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The mass flow rate of hydrogen leakage directly affects hydrogen diffusion and concentration distribution. In this paper, a test platform was constructed to measure mass flow rates during hydrogen leakage in the supply pipelines of the on-board hydrogen system. Hydrogen leakage tests were conducted under two different conditions. Mass flow rates were measured for tube fittings with various loosening angles and hydrogen supply pressures. The data were then fitted to extrapolate mass flow rates of hydrogen leakage beyond the tested conditions. Additionally, mass flow rates were measured for hydrogen supply pipelines with small holes of different shapes and sizes. The effects of pipeline size, hydrogen supply pressure, hole shape, and size on the hydrogen leakage mass flow rate were analyzed. Hydrogen leakage flow coefficients were corrected, and the accuracy of three calculation methods for hydrogen leakage flow was compared and analyzed based on the test results. The results provide a foundation for future numerical simulation models of hydrogen leakage diffusion. • A hydrogen leakage test platform for hydrogen supply pipeline has been set up. • Hydrogen flow rates of tube fittings with different loosening angles are measured. • Hydrogen flow rates of leakage holes with different shapes and sizes are measured. • Three flow calculation methods are comparatively analyzed based on test data. [ABSTRACT FROM AUTHOR]

When a flying vehicle approaches a water or land surface, it induces changes in the fluid flow field pattern known as the "ground effect." This research analyzes the ground effect phenomenon, exploring its impact on aerodynamic coefficients and flow patterns around the NACA0012 airfoil in an incompressible subsonic regime under static and dynamic conditions with pitch movements. Numerical simulations and experimental testing in an incompressible subsonic wind tunnel were deployed. The flow field solution is derived from the Navier-Stokes equations, incorporating the Transition SST turbulence model. Initially, the impact of the ground effect phenomenon was investigated at varying distances from the surface in the static state. Subsequently, the airfoil underwent a sinusoidal pitching oscillation at each distance with a specified frequency and amplitude. This allowed for examining its aerodynamic characteristics over time. The static analysis results reveal alterations in the curve's behavior and pressure distribution on the airfoil surface at close distances to the surface. This is attributed to the ground effect phenomenon, which reduces lift force to a certain height and then increases. Dynamic analysis further demonstrates changes in lift coefficient oscillation amplitude. It also exhibits a minimum and maximum lift point phase difference as the airfoil approaches the surface. [ABSTRACT FROM AUTHOR]

A computational method is employed to solve heat transfer and entropy generation within a circular pipe. The thermal boundary condition assumes a constant wall temperature, while viscosity is taken to be dependent on temperature. A power-law type shear-thinning fluid is utilized in the analysis, with sinusoidal vibration applied horizontally perpendicular to the flow direction. Temperature distributions across the pipe are illustrated. Additionally, the entropy generation rate over the entire fluid volume under vibration was examined, comparing the results between steady flow and vibrational flow for both types of fluids. It was found that radial mixing is more pronounced in non- Newtonian fluids as vibration increases the strain rate, which is higher for low Reynolds numbers. The research provides a quantitative analysis of heat transfer and entropy generation for both Newtonian and shear-thinning fluids at different Reynolds numbers. It was observed that the effectiveness of superimposed vibrational flow is limited, especially for low Reynolds numbers and flow behavior index characteristic of shear-thinning fluids. [ABSTRACT FROM AUTHOR]

Unsteady separated flow affects the aerodynamic performance of many large-scale objects, posing challenges for accurate assessment through low-fidelity simulations. Full-scale wind tunnel testing is often impractical due to the object's physical scale. Small-scale wind tunnel tests can approximate the aerodynamic loading, with tufts providing qualitative validation of surface flow patterns. This investigation demonstrates that tufts can quantitatively estimate unsteady integral aerodynamic lift and pitching moment loading on a wing. We present computational and experimental data for a NACA0012 wing, capturing unsteady surface flow and force coefficients beyond stall. Computational data for varying angles of attack and Reynolds numbers contain the lift coefficient and surface flow. Experimental data, including lift and moment coefficients for a tuft-equipped NACA0012 wing, were obtained at multiple angles of attack and constant Reynolds number. Our results show that a data-driven surrogate model can predict lift and pitching moment fluctuations from visual tuft observations. [ABSTRACT FROM AUTHOR]

In the feed industry, counterflow coolers are widely used cooling devices. The flow characteristics and pressure loss should be focused on during the design and optimization stages. Due to the complex accumulation of feed particles, it is difficult to accurately analyze the flow field behavior inside the cooler through experiments. Therefore, a detailed study was conducted with a cooler from Buhler using a simulation approach. First of all, the significant influence of the porous jump boundary of flap outlet in the simulation model on the flow field and temperature distribution was revealed. Second, limitations of the Ergun equation in estimating the drag coefficients of the porous medium and the porous jump boundary were explored. Finally, a rapid calculation model for pressure loss was established based on simulation data. Within a wide range of resistance coefficient inputs, the relative error between the model calculation and the corresponding simulation results is very small. Using this model to input a series of resistance coefficients, combined with a small number of overall pressure loss measurements for comparison, the resistance coefficient of the porous medium of the new material can be determined, solving the problem in determining this coefficient through typical measurement experiments at low flow velocity and the lack of effective estimation formulas. This research can provide practical references for improving cooling equipment and enhancing cooler efficiency, and the rapid calculation model can be extended to any fluid machinery containing porous media materials that satisfy Darcy–Forchheimer's law. [ABSTRACT FROM AUTHOR]

Vegetation communities can drastically influence the hydrodynamic characteristics of the overland flow, change the overland flow resistance mechanism, and regulate soil erosion. To investigate the effect of grass-shrub vegetation and litter combinations on overland flow resistance, simulated rainfall experiments were carried out. The experiments involved a 15° gradient slope, five rainfall intensities (I = 60–120 mm h−1), five grass-shrub coverages (Cgs), and six litter volumes (Cl). The results showed that the mean values of form resistance under Cgs = 15%–75% ranged from 0.195 to 1.775, and the mean values of form resistance under Cl = 5–25 g m−2 ranged from 0.609 to 2.160. The form resistance of grass-shrub slopes with the addition of litter was 1.82–12.47 times higher than that under a single grass-shrub cover. The order of magnitude of the factors influencing the slope form resistance coefficients of the grass-shrub + litter was Cl > Cgs > Cl × Cgs > I. With varying vegetation kinds and coverage rates, I had diverse effects on form resistance. The resistance superposition principle does not hold under combined vegetation cover conditions. The degree of difference (Δ f form ) in form resistance was inversely proportional to I and directly proportional to Cl. Through dimensional and multiple nonlinear regression analyses, a general model for calculating form resistance was established (Adj. R2 = 0.99, NSE = 0.97). Theoretically, the results of this study can be used to evaluate soil and water conservation during vegetation community succession and restoration. [ABSTRACT FROM AUTHOR]

• Heat transfer coefficient of three component zeotropic mixture was measured. • A specially designed test section was used for local heat transfer measurement. • An asymmetrical distribution of heat transfer coefficient was observed. • A prediction correlation utilizing the mixture resistance was developed. Plate heat exchangers are gaining popularity as condensers for their compact design and high efficiency. However, the uneven fluid distribution in channels poses a challenge to effective heat transfer. Existing literature lacks experimental analysis of local heat transfer coefficients for pure and zeotropic mixture refrigerants in plate heat exchangers. This study experimentally analyzed the local heat transfer of the three-component zeotropic mixture R455A at various conditions (mass flux 20, 30, and 50 kg m−2 s−1 and saturation temperatures 30 and 35 °C). Results show that the heat transfer coefficient increases with flow rates and decreases with saturation temperature. However, results indicated lower heat transfer coefficients compared to pure refrigerants due to mixture effects. In addition, the local distribution of the heat transfer coefficient revealed that the heat transfer coefficient is highest at the center compared to the edges of the channel due uneven distribution of refrigerants within the channel. This HTC pattern confirms an asymmetrical flow within the plate. A new correlation is being developed to predict the heat transfer coefficient of the ternary mixture, showing improved accuracy than previously proposed correlations. [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.)

