Optimal Design of High-Speed Partial Flow Pumps using Orthogonal Tests and Numerical Simulations

To investigate the influence of structural parameters on the performances and internal flow characteristics of partial flow pumps at a low specific speed of 10000 rpm,special attention was paid to the first and second stage impeller guide vanes.Moreover,the impeller blade outlet width,impeller inlet diameter,blade inclination angle,and number of blades were considered for orthogonal tests.Accordingly,nine groups of design solutions were formed,and then used as a basis for the execution of numerical simulations(CFD)aimed at obtaining the efficiency values and heads for each design solution group.The influence of impeller geometric parameters on the efficiency and head was explored,and the“weight”of each factor was obtained via a range analysis.Optimal structural parameters were finally chosen on the basis of the numerical simulation results,and the performances of the optimized model were verified accordingly(yet by means of CFD).Evidence is provided that the increase in the efficiency and head of the optimized model was 12.11%and 23.5 m,respectively,compared with those of the original model.

Effect of movability of water on the low-velocity pre-Darcy flow in clay soil

Water seepage in soil is a fundamental problem involving various scientific and engineering fields.According to the literature,low-velocity water seepage in low-permeability porous media,such as clay,does not follow Darcy's law,also known as pre-Darcy flow.The formation of immovable water due to water adsorption on the pore wall is believed to be responsible for the formation of pre-Darcy flow.However,this view lacks direct solid evidence.To investigate the pre-Darcy water flow in clay,head permeability experiments are conducted on six clay samples with different densities.The results indicate that water seepage in clay at low hydraulic gradients does not follow Darcy's law.A clear nonlinear relationship between flow velocity and hydraulic gradient is observed.Water flow in clay can be divided into the pre-Darcy flow and Darcy flow regions by the critical hydraulic gradient,which is 10-12 for the Albic soil with dry density between 1.3 g/cm^(3)and 1.8 g/cm^(3).According to the disjoining pressure theory,immovable water due to water adsorption on the pore wall is the primary reason for water flow deviating from Darcy's law in clay.The results indicate that the percentage of movable water ranges from 39.7%to 59.3%for the six samples at a hydraulic gradient of 1.As the hydraulic gradient increases,the percentage of moveable water also increases.Additionally,there is a strong correlation between the percentage of movable water and the variation in hydraulic conductivity with the hydraulic gradient.Furthermore,a quantitative relationship between the percentage of movable water and the hydraulic conductivity has been established.The results of this study suggest that water adsorption on the pore wall not only affects the water movability,but is also closely related to the pre-Darcy flow phenomenon in clay.

Regulation effect of the grille spacing of a funnel-type grating water–sediment separation structure on the debris flow performance

The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve the water–sediment separation ability of the structure.The new funnel-type grating water–sediment separation structure(FGWSS)combines vertical and horizontal structures and provides a satisfactory water–sediment separation effect.However,the regulation effect of the grille spacing of the structure on the debris flow performance has not been studied.The regulation effect of the structure grille spacing on the debris flow performance is studied through a flume test,and the optimal structure grille spacing is obtained.An empirical equation of the relationship between the relative grille spacing of the structure and the sediment separation rate is established.Finally,the influence of the water–sediment separation structure on the regulation effect of debris flows is examined from two aspects:external factors(properties of debris flows)and internal factors(structural factors).The experimental results show that the gradation characteristics of solid particles in debris flows constitute a key factor affecting the regulation effect of the structure on the debris flow performance.The optimum grille spacing of the FGWSS matches the particle size corresponding to the material distribution curves d85~d90 of the debris flow.The total separation rate of debris flow particles is related to the grille spacing of the structure and the content of coarse and fine particles in the debris flow.

Analysis of the Flow Field and Impact Force in High-Pressure Water Descaling

This study aims to improve the performances of the high-pressure water descaling technology used in steel hot rolling processes.In particular,a 2050 mm hot rolling line is considered,and the problem is investigated by means of a fluid–structure interaction(FSI)method by which the descaling effect produced by rolling coils with different section sizes is examined.Assuming a flat fan-shaped nozzle at the entrance of the R1R2 roughing mill,the outflow field characteristics and the velocity distribution curve on the strike line(at a target distance of 30–120 mm)are determined.It is found that the velocity in the center region of the water jet with different target distances is higher than that in the boundary region.As the target distance increases,the velocity of the water jet in the central region decreases.Through comparison with experimental results,it is shown that the simulation model can accurately predict the impact position of the high-pressure water on the impact plate,thereby providing a computational scheme that can be used to optimize the nozzle space layout and improve the slabs’descent effect for different rolling specifications.

