Search

To address the limited consideration of coarse particles in existing studies on gravity flow of caved ore and rock, this study conducted physical and numerical draw tests. The purpose was to investigate the flow characteristics of caved ore and rock under the influence of different numbers, relative positions, and spacing of coarse particles. The analysis focused on the perspective of interparticle interaction, considering the evolution laws of unbalanced force, void fraction, and force chains. The main research findings are as follows: (1) As the number of coarse particles increases from one to four, the size ratio of coarse and fine particles, which has similar effects on the shape of IMZ, decreases from 6.0 to 4.0. (2) When two coarse particles are arranged vertically and in contact, there is no significant separation between them, and the agglomeration effect of the force chain is the most prominent. [ABSTRACT FROM AUTHOR]

The consumption of aquaculture products and, in turn, the importance of the aquaculture industry are increasing with the depletion of global fishery resources. In the flow-through aquaculture systems used in Korea, olive flounders are overcrowded near the central outlet, causing stress, and the sharp central outlet hole injures the olive flounders. Therefore, in this study, we propose a central outlet cap that can prevent overcrowding and injuries in olive flounders near the central outlet in a flow-through aquaculture system. An L27(35) orthogonal array was constructed using five central outlet cap design variables, and computational fluid dynamics (CFD) analysis was performed for each experimental point. The pressure drop between the tank inlet and the central outlet was evaluated, and the experimental point with the highest pressure drop was identified. In addition, the internal fluid velocity of the experimental point with the highest pressure drop value was confirmed to be improved compared to the initial flow-through aquaculture system. The central outlet cap designed in this study is expected to be economically beneficial to aquaculture by reducing the overcrowding of olive flounder and preventing injury to olive flounder while improving the internal fluid velocity. [ABSTRACT FROM AUTHOR]

After transporting oil with a mobile pipeline, it is necessary to empty the oil within the pipeline. A common method is to inject water into the inlet to push the oil out. However, due to the effects of buoyancy and surface tension, the oil within the pipeline tends to accumulate at the elevated section, forming a stagnant oil layer, which will limit the evacuation efficiency. Based on the multiphase flow theory, a hydrodynamic model of oil–water flow was utilized to describe the pressure distribution and the thickness of the stagnant oil layer within the pipeline. A numerical model for oil-carrying water flow in a downward-inclined mobile pipeline was established, and the model was solved under given initial and boundary conditions to obtain the characteristics of the oil-carrying water flow within the pipeline. The calculation results indicate that the initial water phase velocity has a promoting effect on the oil-carrying capacity of water flow. The pipe diameter is negatively correlated with the capacity. The initial thickness of the oil is not directly related to the capacity but can increase the oil phase front velocity, which can enable the oil phase to be emptied more quickly. When the initial water phase velocity is lower than the critical water phase velocity, an increase in the inclination angle will weaken the capacity of water flow to carry oil. Conversely, when the velocity of the initial water phase is higher than the critical water phase velocity, an increase in the inclination angle will enhance the capacity. [ABSTRACT FROM AUTHOR]

The pressure ratio of a compressor increases when the engine performance is improved, which leads to a higher air velocity in the combustion chamber. This aggravates the pressure loss in a conventional diffuser, which is proportional to the square of the inlet velocity. It is, therefore, an urgent need for a new diffuser technology. Regardless of whether high-temperature, or low-pollution, combustion chambers are being used, the significant difference when compared with other chambers is the notable increase in the combustion air and its entry through the dome of the flame tube. However, the increased amount of air in the dome causes a mismatch between the diffuser outlet and the dome intake of the flame tube. Therefore, to solve the problem of an excessive total pressure loss and a mismatch of the intake air in the combustor, a novel air-bleeding aerodynamic diffuser has here been proposed. The effects of various parameters (including the number of air-bleed holes, the position of the first row of holes, and the position of the second row of holes) and their interactions on the performance of this diffuser have then been investigated by using the experimental design presented by Taguchi. The maximum static pressure recovery was achieved by using a genetic algorithm combined with the CFD method. Among the three parameters, the results revealed that the position of the first row of holes had the largest impact on the performance of the diffuser. Also, the optimal values of the three parameters varied for the inlet Mach numbers 0.10, 0.15, and 0.20. The relative difference between the predicted values and the values obtained by the numerical simulations were all below 3%, which showed the reliability of the predictions. As compared with the reference case, the optimized results for the three working conditions increased by 19.16%, 21.38%, and 40.62%, respectively. [ABSTRACT FROM AUTHOR]

Currently, the primary method for controlling red tides in the ocean involves spraying water solutions with special chemicals as solutes. High-pressure spraying results in the formation of typical jet structures. In this study, numerical simulation methods are employed to investigate the velocity variations, turbulent characteristics, and gas content distribution of jet flow fields under different initial jet flow pressures, cone angles, and nozzle diameters. Based on practical application scenarios, cluster analysis is used to explore the similarities and differences in jet equivalent diameters under different parameter conditions. The research findings indicate the following. (1) The difference of jet velocity distribution at the far field exit will be enlarged with the increase in the nozzle cone angle. When the nozzle cone angle is 4 mm, the velocity uniformity at the outlet is the best. (2) The TKE of the flow field has no consistent change law along the central axis. At the jet exit, the TKE shows an obvious multi-peak structure. (3) The gas content demonstrates a typical "double-valley" feature at the jet outlet cross-section. Increasing the initial pressure leads to a decrease in the gas content within the jet due to reduced entrainment, while the entrainment range remains largely constant. (4) Cluster analysis reveals that the similarity of jet flow width when it reaches the water surface is minimal compared to other operating conditions when the initial pressure is 0.36 MPa, the cone angle is 115°, and the nozzle diameter is 2 mm. All conditions can be categorized into two or three groups to ensure jet effectiveness. The study results provide scientific guidance for selecting spray devices for controlling red tides in the ocean. [ABSTRACT FROM AUTHOR]

Based on one-dimensional water hammer theory and combined with an engineering example, the selection of the flow characteristics of the end control valve of gravity flow system with wide-range flow variation is numerically studied from three aspects: the influence of flow characteristics of control valve on its steady-state opening-degree, the determination of the most unfavorable flow conditions of valveclosing water hammer, and the influence of flow characteristics of contrive valve on valve-closing water hammer. And the flow characteristics of linear type, parabola type and equal percentage type are compared. The results show that: 1 The equal percentage flow characteristic is more conducive to the stable operation of the control valve under the low flow condition. Under this condition, the steady-state opening-degree of the equal percentage type control valve is larger, which can avoid cavitation and vibration caused by too small opening. 2 The most unfavorable flow condition of the valve-closing water hammer should consider the minimum initial flow condition, under which the water hammer pressure of the input point of the control valve is largest because of the largest initial pressure and the shortest closing time. 3 The equal percentage flow characteristic is more conducive to reducing the control valve-closing water hammer pressure. Under the same initial flow rate and valve closing rate, the control valve with equal percentage type flow characteristics has a larger initial opening-degree, a longer actual closing time, and a smaller change gradient of flow coefficient in the small opening-degree range, so the extreme value of the valve-closing water hammer pressure is smaller, which is more conducive to pipeline safety. [ABSTRACT FROM AUTHOR]

