and suction capacity formed by the reverse circulation drill bit, and an acceleration of the upward flow velocity of the rock cores (samples) located at the bottom of the borehole. Additionally, the reverse circulation performance formed by the reverse circulation drill bit with staggered arranged inner jet holes is superior to that of the reverse circulation drill bit with uniformly distributed inner jet holes. Under the same simulation conditions, the static pressure (i.e., negative pressure) and the upward flow velocity formed by the JB6 model are 2.34 kPa and 30.778 m/s higher than those formed by the JB3-3 model, while these two values formed by the JC6 model are 0.197 kPa and 3.689 m/s higher than those formed by the JB6 model, respectively. In conclusion, an asymmetric structural design would be more reasonable for the design of the inner jet holes-type reverse circulation drill bit. Full article

The low-pressure edge of a pump-turbine runner blade is more prone to cavitation than other parts. The installation angle of the blade’s low-pressure edge is one of the key parameters affecting the cavitation performance of the pump-turbine. Based on the installation angle of the blade’s low-pressure edge obtained by the principle of normal outflow of the turbine runner, two other installation angles of the low-pressure edge are constructed by increasing the installation angle of the low-pressure edge toward the band direction. Three types of blades are designed based on the parametric design program of the pump-turbine runner. The Zwart cavitation model is adopted to carry out full-channel steady numerical simulations for the three runners. The efficiencies and internal flow fields of the draft tube under turbine operating conditions are compared. The cavitation characteristics in pump mode, the distribution of the turbulent flow field, and the pressure distribution on the blade surface are analyzed. The influence laws of the installation angle of the blade’s low-pressure edge on pump-turbine performance is summarized. A design method for anti-cavitation of Francis pump-turbine runners has been explored. The results show that the LP1 blade can achieve normal outflow under the turbine’s rated operating condition, but due to the large inflow attack angle under pump operating conditions, the cavitation performance in pump mode is very poor. By increasing the installation angle of the blade’s low-pressure edge toward the band direction, the efficiencies and cavitation performances of the pump mode can be improved. The LP3 blade reduces the inflow attack angle while optimizing the pressure distribution on the blade’s suction surface, thereby reducing the superimposed effect of two phenomena under large-discharge pump operating conditions with low cavitation numbers: flow separations on the pressure surface caused by inflow impact, and flow separations on the suction surface of adjacent blades caused by cavitation. As a result, the cavitation performance of the LP3 blade is significantly better than that of the LP1 and LP2 blades. The proposed anti-cavitation design method is simple and effective and can be applied to the research and modification design of Francis pump-turbine runners. Full article

Granite residual soil is widely employed as subgrade fill material, but its tendency to undergo wetting-induced deformation under moisture infiltration poses significant challenges to pavement stability. To address this issue, this study introduces an innovative wetting device capable of precisely controlling moisture content increase, enabling multi-step wetting tests under controlled conditions. Saturated wetting tests were also conducted using both single-line and double-line methods, and the results were compared. Pore size distribution curves for granite residual soil samples with different initial states were measured using Mercury Intrusion Porosimeter (MIP) tests. Results indicate that for both the single-line method and the double-line method, the ${\epsilon }_V$-lgp curve for samples subjected to different compaction efforts remains parallel across varying initial moisture content. The increase in vertical stress will constrain the water adsorption and swelling potential. Whereas an increase in compaction effort leads to greater swelling potential, which is mitigated by an increase in initial moisture content. By integrating the test results of the soil water characteristic (SWCC) curve, the relationship between normalized wetting deformation and matric suction is primarily influenced by the initial state of the soil sample and remains unaffected by vertical stress during multi-step wetting. Based on the test results, an empirical wetting prediction model was formulated, accounting for the influence of vertical stress, initial matric suction, and matric suction after wetting. Fitting results confirmed that the established model achieved high prediction accuracy (R² > 0.9), supporting its application in practical engineering endeavors. Full article