Impact of water table on hierarchically nested groundwater flow system

Water table configuration gives rise to hierarchically nested groundwater flow systems.However,there remains a lack of comprehensive understanding regarding the controlling factors of water table and its impact on flow systems.Moreover,it remains challenging to identify characteristics of water table space variation through limited groundwater observations at the regional scale.Based on two ideal two-dimensional cross-section analytical models,this study presents a simplified approach to preliminarily assess the nonlinear interactions between water table variation and three driving factors:Topography,geol-ogy and climate.Two criteria,C1 and C2,are utilized to address issues at different scales ranging from basin to local:(i)the influence of various factors on water table configuration;and(ii)the influence of water table on groundwater flow pattern.Then,the Ordos Plateau is taken as an example to explore the role of the water table in nested groundwater systems using the provided approach and criterion.The applica-tion of this approach in the Ordos Plateau demonstrates its appropriateness as a practical method for prelim-inarily determining the characteristics of water table configuration and its impact on flow systems.The study explores the mechanism influencing spatial variation in the water table and improves understanding of the interaction between topography,geology,and climate on groundwater flow patterns.

Performance of a Horizontal Flow Constructed Reed Bed Filter for Municipal Wastewater Treatment: The Case Study of the Prototype Installed at Gaston Berger University, Saint-Louis, Senegal

In Saint-Louis, Senegal, a constructed wetland with horizontal flow reed beds (FHa and FHb) has demonstrated significant efficacy in treating municipal wastewater. Analyzing various treatment stages, the system showed only a slight temperature variation, from an influent average of 26.3°C to an effluent of 24.7°C. Electrical conductivity decreased from 1331 mS/cm to 974.5 mS/cm post-primary treatment, with suspended solids (SS) dramatically reduced from 718.9 mg/L to 5.7 mg/L in the final effluent. Biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) saw a notable decrease, from initial levels of 655.6 mg/L and 1240 mg/L to 2.3 mg/L and 71.3 mg/L, respectively. Nitrogenous compounds (N-TN) and phosphates () also decreased significantly, indicating the system’s nutrient removal capacity. Microbiological analysis revealed a reduction in fecal coliforms from 7.5 Ulog/100ml to 1.8 Ulog/100ml and a complete elimination of helminth eggs. The presence of Phragmites and Typha was instrumental in enhancing these reductions. The system’s compliance with the Senegalese standards for disposal into natural environments, WHO recommendations for unrestricted water reuse in irrigation, and the European legislation for water reuse was established. The effluent quality met the stringent criteria for various classes of agricultural reuse, illustrating the system’s potential for sustainable water management. This wetland model presents a robust solution for water-stressed regions, ensuring environmental protection while supporting agricultural needs. The study calls for ongoing research to further refine the system for optimal, reliable wastewater treatment and water resource sustainability.

Dynamic Characteristics of High-speed Water-Lubricated Spiral Groove Thrust Bearing Based on Turbulent Cavitating Flow Lubrication Model

The water-lubricated bearings are usually the state of turbulent cavitating flow under high-speed conditions. And the distribution of cavitation bubbles and the interface effect between the two phases have not been included in previous studies on high-speed water-lubricated bearings. In order to study the influence of interface effect and cavitation bubble distribution on the dynamic characteristics of high-speed water-lubricated spiral groove thrust bearings(SGTB).A turbulent cavitating flow lubrication model based on two-phase fluid and population balance equation of bubbles was established in this paper. Stiffness and the damping coefficients of the SGTB were calculated using the perturbation pressure equations. An experimental apparatus was developed to verify the theoretical model. Simulating and experimental results show that the small-sized bubbles tend to generate in the turbulent cavitating flow when at a high rotary speed, and the bubbles mainly locate at the edges of the spiral groove. The simulating results also show that the direct stiffness coefficients are increased due to cavitation effect, and cross stiffness coefficients and damping coefficients are hardly affected by the cavitation effect. Turbulent effect on the dynamic characteristics of SGTB is much stronger than the cavitating effect.

Numerical Simulation of the Influence of Water Flow on the Piers of a Bridge for Different Incidence Angles

A two-dimensional mathematical model is used to simulate the influence of water flow on the piers of a bridge for different incidence angles.In particular,a finite volume method is used to discretize the Navier-Stokes control equations and calculate the circumferential pressure coefficient distribution on the bridge piers’surface.The results show that the deflection of the flow is non-monotonic.It first increases and then decreases with an increase in the skew angle.