In this paper, the flow characteristics of a continuous-type liquid–liquid pintle injector are described, focusing on the differential impact of a non-uniform center-flow distribution on single- and bi-injection methodologies as well as the cavitation effect on the spray angle. Using cold-flow experiments, jet-type flows of the center propellant caused by a non-uniform flow distribution were observed during a single injection. This resulted in an augmented pressure drop, as opposed to the flow characteristics of uniform single-film injection. By contrast, bi-injection modalities exhibited a substantial reduction in the pressure drop of the center propellant, underscoring a more equitable flow distribution. Moreover, the occurrence of cavitation in the center propellant was found to markedly affect the spray angle. By considering the injection exit area reduction caused by cavitation, the spray-angle prediction accuracy increased. The findings of this study are expected to reveal the interplay between flow distribution and pressure drop as well as that between cavitation and the spray angle in pintle injectors. Through this understanding, this study provides crucial considerations for the development of more efficient propulsion systems. [ABSTRACT FROM AUTHOR]

A curved channel is a common flow form in nature, often hosting aquatic vegetation along rivers. The stem thickness of this vegetation affects its resistance to flow and subsequently influences flow characteristics. To explore the impact of stem thickness on river flow in curved channels, we developed a Reynolds stress model based on real river flow conditions and vegetation data. The flow characteristics were analyzed in terms of flow velocity, Reynolds stress and turbulence intensity by varying the stem thickness of the vegetation in the vegetated area. The results of the study reveal that: (1) Water velocity in the vegetated area is significantly reduced compared to the non-vegetated area, with a greater reduction observed for thicker stems. Increasing the vegetation diameter by 3 mm resulted in a velocity decrease of 2.31–26.55%. (2) Thicker vegetation stems lead to more intense energy exchange in water flow. A 3 mm increase in vegetation diameter increased Reynolds stress by 91.81–139.70%. (3) Turbulent kinetic energy in the vegetated area is significantly higher than in the non-vegetated area, with greater turbulence intensity observed for thicker vegetation stems. Increasing the vegetation diameter by 3 mm resulted in a turbulent kinetic energy increase of 115.19–218.55%. HIGHLIGHTS Less research has been done on the effect of vegetation stem thickness on water flow in curved channels.; The feasibility of studying the flow characteristics of curved river channels through simulation is verified.; Analysis of sedimentation by comparing concave and convex shores.; The results can guide the construction of river channels and the design of aquatic systems.; It can provide relevant data for the subsequent research on the influence of vegetation stem coarseness on water flow characteristics.;

Concerning dual-carbon applications, establishing a new energy-dominated power system to achieve carbon peaking and carbon neutrality objectives is imperative. Pumped storage units excel in this context, owing to their unique advantages. During the load-shedding process of the pump turbine, the intricate flow patterns and cavitation phenomena substantially influence the flow field. This study introduces a cavitation model to perform numerical simulations of load rejection processes in pumped storage power plants, aiming to thoroughly investigate the impact of cavitation phenomena on the units. The results indicate that as the rotational speed increases, the dynamic and static interference within the no-blade region becomes notable, resulting in pressure pulsations within the guide vane region and exacerbating structural deformation and fatigue failures. Moreover, deviations from the designated operational point disrupt the symmetry of the flow field, leading to irregular changes in radial forces. Accounting for the mass disturbance and changes in wave velocity attributable to a cavitation phase transition, pressure fluctuation amplitude increases within the draft tube, consequently engendering complex flow phenomena. These findings offer indispensable guidance for the optimal design and safe operation of pump turbines within new power systems.

The pressure ratio of a compressor increases when the engine performance is improved, which leads to a higher air velocity in the combustion chamber. This aggravates the pressure loss in a conventional diffuser, which is proportional to the square of the inlet velocity. It is, therefore, an urgent need for a new diffuser technology. Regardless of whether high-temperature, or low-pollution, combustion chambers are being used, the significant difference when compared with other chambers is the notable increase in the combustion air and its entry through the dome of the flame tube. However, the increased amount of air in the dome causes a mismatch between the diffuser outlet and the dome intake of the flame tube. Therefore, to solve the problem of an excessive total pressure loss and a mismatch of the intake air in the combustor, a novel air-bleeding aerodynamic diffuser has here been proposed. The effects of various parameters (including the number of air-bleed holes, the position of the first row of holes, and the position of the second row of holes) and their interactions on the performance of this diffuser have then been investigated by using the experimental design presented by Taguchi. The maximum static pressure recovery was achieved by using a genetic algorithm combined with the CFD method. Among the three parameters, the results revealed that the position of the first row of holes had the largest impact on the performance of the diffuser. Also, the optimal values of the three parameters varied for the inlet Mach numbers 0.10, 0.15, and 0.20. The relative difference between the predicted values and the values obtained by the numerical simulations were all below 3%, which showed the reliability of the predictions. As compared with the reference case, the optimized results for the three working conditions increased by 19.16%, 21.38%, and 40.62%, respectively.

Concerning dual-carbon applications, establishing a new energy-dominated power system to achieve carbon peaking and carbon neutrality objectives is imperative. Pumped storage units excel in this context, owing to their unique advantages. During the load-shedding process of the pump turbine, the intricate flow patterns and cavitation phenomena substantially influence the flow field. This study introduces a cavitation model to perform numerical simulations of load rejection processes in pumped storage power plants, aiming to thoroughly investigate the impact of cavitation phenomena on the units. The results indicate that as the rotational speed increases, the dynamic and static interference within the no-blade region becomes notable, resulting in pressure pulsations within the guide vane region and exacerbating structural deformation and fatigue failures. Moreover, deviations from the designated operational point disrupt the symmetry of the flow field, leading to irregular changes in radial forces. Accounting for the mass disturbance and changes in wave velocity attributable to a cavitation phase transition, pressure fluctuation amplitude increases within the draft tube, consequently engendering complex flow phenomena. These findings offer indispensable guidance for the optimal design and safe operation of pump turbines within new power systems. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rapid development of new energy vehicles demands significant improvements in connector structures and performance standards. Wire harness connectors, crucial for linking various electrical components, face challenges due to their small size and thin-walled structure, which can lead to dimensional shrinkage and warping during injection molding. To address these issues, this study optimizes the injection molding process by fine-tuning parameters such as melt temperature, mold temperature, injection time, holding pressure/time, and cooling time. By integrating the Taguchi method with grey relational analysis, the study enhances the molding process for thin-walled composite connectors. This combined approach provides a comprehensive framework for optimizing multiple quality objectives and improving the overall performance of injection-molded composite components. [ABSTRACT FROM AUTHOR]