This paper takes a small three-stage centrifugal pump as the research object. Based on the RNG k-ε turbulence model and the TFM two-phase flow model, the numerical simulation of the internal gas–liquid two-phase flow was carried out, and the influence of the inlet gas content rate of the small multistage centrifugal pump on its internal flow was analyzed. The research results show that the head and efficiency of the multistage centrifugal pump will decrease with the increase in the inlet gas content rate. As the gas content increases from 0% to 5%, the head of the multistage centrifugal pump decreases by 3% and its efficiency drops by 5%. The trend of the continuous increase in the pressure on the blade surface does not change with the increase in the inlet gas content rate. The bubble area on the surface of the first-stage impeller blade increases with the increase in the gas content rate. When the inlet gas content rate condition reaches 5%, the bubbles cover the middle section of the blade suction surface. The flow vortex structure is mainly composed of blade separation vortices and mouth ring clearance leakage vortices. The vortices inside the impeller are concentrated in the blade outlet and rim area, while the vortices inside the guide vanes are located in the flow channel area of the anti-guide vanes. With the increase in the gas content rate, the amplitude of pressure pulsation in the flow channel inside the pump decreases. Full article

During the continuous operation of trailing suction hopper dredger (TSHD), equipment workload exhibits significant time-varying characteristics. Maintaining dynamic symmetry between power generation and consumption is crucial for ensuring system stability and preventing power supply failures. Key challenges lie in dynamic perception, accurate prediction, and real-time power management to achieve this equilibrium. To address this issue, this paper proposes and constructs a “prediction-driven dynamic power management method.” Firstly, to model the complex temporal dependencies of the workload sequence, we introduce and improve a dilated convolutional long short-term memory network (Dilated-LSTM) to build a workload prediction model with strong long-term dependency awareness. This model significantly improves the accuracy of workload trend prediction. Based on the accurate prediction results, a dynamic power management strategy is developed: when the predicted total power consumption is about to exceed a preset margin threshold, the Power Management System (PMS) automatically triggers power reduction operations for adjusfigure loads, aiming to maintain grid balance without interrupting critical loads. If the power that the generator can produce is still less than the required power after the power is reduced, and there is still a risk of supply-demand imbalance, the system uses an Improved Grey Wolf Optimization (IGWO) algorithm to automatically disconnect some non-critical loads, achieving real-time dynamic symmetry matching of generation capacity and load demand. Experimental results show that this mechanism effectively prevents generator overloads or ship-wide power failures, significantly improving system stability and the reliability of power supply to critical loads. The research results provide effective technical support for intelligent energy efficiency management and safe operation of TSHDs and other vessels with complex working conditions. Full article

As wind energy development continues to expand toward nearshore and deep-sea regions, enhancing the aerodynamic efficiency of vertical axis wind turbines (VAWTs) in complex marine environments has become a critical challenge. To address this, a composite flow control strategy combining leading-edge suction and trailing-edge gurney flap is proposed. A two-dimensional unsteady numerical simulation framework is established based on CFD and the four-equation Transition SST (TSST) transition model. The key control parameters, including the suction slot position and width as well as the gurney flap height and width, are systematically optimized through orthogonal experimental design. The aerodynamic performance under single (suction or gurney flap) and composite control schemes is comprehensively evaluated. Results show that leading-edge suction effectively delays flow separation, while the gurney flap improves aerodynamic characteristics in the downwind region. Their synergistic effect significantly suppresses blade load fluctuations and enhances the wake structure, thereby improving wind energy capture. Compared to all other configurations, including suction-only and gurney flap-only blades, the composite control blade achieves the most significant increase in power coefficient across the entire tip speed ratio range, with an average improvement of 67.24%, demonstrating superior aerodynamic stability and strong potential for offshore applications. Full article

To investigate the effects of clearance variations induced by back wear ring wear on internal flow and noise within centrifugal pumps at the design flow rate (Q_o = 25 m³/h), a combined Computational Fluid Dynamics (CFD) and Acoustic Finite Element Method (FEM) approach was employed. The SST-SAS turbulence model and Lighthill’s acoustic analogy, were applied to simulate the internal flow and acoustic fields, respectively, across four different clearance values. The impact laws of various back wear-ring clearances on flow-induced noise were analyzed. The results indicate that the head and efficiency of the centrifugal pump gradually decrease with the increase in the back wear-ring clearance. When the clearance reaches 1.05 mm, the head drops by 4.35% and the efficiency decreases by 14.86%. The radial force on the impeller decreases, while the axial force increases and its direction reverses by 180 degrees. The acoustic source strength at the rotor–stator interface, near the volute tongue, and at the outlet of the back wear ring increases with larger clearance; furthermore, high-sound-source regions expand around the balance holes and near the impeller suction side. The dominant SPL frequency for all clearance cases was the blade passing frequency (BPF). As clearance increases, the overall SPL curve shifts upwards; however, the variation gradient decreases noticeably when the clearance exceeds 0.75 mm. The overall internal SPL increases, with the total SPL under 1.05 mm being 1.8% higher than that under 0.15 mm. In total, the optimal back ring clearance is 0.45 mm, which achieves a 38% noise reduction while maintaining a 97.9% head capacity. Full article

