Search Results (52)

Conventional active vehicle height control systems predominantly employ hydraulic or pneumatic suspension mechanisms. Although these established approaches have achieved widespread adoption in automotive applications, they remain fundamentally constrained by three critical drawbacks: (1) inadequate dynamic response characteristics, (2) high energy consumption, and (3) inherent mechanical complexity. The ongoing electrification revolution in vehicle technologies has spurred significant research interest in linear electromagnetic suspension systems. Nevertheless, their practical implementation encounters dual technical barriers: (a) complex multi-phase motor configurations requiring precise coordination, and (b) substantial thrust ripple generation under dynamic operating conditions. To address these critical limitations, our research proposes a novel motor structure, known as the flat rectangular slot structure, which offers advantages such as simple installation and high thrust with low current. Additionally, we have designed a double-vector control strategy for the motor control section, which modifies the finite-set model predictive control and enhances the accuracy of the model’s calculations. By integrating the vehicle model, we have developed a multi-layer hierarchical control strategy for the vehicle height controller. In the first layer, a PI controller is used to convert the target height into current, which is then input into the value function. In the second layer, we improve the control strategy for the linear motor by optimizing the finite-set model predictive control through the double-vector control. Through multi-step predictive calculations, we determine the optimal sector, enabling the motor to receive the corresponding control force. In the third layer, the motor thrust is input into the vehicle model to achieve closed-loop control of the vehicle body. Finally, we conduct simulation verification of the proposed control strategy. The simulation results indicate that the double-vector control significantly reduces the fluctuation in the sprung mass displacement by approximately 70% compared to single-vector control, the response speed is increased by approximately 20%, and the thrust required to achieve the target vehicle height is reduced by 5.7%. Therefore, the proposed double-vector control strategy can significantly enhance the stability of the automotive electronic control suspension, opening up new research avenues for the study of suspension stability control and energy saving in vehicles. Full article

The vertical slot fishway (VSF) has proven effective in mitigating the severe fragmentation of rivers caused by artificial hydraulic structures. While fishways with steeper slopes exhibit better economic performance, increased slope can raise the flow velocity and turbulence, which may hinder fish migration. To address this issue, this study investigated the application of a VSF with a staggered baffle configuration. Through numerical modeling, the hydraulic characteristics of the VSF under various slope ratios and chamber length-to-width (L/B) ratios were investigated, with data validated by physical models. An increase in the slope gradient resulted in higher flow velocities, greater maximum attenuation rates of mainstream velocity, and elevated turbulent kinetic energy (TKE) at the corners of the rectifier baffles and the ends of the divider baffles. Additionally, the overall maximum volumetric energy dissipation ($D_{\epsilon }$) increased, although its distribution pattern remained unaffected. Conversely, increasing the chamber L/B ratio significantly altered the distribution patterns of the flow velocity, TKE, and $D_{\epsilon }$, influencing their generation mechanisms. For instance, a higher chamber L/B ratio caused the maximum flow velocity (V_m) to deviate from the vertical slot and raised the maximum attenuation rate of the mainstream velocity. The L/B ratio also caused changes in the TKE distribution; as the ratio increased, the proportion of the chamber’s internal region with $D_{\epsilon }\le 150 \mathrm{W}/{\mathrm{m}}^3$ initially decreased and then increased. Overall, considering the flow velocity, TKE, and $D_{\epsilon }$, it is recommended that the chamber L/B ratio be maintained between 0.9 and 1.1 for slope ratios ranging from 1:20 to 1:50. The research results will offer practical insights for engineering applications, in engineering construction, contribute theoretical guidance for the optimized design of fish passages, promote sustainable hydraulic engineering practices, and aid in the protection of aquatic biodiversity. Full article

To investigate the flow characteristics of a novel dual-slot overflow channel, a research approach integrating physical experiments and numerical simulations was adopted. A three-dimensional model of the overflow channel was developed, employing the RNG k-ε turbulence model and the VOF two-phase flow model to optimize the numerical simulation of the high-low dual-slot flow field. Physical experiments were conducted to verify and analyze the hydraulic characteristics of the high-low overflow channel, including the longitudinal water surface profile and flow patterns. The numerical simulation results aligned well with the physical model test results. By analyzing the flow field of the dual-slot counterflow spillway, the flow characteristics at both the spillway and outlet sections were identified. This study focused on the water surface profile along the spillway, the pressure distribution, and the counterflow characteristics of the protruding water tongue, and explored optimization strategies for the WES surface and spillway design. Physical model tests were conducted on the final optimized design, yielding good agreement between the theoretical predictions and experimental results, thereby confirming the feasibility of the energy dissipation methods for both high and low spillways. The research outcomes offer valuable references for related engineering applications. Full article