Fishways act as ecological corridors, enabling migratory fish species to surmount barriers such as weirs or dams, which are crucial for the restoration of river ecosystems. The island-type fishway is a novel design that utilizes a combination of island structures and valvular configurations to dissipate the kinetic energy of water flow, decelerate the water velocity, and thus reduce the challenge faced by fish attempting to ascend the watercourse. The impact of valvular configurations on the hydrodynamic characteristics within an island-type fishway was explored. The results showed that the main high-velocity flow exhibits a nearly "S"-shaped characteristic, while a low-velocity region develops downstream of the valvular. The valvular configuration has a significant effect on the internal flow dynamics of the island-type fishway. Specifically, the smaller the valvular arc angle, the broader the high-velocity main flow becomes, and the smaller the area of the low-velocity region. When the valvular arc angle is set at 180°, the area dominated by low flow velocities maintains a coverage of over 60%. As the valvular arc angle decreases, turbulent kinetic energy rises, leading to an approximate 70% increase in the maximum turbulent kinetic energy across different water layers relative to the model with the initial angle setting. Within the range of valvular arc angles studied, an island-type fishway with a 180° valvular arc angle is most conducive to supporting the upstream migration of fish. This study can provide a reference for the further development of island-type fishways. [ABSTRACT FROM AUTHOR]

The long-term effects of the centrifugal force of water flow in a curved river channel result in the scouring of the concave bank and the silting of the convex bank. This phenomenon significantly impacts the stability of bank slopes and the surrounding ecological environment. A common hydraulic structure, the spur dike, is extensively employed in river training and bank protection. Focusing on a 180° bend flume as the research subject, this study examines the effects of spur dike placement on the concave bank side of the bend. To this end, a second-order accurate computational format in computational fluid dynamics (CFD) and the RNG k-ε turbulence model were employed. Specifically, the influence mechanism of the pick angle and the river-width-narrowing rate on the flow dynamics and eddy structures within the bend were investigated. The results indicated that both the river-width-narrowing rate and pick angle significantly influence the flow structure of the bend, with the pick angle being the more dominant factor. The vortex scale generated by a positive pick angle of the spur dike is the largest, while upward and downward pick angles produce smaller vortex scales. Both upward and positive pick angles have larger areas of influence, and the maximum value of turbulent kinetic energy occurs at the back of the secondary spur dike. In contrast, the downward pick angle has a smaller area of influence for turbulent kinetic energy, resulting in a smaller vortex at the back of the spur dike and leading to smoother water flow overall. In river-training and bank-protection projects, the selection of the spur dike angle is crucial for controlling scour risk. The findings provide valuable insights for engineering design and construction activities. [ABSTRACT FROM AUTHOR]

The blade fracture of horizontal centrifugal pump will not only affect the hydraulic performance of the pump, but also affect the safety and stability of the whole unit. In this paper, for horizontal centrifugal pumps, five single-blade fracture schemes are designed and numerical simulations are carried out under different operating conditions. The results show that with the increase of fracture size, the influence on the hydraulic characteristics of the pump shows a decreasing trend, and it will also affect the turbulent kinetic energy distribution near the impeller inlet, so that the internal flow becomes complex and the flow loss increases. The radial force on the impeller changes periodically, and its magnitude shows a nonlinear decreasing change with the increase of the fracture size. The pressure pulsation analysis of several monitoring points in the worm shell shows that as the fracture size increases, the amplitude of the lobe frequency slowly rises, and the shaft frequency, which is second only to the lobe frequency, becomes higher and higher and begins to dominate. A study of the rotor system shows that the maximum deformation of the impeller occurs at the edge of the impeller cover and the maximum equivalent stress occurs at the blade exit; blade fracture causes a significant reduction in the latter third-order intrinsic frequency. [ABSTRACT FROM AUTHOR]

Kaplan turbine units can adjust their blades to achieve wider outputs without a significant loss of efficiency. The combination of guide vane angle (GVA) and blade angle (BA) is selected based on efficiency curves obtained from cam tests. However, the vibration characteristics are not considered in the test. The vibration and flow characteristics are complex with different combinations of guide vane and blade angles. Different cam relation selection principles lead to varying machine vibration and flow characteristics. In this research, the flow and vibration characteristics were obtained by means of field test and numerical simulation. Vibration, pressure pulsation, and other stability indicators have been extracted and investigated under off-cam conditions. The flow and variation rules of different indicators have been thoroughly researched. The findings suggest that the magnitude of vibration in the X direction surpassed that in the Y direction for the head cover, upper frame, and lower frame under 22 experimental conditions. The disparity between the head cover and upper frame in both directions was not significant, whereas a substantial contrast existed between the lower frame in the X and Y directions. The calculation results indicate that when the guide vane angle was small, vortices appeared near the high-pressure edge of the runner in the vaneless region and caused disorganized flow lines in the runner, and this complex vortex behavior led to multiple frequency components in the pressure pulsation frequency domain. The conclusions provide references for the designers of Kaplan turbine units and improves the operating safety of Kaplan turbine power stations. [ABSTRACT FROM AUTHOR]

In recent years, jacket foundations have been increasingly employed in offshore wind farms. Their complex design comprising piles and trusses poses challenges for conducting comprehensive flow field measurements using physical experiments. Consequently, the influence of the flow field on local scour around these foundations remains unclear. Therefore, numerical simulation methods are essential to depict the surrounding flow characteristics. This study utilizes large eddy simulation (LES) turbulence models within OpenFOAM to simulate the flow field around jacket foundations on flat-bed and equilibrium scour bathymetry. A flume experiment was conducted for numerical model establishment and validation. The close agreement between experimental and numerical results indicates that the LES model accurately reflects the flow patterns around the jacket foundation. Time-averaged and instantaneous flow characteristics, average kinetic energy (AKE), turbulence structure, and bed shear stress were analyzed. The results indicate that flow intensity is reduced due to the shielding effect and energy dissipation by the truss structure of the jacket foundation. Furthermore, the AKE of the flow upstream of the rear piles decreases by 18.9% in the flat-bed state and 28.0% in the equilibrium state, indicating more energy dissipation and less scour at the rear piles in the equilibrium state. The research findings offer valuable insights into the design and scour protection strategies for jacket foundations. [ABSTRACT FROM AUTHOR]

Graphene foam composite is a promising candidate for advanced thermal management applications due to its excellent mechanical strength, high thermal conductivity, ultra-high porosity and huge specific surface area. In this study, a three-dimensional physical model was developed in accordance with the dodecahedral structure of graphene foam composite. A comprehensive numerical simulation was carried out to investigate the fluid flow and convective heat transfer in open-cell graphene foam composite by using ANSYS Fluent 2021 R1 commercial software. Research results show that, as porosity increases, the pressure gradient for graphene foam composite with circular and triangular cross-section struts is reduced by 65% and by 77%, respectively. At a given porosity of 0.904, when the inlet velocity increases from 1 m/s to 5 m/s, the pressure gradient is increased by 11.3 times and 13.8 times, and the convective heat transfer coefficient is increased by 54.5% and 43% for graphene foam composite with circular and triangular cross-section struts, respectively. Due to the irregularity of the skeleton distribution, the pressure drop in Y direction is the highest among the three directions, which is 8.7% and 17.4% higher than that in the Z and X directions at the inlet velocity of 5 m/s, respectively. The convective heat transfer coefficient in the Y direction is significantly lower than that along the X and Z directions. Furthermore, triangular cross-section struts induce a greater pressure drop but offer less effective heat transfer compared to circular struts. The research findings may provide critical insights into the design and optimization of graphene foam composites, and promote their potential for efficient thermal management and gas/liquid purification in engineering applications. [ABSTRACT FROM AUTHOR]