To solve the problem that the control of shock wave elimination is weakened under off-design conditions, the design concept of a variable-geometry inlet scheme that combines the variable-geometry cowl (translating and diagonalizing) with regulating shock wave elimination is introduced in this paper. The variable-geometry inlet is designed by the theories of oblique shock wave and isentropic wave as well as the Oswatitsch theory. Regulatory law of the variable-geometry cowl based on shock wave elimination is obtained by the geometric relationships between cowl compression angle, cowl shock wave angle, and optimal control point or range. Numerical simulations are conducted to investigate flow field characteristics, control mechanism, and working performance of the inlet. Results reveal that expansion waves have a significant impact on the cowl shock wave and boundary layer interaction, and flow separation. Furthermore, variable-geometry inlet with translating and diagonalizing cowl based on the regulation of shock wave elimination effectively controls and even completely eliminates the flow separation. In terms of inlet performance, the total pressure loss of the variable-geometry inlet decreases such that the total pressure recovery coefficients of the translating cowl and diagonalizing cowl inlets are increased by maximum values of 3.39 % and 9.97 %, respectively. However, the mass flow coefficient of translating cowl inlet decreases, whereas that of the diagonalizing cowl inlet is equivalent to that of the fixed-geometry inlet. The working range can be widened by changing the internal contract ratio of the inlet through translating or diagonalizing the cowl. The results confirm that the scheme of variable geometry inlet with diagonalizing cowl is practicable and reliable and has important guiding significance and value for inlet design. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of a multi-door check valve using computational fluid dynamics (CFD) and finite element analysis (FEA) to evaluate flow performance under pressure test conditions, with an emphasis on its ability to prevent backflow. Check valves are essential components in various industries, ensuring fluid flow in one direction only while preventing reverse flow. The non-return multi-door reflux valve is increasingly preferred due to its superior backflow prevention, fluid control, and effective flow regulation. Rigorous testing under varying pressure conditions is essential to ensure that these valves perform optimally. This study uses CFD and FEA simulations to evaluate the structural integrity and flow characteristics of the valve, including pressure drop, flow velocity, backflow prevention effectiveness, and flow coefficient. A high-fidelity 3D model was created to simulate the valve's behavior under various conditions, analyzing the effects of parameters such as the number of doors, their orientation, geometry, and operating conditions. The CFD results demonstrated a significant reduction in backflow and pressure drop across the valve. However, localized turbulence and flow separation near the valve doors, particularly under partially open conditions, have raised concerns about potential wear. The velocity profiles indicated a uniform distribution at full opening with laminar velocity profiles and minimal resistance to flow. The results of the FEA showed that the stresses induced by the fluid forces were below critical levels, with the highest stress concentrations observed around the hinge points of the valve doors. Although the valve structure remained intact under normal operating conditions, some areas may have required reinforcement to ensure long-term durability. Combined CFD and FEA analyses demonstrated that the valve effectively preserves system integrity, prevents backflow, and maintains consistent performance under various pressure and flow conditions. These findings provide valuable insights into design improvements, performance optimization, and enhancing the efficiency and reliability of reflux valve systems in industrial applications. [ABSTRACT FROM AUTHOR]

In this study, the yield stress equation, flow rules and physical properties of barium titanate (BaTiO3) are experimentally obtained. These basic equations and coefficient of flow stress are introduced to finite element method, and sintering behavior of barium titanate bulk is simulated. From the uniaxial compression test, the yield stress equation of BaTiO3 is expressed by Shima's equation, and flow rule is written by plastic equation. The coefficient of flow stress of BaTiO3 is significantly smaller than that of alumina, and the value is different when the grain size is different. The experimental sintering deformation is quantitatively reproduced by numerical simulation, where basic equation and physical properties are experimentally introduced. In addition, the coefficient of flow stress could be determined by simulation sensitivity analysis. Through this study, experimentally obtained yield stress equation, flow rules, and coefficient of flow stress are numerically validated. [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]

This study explores the flow dynamics and sediment entrainment mechanisms around a circular array of emerged cylinders in a shallow channel. Eddy resolving simulations reveal the formation of vortex street-type shallow wakes, influenced by cylinder diameter and submergence ratio. The research emphasizes the impact of flow conditions on wake instabilities, coherent structures, and sediment transport, shedding light on the complex interactions in shallow water environments. [Extracted from the article]

In the present study, we develop a theoretical model for predicting hydrogen jet ignition in a shock tube with a partially opened diaphragm for hydrogen as a driver gas and air as a driven gas. Effects of pressure losses associated with the gradual diaphragm opening process are taken into account by developing a new discharge coefficient model. The discharge coefficient for incompressible flows is first calculated and then converted into the discharge coefficient for compressible flows. Three regimes are identified for the discharge coefficient, which depend on whether the ruptured portion of the diaphragm, which remains attached to the orifice, is negligible or not. We extensively validate the new model against experimental results from the literature. We show that the critical initial pressure ratio across the diaphragm and the shock-wave strength required for ignition can be calculated in a conservative manner with a maximum relative error equal to 9% and 10%, respectively, for the ratio of diaphragm opening area to driven-section cross-sectional area from 0.125 to 1.0. Finally, we explore, via our new model, the influence of different parameters on the shock-wave Mach number and ignition limits. We show that all our model predictions can be generalized into two simple dimensionless correlations. [Display omitted] • Three regimes are identified for the discharge coefficient. • Model predicts the ignition limits within 9% of experimental values. • The ignition limit is constant for area ratios between 0.52 and 1.0. • Model predictions can be generalized into two correlations. [ABSTRACT FROM AUTHOR]

This paper examines the enactment of a two-dimensional, steady, non-Newtonian nanofluid flow over a stretching sheet. The utilization of magnetic influences acting in the direction normal to the Darcy–Forchheimer boundary layer flow of the Sutterby nanofluid with variable thermal conductivity is taken into consideration. This study takes into account the effects of thermophoresis and Brownian motion. The study found that a 15% increase in magnetic field strength resulted in a 10% increase in heat transfer rate. Similarly, a 20% increase in nanoparticle volume percentage causes a 12% increase in the convective heat transfer coefficient. The problem’s model is formulated in the form of partial differential equations (PDEs), transformed via similarity transformation into nonlinear ordinary differential equations (ODEs). Applying the finite difference method yields the solution to reduced equations. EMHD Darcy–Forchheimer flow and nanofluid dynamics are combined in cutting-edge technology. This is important for many industrial and technical applications. Moreover, providing a strong computational framework provides a precise simulation of the flow behavior. By providing insights into the intricate interactions between electromagnetic forces, porous medium effects, and variable thermal conductivity in nanofluids flow across a stretched sheet, this study makes an essential contribution to the science of fluid dynamics. This research is very significant and enlightening for researchers and professionals who are interested in the design and optimization of heat transfer systems. The fluid flow is examined thoroughly and graphically, and the relationship between the profiles of velocity, temperature, and concentration and other important physical limitations is investigated. The effect of various physical parameters on concentration, velocity, temperature, skin friction, Nusselt number and heat flow coefficient is verified and examined using graphs and tables. [ABSTRACT FROM AUTHOR]