To address the issue of excessive transient noise during the opening and closing of a sea valve, a method for reducing pressure fluctuations during the opening of the electromagnetic hydraulic distributor has been proposed by analyzing the structure and working principle of the distributor. Based on theoretical calculation and simulation analysis, the size and shape of the buffer slot of the flow hole are determined under the condition that the stable working flow rate remains unchanged. An improved electromagnetic hydraulic distributor is developed and tested. The results indicate that this method can effectively control the opening and closing transient noise of the sea valve. Full article

Hydraulic slotting is an effective technology that enhances gas extraction operations and prevents gas disasters in coal mines. Slotting parameters and spatial arrangements substantially affect permeability enhancements. The pressure-release range and effective extraction area under different slotting spatial parameters were obtained by constructing a hydraulic slotting pressure-release permeability and three-dimensional (3D) slotting numerical models. These models quantitatively characterized the influence rules of multiple slotting spatial arrangement parameters on the extraction efficiency at a 3D scale, clarified the interactions of multiple slottings and their combined effects on pressure relief and permeability enhancement, and verified the results using field engineering tests. The results showed that hydraulic slotting significantly alters local stress and strain distributions, creating high-strain and high-stress zones with clear spatial attenuation. The process enhances fracture development, reducing gas pressure from 1 MPa to 0.08 MPa, thereby improving extraction efficiency. Enlarging the slot dimensions from 1.5 to 2.5 m increases the gas pressure-relief efficiency by up to 41% and nearly triples the impact radius. Wider slot spacing (1.5 m to 3.5 m) and additional slots (from one to three) further reduce the borehole gas pressure by 23% to 25%, optimizing hydraulic slotting technology for practical applications. Full article

Hydraulic slotting technology is an effective pressure relief method for coal seams with high stress and burst risks. Based on FLAC3D and field applications, the stress and energy evolution of coal under different slotting radiuses, slotting spacings, and slotting ranges are studied. The results show that the pressure relief effect of slotting is mainly affected by the spacing and radius of the slotting. When the cutting radius increases from 0.5 m to 1.5 m, the average stress in the cutting range decreases from 10 MPa to 7.1 MPa, and the average energy decreases from 155.7 kJ/m³ to 117.1 kJ/m³. When the slotting spacing decreases from 3 m to 1 m, the stress release increases from 62% to 72%, and the energy release increases from 77.8% to 80.3%. The difference in the slotting area only affects the transfer distance of the peak point. In the field application, the microseismic frequency near the test area after hydraulic slotting is reduced from 32 times to 19 times, and the total microseismic energy is reduced from 2.67 × 10⁴ J to 1.02 × 10³ J, which can effectively realize the high stress transfer of the roadway. It can be seen that the hydraulic slotting technology can strongly relieve the pressure at fixed points in the high stress concentration area of the coal seam. Full article

Oil-filled motors (OFMs) are widely used in deep-sea exploration and oil well extraction. During motor operation, the rotor stirs the oil in the air gap, causing viscous loss. Viscous loss affects the temperature distribution inside the motor. Accurately calculating the viscous loss and temperature rise in OFMs can provide a basis for optimizing the motor’s structural design. Motor structural parameters, including the rotor’s outer diameter, air gap, and slot opening, have a significant impact on viscous loss. The working conditions of OFMs, such as rotor speed and environmental temperature, also affect viscous loss. The viscosity of hydraulic oil is highly influenced by temperature, and changes in viscosity can lead to changes in viscous loss. These changes in viscous loss, in turn, alter the temperature distribution. Therefore, the coupling relationship between viscous loss and temperature must be considered. Additionally, when Taylor vortices occur in the fluid, the surface roughness of the rotor also has a significant influence on viscous loss. Currently, both domestic and international research on viscous loss and thermal analysis struggle to simultaneously consider the coupling of viscous loss and the temperature field, rotor surface roughness, and the effect of motor structure. This paper summarizes the methods used in recent years for studying viscous loss and thermal analysis, and puts forward some suggestions for future research on the coupling of the OFM temperature field and viscous loss. Full article