In order to determine the recommended flow velocity for the safe and energy-saving transport of ice-slurry-type light particle slurries, it is necessary to study the flow characteristics of light particle slurries, especially the critical flow velocity. Therefore, in this paper, a numerical simulation method based on the mixed turbulence model with the RANS (Reynolds averaged Navier Stokes) equation is used, and a new concentration distribution method is proposed for the first time to derive the critical flow velocity, as follows: the flow velocity of the light particle slurry when the ratio of the solid volume fraction vf at the position of 0.08D above the bottom of the pipeline to that at the center of the pipeline, vf/vf(y) = 0.75, is taken as the critical flow velocity. The flow changes in the slurry (polyethylene particles with a density of 922 kg/m3 and water) under 0.1–1.0 m/s (at intervals of 0.1 m/s) were investigated experimentally, and the pressure drop data obtained from the experiments were used to determine the recommended flow rate for safe and energy-saving transportation of the light particle slurry. The pipe diameter used for the experiments and simulations was 28 mm, and the solid-phase particle sizes were 0.3 mm, 0.4 mm, and 0.5 mm, with solid-phase contents of 5 vol%, 10 vol%, 15 vol%, and 20 vol%. In addition, the experimental and numerical simulation results show that an increase in solid-phase content and particle size leads to an increase in critical flow velocity. [ABSTRACT FROM AUTHOR]

The optimization of film-unloading and film–soil separation components can effectively improve the residual film unloading rate and reduce impurity content. So, the DEM models of soil and residual film were established and the suspension and flow characteristics under fluid action were analyzed based on the CFD—DEM coupling simulation in this article. The matching parameters of the film-unloading and film-lifting device were optimized with the Box–Behnken test. When the wind velocity was between 1.65 and 10.54 m · s − 1 , the film–soil separation effect was the best, with a film–impurity separation rate of 96.6%. The optimized parameter combination of the film-unloading device and film-lifting device is A = 9°, B = 40 mm, and C = 40 mm (A, B, and C represent the angle between the teeth and the normal of the air inlet, the minimum distance between the teeth and the air inlet, and the width of the air inlet, respectively). With the optimized parameter, the best film unloading effect is achieved, the minimum wind velocity of film unloading is 2.6 m · s − 1 . This article provides theoretical and simulation methods for assessing the flow characteristics of flexible particles and parameter optimization of air suction devices, which is conducive to the high-purity recovery of residual film. [ABSTRACT FROM AUTHOR]

A variable-speed pump-turbine is the core component of a hydraulic storage and energy generation station. When the pump-turbine operates at a constant speed, its response to the power grid frequency is poor. In order to improve the hydraulic efficiency of the pumped storage unit, variable-speed units are used. However, there has been no numerical study on the effect of the rotational flow characteristics within the gap of a variable-speed pump-turbine. This paper calculates the flow characteristics within the gap of a variable-speed pump-turbine under three typical pump modes (maximum head minimum flow condition, minimum head maximum flow condition, and maximum speed condition). The research results indicate that the rotational speed significantly affects the pressure distribution, velocity distribution, and turbulent kinetic energy distribution within the crown and band gaps. The higher the speed, the larger the area of the high-pressure region before the runner inlet compared to other operating conditions, and similarly, the low-pressure area after the runner outlet is also larger than in other operating conditions. The change in speed mainly affects the internal flow field of the crown gap, with the most noticeable changes occurring in the pressure and flow velocity at the inlet and outlet of the crown gap. There is a clear trend of pressure drop and velocity increase within the gap as the speed increases. However, with the increase in speed, the pressure distribution and flow velocity within the band gap remain almost the same. In addition to speed changes, it is observed that the pressure within the gap and the flow velocity within the passages are also related to the head, especially in the condition of maximum head, where this relationship becomes more noticeable. [ABSTRACT FROM AUTHOR]

Integrating a vapor ejector with an air-cooled absorption cooling system (ACS) requires understanding how the ejector responds to varying condenser conditions and how the geometrical parameters affect the system's performance. This study provides a numerical investigation of the flow characteristics inside supersonic vapor ejectors. The primary objectives were identifying the best nozzle design for ACS and explaining how the secondary flow responds to different back pressures. The developed model was validated against experimental data and a one-dimensional model. Despite exhibiting increased flow fluctuations, the convex nozzle achieved an entrainment ratio of 0.4. This value was 4.9 % and 7 % higher than the values obtained by the straight and the concave nozzles, respectively. In contrast, the concave nozzle exhibits better flow stability and pressure recovery, which are considered appealing for the air-cooled ACS. The straight nozzle emerged as a balanced alternative, offering moderate entrainment alongside favorable flow stability. Moreover, secondary flow behavior at different operating modes was elaborated. Secondary flow choked at back pressures between 60–70 kPa, indicating optimal entrainment. However, at 75–80 kPa, while the secondary flow was entrained, it failed to reach sonic speed due to high-pressure waves, resulting in the sub-critical condition. Further increases in back pressure to 85–90 kPa induced back-flow due to elevated local static pressure. Mach number profiles at the mixing tube entrance remained consistent under critical operation but deviated post-critical back pressure, reflecting altered flow characteristics downstream of the mixing tube. Such elaboration of flow dynamics within ejectors paves the way for innovative designs of vapor ejectors, potentially developing ACS.

Dynamic response, fatigue, and stability issues of a structure are closely related to flow behavior past a bluff body structure. Flow past the free-end rectangular prism is investigated numerically using a Large Eddy Simulation (LES) turbulence model at Re = 22000. The prism model has a constant depth (D) to width (H) ratio D/H = 0.5 for span length variation L (= 10; 7,5; 5,0 and 2,5H). Effects of the free end on the flow characteristics showed that the flow pattern, velocity vector, and fluid forces component are changed. The presence of the free end is closed related to the flow characteristics alteration in the wake, which is presented graphically in this paper. This study suggests the critical aspect ratio of the slender rectangular is 2,5

Based on the well logging requirements of horizontal stripper wells, the flow characteristics of the oil-water two-phase flow in the invisible horizontal tri-electrode capacitive sensor (HTCS) measurement pipeline are studied. First, an experimental device and a numerical validation model of a horizontal 20 mm glass pipeline are established to study the flow characteristics of the oil-water two-phase flow. Then, the flow characteristics of the horizontal oil-water two-phase flow in the measurement pipeline under different horizontal inclination angles are studied and the flow patterns and inclination angles suitable for the new tri-electrode capacitive sensor are discussed. Finally, using the horizontal oil-water two-phase flow loop platform of the largest oil and gas testing center in China, the dynamic response of the new capacitive sensor is studied under different inclination angles, flow rates, and water-cut conditions, and the dynamic response law is analyzed based on the simulation results.