Dispersion coefficients and the average solute transport velocity are pivotal for groundwater solute transport modeling. Accurately and efficiently determining these parameters is challenging due to difficulties in directly correlating them with pore‐space structure. To address this issue, we introduced the Physics‐enhanced Convolutional Neural Network‐Transformer (PhysenCT‐Net), an innovative model designed to concurrently estimate the longitudinal dispersion coefficient and average solute transport velocity in three‐dimensional porous media. PhysenCT‐Net exhibited excellent predictive performance on unseen testing datasets and significantly reduced computational demands. Comprehensive evaluations confirmed its robust generalization across various flow conditions and pore structures. Notably, the longitudinal dispersion coefficient predictions closely align with established empirical relationships involving Péclet number, affirming the model's physical interpretability and potential to aid in simulating transport phenomena in porous media. Plain Language Summary: The migration of solutes in geological media is a complex process that involves both dispersion and advective motions. Therefore, the dispersion coefficient and advective flow rate are crucial parameters for modeling and predicting solute migration, with the former being determined by the complex flow field and solute diffusion coefficient within the medium. These two parameters are typically obtained through the experiment results of solute concentration distribution or through complex numerical simulations, which take a lot of time and resources. In this letter, we introduce a deep learning model that can provide a more efficient way to determine the two parameters describing substance movements. The model uses three‐dimensional images and properties of the media, the diffusion coefficient of solute and the mean flow speed of water as the inputs. We tested the model under a variety of conditions, and the dispersion coefficients predicted by the trained model agreed well with physical laws. The model can not only improve how we estimate these parameters, but also help us understand the physical laws that govern how substances move through groundwater. This could lead to better ways of modeling and managing these important water resources. Key Points: Accurately predicting key parameters of the advection‐dispersion equation for solute transport in porous mediaDeveloping direct mapping relationships between three‐dimensional porous media images and parameters by the physics‐enhanced neural networkNetwork demonstrates exceptional prediction accuracy and generalization, providing parameters that align with empirical formulas [ABSTRACT FROM AUTHOR]

This paper investigates the application of Schlieren flow visualization for detecting leaks in pipelines carrying high-temperature fluids. Two experimental setups were constructed: one with a 25 mm PTFE tube featuring a 2 mm diameter perforation, and another with a 100 mm diameter pipe insulated with an aluminum jacket and featuring a 12 mm leak gap. A single-mirror-off-axis Schlieren system, employing a 150 mm diameter parabolic mirror, was used to visualize the leaks. The temperature of the leaking air varied between 20 and 100 °C, while the ambient temperature was maintained at 14 °C. To quantify the leaks, the coefficient of variation for pixel intensity within the leak region was calculated. Results showed that for the PTFE tube, leaks became detectable when the temperature difference exceeded 34 °C, with the coefficient of variation surpassing 0.1. However, in the insulated pipe, detecting clear leak patterns was challenging. This research demonstrates the potential of Schlieren visualization as a valuable tool in enhancing pipeline leak detection. [ABSTRACT FROM AUTHOR]

Due to their superior technical and hydraulic performance and minimal environmental impact, porous weirs have emerged as a feasible alternative to traditional impermeable solid weirs in water transmission and distribution systems. This research study assesses the hydraulic performance of porous broad-crested weirs (PBCWs) with sloping crests. To accomplish this, 30 PBCW models were designed and tested under various operating conditions, including free and submerged flow scenarios. A comparative analysis was conducted to evaluate the performance of PBCWs with and without sloping crests, with the results being compared against a solid broad-crested weir (SBCW) model. The findings revealed that PBCWs with an upstream crest slope exhibited an average increase of 38% in the discharge coefficient compared to similar SBCWs. Similarly, PBCWs with a downstream crest slope demonstrated an average increase of 28% in the discharge coefficient. Additionally, PBCWs with sloping crests showcased heightened sensitivity to changes in tailwater levels compared to PBCWs with horizontal crests, with PBCWs featuring an upstream crest slope being more responsive than those with a downstream crest slope. Finally, leveraging extensive experimental data, empirical equations were derived using nonlinear multi-variable regression and gene-expression programming techniques to accurately represent the free flow discharge coefficient and submerged flow discharge reduction factor. [ABSTRACT FROM AUTHOR]

The present paper focuses on the optimization of large-flow coefficient centrifugal compressors, utilizing a mature centrifugal compressor impeller with a flow coefficient of 0.16 under design point condition in engineering as the research subject. Due to the more complex flow mechanism and more design parameters in the impeller with large flow coefficient, the traditional artificial optimization method is insufficient. In present paper, the impeller with a large flow coefficient is optimized using the concept of combining physical principles and artificial intelligence tools. Firstly, the impeller underwent a redesign based on the theory of maximum flow capacity, with the aim of reducing the Mach number at the impeller inlet to enhance the compressor's performance. And the efficiency of the impeller at the design point has been increased from 88.6% to 89.9%. In order to further improve the performance of the impeller, an optimization algorithm grounded in gradient variation was employed to facilitate the automatic compressor optimization, and the flow losses at the impeller's top under low-flow conditions has been mitigated. The results of three-dimensional numerical simulation showed that the operating range of the new impeller is 7% wider than that of the original impeller. [ABSTRACT FROM AUTHOR]

The present study is aimed at reducing the drag loads on cylinders by using a passive control technique which consists in shape modification for streamlined and bluff bodies, particularly those used in aeronautics. Various shapes of elliptic and ovate-elliptic cross sections were tested with studying the effect of geometric parameters, namely, the radius ratio and axial ratio. The flow around the proposed geometries was studied numerically using k–ε, k–ω, and Spalart–Allmaras turbulence models at the Reynolds numbers from 104 to 2.4·104. The results obtained were compared with those for a circular cylinder of constant radius, showing a significant weakening of aerodynamic forces acting on the cylinder with modified shapes, especially at high Reynolds numbers, for both elliptic and ovate-elliptic geometries with a better performance for the latter. [ABSTRACT FROM AUTHOR]

Consideration is given to problems of calculating the exhaust from the engine cylinder through a "valve–valve pipe" system at all flow modes. It has been shown that there is a need to determine the exhaust parameters precisely in the cross section of the valve pipe outlet and also to clarify the moment of blocking the flow in the valve and at the valve pipe outlet. Based on the idea of analogy with a sudden expansion of the passage section of a conditional channel, relations have been obtained for determining the flow coefficient of the valve system. The results of calculations using these relations are in good agreement with the results of blowdowns of the valve system of a real engine. To simplify flow calculations and visualize the flow modes in the system using the criteria of the similarity theory and gas-dynamic functions, a method has been developed for constructing a universal two-parameter gas-dynamic characteristic (map) of a valve system similar to maps of compressors and turbines. In this case, the values of flow coefficients in all the modes represented by the maps will be almost the same for systems of various scale and having identical parameters of geometric expansion. [ABSTRACT FROM AUTHOR]