Permeability evolution and gas flow in wet coal under non-equilibrium state:Considering both water swelling and process-based gas swelling

Accurate knowledge of gas flow within the reservoir and related controlling factors will be important for enhancing the production of coal bed methane.At present,most studies focused on the permeability evolution of dry coal under gas adsorption equilibrium,gas flow and gas diffusion within wet coal under the generally non-equilibrium state are often ignored in the process of gas recovery.In this study,an improved apparent permeability model is proposed which accommodates the water and gas adsorption,stress dependence,water film thickness and gas flow regimes.In the process of modeling,the water adsorption is only affected by water content while the gas adsorption is time and water content dependent;based on poroelastic mechanics,the effective fracture aperture and effective pore radius are derived;and then the variation in water film thickness for different pore types under the effect of water content,stress and adsorption swelling are modeled;the flow regimes are considered based on Beskok’s model.Further,after validation with experimental data,the proposed model was applied to numerical simulations to investigate the evolution of permeability-related factors under the effect of different water contents.The gas flow in wet coal under the non-equilibrium state is explicitly revealed.

Operational guidance for aeration and flow augmentation for the Chicago Area Waterway System—A case study

The Chicago Area Waterway System(CAWS)is a 133.9 km branching network of navigable waterways controlled by hydraulic structures,in which the majority of the flow is treated wastewater effluent and there are periods of substantial combined sewer overflows.The CAWS comprises a network of effluent dominated streams.More stringent dissolved oxygen(DO)standards and a reduced flow augmentation allowance have been recently applied to the CAWS.Therefore,a carefully calibrated and verified one-dimensional flow and water quality model was applied to the CAWS to determine emission-based real-time control guidelines for the operation of flow augmentation and aeration stations.The goal of these guidelines was to attain DO standards at least 95%of the time.The“optimal”guidelines were tested for representative normal,dry,and wet years.The finally proposed guidelines were found in the simulations to attain the 95%target for nearly all locations in the CAWS for the three test years.The developed operational guidelines have been applied since 2018 and have shown improved attainment of the DO standards throughout the CAWS while at the same time achieving similar energy use at the aeration stations on the Calumet River system,greatly lowered energy use on the Chicago River system,and greatly lowered discretionary diversion from Lake Michigan,meeting the recently enacted lower amount of allowed annual discretionary diversion.This case study indicates that emission-based real-time control developed from a well calibrated model holds potential to help many receiving water bodies achieve high attainment of water quality standards.

Observed characteristics of flow,water mass,and turbulent mixing in the Preparis Channel

Preparis Channel is the very important exchange path of energy and materials between the northern Bay of Bengal and Andaman Sea(AS).A set of hydrographic measurements,a microstructure profiler,and a deep mooring were used to determine the characteristics of water masses,turbulent mixing,and flows in the Preparis Channel.The unprecedented short-term mooring data reveal that a deep current in the deep narrow passage(below 400 m)of the Preparis Channel flows toward the Bay of Bengal(BoB)with a mean along-stream velocity of 25.26 cm/s at depth of 540 m;above the deep current,there are a relatively weak current flows toward the AS with a mean along-stream velocity of 15.46 cm/s between 500 m and 520 m,and another weak current flows toward the BoB between 430 m and 500 m.Thus,a sandwiched vertical structure of deep currents(below 400 m)is present in the Preparis Channel.The volume transport below 400 m is 0.06 Sv(1 Sv=106 m^(3)/s)from the AS to the BoB.In the upper layer(shallower than 300 m),the sea water of the AS is relatively warmer and fresher than that in the BoB,indicating a strong exchange through the channel.Microstructure profiler observations reveal that the turbulent diffusivity in the upper layer of the Preparis Channel reaches O(10−4 m^(2)/s),one order larger than that in the interior of the BoB and over the continental slope of the northern AS.We speculate that energetic high-mode internal tides in the Preparis Channel contribute to elevated turbulent mixing.In addition,a local“hotspot”of turbidity is identified at the deep mooring site,at depth of about 100 m,which corresponds to the location of elevated turbulent mixing in the Preparis Channel.