Kaplan turbines are widely utilized in low-head and large flow power stations. This paper employs Computational Fluid Dynamics (CFD) to complete numerical calculations of the full flow channel under different blade angles and various guide vane openings, based on 25 off-cam experimental working conditions. The internal flow characteristics of the runner blade and draft tube are analyzed, and a discriminant number for quantitatively assessing the flow uniformity of the draft tube is proposed. The results indicate that low-frequency and high-amplitude pressure pulsations occur on the high- and low-pressure edge of the blade when the opening is small, with pulsations decreasing as the opening increases. The inner flow line of the draft tube is disturbed when both the blade angle and opening are small. Additionally, the secondary frequency of the draft tube inlet is double that of the vane passing frequency. The discriminant number of the flow inhomogeneity approaches 0 under optimal flow conditions. The number increases continuously with the decrease in efficiency, and the flow in the three piers of draft tube becomes more nonuniform. The research results provide a reference for enhancing performance and ensuring the operational stability of Kaplan turbines. [ABSTRACT FROM AUTHOR]

Some numerical simulations were used to study the effects of blowing ratio (0.25–0.5), hole diameters(0.65~1 mm), and hole inclination angle (30~60°) of the film cooling structure on the cooling and aerodynamic characteristics of the axisymmetric plug nozzle under the condition of transonic. The results showed that the bow shocks appear near the film holes on the plug wall in the supersonic region, which cause the wall cooling effectiveness of the plug to decrease. Compared with the baseline plug, the blowing ratio ranged from 0.25 to 0.5, the wall average temperature of the rear plug decreased by 34.4~48.1%, the thrust coefficient and total pressure recovery coefficient decreased by 0.31~0.61% and 0.52~0.93%, respectively. When the perforated percentage is constant, the wall cooling effectiveness increases with the decrease of the hole diameters. The increase in the inclination angle of the film holes lead to the decrease in cooling effectiveness and aerodynamic performance. This is because the penetration ability of the cooling air to the mainstream is enhanced, and the obstruction to the mainstream boundary layer is increased, resulting in the increase of bow shock intensity near the film holes in the supersonic region. [ABSTRACT FROM AUTHOR]

To conduct a more in-depth study of the flow mechanism of power-law fluids within sewage pumps, this paper focuses on self-priming sewage pumps, with typical power-law fluid (Carboxymethyl Cellulose, CMC) as the conveying medium. The constitutive equations for sewage and typical power-law fluid (CMC solution) were established using the power-law model. Through numerical calculation methods, the non-steady flow field inside the pump of different concentration power-law fluids was analyzed from various aspects such as velocity, pressure, vorticity, and wall shear stress. The pressure pulsations at key locations in the pump flow field were monitored and analyzed. At the rated flow rate, when the concentration of CMC solution increased from 0.5% to 2.0%, the channel pressure and tongue pressure decreased by 16.5% and 3.5%, respectively. This indicates that the pressure on the impeller blades, within the flow passages, and at the tongue of the volute all decrease with the increase in concentration of CMC solution. This may alter the fluid flow pattern, leading to more vortex motion and shear deformation, while also reducing the pump's pressure boosting capability, thereby affecting the pump's performance stability. It can be inferred from quantitative comparisons that changes in rheological properties had a significant impact on the flow characteristics of sewage pumps. This paper reveals that some flow characteristics of power-law fluids in sewage pumps, providing a theoretical and reference basis for the performance optimization and flow mechanism research of sewage pumps. [ABSTRACT FROM AUTHOR]

Shale oil is stored in nanoscale shale reservoirs. To explore enhanced recovery, it is essential to characterize the flow of hydrocarbons in nanopores. Molecular dynamics simulation is required for high-precision and high-cost experiments related to nanoscale pores. This technology is crucial for studying the kinetic characteristics of substances at the micro- and nanoscale and has become an important research method in the field of micro-mechanism research of shale oil extraction. This paper presents the principles and methods of molecular dynamics simulation technology, summarizes common molecular models and applicable force fields for simulating shale oil flow and enhanced recovery studies, and analyzes relevant physical parameters characterizing the distribution and kinetic properties of shale oil in nanopores. The physical parameters analyzed include interaction energy, density distribution, radial distribution function, mean-square displacement, and diffusion coefficient. This text describes how molecular dynamics simulation explains the mechanism of oil driving in CO2 injection technology and the factors that influence it. It also summarizes the advantages and disadvantages of molecular dynamics simulation in CO2 injection for enhanced recovery of shale oil. Furthermore, it presents the development trend of molecular dynamics simulation in shale reservoirs. The aim is to provide theoretical support for the development of unconventional oil and gas. [ABSTRACT FROM AUTHOR]

Injection mandrel is one of the key components to control the water injection rate of each layer in the layered injection process in the oilfield. The imbalance between the layers can be changed by an optimized injection mandrel to control the appropriate injection rate. This study introduces an approach to optimize water injection in oilfields, focusing on a new eccentric injection mandrel with adjustable flat nozzles. Firstly, computational fluid dynamics (CFD) simulations were carried out using FLUENT software to model and analyze the flow characteristics of the injection mandrel. The simulation results were validated through experimental comparisons, demonstrating excellent consistency. Secondly, the nozzle shapes were identified and optimized. The semicircle nozzle demonstrating superior regulation performance due to its smallest differential pressure and a robust linear relationship between flow rate and opening degree. Finally, orthogonal tests are designed for three influencing factors of the eccentric injection mandrel: number of injection holes, injection hole diameter, and nozzle shape. The simulation results show that the number of injection holes is 36, the diameter of injection holes is 3.2 mm, and the eccentric injection mandrel has relatively better performance. After optimization, the differential pressure between the inlet and outlet is reduced by 57.14%, and the average shear stress on the fluid is reduced by 3.88%. This innovative methodology, employing CFD simulations and orthogonal tests, offers precise water injection rate control, reducing water wastage, and optimizing energy consumption in water injection systems. [ABSTRACT FROM AUTHOR]

Film cooling needs to be applied to serpentine nozzles due to an increase in thermal load. Adverse pressure gradients (APGs) near the upper wall of such nozzles hinder the forward flow of the coolant, and they may even induce a recirculation zone that complicates the cooling of the film in serpentine nozzles under different APGs. In this study, the film cooling characteristics of a serpentine nozzle under various APGs are investigated through numerical simulations. The studied pressure gradients include strong, moderate, and weak APGs. The results show that the APG weakened the adhesion of the coolant to the surface, thereby reducing the film cooling effectiveness (FCE) and the convective heat transfer coefficient (CHTC). The stronger the APG, the greater its obstructive effect. However, the recirculation zone induced by the strong APG was composed of the coolant, and it adhered tightly to the wall, thereby significantly strengthening the FCE and CHTC. The CHTC under the moderate APG significantly increased due to the convergence of two jets ejected from different holes. For the four blowing ratios, the area-averaged FCE under the strong APG was 29.8% and 24.5% higher than that under the moderate and weak APGs, while the area-averaged ratios of the CHTC under the moderate APG were 1.6% and 16.7% higher than those under the strong and weak APGs. Therefore, more holes should be arranged on the film in the zones of moderate and weak APGs. [ABSTRACT FROM AUTHOR]

