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Copyright of Materiały Budowlane is the property of Wydawnictwo SIGMA-NOT 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.)

As a three-dimensional flow channel, the laminated filter has a complex structure, and it is easy to appear phenomena such as too short blocking time and increasing head loss caused by sand interception in the operation process. According to the relationship between head loss and cross-sectional area, an annular flow channel laminated filter was proposed. The circumferential flow channel was added on the lamination surface, which increased the flow direction of the flow channel and played the role of dividing the radial flow channel, achieving the purpose of hierarchical multi-layer filtration in the lamination and improving the number of available flow channels. In order to explore the advantages and disadvantages of the linear flow channel and annular flow channel laminated filter for irrigation water filtration capacity. Through indoor comparative experiments, 120 mesh laminated filter, namely the filter particle size of 125 μm was used to test the head loss and filtration performance of the two filters under four kinds of sand grading median particle size (106, 121, 126 and 165 μm), three kinds of sediment content (0.10, 0.15 and 0.2 g/L) and five kinds of inlet flow (1.5, 2.0, 2.5, 3.0 and 3.5m3 /h), a total of 60 groups of tests. The dependent variables were the head loss, the sediment retention capacity and the median particle size of the interception, and the independent variables were the inlet flow, the sediment concentration and the median particle size of the inlet. The evaluation indexes were the head loss, the plugging uniformity, the sediment retention capacity and the particle size distribution of the interception sediment. The multiple regression equation was established to verify the correlation between the head loss and the filtration capacity. The entropy weight method was used to determine the optimal lamination of the head loss and the filtration capacity. The results show that: under the condition of clear water, the maximum flow head loss of the annular flow laminated filter is 9.1% lower than that of the trapezoidal linear filter. Under the condition of sandy water, the time for the head loss to reach 8m is 1.5～10 times longer than that of the trapezoidal linear filter, and the maximum head loss is reduced by 52.5%. The total sediment retention capacity is increased by 0.5%～6.3%, and the average sand removal rate is increased by 0.22% for the sand with the median particle size greater than 110μm. The siltation channels of the trapezoidal linear filter account for 25%～ 86% of the total number of channels of the trapezoidal lamination, while no siltation phenomenon is observed in the operation cycle of the annular lamination. The head loss of the two kinds of laminated filters was positively correlated with the sediment concentration, inlet flow and inlet median particle size, the sediment retention was positively correlated with the sediment concentration, inlet flow and inlet median particle size, and the interception median particle size was positively correlated with the sediment concentration and inlet median particle size. The annular flow channel laminated filter was more suitable for irrigation water with high sediment concentration and high median particle size distribution than the trapezoidal linear laminated filter. Therefore, the optimal laminated filter can be designed by considering the change of the geometric distribution of the flow channel of the laminated filter, which can reduce the filter head loss and extend its backwashing cycle without reducing the filtration capacity. [ABSTRACT FROM AUTHOR]

To investigate the hydraulic effects and performance of the micro-pressure filtration and cleaning tank under conditions with sandy and brackish water, physical model tests were conducted with five groups of flow rates (6–14 m³ h−1), four groups of sediment contents (0.5–2.0 g l−1), five groups of mineralisation degrees (0–5.0 g l−1), and three groups of screen apertures (0.125, 0.150, and 0.180 mm). Dimensional analysis, multiple linear regression analysis, and the non-dominated sorting genetic algorithm II (NSGA-II) were used to analyse the test results. The results showed that the optimal operating conditions of the micro-pressure filtration and cleaning tank under the scope of this test were a screen aperture of 0.175 mm, a flow rate of 13 m3 h−1, a sediment content of 1.8 g l−1, and a mineralisation degree of 4.7 g l−1. The micro-pressure filtration and cleaning tank was intermittently discharged and rinsed, the discharge time was 30–40 s, and the flow rate of discharge and rinsing was 5.54 m3 h−1. Prediction models of the head loss and the filtration efficiency of the filter were established. The coefficients of determination (R2) were greater than 0.9, the average relative errors of the predicted and measured values were 2.98% and 2.17%, respectively, and the corresponding root mean square errors were 0.0549 m and 0.642. The research results can be used as a reference for in-depth investigations on the performance of the micro-pressure filtration equipment in front of pumps. • Head loss and filtration efficiency models of pre-pump filters were established. • Optimal working condition of the filter was obtained using NSGA-II. • Optimal discharge time and discharge flow rate were determined. [ABSTRACT FROM AUTHOR]