To address the inaccuracy of the Thornhill-Craver method in predicting gas-lift valve flow rates,research on gas-lift valve flow was conducted using air as the medium on a gas-lift valve test platform. Experiments were carried out on gas-lift valves with orifice sizes of 2. 8, 3. 2, 4. 8 and 6. 4 mm,resulting in a functional relationship between valve stem travel and flow coefficient,as well as critical pressure ratio for different orifice sizes. By considering the dynamic changes in surface pressure of the valve ball under operating conditions and introducing the degree of valve opening, the method for solving the valve stem stroke was optimized. A model for the flow area of the gas-lift valve was developed,and a new method for calculating the flow area was derived using known parameters. Based on experimental and theoretical analysis,a new model for predicting the flow rate of gas-lift valves was established. The research results indicate that the new model accurately predicts the flow rates of gas-lift valves for different orifice sizes and under various working conditions,with an average relative error of 3. 34%,which is a significant improvement over the Thornhill-Craver method. This is of great importance for determining the working state of gas-lift valves downhole and for improving the precision of gas-lift design. [ABSTRACT FROM AUTHOR]

We investigate the complex-time analytic structure of solutions of the three-dimensional (3D)-axisymmetric, wall-bounded, incompressible Euler equations, by starting with the initial data proposed in Luo and Hou ["Potentially singular solutions of the 3D axisymmetric Euler equations," Proc. Natl. Acad. Sci. U. S. A. 111(36), 12968–12973 (2014)], to study a possible finite-time singularity. We use our pseudospectral Fourier–Chebyshev method [Kolluru et al., "Insights from a pseudospectral study of a potentially singular solution of the three-dimensional axisymmetric incompressible Euler equation," Phys. Rev. E 105(6), 065107 (2022)], with quadruple-precision arithmetic, to compute the time-Taylor-series coefficients of the flow fields, up to a high order. We show that the resulting approximations display early-time resonances; the initial spatial location of these structures is different from that for the tygers, which we have obtained in Kolluru et al. ["Insights from a pseudospectral study of a potentially singular solution of the three-dimensional axisymmetric incompressible Euler equation," Phys. Rev. E 105(6), 065107 (2022)]. We then perform asymptotic analysis of the Taylor-series coefficients, by using generalized ratio methods, to extract the location and nature of the convergence-limiting singularities and demonstrate that these singularities are distributed around the origin, in the complex- t 2 plane, along two curves that resemble the shape of an eye. We obtain similar results for the one-dimensional (1D) wall-approximation (of the full 3D-axisymmetric Euler equation) called the 1D Hou–Luo model, for which we use Fourier-pseudospectral methods to compute the time-Taylor-series coefficients of the flow fields. Our work examines the link between tygers, in Galerkin-truncated pseudospectral studies, and early-time resonances, in truncated time-Taylor expansions of solutions of partial differential equations, such as those we consider. [ABSTRACT FROM AUTHOR]

Pulsators are widely used to study the dynamic characteristics of liquid flow components. However, it is difficult to adapt the existing actuators to the excitation requirements under high pressures, low temperatures, and toxic media. This study describes the design of a novel pressure pulsation device and presents the results of simulations and experimental tests. The flow field is simulated under a series of working conditions, and the effects of the rotation speed, flow rate, inlet pressure, and gap between the rotor and stator on the peak-to-peak amplitude, spectral amplitude, and flow resistance coefficient of the actuator outlet are analyzed. A prediction model for the corresponding parameters is developed using multiple linear regression. In high-pressure (20 MPa) hydraulic pipeline tests, the excitation device can generate pulsating flow with peak-to-peak amplitudes of more than 7 MPa in the time domain and 2 MPa in the frequency domain. The upstream and downstream regions of the internal flow field are periodically joined and detached by the blade rotation, which results in periodic variations in flow velocity and pressure. The relative error between the model predictions and the three-dimensional simulation and experimental values is less than 7%, satisfying industrial requirements. This work facilitates a solution to the problem of dynamic excitation when analyzing the response characteristics of fluid equipment in high-pressure pipelines and provides a method for forecasting actuator output effects. [ABSTRACT FROM AUTHOR]

The simulation of thermal–fluid–solid coupling in turbines is critically important for design optimization. Historically, most research on thermal–fluid–solid coupling has been conducted in three-dimensional, often with computational speeds that do not meet practical expectations. This study proposes a one-dimensional performance prediction and multi-objective optimization design methodology for turbines, integrating aerothermodynamics and structural strength, to facilitate rapid multidisciplinary coupling design optimization at a low-dimensional level. Initially, a multidisciplinary coupled turbine performance prediction model is established, incorporating the combined effects of turbine aerothermodynamics and structural mechanics. This model links the thermodynamics of the blade passage with the stress and strain of the blade. The predictive accuracy of this model is validated against experimental data from a four-stage axial flow turbine, showing a maximum error of 1.56% for the total temperature ratio and 1.69% for the total expansion ratio. Subsequently, using blade parameters, degree of reaction, load coefficient, and flow coefficient as optimization variables and targeting the turbine's overall isentropic efficiency and power as optimization objectives, a rapid Non-dominated Sorting Genetic Algorithm II and the Technique for Order Preference by Similarity to an Ideal Solution are employed to optimize the last stage of the four-stage axial flow turbine. The optimized turbine demonstrates an increase in overall isentropic efficiency by 1.333% and an increase in overall power by 3.329%, while satisfying structural strength requirements. The novelty of this study lies in its rapid optimization design and performance prediction method for the coupled aerothermodynamics and structural mechanics at a one-dimensional level. [ABSTRACT FROM AUTHOR]

With the development of engineering applications and the increase in system complexity, some particular fields, such as liquid rocket engine turbopumps, aircraft engine fuel systems, and marine natural flow cooling systems, are increasingly focusing on the performance characteristics of pumps under natural flow conditions. The pump is in the form of resistance components under natural flow conditions without a power drive. The impeller undergoes passive rotation by the impact of inlet flow. Due to the specificity of its operating conditions and performance indicators, the pump's natural flow performance cannot be evaluated by regular methods. Therefore, this paper proposed a numerical prediction method for pump natural flow performance based on a coupled computational fluid dynamics coupled with six-degrees-of freedom model. The performance of a multistage pump with guide vanes was evaluated under different natural flow conditions, and the accuracy was verified by experimental measurements. The transient variation mode of pump performance parameters with time at the initial stage of natural flow impact was analyzed. The flow field's transient evolution characteristics and the wall shear stress variation during natural flow were investigated. It was found that the impeller's passive rotational speed increases linearly with the natural flow rate, while the hydraulic loss shows an exponentially increasing trend. Meanwhile, the natural flow loss coefficient shows an exponentially decreasing trend and gradually tends to a stable value. The high turbulent kinetic energy inside the impeller is mainly distributed in the flow separation region and large velocity gradients. The distribution of shear stresses is closely related to the flow behavior inside the pump and the geometrical features of the hydraulic components. [ABSTRACT FROM AUTHOR]