As one of the most important and economically enhanced oil-recovery technologies, water flooding has been applied in various oilfields worldwide for nearly a century. Stratified water injection is the key to improving water-flooding performance. In water flooding, the water-injection rate is normally optimized based on the reservoir permeability and thickness. However, this strategy is not applicable after oilfields enter the ultra-high-water-cut period. In this study, an original method for optimizing water-flooding parameters for developing multi-layer sandstone reservoirs in the entire flooding process and in a given period is proposed based on reservoir engineering theory and optimization technology. Meanwhile, optimization mathematical models that yield maximum oil recovery or net present value (NPV) are developed. The new method is verified by water-flooding experiments using Berea cores. The results show that using the method developed in this study can increase the total oil recovery by approximately 3 percent compared with the traditional method using the same water-injection amounts. The experimental results are consistent with the results from theoretical analysis. Moreover, this study shows that the geological reserves of each layer and the relative permeability curves have the greatest influence on the optimized water-injection rate, rather than the reservoir properties, which are the primary consideration in a traditional optimization method. The method developed in this study could not only be implemented in a newly developed oilfield but also could be used in a mature oilfield that has been developed for years. However, this study also shows that using the optimized water injection at an earlier stage will provide better EOR performance. [ABSTRACT FROM AUTHOR]

During the actual construction of tunnel sidewall lining, construction workers often use only one or two windows per layer for pouring in order to reduce the construction sequence, which often leads to a reduction in the quality of tunnel sidewall concrete pouring. Therefore, this study analysed the necessity of the window-by-window pouring of sidewall lining through the study of concrete flow characteristics of the tunnel sidewall lining pouring process, and the reasonable spacing of pouring windows was analysed. This study firstly verified the accuracy of the simulation parameters and the feasibility of the simulation method of the lining pouring process through indoor experiments and simulation analyses, and then it numerically simulated and analysed the flow of concrete during the lining pouring process of tunnel sidewalls. The following conclusions were made: the smaller the slump of the freshly mixed concrete, the higher the pumping flow rate; additionally, the shorter the one-time pouring distance, the smaller the spacing of the trolley feeding window should be. Furthermore, this study makes suggestions for the reasonable spacing of pouring trolleys under several working conditions. [ABSTRACT FROM AUTHOR]

The evolution of geometry and flow characteristics under stress is of great significance for many natural and technological processes. In this paper, a three-dimensional rough single fracture model is reconstructed based on three-dimensional morphology scanning technology. The geometric deformation and flow characteristics of natural fracture inside tight sandstone under varied shear displacements and loads are simulated using the finite element method. The results show that the primary factors causing variations in flow characteristics are geometrical deformations under stress such as reduced apertures, expanded contact areas, and degradation of roughness. With the increasing stress, the aperture and contact area of the fracture would experience an evident decrease and increase, respectively, leading to an increase in the flow resistance. Simultaneously, the degradation of roughness would exacerbate these changes in the aperture and contact area. For the rougher fracture, the permeability and flow area can be maintained higher value due to its smaller geometric deformation and a more uniform stress distribution. Furthermore, shear displacement modifies the mismatch between the top and lower fracture surfaces, resulting in a decrease in flow rate and permeability. [ABSTRACT FROM AUTHOR]

The Savonius hydrokinetic turbine (SHT) is widely used for generating electricity from running water. However, most optimization work has been carried out on conventional blades with similar concave and convex profiles. This study aims to enhance SHT performance by modifying the rotor blades' outer surface radius (0.079, 0.087 and 0.095 m) to create a semi-elliptical shape, thus reducing opposing forces. The tip speed ratio (TSR) varies from 0.5 to 1.3 with an interval of 0.1. A constant channel velocity of 0.8 m/s at Re = 2.25 x 105 is considered for the analysis. The flow field has been numerically investigated using the SST k - ω model. This study comprises the angular variation in the coefficients of power (Cp) and torque (Cm), performance curves of the rotor, and pressure distribution on the blade surface at different angular positions. It is observed that the rotor with a radius of 0.095 m has a maximum Cp value of 0.142, which is 7.57% and 18.33% higher than the Cp values of rotors with radii of 0.079 m and 0.087 m, respectively. The maximum power output of the rotor with a radius of 0.095 m is 2.32 W, whereas the power outputs of the rotors with radii of 0.087 m and 0.079 m are 2.16 W and 1.96 W, respectively. An increase in the instantaneous values of Cm between rotation angles 0° to 115° is observed, during which the returning blades mainly interact with the incoming stream. The pressure decreases as the radius of the semi-elliptical outer surface increases at rotor positions ranging from 0° to 225°, but it increases at rotor positions ranging from 270° to 315°. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hydrodynamic cavitation (HC) has emerged as a promising technology for water disinfection. Interestingly, when subjected to specific cavitation pressures, jet pump cavitation reactors (JPCRs) exhibit effective water treatment capabilities. This study investigated the cavitation flow and vorticty transport in a JPCR with various area ratios by utilizing computational fluid dynamics. The results reveal that cavitation is more likely to occur within the JPCR as the area ratio becomes smaller. While as the area ratio decreases, the limit flow ratio also decreases, leading to a reduced operational range for the JPCR. During the cavitation inception stage, only a few bubbles with limited travel distances are generated at the throat inlet. A stable cavitation layer developed between the throat and downstream wall during the limited cavitation stage. In this phase, the primary flow carried the bubbles towards the outlet. In addition, it was found that the vortex stretching, compression expansion, and baroclinic torque terms primarily influence the vorticity transport equation in this context. This work may provide a reference value to the design of JPCRs for water treatment.

Abstract Injection mandrel is one of the key components to control the water injection rate of each layer in the layered injection process in the oilfield. The imbalance between the layers can be changed by an optimized injection mandrel to control the appropriate injection rate. This study introduces an approach to optimize water injection in oilfields, focusing on a new eccentric injection mandrel with adjustable flat nozzles. Firstly, computational fluid dynamics (CFD) simulations were carried out using FLUENT software to model and analyze the flow characteristics of the injection mandrel. The simulation results were validated through experimental comparisons, demonstrating excellent consistency. Secondly, the nozzle shapes were identified and optimized. The semicircle nozzle demonstrating superior regulation performance due to its smallest differential pressure and a robust linear relationship between flow rate and opening degree. Finally, orthogonal tests are designed for three influencing factors of the eccentric injection mandrel: number of injection holes, injection hole diameter, and nozzle shape. The simulation results show that the number of injection holes is 36, the diameter of injection holes is 3.2 mm, and the eccentric injection mandrel has relatively better performance. After optimization, the differential pressure between the inlet and outlet is reduced by 57.14%, and the average shear stress on the fluid is reduced by 3.88%. This innovative methodology, employing CFD simulations and orthogonal tests, offers precise water injection rate control, reducing water wastage, and optimizing energy consumption in water injection systems.