Air can have an adverse effect on the performance of an aero-engine lubrication system. A numerical analysis was conducted to explore the influence of inlet void fraction and pipe layout on the characteristics of oil-gas two-phase flow in a 90° elbow. The pipes were arranged horizontally and vertically with inlet void fractions of 0.05-0.15. The laws governing flow velocity, void fraction, and pressure along the pipe were determined separately. The results revealed the formation of large-scale vortices with high gas volume fractions inside both types of elbows, which exacerbate oil-gas separation and cause additional head loss. The maximum pressure drop was observed at approximately one pipe diameter downstream of the elbow outlet, which initially increases with the inlet void fraction and then gradually stabilizes. Asymmetric secondary flow vortices in the horizontal elbow were found to enhance oil-gas separation and accelerate lubricating oil to greater extent than in a vertical elbow under the same conditions. Consequently, the maximum pressure drop caused by flowing through the horizontal elbow is higher than that in the vertical elbow. [ABSTRACT FROM AUTHOR]

One of the most basic issues in fluid mechanics is the description of flow in closed flows; more precisely, the calculation of pressure drops and the description of the flow form. Therefore, in this paper, the numerical simulation of the flow through the elbow was presented. This case was used to comprehensively describe the most important phenomena that should be taken into account during closed flows. The elbow was chosen as one of the most frequently used fittings in practice. The simulation was made with ANSYS Fluent, with the use of the turbulent model k-ω, SIMPLE simulation method, and at Reynolds number R e = 500 − 100 , 000 . The minor and major pressure loss were presented and discussed in the paper. The minor loss coefficient at the high Reynolds number was equal to around 0.2, which is close to the value of 0.22 used in engineering calculations. The influence of the Reynolds number on the shift of the stream separation point in the elbow was described. The secondary flow in the elbow was observed and the vortex structure was discussed and shown with the use of the Q-criterion (Q iso surface for level 0.005). This analysis allowed us to better visualize and describe the complex flow structure observed in the investigated case. [ABSTRACT FROM AUTHOR]

Copyright of Water Conservancy Science & Techonlogy & Economy is the property of Water Conservancy Science & Technology & Economy Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of natural additives in pipeline transportation has gained significant attention in recent years due to their potential to enhance the stability and rheology of the suspension. In this study, the dispersing and stabilizing properties of the saponin extracted from the fruits of Sapindus laurifolia are examined in the pipeline transportation of limestone. The physicochemical, morphological, and flow characteristics of limestone samples less than 75 μm are determined. The rheological behaviors of the suspension have been examined by varying the shear rate, solid, and dispersion concentrations. The critical micelle concentration of the dispersant was determined to be 1.8 wt%. In the tested concentration ranges of 40–70%, the Hershel–Bulkley model best matched the data. When the surfactant was added to the suspension, the water's surface tension was lowered, increasing the wettability of the limestone particles and decreasing particle-particle contact. Increases in zeta potential measurements confirmed that the steric component primarily stabilizes limestone water suspension. Finally, the dispersant's economic impact was studied depending on slurry head loss and specific energy consumption. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office 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.)

【Objective】 Pump often has a filter installed in the front of it to filter sediments and debris. This paper studied its efficiency and performance. 【Method】 The study was based on physical model, with flow rate being 2-8 m3/h, sediment content being 0.5-2.0 g/L. The area of the filter varied from 1 105 to 2 060 cm2, and water separator type was Type 1, Type 2, Type 3. Without a separator was the control. A prediction model was used to evaluate sediment interception and total filtration efficiency. Based on these measurements, we determined the optimal operating conditions for the pump. 【Result】 The factors that influenced water head loss across the filter were ranked in the order of inlet flow > sediment content > filter area; the factors that affected the quality of sediment interception were ranked in the order of sediment content > filter area > inlet flow; the factors impacting the total filtration efficiency were ranked in the order of filter area > sediment content > inlet flow. The accuracy of the PPR model for predicting sediment interception quality and total filtration efficiency was 100%, with a relative error less than 10%, while its accuracy for predicting water head loss across the filter was 70%, which needs further improvement. The optimal operating conditions for the filter were sand content 2 g/L, inlet water flow rate 7 m3/h, and filter area 2 060 cm2. 【Conclusion】 The PPR prediction model was accurate for sediment interception and total filtration efficiency, but it resulted in errors for calculating water head loss across the filter. Dimensional analysis and multiple regression can be used as an alternative to predict the water head loss.