Photothermal-photocatalytic thin-layer flow system for synergistic treatment of wastewater

The integration of the photocatalytic effect into solar steam is highly desirable for addressing freshwater shortages and water pollution.Here,a ternary film structure for the adsorption and photothermal and photocatalytic treatment of wastewater was designed by combining the technique of self-assembled carbon nano paper with a nitrogen composite titanium dioxide(N-TiO_(2))deposited on the surface of carbon nanotubes(CNT)using polyvinylidene fluoride(PVDF)as a substrate.The photogeneration of reactive oxygen species can be promoted by rapid oxygen diffusion at the three-phase interface,whereas the interfacial photothermal effect promotes subsequent free radical reactions for the degradation of rhodamine B(93%).The freshwater evaporation rate is 1.35 kg·m^(-2)·h^(-1)and the solar-to-water evaporation efficiency is 94%.Importantly,the N-TiO_(2)/CNT/PVDF(N-TCP)film not only effectively resists mechanical damage from the environment and maintains structural integrity,but can also be made into a large film for outdoor experiments in a large solar energy conversion device to collect fresh water from polluted water and degrade organic dyes in source water simultaneously,opening the way for applications in energy conversion and storage.

Effect of cavity flow control on high-speed train pantograph and roof aerodynamic noise

The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains.Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph.However,less attention has been paid to the pantograph recess compared with the pantograph.In this paper,the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess,which is represented as a rectangular cavity and numerically investigated at 1/10 scale.Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation,and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction.The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications,and consequently,the noise radiated from the cavity is reduced.Furthermore,effects of the rounded cavity edges on the flow and noise of the pantographs(one raised and one folded)are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges.Different train running directions are also considered.Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph,whereas the flow velocity in the cavity is slightly increased by the rounding.Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph,whereas weaker fluctuations are found on the panhead of the raised pantograph.This study shows that by rounding the cavity edges,a reduction in radiated noise at the side and the top receiver positions can be achieved.Noise reductions in the other directions can also be found.

PIV analysis and high-speed photographic observation of cavitating flow field behind circular multi-orifice plates

Based on a self-developed hydrodynamic cavitation device with different geometric parameters for circular multi-orifice plates,turbulence characteristics of cavitating flow behind multi-orifice plates,including the effects of orifice number and orifice layout on longitudinal velocity,turbulence intensity,and Reynolds stress,were measured with the particle image velocimetry(PIV)technique.Flow regimes of the cavitating flow were also observed with high-speed photography.The experimental results showed the following:(1)high-velocity multiple cavitating jets occurred behind the multi-orifice plates,and the cavitating flow fields were characterized by topological structures;(2)the longitudinal velocity at each cross-section exhibited a sawtooth-like distribution close to the multi-orifice plate,and each sawtooth indicated one jet issuing from one orifice;(3)there were similar magnitudes and forms for the longitudinal and vertical turbulence intensities at the same cross-section;(4)the variation in amplitude of Reynolds stress increased with an increase in orifice number;and(5)the cavitation clouds in the flow fields became denser with the increase in orifice number,and the clouds generated by the staggered layout of orifices were greater in number than those generated by the checkerboard-type one for the same orifice number.The experimental results can be used to analyze the mechanism of killing pathogenic microorganisms through hydrodynamic cavitation.

A Hydrogen Iron Flow Battery with High Current Density and Long Cyclability Enabled Through Circular Water Management

The hydrogen-iron(HyFe)flow cell has great potential for long-duration energy storage by capitalizing on the advantages of both electrolyzers and flow batteries.However,its operation at high current density(high power)and over continuous cycling testing has yet to be demonstrated.In this paper,we discuss our design and demonstration of a water management strategy that supports high current and long cycling performance of a HyFe flow cell.Water molecules associated with the movement of protons from the iron electrode to the hydrogen electrode are sufficient to hydrate the membrane and electrode at a low current density of 100 mA cm^(-2)during the charge process.At higher charge current density,more aggressive measures must be taken to counter back-diffusion driven by the acid concentration gradient between the iron and hydrogen electrodes.Our water management approach is based on water vapor feeding in the hydrogen electrode,and water evaporation in the iron electrode,thus enabling the high current density operation of 300 mA cm^(-2).