[Objective] Pipelines with undulating profiles are susceptible to liquid accumulation at low-lying positions along their route,particularly when utilized for gathering and transmission of wet natural gas and transmission of oil-gas blends. Considering the significant difference in inclination angle between gathering and transmission pipelines and gas wells, foam drainage technology, already wellestablished for the removal of liquid accumulation from gas wells, needs to be further demonstrated before its application to transmission pipelines carrying oil-gas blends. [Methods] Gas-liquid multiphase pipe flow experiments were conducted using an experimental loop setup,aimed at investigating the impact of foam on the characteristics of gas-liquid multiphase flow at various inclination angles and elucidating the mechanism of plug formation in foam-containing multiphase flow. Additionally, the study examined the impact of changes in foam system properties induced by the presence of inorganic salts on the characteristics of foam-containing multiphase flow. Flow regime-specific analysis was conducted on flow characteristic parameters and pressure difference features. [Results] In pipelines with undulating profiles and significantly different inclination angles compared to gas wells, the addition of surfactant was found effective in removing accumulated liquid and mitigating the occurrence of sectional slugged flow conditions. To investigate the drainage effect of water-based Sodium Dodecyl Sulfate(SDS) foam under the influence of inorganic salts, a further study was conducted with the presence of NaCl and MgCl2 as environmental impact factors, and using metal grid sensors, a high-speed camera system, and pressure sensors. The findings revealed that the variation in foam properties resulting from the effect of inorganic salts had a substantial impact on the efficiency of foam drainage. Furthermore, it was observed that an excessive formation of stable foam within the pipeline caused a substantial increase in pressure drop along the route.[Conclusion] When applying foam drainage technology to gathering and transmission pipelines with liquid accumulation, stability becomes a critical factor in selecting an appropriate foam system. Further research should focus on investigating the relationship between the influence of the foam layer on the flow characteristics of the medium in pipelines and the overall performance of the foam system.

In response to growing environmental and ecological awareness, eco-friendly in-stream structures such as vanes have been implemented in different parts of the world to enhance stream conditions. FLUENT (ANSYS) was used to perform three-dimensional large eddy simulation to investigate the effect of the vanes permeability rate on flow characteristics. To evaluate the numerical model accuracy, numerical and experimental free surface profiles compared. It is observed that simulated free surface profiles agree reasonably well with measured values. The effect of different permeability rates is obvious in the flow characteristics such as depth-averaged velocity distribution, tip velocity variations, formation of the secondary flows in the flow field, turbulent kinetic energy, and mean kinetic energy contours. On average, maximum velocity values in the flow field is 1,54 times the approach velocity. Tip velocity decreases up to 30,6 % for the 70,0 % permeable vane. Maximum turbulent kinetic energy and mean kinetic energy for the 70,0 % permeable vane decrease up to 58,0 % and 43,3 %, respectively. Generally significant velocity and flow pattern variations around the impermeable vane can be attributed to the local effect of the vane structure and channel cross sectional constriction in comparison to the permeable vanes.

The Savonius hydrokinetic turbine (SHT) is widely used for generating electricity from running water. However, most optimization work has been carried out on conventional blades with similar concave and convex profiles. This study aims to enhance SHT performance by modifying the rotor blades' outer surface radius (0.079, 0.087 and 0.095 m) to create a semi-elliptical shape, thus reducing opposing forces. The tip speed ratio (TSR) varies from 0.5 to 1.3 with an interval of 0.1. A constant channel velocity of 0.8 m/s at Re = 2.25 × 105 is considered for the analysis. The flow field has been numerically investigated using the SST k - ω model. This study comprises the angular variation in the coefficients of power (Cp) and torque (Cm), performance curves of the rotor, and pressure distribution on the blade surface at different angular positions. It is observed that the rotor with a radius of 0.095 m has a maximum Cp value of 0.142, which is 7.57% and 18.33% higher than the Cp values of rotors with radii of 0.079 m and 0.087 m, respectively. The maximum power output of the rotor with a radius of 0.095 m is 2.32 W, whereas the power outputs of the rotors with radii of 0.087 m and 0.079 m are 2.16 W and 1.96 W, respectively. An increase in the instantaneous values of Cm between rotation angles 0◦ to 115◦ is observed, during which the returning blades mainly interact with the incoming stream. The pressure decreases as the radius of the semi-elliptical outer surface increases at rotor positions ranging from 0◦ to 225◦, but it increases at rotor positions ranging from 270◦ to 315◦.

The consumption of aquaculture products and, in turn, the importance of the aquaculture industry are increasing with the depletion of global fishery resources. In the flow-through aquaculture systems used in Korea, olive flounders are overcrowded near the central outlet, causing stress, and the sharp central outlet hole injures the olive flounders. Therefore, in this study, we propose a central outlet cap that can prevent overcrowding and injuries in olive flounders near the central outlet in a flow-through aquaculture system. An L27(35) orthogonal array was constructed using five central outlet cap design variables, and computational fluid dynamics (CFD) analysis was performed for each experimental point. The pressure drop between the tank inlet and the central outlet was evaluated, and the experimental point with the highest pressure drop was identified. In addition, the internal fluid velocity of the experimental point with the highest pressure drop value was confirmed to be improved compared to the initial flow-through aquaculture system. The central outlet cap designed in this study is expected to be economically beneficial to aquaculture by reducing the overcrowding of olive flounder and preventing injury to olive flounder while improving the internal fluid velocity.

In this paper, the flow characteristics of a continuous-type liquid–liquid pintle injector are described, focusing on the differential impact of a non-uniform center-flow distribution on single- and bi-injection methodologies as well as the cavitation effect on the spray angle. Using cold-flow experiments, jet-type flows of the center propellant caused by a non-uniform flow distribution were observed during a single injection. This resulted in an augmented pressure drop, as opposed to the flow characteristics of uniform single-film injection. By contrast, bi-injection modalities exhibited a substantial reduction in the pressure drop of the center propellant, underscoring a more equitable flow distribution. Moreover, the occurrence of cavitation in the center propellant was found to markedly affect the spray angle. By considering the injection exit area reduction caused by cavitation, the spray-angle prediction accuracy increased. The findings of this study are expected to reveal the interplay between flow distribution and pressure drop as well as that between cavitation and the spray angle in pintle injectors. Through this understanding, this study provides crucial considerations for the development of more efficient propulsion systems.