Purpose: to state hydraulic characteristics and determine priority directions for improving the irrigation module design for combined drip and micro-sprinkler irrigation. Materials and methods. The study is based on the joint use of theoretical methods – a well-known mathematical model for calculating the hydraulic characteristics of the irrigation module and experiment, which allows assessing the problem state and scale solutions in any necessary proportions. Results. According to calculations, the uniformity of watering is maintained at an acceptable level at a lower head level in the range of 1.56–1.68 atm when installing six microsprinklers on a drip line. When installing eight sprinklers, the water head along the length of the drip pipeline decreased to an unacceptable 1.39–1.40 atm. Experimental studies have shown that there is only an option with two sprinklers installed on the pipeline above the level of 1.5 atm. Already with the installation of four sprinklers, the water head along the length of the pipeline decreased to 1.45–1.47 atm. At the same time, the variation in the actual microsprinkler performance reached 16 % or more. The discrepancy between experimental and model data is explained by the fact that the calculation model does not fully take into account local resistances that arise when connecting sprinklers. Conclusions. Two main reasons of the increased uneven distribution of irrigation water over the irrigated area have been identified. The first reason is a significant increase in water flow in the irrigation pipeline when emitters and sprinklers work together. The solution to this problem is to develop structures that make it possible to separate the water flow through emitters and through sprinklers in time. The second reason is an increase in local resistance in the water diversion units to the sprinklers. The solution to this problem is to develop special water diversion structures that would be characterized by minimal local resistance.

In this experimental work, the 2-phase air-water non-boiling ascending fluid flow in a vertical tube with helical corrugations has been investigated. The results showed that the head loss values decreased with an increase of the volume fraction. Also, by comparing the head loss values for each corrugation pitch, it can be observed that as the corrugation pitch goes down, the head loss values significantly increase. As a result, the intensity of vapors increases perpendicular to the main flow of water, which leads to an increase in the intensity of disturbance in the flow, and then the head loss increases. The Nusselt number goes down when the volume fraction experiences an increment. Looking at the figures related to Nusselt number, it is easy to see that the curves are drawn for a constant air flow rate. Consequently, an increase in volume fraction (VF) is equal to a decrease in the water flow rate. By reducing the water flow rate, the intensity of the main flow is reduced the intensity of turbulence is also reduced and the heat transfer coefficient is reduced. As a result, the amount of heat transfer has increased due to air injection. It should be noted that pipes with the largest corrugation pitch had the best Cost-benefit ratio (C.B.R.) factor values (which means the lowest value). This means that air injection in larger corrugation pitch tubes was more beneficial than in smaller corrugation pitch tubes.

Air can have an adverse effect on the performance of an aero-engine lubrication system. A numerical analysis was conducted to explore the influence of inlet void fraction and pipe layout on the characteristics of oil-gas two-phase flow in a 90° elbow. The pipes were arranged horizontally and vertically with inlet void fractions of 0.05-0.15. The laws governing flow velocity, void fraction, and pressure along the pipe were determined separately. The results revealed the formation of large-scale vortices with high gas volume fractions inside both types of elbows, which exacerbate oil-gas separation and cause additional head loss. The maximum pressure drop was observed at approximately one pipe diameter downstream of the elbow outlet, which initially increases with the inlet void fraction and then gradually stabilizes. Asymmetric secondary flow vortices in the horizontal elbow were found to enhance oil-gas separation and accelerate lubricating oil to greater extent than in a vertical elbow under the same conditions. Consequently, the maximum pressure drop caused by flowing through the horizontal elbow is higher than that in the vertical elbow.

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office 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.)