Hydraulic measures such as hydraulic slotting and hydraulic fracturing are commonly used in coal seam pressure relief and permeability enhancement. Two-phase flow patterns of CH₄–water in pore-sized coal seams after hydraulic measures are critical to improve gas extraction efficiency. The phase field module in COMSOL Multiphysics™ 5.4 and the classical ordered porous media model were used in this paper. The characteristics of CH₄–water two-phase immiscible displacement in coal seams under different capillary numbers (Ca) and viscosity ratios (M) were simulated and quantitatively analyzed. By changing the contact angle of the porous media, the flow patterns of CH₄–water two-phase in coal with different wettability were simulated. Results show that wettability significantly affects the displacement efficiency of CH₄. Additionally, by constructing a dual-permeability model to simulate the varying local permeability of the coal, the flow patterns of different Ca and M in dual-permeability media were further investigated. It is found that CH₄ preferentially invades high-permeability regions, and the displacement efficiency in low-permeability regions increases with higher Ca and M, providing a reference for gas extraction from coal seams after hydraulic measures. Full article

This study investigates the behavior of chubs (Squalius cephalus) of mid-body length (9.7–15.6 cm) with respect to turbulent flow conditions in a pool representing an experimental vertical slot fishway. Velocity and turbulence were characterized using PIV data. The influence of turbulent flow on fish behavior was assessed through the number of successful fish passage attempts, the associated passage times, and the spatial distribution of fish in the pool. Turbulence conditions were modified by the addition of one or three vertical rigid cylinders inside the pool. The results show that these adaptations may facilitate the passage of chubs. Results provide valuable insights and information to understand the relationship between fish behavior and hydraulic conditions, especially in the context of improving the design of fishways. Full article

Research shows that the novel vertical-slot, double-pool fishway can reduce the flow velocity at the vertical slots of the fishway, enhance the efficiency of the water flow in the chambers, and increase the fish passage area and migratory corridor for fish. Utilizing Fluent, two-dimensional and three-dimensional models of the novel fishway were established, and numerical simulation analysis was conducted on their hydraulic characteristics. The results indicate that the flow velocity at the cross-section of the middle vertical slot in the fishway pool decreases horizontally from left to right and increases vertically from top to bottom, with similar water flow distribution patterns on different vertical lines. The flow conditions and hydraulic characteristics of the surface, middle, and bottom layers in the pool are similar, mainly characterized by planar, two-dimensional flow. The error between the trajectory of the water flow in the main flow area and the maximum velocity value is within 10%. The novel vertical-slot, double-pool fishway retains the planar binary characteristics of traditional vertical-slot fishways. The results of the two-dimensional numerical simulation can be analogized to the vertical uniformization of the three-dimensional numerical simulation, providing support for the study of its two-dimensional numerical simulation of hydraulic characteristics and presenting a theoretical basis for the structural design and construction of fishways. Full article

In the field of pump impeller studies, tip leakage flow (TLF) and the resultant tip leakage vortex (TLV) significantly influence hydraulic efficiency, cavitation, and noise generation. This paper builds a novel square-cavity jet model combined with Large Eddy Simulation (LES) technology to obtain precise the dynamic properties of the TLV, significantly simplifying the computational resources required for numerical simulations. The novel square-cavity jet model simplifies a single blade channel to a square-cavity, and then adds a longitudinal slit on the top wall of the square-cavity. The analysis of both instantaneous and time-averaged flow fields indicates that the interaction between the main flow and the jet is the primary source of TLV generation. This study successfully captures the formation process of the TLV and accurately reveals its turbulent coherent structures. The evolution of the TLV is divided into three main parts: the first part is the jet slot, predominantly characterized by negative vorticity flow. The second part is the TLV formation, which is mainly composed of significant negative streamwise vortices. The third part is the development of the TLV, where positive and negative vorticities begin to interact, resulting in a more complex overall structure. The entire evolution of the TLV phenomenon starts with a concentrated negative vortex, which, after breakdown, develops at a certain angle to the slot and continuously advances towards the sidewall, ultimately resulting in the formation of a large-scale intermingled group of small-scale positive and negative vortices. This research not only provides a new physical model for investigating the tip leakage phenomenon in axial flow pumps but also offers a powerful tool and methodology for future studies in similar complex flow domains. Full article

Bridge pier scouring is a significant concern in hydraulic engineering, requiring thorough investigation under various conditions to estimate maximum scour depth and mitigate the risk of bridge failure. This study aims to conduct a numerical simulation of flow around a bridge pier with slots in the presence of floating debris, with the objective of analyzing variations in parameters such as velocity, shear stress, turbulent intensity, and turbulent kinetic energy. The FLOW−3D software package (Version 11), along with the k−ε (RNG) turbulence model, was employed for the simulation. The results indicate that the presence of a slot in the bridge pier provided a smooth pathway for the flow, resulting in a reduction in the pressure gradient and alleviating the negative impacts on the flow. This, in turn, led to a decrease in the velocity of the flow. Additionally, turbulence intensity around the pier ranges between 0 and 49, while turbulent kinetic energy varies from 0 to 0.005. The findings reveal that models without slots exhibit higher turbulence and vorticity levels, as well as greater flow separation, compared to models with slots. This disparity can be attributed to the slot’s ability to neutralize detrimental lateral and downward flows. Furthermore, the results demonstrate a gradual decrease in shear stress as the flow approaches slotted bridge piers, accompanied by a reduction in vortex intensity. These findings suggest that the accumulation of floating debris can counteract the influence of slots in reducing scour around bridge piers, necessitating thorough consideration during the design phase. Full article