In this study, the hydrodynamic forces and power absorption performance of an autonomous underwater vehicle (AUV)-based two-body wave energy converter (2BWEC) are investigated. A theoretical model is developed within the framework of linear potential flow to solve for added mass, radiation damping, and wave excitation force using the matched eigenfunction expansion method (MEEM). A computational fluid dynamics (CFD) model is employed to account for vortex-shedding effects of the floater and inner cylinder with a damping plate under various excitation conditions. Empirical formulas for supplementary added mass and drag coefficients caused by flow separation are proposed based on curve-fitting the differences between CFD results and MEEM calculations. These formulas are integrated into motion equations to enhance accuracy in evaluating the power absorption of the 2BWEC. It has been found that in the context of viscous flow, both the added mass and damping coefficients are increased, particularly for the inner cylinder with a damping plate. In addition, the viscous hydrodynamic coefficients exhibit strong dependence on the Keulegan–Carpenter number, while showing insensitivity to changes in the frequency parameter β. The supplementary (viscous) added mass provides additional inertia for the AUV with a limited mass itself, which is advantageous for the power absorption of the AUV-based 2BWEC. Conversely, the presence of viscous damping from the damping plate impedes wave energy capture. [ABSTRACT FROM AUTHOR]

With the large -scale ships and the complexity of the dynamic environment in the berthing waters, when usingappendix F of the current JTS 144-1—2010 Load Code for Harbor Engineering to calculate the ship flow force, it is found thatthere are many deficiencies in the formula, mainly as follows: 1) the applicable range of relative water depth is narrow; 2) Thecalculation methods for flow direction angle sections are not unified; 3) the action points of longitudinal and transverse flowcomponents are not clear; 4) the introduction of relevant data defects, etc. Seriously restrict the promotion and application ofstandards and specifications. Therefore, based on the research on the revision of the standard, by collecting and comparing thedata of foreign standards and guidelines, as well as combining the results of a large number of ship physical model tests carriedout by the author in the early stage, the applicable conditions of relative water depth in the current standard flow forcecalculation formula are expanded from 1.5 to 6.0; A new coordinate system with the center of the ship as the force applicationpoint was proposed, which adopts a revised method for calculating water flow force composed of three parts: transverse force,longitudinal force, and eccentric moment, meeting the purpose of standard revision. [ABSTRACT FROM AUTHOR]

Spatiotemporal change in precipitation induced by climate change can be a concern for riverine disasters. The relationship between precipitation and flow discharge in the 8 rivers from northeast to southwest of Japan (either mainstream or tributary) in which neither manmade dam nor reservoir is present was investigated based on observed data at the stream gauging stations managed by the Ministry of Land, Infrastructure, Transport and Tourism of the Japanese government. Observed data of air temperature, precipitation, etc. by the Japan Meteorological Agency vicinity of the gauging station in the 8 rivers basins were also used in the analyses. The precipitation concentration index (PCI) which is the Gini coefficient of precipitation during a year, and the Gini coefficient of flow discharge were computed for about half a century. The results reveal that annual maximum flow discharge can be related closely to the extreme rainfall events such as annual maximum daily or hourly precipitation. Obtained trends of the PCI were all positive and statistically significant at the 1% level, indicating that an in – equality in rainfall distribution during a year has been accelerated as the air temperature has risen in the basins. Whereas obtained trends of the Gini coefficient of the flow discharge were either positive or negative, and very weakly correlated with the trends in the PCI. Temporal precipitation distributions in a year have changed in the 8 rivers basin, i.e. light rain days (0 – 1 mm/day) have increased whereas rain days with 1 – 10 mm/day have decreased, while no such trend is seen in flow discharge in the 8 rivers. The interaction between surface and subsurface flows, and soil moisture may play important roles in moderating the effects of spatiotemporal change in precipitation. The flow discharge, however, can increase immediately in response to the precipitation when rainfall intensity is sufficiently strong. [ABSTRACT FROM AUTHOR]

At present, there are two independent technologies and equipment for the test of the reciprocating compressor plate valve: the sealing test and blowing test. This method has single function and complicated test operation and may rely on theoretical calculations, which reduces the reliability of the test conclusion because the motion law of valve disk during opening and closing is extremely complicated. The existing test methods cannot meet the needs of more in-depth and accurate research, development and improvement of the plate valve. This study proposes a test device and method that can not only quantitatively test the performance of the plate valve but also qualitatively test the dynamic process of the suction valve plate, which can greatly reduce the testing time provide more intuitive and accurate valve plate motion tracks and valve paths. This paper takes the primary plate suction valve as the test object and adopts the automated multi-functional system to accurately obtain the valve's sealing property, effective flow area, thrust coefficient, flow coefficient, drag drop, valve gap Mach number, initial opening pressure difference, maximum opening, and residence time of the valve plate on the valve lift guard to provide necessary data for valve design and performance evaluation. The test results of valve opening time are verified by industrial reciprocating compressor, which proves the accuracy and practicability of the system. [ABSTRACT FROM AUTHOR]

An energy and exergy analysis of an experimental air-conditioning absorption system operating with the ammonia-lithium nitrate mixture has been performed. The system was operated under controlled and steady-state conditions. The main operating parameters, such as flow ratio, coefficient of performance, exergy coefficient of performance, and exergy destruction in each one of the main components, were determined at different heat sources and condensing temperatures. The coefficients of performance varied between 0.5 and 0.65, while the exergy coefficients of performance varied between 0.1 and 0.2. Clear trends were found for the coefficient of performance and flow ratio as a function of the generator and condenser temperatures; however, no trends were found in the exergy coefficients of performance due to the high variability of the ambient temperature. The highest values of the exergy destruction occurred in the generator, followed by the condenser and the evaporator, while the lowest values were obtained in the absorber and the economizer. [ABSTRACT FROM AUTHOR]

Considerable parts of riparian forests around the world are covered by deciduous trees and tall shrub species with rigid trunk and flexible-broadleaf. Experiments are conducted on artificial rigid and flexible models to estimate drag coefficient and resistance to flow for deciduous trees in forest floodplains under nonsubmerged condition. The rigid and flexible models with similar size and configuration are tested in a laboratory flume to clearly determine the effects of vegetation flexibility and density, and the flow velocity and depth on the roughness coefficients. Ratios of the flexible to rigid drag forces and drag coefficients indicate considerable effects of flexibility on the roughness coefficients. In this study, the flexural rigidity of the tree leaf is used in the roughness equations to account for vegetation flexibility instead of the traditionally used tree trunk flexural rigidity. This is based on the assumption that foliage flexibility governs tree reaction to the flow for most species of deciduous trees and leafy tall shrub families. The developed roughness coefficient equations are scaled up to determine the variation of Manning's n -value with increase of flow depth for a riparian canopy of black willow. The estimated Manning's n -values are compared with the reported Manning n -values for the same black willow canopy. [ABSTRACT FROM AUTHOR]

The hydrodynamic coefficient of an underwater manipulator varies with changes in posture and flow field, presenting significant challenges for precise control and localization. This study, conducted numerical simulations to investigate the patterns of variation in flow field and hydrodynamic coefficients. Results showed that hydrodynamic performance remained consistent when the posture of the manipulator was either axisymmetric or origin-symmetric. Upon rotation, axial flow extended across the entire downstream surface, and the Karman vortex street entirely eliminated. Pressure coefficients on the back pressure surface of the manipulator increased with the Reynolds number within the range of 6x10³ ≤ Re ≤ 3x104, while the pressure coefficient on the upstream surface remained unchanged. Within this range, drag coefficients for the upper and lower arms decreased by 27.4% and 23.9%, respectively. The hydrodynamic performance of the lower arm was independent of the upper arm's posture, with a maximum drag coefficient of 1.48 achieved at α = -90°. As the posture angle of the manipulator varied from 30° to 60°, the pressure coefficient on the upstream surface decreased from 0.75 to 0.25. [ABSTRACT FROM AUTHOR]