Currently, the primary method for controlling red tides in the ocean involves spraying water solutions with special chemicals as solutes. High-pressure spraying results in the formation of typical jet structures. In this study, numerical simulation methods are employed to investigate the velocity variations, turbulent characteristics, and gas content distribution of jet flow fields under different initial jet flow pressures, cone angles, and nozzle diameters. Based on practical application scenarios, cluster analysis is used to explore the similarities and differences in jet equivalent diameters under different parameter conditions. The research findings indicate the following. (1) The difference of jet velocity distribution at the far field exit will be enlarged with the increase in the nozzle cone angle. When the nozzle cone angle is 4 mm, the velocity uniformity at the outlet is the best. (2) The TKE of the flow field has no consistent change law along the central axis. At the jet exit, the TKE shows an obvious multi-peak structure. (3) The gas content demonstrates a typical “double-valley” feature at the jet outlet cross-section. Increasing the initial pressure leads to a decrease in the gas content within the jet due to reduced entrainment, while the entrainment range remains largely constant. (4) Cluster analysis reveals that the similarity of jet flow width when it reaches the water surface is minimal compared to other operating conditions when the initial pressure is 0.36 MPa, the cone angle is 115°, and the nozzle diameter is 2 mm. All conditions can be categorized into two or three groups to ensure jet effectiveness. The study results provide scientific guidance for selecting spray devices for controlling red tides in the ocean.

To explore the influence of the flow straightener (FS) on the internal flow field of the three-phase jet fire monitor (TPJFM), this study conducted an analysis of the flow characteristics within the TPJFM. Through numerical simulations based on ANSYS/FLUENT, the velocity, turbulent kinetic energy, pressure, velocity uniformity, and outlet performance of the internal flow field of the TPJFM were evaluated for different FS installation positions, installation angles, and structures. Results show that, the structural form of the FS significantly influences the internal flow field. The advanced rectification capability of the FS can immediately return the fluid in the grid to a laminar flow state. However, the exchange of kinetic energy between the regions increases turbulent kinetic energy and reduces outlet velocity. The FS blade and symmetry plane of the powder pipe overlap can effectively reduce the turbulence kinetic energy generated by the powder pipe. Reasonable FS parameters can enhance the flow characteristics of the flow field and improve jet performance. These findings could serve as an important reference for designing an optimized TPJFM structure. [ABSTRACT FROM AUTHOR]

The flow characteristics of the primary side of the helical coil once-through steam generator (OTSG) have a significant impact on the safe operation of the reactor. Different from the land-based stationary working conditions, the flow of the primary side of the OTSG is influenced by sea waves and winds under ocean conditions. The rigid body motion model is used to calculate the flow of the primary side under different ocean conditions, including heeling, trimming, rolling, pitching, heaving, and combined conditions. The results show that under heeling and trimming conditions, the static pressure of the primary side is different from that under vertical conditions due to the influence of gravity, but its impact on the flow field is relatively small. Under rolling and pitching conditions, the mean flow velocity and pressure drop change periodically with the movement of the OTSG, and the smaller the sway angle, the smaller the variation amplitude of the mean flow velocity and pressure drop. Under the heaving condition, the variation amplitude of the mean flow velocity is greater than that under rolling and pitching conditions, and reverse flow occurs. Under the combined heaving and rolling condition, the mean flow velocity and pressure drop are influenced by the period and amplitude of both the two motions. [ABSTRACT FROM AUTHOR]

With a large number of railroad and highway tunnels opening for operation, the diseases caused by hidden lining defects are increasing. The study of flow characteristics of freshly mixed concrete during tunnel lining casting is the key to revealing the formation mechanism of hidden defects. This paper revealed the location of blank lining formation by investigating the circumferential and longitudinal flow characteristics of concrete in the vault during tunnel pouring to provide suggestions for improving the quality of tunnel lining pouring for the various projects. This paper adopted the method of indoor testing, selected the suitable working conditions and flow parameters, validated the accuracy of the test with a numerical simulation, and simulated the secondary lining pouring process of the tunnel arch from the circumferential direction and longitudinal direction. This revealed the flow characteristics of the freshly mixed concrete in the process of pouring the arch lining. The flow of concrete in the arch lining was basically characterized by two major features which were similar to the flow in the pumping pipe and the layered flow. It also revealed the relationship between the concrete flow rate, flow distance, and the location of the formation of the blank lining risk zone with the slump of the concrete, the pumping pressure, and the radius of the tunnel. [ABSTRACT FROM AUTHOR]

Mortise and tenon are very important parts of gas turbine dealing operation safety. Additionally, the temperature distribution of the turbine blade and disk is affected by the heat transfer characteristics in its gap. Then, the S-shaped mortise and tenon gap were numerically studied under rotating conditions, and the flow and heat transfer characteristics were analyzed. First, the heat transfer coefficient (HTC) of the mortise and tenon surfaces was measured with thermochromic liquid crystal. Then, the numerical method was verified using the test results, and the grid independence analysis was conducted. Finally, the flow and heat transfer characteristics of the gap under static and rotating conditions were numerically studied, five different Reynolds numbers (Re = 15,000, 20,000, 25,000, 30,000, 35,000) and five gap widths (d = 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm) were conducted and analyzed in detail. The results show that, under the rotating condition, the pressure distribution in the gap is different from that of the static condition; the pressure increases along the radial direction due to the action of centrifugal force and reaches its maximum value at the corner of the "S" shaped structure. With the increase in Re, the heat transfer intensity of the gap increases gradually. Additionally, the heat transfer intensity of the gap increases with an increase in its width. [ABSTRACT FROM AUTHOR]

The plunger valve has an important role in a large compressor system as its operating characteristics directly affect the aerodynamic boundary condition of the compressor equipment. In this study, dynamic modeling and analysis method of the plunger valve are proposed for an accurate control of the system. By considering the interaction between the dynamic flow in the valve and actuator action, a lumped parameter model for the fluid-structure interaction force and multibody dynamic model of the actuator are developed based on intrinsic correlation parameters. A combination analysis to simultaneously predict valve flow and actuator dynamic characteristics is proposed. The predicted results are in a good agreement with experimental data, which validates the proposed model and analysis method. The analysis results show that the coupling effect between the valve flow and actuator is significant and has an important role in valve control, particularly when the valve opening is smaller. Compared to the experimental data and computational fluid dynamics results, the presented methods are accurate for valve control and effective for prediction of flow rate. [ABSTRACT FROM AUTHOR]

We have investigated the use of a novel dual-stage firefighting strategy, where an inert gas is deployed as a carrier agent to discharge foamed water, obtained by mixing environmentally friendly surface-active agents. Here we also report specifically on some in-house built practical strategies. With a view to gauging the relative fire suppression efficacies of the selected agents, each one was discharged as a fine spray onto fires involving hexane, and also optionally where a typical Li-ion battery electrolyte acted as the fuel. In summary, it can be inferred that the air- or nitrogen-detergent formulations showed enhanced fire suppression attributes, in small-scale experiments, as compared with the aqueous medium alone. Furthermore, in almost all cases, the fire extinction property can be attributed mainly to the physical phenomena, produced by the flow of the inert gas, or air and enhanced wettability of the medium. Given that the fire tests were done at a relatively small scale, no definite conclusions can be drawn than those provided above; however, this study warrants further investigation, especially, at a larger scale. [ABSTRACT FROM AUTHOR]