Comparison of Methods for Estimating Crop Water Use: Sap Flow, FAO-56 Penman-Monteith, and Weather Parameters

Knowing crop water uptake each day is useful for developing irrigation scheduling. Many technologies have been used to estimate daily crop water use. Sap flow is one of the technologies that measure water flow through the stem of a plant and estimate daily crop water uptake. Sap flow sensor is an effective direct method for measuring crop water use, but it is relatively expensive and requires frequent maintenance. Therefore, alternative methods, such as evapotranspiration based on FAO 56 Penman-Monteith equation and other weather parameters were evaluated to find the correlation with sap flow. In this study, Dynamax Flow 32-1K sap flow system was utilized to monitor potato water use. The results show sap flow has a strong correlation with evapotranspiration (RMSE = 1.34, IA = 0.89, MBE = -0.83), solar radiation (RMSE = 2.25, IA = 0.72, MBE = -1.80), but not with air temperature, relative humidity, wind speed, and vapor pressure. It is worth noting that the R2 between sap flow and relative humidity was 0.55. This study has concluded that daily evapotranspiration and solar radiation can be used as alternative methods to estimate sap flow.

PREDICTION OF FLOW STRESS OF HIGH-SPEED STEEL DURING HOT DEFORMATION BY USING BP ARTIFICIAL NEURAL NETWORK

The hot deformation behavior of TI (18W-4Cr-1V) high-speed steel was investigated by means of continuous compression tests performed on Gleeble 1500 thermomechan- ical simulator in a wide range of tempemtures (950℃-1150℃) with strain rotes of 0.001s-1-10s-1 and true strains of 0-0. 7. The flow stress at the above hot defor- mation conditions is predicted by using BP artificial neural network. The architecture of network includes there are three input parameters:strain rate,temperature T and true strain , and just one output parameter, the flow stress ,2 hidden layers are adopted, the first hidden layer includes 9 neurons and second 10 negroes. It has been verified that BP artificial neural network with 3-9-10-1 architecture can predict flow stress of high-speed steel during hot deformation very well. Compared with the prediction method of flow stress by using Zaped-Holloman parumeter and hyperbolic sine stress function, the prediction method by using BP artificial neurul network has higher efficiency and accuracy.

A Hydrogen Iron Flow Battery with High Current Density and Long Cyclability Enabled Through Circular Water Management

The hydrogen-iron(HyFe)flow cell has great potential for long-duration energy storage by capitalizing on the advantages of both electrolyzers and flow batteries.However,its operation at high current density(high power)and over continuous cycling testing has yet to be demonstrated.In this article,we discuss our design and demonstration of a water-management strategy that supports high current and long-cycling performance of a HyFe flow cell.Water molecules associated with the movement of protons from the iron electrode to the hydrogen electrode are sufficient to hydrate the membrane and electrode at a low current density of 100 mA cm^(-2)during the charge process.At higher charge current density,more aggressive measures must be taken to counter back-diffusion driven by the acid concentration gradient between the iron and hydrogen electrodes.Our water-management approach is based on water vapor feeding in the hydrogen electrode and water evaporation in the iron electrode,thus enabling high current density operation of 300 mA cm^(-2).

Quantitative research of the liquid film characteristics in upward vertical gas, oil and water flows

The study of liquid film characteristics in multiphase flow is a very important research topic, however,the characteristics of the liquid film around Taylor bubble structure in gas, oil and water three-phase flow are not clear. In the present study, a novel liquid film sensor is applied to measure the distributed signals of the liquid film in three-phase flow. Based on the liquid film signals, the liquid film characteristics including the structural characteristics and the nonlinear dynamics characteristics in three-phase flows are investigated for the first time. The structural characteristics including the proportion, the appearance frequency and the thickness of the liquid film are obtained and the influences of the liquid and gas superficial velocities and the oil content on them are investigated. To investigate the nonlinear dynamics characteristics of the liquid film with the changing flow conditions, the entropy analysis is introduced to successfully uncover and quantify the dynamic complexity of the liquid film behavior.

RESEARCH ON ABRASION OF DEBRIS FLOW TO HIGH-SPEED DRAINAGE STRUCTURE

As one weak topic in research of debris flow,abrasion of debris flow shortens obviously application life of control structure composed of concrete.High_speed drainage structure,one of the most effective techniques to control giant debris flow disaster,has shortened one_third application life due to abrasion by debris flow.Based on velocity calculation method founded by two_phase theory,research of abrasion mechanism of debris flow to high_speed drainage structure was made.The mechanism includes both abrasion mechanism of homogeneous sizing and shearing mechanism of particle of debris flow to high_speed drainage trough structure.Further abrasion equations of both sizing and particle were established by Newton movement theory of debris flow.And abrasion amount formula of the high_speed drainage trough structure is set up by dimensional analysis.Amount to calculating in the formula is consistent with testing data in_situ,which is valuable in design of high_speed drainage structure.