Intravoxel incoherent motion (IVIM) MRI has emerged as a valuable technique for the assessment of tissue characteristics and perfusion. However, there is limited knowledge about the relationship between IVIM‐derived measures and changes at the level of the vascular network. In this study, we investigated the potential use of IVIM MRI as a noninvasive tool for measuring changes in cerebral vascular density. Variations in quantitative immunohistochemical measurements of the vascular density across different regions in the rat brain (cortex, corpus callosum, hippocampus, thalamus, and hypothalamus) were related to the pseudo‐diffusion coefficient D* and the flowing blood fraction f in healthy Wistar rats. We assessed whether region‐wise differences in the vascular density are reflected by variations in the IVIM measurements and found a significant positive relationship with the pseudo‐diffusion coefficient (p < 0.05, β = 0.24). The effect of cerebrovascular alterations, such as blood–brain barrier (BBB) disruption on the perfusion‐related IVIM parameters, is not well understood. Therefore, we investigated the effect of BBB disruption on the IVIM measures in a rat model of metabolic and vascular comorbidities (ZSF1 obese rat) and assessed whether this affects the relationship between the cerebral vascular density and the noninvasive IVIM measurements. We observed increased vascular permeability without detecting any differences in diffusivity, suggesting that BBB leakage is present before changes in the tissue integrity. We observed no significant difference in the relationship between cerebral vascular density and the IVIM measurements in our model of comorbidities compared with healthy normotensive rats. [ABSTRACT FROM AUTHOR]

Computational fluid dynamic (CFD) models and workflows are often developed in an ad hoc manner, leading to a limited understanding of interaction effects and model behavior under various conditions. Machine learning (ML) and explainability tools can help CFD process development by providing a means to investigate the interactions in CFD models and pipelines. ML tools in CFD can facilitate the efficient development of new processes, the optimization of current models, and enhance the understanding of existing CFD methods. In this study, the turbulent closure coefficient tuning of the SST k − ω Reynolds-averaged Navier–Stokes (RANS) turbulence model was selected as a case study. The objective was to demonstrate the efficacy of ML and explainability tools in enhancing CFD applications, particularly focusing on external aerodynamic workflows. Two variants of the Ahmed body model, with 25-degree and 40-degree slant angles, were chosen due to their availability and relevance as standard geometries for aerodynamic process validation. Shapley values, a concept derived from game theory, were used to elucidate the impact of varying the values of the closure coefficients on CFD predictions, chosen for their robustness in providing clear and interpretable insights into model behavior. Various ML algorithms, along with the SHAP method, were employed to efficiently explain the relationships between the closure coefficients and the flow profiles sampled around the models. The results indicated that model coefficient β * had the greatest overall effect on the lift and drag predictions. The ML explainer model and the generated explanations were used to create optimized closure coefficients, achieving an optimal set that reduced the error in lift and drag predictions to less than 7% and 0.5% for the 25-degree and 40-degree models, respectively. [ABSTRACT FROM AUTHOR]

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Background: Maximum diameter measurements are used to assess the rupture risk of abdominal aortic aneurysms (AAAs); however, these are not precise enough to predict all ruptures. Four‐dimensional (4D) flow MRI‐derived parameters provide additional information by visualizing hemodynamics in AAAs but merit further investigation before they are clinically applicable. Purpose: To assess the reproducibility of 4D flow MRI‐derived hemodynamics, to investigate possible correlations with lumen and maximum diameter, and to explore potential relationships with vorticity and aneurysm growth. Study Type: Prospective single‐arm study. Population: A total of 22 (71.5 ± 6.1 years, 20 male) asymptomatic AAA patients with a maximum diameter of at least 30 mm. Field Strength/Sequence: A 3.0 T/Free‐breathing 4D flow MRI phase‐contrast acquisition with retrospective ECG‐gating. Assessment: Patients underwent two consecutive 4D flow MRI scans 1‐week apart. Aortic volumes were segmented from time‐averaged phase contrast magnetic resonance angiographies. Reproducibility was assessed by voxelwise analysis after registration. Mean flow velocity, mean wall shear stress (WSS), mean lumen diameter, and qualitative vorticity scores were assessed. In addition, Dixon MRI and retrospective surveillance data were used to study maximum diameter (including thrombus), intraluminal thrombus volume (ILT), and growth rate. Statistical Tests: For reproducibility assessment, Bland–Altman analyses, Pearson correlation, Spearman's correlation, and orthogonal regression were conducted. Potential correlations between hemodynamics and vorticity scores were assessed using linear regression. P < 0.05 was considered statistically significant. Results: Test–retest median Pearson correlation coefficients for flow velocity and WSS were 0.85 (IQR = 0.08) m/sec and 0.82 (IQR = 0.10) Pa, respectively. Mean WSS significantly correlated with mean flow velocity (R = 0.75) and inversely correlated with mean lumen diameter (R = −0.73). No significant associations were found between 4D flow MRI‐derived hemodynamic parameters and maximum diameter (flow velocity: P = 0.98, WSS: P = 0.22). Data Conclusion: A 4D flow MRI is robust for assessing the hemodynamics within AAAs. No correlations were found between hemodynamic parameters and maximum diameter, ILT volume and growth rate. Level of Evidence: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

During the laser cladding process, complex composition distribution in the molten pool was caused from the Marangoni flow, which leading to one kind of defect termed as macrosegregation. Therefore, comprehensive understanding on the flow behaviors in the molten pool is particularly important for predicting and regulating macrosegregation. In this paper, a three-phase Eulerian model based on the volume averaging method is developed to investigate the effect of Marangoni coefficient variations on the flow and compositional distribution. The flow patterns were photographed and analyzed using a high-speed camera, and then the simulated and experimental results for chromium concentration distribution, size of the cladding layer, depth of the molten pool, and flow pattern were compared and found to be in agreement with each other; thus, the accuracy of the model was validated. Meanwhile, the effects of flow direction and intensity on the composition distribution are comprehensively studied. The results show that the flow direction extremely affects the flow path and evolution process of Cr-enriched melt in the molten pool. At the same time, the flow intensity will change the flow time of Cr-enriched melt in the molten pool and then affect the homogenization of composition distribution. [ABSTRACT FROM AUTHOR]

The inherent properties of soft coal seams and their mechanical environment make long boreholes susceptible to issues like collapse, deformation, and blockages. These problems shorten the service life of the boreholes and hinder extraction efficiency. This paper tackles these challenges by analyzing the deformation and damage patterns of long boreholes in soft coal seams. It examines the stress distribution and deformation characteristics around both protected and unprotected boreholes at different burial depths. Additionally, it recommends using screen pipe protection technology to improve gas extraction and mining operations, as demonstrated in Changping Coal Mine. The results show that screen pipe protection substantially improves the stress distribution and deformation stability of coal seam boreholes. The flow attenuation coefficients of two boreholes equipped with protection technology decreased by 48% and 61%. After 50 days of extraction from boreholes with a protection rate exceeding 90%, gas concentration remained above 50%, which is 2.59 times higher than that of unprotected boreholes. This technology effectively addresses the frequent accidents, poor extraction performance, and inefficiency of long boreholes in soft coal seams, ensuring the mine's safe and efficient production. [ABSTRACT FROM AUTHOR]