The fracture toughness of shale is a key parameter guiding hydraulic fracturing design and optimization. The hollow double-wing slotted (HDWS) specimen is a typical specimen configuration for measuring the mode I fracture toughness of rock. The calibration of the shape factor (f) is the basis for accurately obtaining the fracture toughness of rocks. In this study, the influences of crack length, hole size, and the anisotropy of elastic parameters on f for specimens with three typical bedding orientations—arrester (A), divider (D), and short-transverse (ST) orientations—are systematically investigated using finite element software. The numerical simulation results support the following findings. The mode I f increases monotonically with an increase in hole size. The influence of crack length on f varies depending on hole sizes. Under different bedding orientations, significant anisotropy in f was observed. In addition, the degree of anisotropy in Young’s modulus has a major impact on f, which is related to the bedding orientation of the specimen. The apparent shear modulus ratio has relatively little influence on f. As the hole size and crack length increase, the influence of the anisotropy of elastic parameters on f increases. Based on numerical calculations, hydraulic fracturing experiments were conducted on HDWS specimens of Longmaxi shale with three bedding orientations, and the results showed that the peak pressure and fracture toughness of the samples in the ST direction were the lowest, while those in the A direction were the highest. Full article

A hydraulic cavitation platform was developed in order to examine the occurrence of cavitation in the rectangular throttling groove spool and its correlation with noise characteristics. The test valve is constructed using PMMA material, which possesses excellent transparency. This transparency enables direct visual examination of cavitation occurring at the throttle slot. Additionally, high-speed photography is employed to observe the flow characteristics of the valve port, facilitating the analysis of cavitation morphology changes. Furthermore, a noise meter is utilized to measure and record the noise level and its corresponding spectrum. The flow field and flow phenomena at the rectangular throttling groove spool were studied using high-speed photography, noise spectrum analysis, and other methods. It is discovered that back pressure has the greatest influence on cavitation and flow separation, followed by the influence of intake pressure on cavitation morphology and noise. As the back pressure lowers, the cavitation morphology changes from flaky to cloudy, and the cavitation intensity, distribution area, and noise level increase. Background noise and cavitation noise have distinct frequency differences; cavitation noise in the rectangular throttling groove spool is high-frequency noise, with a frequency of more than 8 kHz, and the higher the frequency, the greater the difference in noise value. The magnitude of the alterations in noise intensity is minimal. The noise values exhibit slight variations of 2.3 dB, 4 dB, and 4.3 dB under varying back pressure circumstances of 3 MPa, 4 MPa, and 5 MPa inlet pressure, respectively. It is recommended to use the frequency of cavitation noise to detect the cavitation state and monitor the cavitation process. In the low-frequency region, the cavitation noise in the rectangular throttle groove valve core is not significantly different. Once the center frequency surpasses 3.15 kHz, a discernible distinction emerges, with the magnitude of the discrepancy in noise value increasing as the frequency rises. In other words, the cavitation cloud does not pulsate at one single frequency, but rather in a range of relatively high frequencies (more than 3.15 kHz). Full article

This research aims to investigate the impact of high-pressure water jet cutting parameters on pressure alleviation around the coal slot. A numerical model of high-pressure water jet cutting coal was developed using FLAC^3D software, allowing for a detailed study of how each cutting parameter affects the pressure relief effect of the slot. The key findings are as follows: as the water jet pressure increases, the plastic area of the coal body around the kerf expands, although the rate of increase diminishes, with the optimal water jet pressure being 30 Mpa. The results suggest that hydraulic slotting measures are particularly beneficial for outburst prevention in high in situ stress coal seams. The pressure relief range exponentially grows with an increase in the kerf depth, signifying that enhancing the kerf depth has a notable effect on improving the hydraulic kerf pressure relief. As the slit width increases, the volume of the slit enlarges, leading to a significant rise in the pressure relief range of the surrounding coal body. Given that an increase in the slit width necessitates an increase in the nozzle outlet diameter and slotting time, the optimal slit width is determined to be 0.2 m. The research concludes that the optimal hydraulic slit spacing is 3 m. This study offers valuable theoretical guidance for high-pressure water jet slotting. Full article