The inclusion of an inducer is an effective approach to improve the cavitation performance of centrifugal pumps, significantly influencing both the internal flow characteristics and the external performance of the pumps. This study examines a miniature high-speed centrifugal pump (MHCP) using numerical simulations based on the k-ε turbulence model, comparing the cases with an inducer and without one. Experimental tests on the pump’s external performance are conducted and flow visualization images are presented to validate the findings. The effects of the inducer on the tip leakage backflow, cavitation performance, and external pump performance are analyzed. The results show that the inducer provides pre-pressurization of the fluid, leading to a higher circumferential velocity at the impeller inlet and a reduced inlet flow angle. This allows for a reduction in the impeller blade inlet angle, resulting in smoother flow streamlines inside the impeller. Moreover, the inducer helps to suppress local low-pressure regions caused by the vortex and cavities generated by the interaction between the tip clearance backflow and the main flow, thereby mitigating cavitation in the non-blade zone. Within the investigated operating range, the pump with an inducer exhibits a significantly improved external hydraulic performance, including an increased head and efficiency, a reduced required net positive suction head (NPSHr), and a broader stable operating range. Full article

To address the issue in high-throughput longitudinal axial-flow grain combine harvester cleaning systems, in which the extended length of the cleaning chamber results in airflow velocity attenuation and makes it difficult to efficiently and rapidly remove light impurities, a front-blowing and rear-suction enhanced cleaning technology and device was developed. Based on the investigation of the movement characteristics of the cleaning airflow within the cleaning chamber, a theoretical model was established to describe the velocity variation of the front-blowing and rear-suction enhanced cleaning airflow. CFD simulation software was employed to conduct a comparative analysis of the airflow field structure before and after improvement, aiming to identify the influence patterns of key structural parameters on the airflow field distribution. An orthogonal experiment with three factors and three levels was conducted on the improved cleaning system, focusing on the suction fan speed, vertical installation height of the suction fan, and horizontal distance between the suction fan and the sieve surface. The influence of each factor on the airflow field was analyzed, and the optimal parameter combination was obtained. When the suction fan speed was 2275 r/min, the vertical installation height was 72.5 mm, the horizontal distance to the sieve surface was 385 mm, and the airflow non-uniformity coefficient at the rear part of the screen surface was 11.17%, with a relative error of 4.39% compared to the optimization result. Finally, bench tests were conducted to verify the accuracy of the simulation results. Compared to that before improvement, the airflow non-uniformity coefficient at the rear part of the screen surface in the cleaning chamber was reduced by 59.43%, significantly improving the uniformity of airflow distribution. These findings provide both theoretical and technical support for improving the cleaning efficiency and operational performance of high-throughput grain combine harvesters. Full article

Previous studies have extensively applied the generalized consolidation theory, which incorporates a two-stress state variable framework, to predict the volumetric behavior of unsaturated expansive soils under varying mechanical stress and matric suction. A key requirement for this approach is a constitutive surface that links the soil void ratio to both net stress and matric suction. A large number of fitting parameters are typically needed to accurately fit a two-variable void ratio surface equation to laboratory test data. In this study, a single-stress state variable framework was adopted to describe the void ratio as a function of effective stress for unsaturated soils. The proposed approach was applied to fit void ratio–effective stress constitutive curves to laboratory test data for two different expansive clays. Additionally, a finite element model coupling variably saturated flow and stress–strain analysis was developed to simulate the volume change behavior of expansive clay subjected to moisture fluctuations. The model utilizes suction stress to compute the effective stress field and incorporates the dependency of soil modulus on volumetric water content based on the proposed void ratio–effective stress relationship. The developed numerical model was validated against a benchmark problem in which a layer of Regina expansive clay was subjected to a constant infiltration rate. The results demonstrate the effectiveness of the proposed model in simulating expansive soil deformations under varying moisture conditions over time. Full article