Purpose. To study the course of heat phenomena in disc brakes using modern computing systems in order to determine and substantiate the operating parameters for the hoisting machine components. Methodology. The research uses software packages, with the help of which a computational-theoretical apparatus is developed for heat mode modeling processes. In particular, the mentioned function is used in the SolidWorks Simulation software with the ability to evaluate the errors of the calculation results. Findings. In the course of the research, the dependence of the hoisting machine disc brake performance on the operating parameters of its components was determined. The research has led to a better understanding of the heat transfer processes in disc braking devices, as well as the ability to study the friction response of various materials and determine optimal parameters that help improve the performance of braking systems. The effectiveness has been proven of the proposed method for analyzing the heat distribution processes of the mine hoisting machine drum components under the influence of operating and emergency braking modes. Originality. For the first time, a methodology for calculating the heating temperature distribution along the brake rim plane during a safety stop has been developed and substantiated. A method has also been developed for determining the temperature field arising under steady-state heating conditions, which occur after repeated operating braking and cooling of the device. In this case, when using the formula for determining the temperature on the brake rim surface, the sample length, the relative velocity between the friction components and the heat flow distribution coefficient are taken into account. The brake disc geometric model developed in the SolidWorks software package makes it possible to study the temperature change on the device rim in real time. Practical value. The proposed design improvement based on the research results of heating processes should improve vehicle safety. The cost of braking systems is expected to be reduced through the use of optimal materials and production technologies. The software methods for modeling and analyzing the temperature influence on brake discs of the Mine Hoisting Machine (MHM) have been improved. Based on the research results, recommendations have been developed for the optimum braking process of machines in various operating conditions. [ABSTRACT FROM AUTHOR]

In shis study, yield stress equation, flow rules and physical properties of barium titanate (BaTiO3) are experimentally obtained. These basic equations and coefficient of flow stress are introduced to finite element method and sintering behavior of barium titanate bulk is simulated. From the uni-axis compression test, yield stress equation of BaTiO3 is expressed by Shima's equation and flow rule is written by plastic equiation. The coefficient of flow stress of BaTiO3 is significantly smaller than literature Alumina and the value is different when the grain size is different. The experimental sintering deformation is quantitatively reproduced by numerical simulation, where basic equation and physical properties are exprerimentally introduced. In addition, the coefficient of flow stress could be determined by simulation sensitivily analysis. Through this study, experimentally obtained yield stress equation, flow rules and coefficient of flow stress are numerically validated. [ABSTRACT FROM AUTHOR]

Background and Objectives Due to the location of Iran in an arid and semi-arid climate, the optimal use of water resources systems and better management in water shortage conditions are necessary. One of the appropriate tools in the field of water resources management is the use of simulation, optimization techniques and the combination of simulation and optimization methods. The main goal of this research is to provide a solution in which, according to the capacity of the reservoir, in addition to achieving the acceptable reliability of supplying demands in the whole period, the percentage of meeting the needs in dry months also increases. Methodology To achieve the optimal operation of the water resources in the Marun and Jareh dams located in the south of Iran, the multi-objective particle swarm optimization (MOPSO) algorithm is linked to the WEAP model to provide a new structure for the water resources management, especially in periods of low water by obtaining the optimal values of water release from the reservoir. In this structure, the WEAP simulator is called directly in the MATLAB environment and executed by the optimization algorithm. In this research, for optimal operation of the system, the amount of water released from the reservoir every month is considered as a decision variable. However, due to the large number of available variables and the high volume of calculations, in the body of the MOPSO optimization model, the flow release coefficients that are considered on a monthly basis are used. Based on these coefficients, every month, a percentage of the water volume in the Marun and Jareh reservoirs is released to supply the needs of the downstream uses, and the rest is stored for the better management of the reservoir, especially in water shortage conditions. Therefore, according to the application of these coefficients on a monthly basis, 12 variables are considered for each dam and 24 decision variables in the whole multi-dam system in the entire next 30-year operation period. Findings The optimization process is carried out using the MOPSO multi-objective algorithm. The number of iterations of the algorithm to reach convergence is considered to be around 1000. Finally, after the optimization, according to the population size of 48 and the implementation of the MOPSO model for 1000 iterations, the solutions close to to optimal are obtained, and the optimal exchange curve (Pareto-optimal front) between the optimization objectives (the function of maximizing the supplying percentage and the function of minimizing the violation of the minimum operation level) is achieved. In Pareto curve the solution with the least amount of penalty due to the violation of the reservoir operation capacity and the highest supplying percentage is chosen as the best answer. Then, these optimal variables are entered in the WEAP surface water model. The average percentage of supplying the needs and the level of reliability of meeting the needs for different uses in optimization scenario. in this scenario, the drinking and industrial demands are fully provided in all months. Also, the average percentage of meeting the agricultural demands of the Marun and Jarrahi basins for August, September, October and November was improved by about 15 to 16%, which is significant and shows a decrease in the severity of failure in these low water months. The supplying percentage in July also increases by about 7%. Conclusion The results obtained from the implementation of the optimizer model showed that the percentage of demand supply in the months that was 0% in the reference scenario reached 30-60% and in most of the dry months, it was calculated around 45%. This showed that the optimizer model was able to reduce the failure severity in the worst case and in years with three to eight consecutive dry months. The results showed that according to the application of hedging in the model, some of the need is stored in the high-water months to be consumed in the low water months. This research showed that planning water resources and allocating them to existing uses only by relying on maximizing the reliability of supplying needs in the entire period, especially in areas with dry climates where we inevitably face severe water shortages in several months of the year, is not a suitable solution and leads to irreparable financial losses and social consequences. Instead, using the solution of this research will lead to better management of the reservoir and reduce the severity of the failure to supply the needs in the dry months of low water. [ABSTRACT FROM AUTHOR]

Several means are used for flow measurement, including the flumes that are of interest to the present study. The operating principle of the flume is based on the lateral contraction of the walls of a trapezoidal channel that ends in a triangular section extended by a throat of the same section. The convergent part of the flume accelerates the flow from a subcritical state to a critical state in the throat where a control section is created. Thus, the flow can be determined by taking a single depth reading in the inlet cross-section of the flume. The recommended device is simple and compact in shape, requiring a minimum of space compared to known trapezoidal flumes. Furthermore, the device has been designed to be used in open channels regardless of the shape. Therefore, the flume has the property of being of a universal range. A rigorous theoretical development led to the derivation of the governing discharge coefficient Cd relationship, solely depending on the dimensionless parameter M1 = mh1/b1, where m is the side slope of the flume, h1 is the upstream flow depth, and b1 is the inlet cross-section width of the converging part of the flume. Based on 1023 pairs of values Q-h1 collected from twelve tested flumes of different practical dimensions, the in-depth analysis of laboratory observations corroborated the validity and reliability of the theoretical relationship governing Cd within the wide range 0.10 ≤ M1 ≤ 0.95, since the maximum deviation is only 0.215% when compared to observations. Among the twelve tested devices, only the results of the observations carried out on one device will be presented herein. The observations collected on this device are considered the most unfavourable compared with those carried out on the eleven other tested devices, especially regarding the deviation affecting the discharge coefficient Cd. [ABSTRACT FROM AUTHOR]

The present study examines numerically a three-dimensional (3D) laminar and stationary flow around an idealized metal foam cell shaped as an empty cube with cylindrical edges. The physical configuration adopted consists of an isolated cell placed inside a plane channel crossed by air as a working fluid. The numerical investigation is carried out using the dimensionless Navier-Stokes equations resolved by finite volume method. The flow configurations given for several Reynolds numbers are described entirely using 2D and 3D maps. The plane maps give streamlines at the side and top fiber planes: the vertical side of the cell is normal to the flow. In addition, the critical locations and zones characterizing the flow are also localized: the saddle points, separation nodes, attachment points, foci of the recirculation zones, and the attachment lines. For the Reynolds number in the range 75 ≤ Re ≤ 500, the results show that the topography of the streamlines at the vertical plane in the middle of the lateral fibers of the cell (z = 5.3Dp) is developed into arc-shaped vortex rollers in the gap. In the wake, two saddle points reveal the zones of influence of these spiral structures, formed by two vortices (Bt and Nw) and zones of upwash and downwash. At a high value of Re (Re = 500), the upwash weakens but does not disappear. Two recirculation bubbles are associated with the two saddles, in the gap and the wake of the upper fibers, parallel to the flow. At Re =500, the distribution flow loses its symmetry and displays matter transfer between the two recirculation. The displacement of the saddle point in the wake is 9.65 times that in the gap. No vortex shedding is observed in the wake of cell due to the nullity of the frequency shedding (f = 0).The results indicate also that decreasing the pore diameter favors recirculation inside the cell gap. These recirculation lengths (Lrz, Lry) located respectively in the wake of planes z = 5.3Dp and y = Dp reduce the drag coefficient in equal proportion (51%) in the range 75 ≤ Re ≤ 500. It appears that the wake of the lateral fibers of the z=5.3Dp plane contributes better to the drag coefficient. We consider that the predominance of downwash associated with the instability of saddle point S.2 in the wake when Re increases leads to a decrease in the drag coefficient in the wake. [ABSTRACT FROM AUTHOR]

Aiming at the compliant end face gas film seal structure, based on the linearized Boltzmann equation, the Poiseuille flow coefficient is introduced, and the generalized Reynolds equation and the sealing performance parameter solution formula considering the boundary slip flow effect are established. Through Newton–Raphson iterative calculation, the degree of influence of the slip flow effect under different working conditions is analyzed, and the internal relationship between structural parameters and sealing performance is compared. The results show that the slip flow effect can have a large impact on the pressure distribution in the fluid field close to the low-pressure side. Due to the existence of the step phenomenon of boundary velocity, it is not conducive to increasing the gas film opening force and controlling the mass leakage rate, but it can play a positive role in reducing the viscous friction power consumption. In the case of a smaller sealing gas film thickness and lower medium pressure, the slip flow effect is significant, which will have a greater impact on the sealing performance, and at this time, the slip flow effect can not be ignored. In addition, the change in seal structure parameters will also have a large impact on the sealing performance. With an increase in the wave foil thickness, the compliant end face evolves towards the rigid end face, the fluid wedge effect is weakened, and the gas film opening force and mass leakage rate are reduced. The stiffness-to-leakage ratio shows a strong nonlinear decreasing trend with an increase in the wave foil chord length and pitch, which eventually tends to a stable value. The results of this paper provide a theoretical basis for the matching design of the structural parameters of compliant end-face gas film seals under different service conditions. [ABSTRACT FROM AUTHOR]

Water resource management is an important issue in a region where water resources are far from residential areas. Pipelines can provide a water connection between water resources and residential areas. Control valves are useful in controlling the supply of water based on a time table, faciliting effective manangement of the amount of water supplied. A control valve system with an independent electric energy source (CVS-IEES) can minimize maintenance costs in desert or jungle areas, where maintenance by human efforts may be insufficient. This study suggests that two types of tests, namely, repeatability and flow coefficient tests, can provide the impetus for designing the CVS-IEES. The repeatability test measures the number of repeatable operations of opening and closing an on/off valve. Test result showed that a fluid volume of 15 L at a pressure difference of 5 bar (gage) was feasible for operating a pneumatic on/off valve with a pipe size of 200 mm within 1 s, and the torque must be 7500 N·m. The flow coefficient test result was a function of the valve opening ratio (or aperture rate). The flow coefficient of a control valve with a pipe size of 50 mm was Kv = (2.48 ± 0.20) m3/bar0.5·h at q = 3.94 m3/h. The measurement uncertainty of 0.20 m3/bar0.5·h enables the CVS-IEES designers to estimate the accuracy when controlling the amount of supplied water. [ABSTRACT FROM AUTHOR]

The Oscillating Water Column (OWC) is the most promising self-rectifying device for power generation from ocean waves; over the past decade, its importance has been rekindled. The bidirectional airflow inside the OWC drives the Wells turbine connected to a generator to harness energy. This study evaluated the aerodynamic performance of two hybrid airfoil (NACA0015 and NACA0025) blade designs with variable chord distribution along the span of a Wells turbine. The present work examines the aerodynamic impact of the variable chord turbine and compares it with one with a constant chord. Ideally, Wells rotor blades with variable chords perform better since they have an even axial velocity distribution on their leading edge. The variable chord rotor blade configurations differ from hub to tip with taper ratios (Chord at Tip/Chord at Hub) of 1.58 and 0.63. The computation is performed in ANSYS™ CFX 2023 R2 by solving three-dimensional, steady-state, incompressible Reynolds Averaged Navier–Stokes (RANS) equations coupled with a k-ω Shear Stress Transport (SST) turbulence model in a non-inertial reference frame rotating with the turbine. The accuracy of the numerical results was achieved by performing a grid independence study. A refined mesh showed good agreement with the available experimental and numerical data in terms of efficiency, torque, and pressure drop at different flow coefficients. A variable chord Wells turbine with a taper ratio of 1.58 had a peak efficiency of 59.6%, as opposed to the one with a taper ratio of 0.63, which had a peak efficiency of 58.2%; the constant chord Wells turbine only had a peak efficiency of 58.5%. Furthermore, the variable chord rotor with the higher taper ratio had a larger operating range than others. There are significant improvements in the aerodynamic performance of the modified Wells turbine, compared to the conventional Wells turbine, which makes it suitable for wave energy harvesting. The flow field investigation around the turbine blades was conducted and analyzed. [ABSTRACT FROM AUTHOR]

To improve the leakage performance of the turbine interstage seal, a stepped labyrinth seal structure with a diversion channel is designed. The influence of the diversion channel on the leakage and heating characteristics of the labyrinth seal is investigated under various pressure ratios and rotational speeds, and compared with the smooth labyrinth seal. The results show that adding a diversion channel on the casing enhances the sealing effect of the labyrinth seal by allowing airflow at the outlet to be rolled and sucked into the channel under the effect of centrifugal force. The larger the circumferential clearance rate βof the diverter channel, the better the sealing performance. When the circumferential clearing rate β is 3, the insulated wall flow coefficient is 13.47% and the insulated wall wind resistance temperature rises by 48.7 K. The increase in the number of diversion channels intensifies the leakage of the seal. As the pressure ratio grows, the sealing leakage increases, and the diversion channel may guide the core flow return, so the leakage growth rate gradually slows down while the insulated wall wind resistance temperature rise growth rate increases. As the rotational speed increases from 3×10³ r/min to 2.1×104 r/min, the airflow friction diffusion worsens, the labyrinth seal insulated wall flow coefficient decreases, the insulated wall wind resistance temperature rises. and the diversion channel improves the labyrinth seal's sealing effect at high rotational speed. [ABSTRACT FROM AUTHOR]