A mesh filter is one of the key components of micro-irrigation systems, which plays an important role in filtering impurities and slowing down dripper blocking. The filter head loss tends to increase with the increase of intercepted impurities, resulting in screen breakage or forcing system shutdown. This study adopted the method of inductive analysis of literature data to carry out K-means cluster analysis on the head loss data of vertical, composite, horizontal, torpedo, flap, Y-type and handcranked cleaning of 7 types of mesh filters at different stages, and summarized the trend of dynamic change of head loss. Then, in order to clarify the reasons for the surge in head loss for the Y-mesh filter, the study designed three types of flow rates of 2.5, 3.5, and 4.5 m3 /h, three sediment concentrations of 60, 80, and 100 mg/L and four grades of sand-containing water mainly of >54-75 ( Grade Ⅰ ), >75-100 ( Grade Ⅱ ), >100-125 ( Grade Ⅲ ), and >125-150 μm ( Grade Ⅳ) respectively, and carried out a full-scale experiment to test the effects of different flow rates, sediment concentrations, and sand grades on the head loss of the filter. With the main objectives of reducing the head loss surge and improving the sand stopping effect, a CRITIC-TOPSIS comprehensive evaluation was carried out with the evaluation indexes of increase rate of head loss during steady increase stage, increase rate of head loss during sudden increase stage, clogging uniformity, total operation time, total head loss and desanding rate to optimize the suitable operating conditions of the Y-filter. The results showed: 1) The change in different types of mesh filters head loss over time was divided into a steady increase stage and a sudden increase stage, the sudden increase in the stage of the head loss had larger growth rate and shorter operation time; The ratio of the duration of both stages was greater than 0.5, and the filter clogging uniformity was greater than 1. 2) Under the same flow rate and concentration, grade Ⅲ and grade Ⅳ were more likely to produce head loss surge than grade Ⅰ and grade Ⅱ. Under the same flow rate, the head loss surge was more likely to occur under high concentration conditions. Under the same concentration, the head loss surge was most likely to occur when the flow rate was 3.5 m3 /h. 3) The results of CRITIC-TOPSIS comprehensive evaluation showed that the top three indexes affecting the hydraulic performance were 100-125, 125-150 and 75-100 μm water with the flow rate of 2.5 m3 /h and the sediment concentration of 60 mg/L, and their comprehensive score indexes were 0.726, 0.712 and 0.711, respectively. The combinations of low sediment concentrations and larger particle gradations, as well as those with high sediment concentrations and smaller particle gradations, performed well at a flow rate of 2.5 m³ /h. However, when the flow rate increased to 4.5 m3 /h, the combinations of the higher sediment concentrations and the larger particle sizes exhibited superior comprehensive performance. In contrast, those with low sediment concentrations and small particle gradations demonstrated relatively consistent performance across all the three flow rates tested. The study can provide valuable information for reducing head loss and increasing operation time of filter. [ABSTRACT FROM AUTHOR]

We consider a steady water flow in a channel where a vertical grid is clogged by a rectangular patch of aquatic vegetation. Laboratory experiments are conducted to observe the decrease in the water table within the patch, as well as the subsequent head loss, as a function of the patch length, the flowrate and the upstream water height. Various models of porous media are used to produce theoretical formulae describing the water surface profile within the patch, among which the Barree–Conway model proves to perform reasonably well. However, for large enough Froude numbers a seepage face or water chute appears past the vegetation patch while non-hydrostatic effects become important. Under the latter condition, the accuracy of our analytic solution is less satisfactory, while remaining accurate enough for practical purposes. As confirmed by numerical simulations, with the specific aquatic plants used in our experiments the porous flow is not Darcian, so that the seepage and head loss could not be explained by the exact Polubarinova–Kochina theory. [ABSTRACT FROM AUTHOR]

Weirs are often used in laboratories, industries, and irrigation channels to measure discharge. The discharge capacity of a structure is vital for its safety and plays an important role in the combined gateweir flow, which is a complicated phenomenon in hydropower. This study carried out experiments on a combined hydraulic structure, which included a compound sharp-crested weir made up of two rectangles along with an inverted semicircular sharp gate. Installed on a straight channel, this structure served as a control instrument. The study aimed to investigate the downstream hydraulic jump characteristics of this combined structure, specifically, the sequent depth ratio (y2/y1), the hydraulic jump height ratio (Hj/y1), the energy loss ratio through the jump (EL/Eu), and the jump length ratio (Lj/y1). The width of the upper rectangle on the weir was set at 20 cm. The width of the lower rectangle (W2) was set at 5, 7, and 9 cm, while its depths (z) were fixed at 6, 9, and 11 cm. The gate's diameters varied between 8, 12, and 15 cm. These measurements were alternated with varying initial Froude numbers (Fn1) ranging between 1.32 and 1.5. The results showed that the dimensions of both the weir and the gate influenced the hydraulic jump characteristics. Empirical formulas were developed to predict y2/y1, Hj/y1, EL/Eu, and Lj/y1 based on the differing dimensions of the combined structure. The findings and analysis of this study are limited to the range of data that were tested. [ABSTRACT FROM AUTHOR]

In this paper, a numerical simulation model of the flow field inside the diaphragm valve is established based on the k-ε turbulence model (where k represents the turbulent kinetic energy and ε represents the turbulent dissipation rate). The mass flow at the inlet and static pressure at the outlet are used as the numerical calculation conditions, and the accuracy of the model is verified through experiments. Based on this, the model is applied to analyze the internal flow characteristics and pressure field distribution of the valve body under different import flow rates (2.787-33.273 kg/s), and an accurate quantitative relationship between import flow rate and valve body head loss is established. The results show that: 1 the numerical simulation can better predict the head loss of the valve body under different flow conditions. When the inlet flow numbers are 5.546, 11.091 and 16.637 kg/s respectively, the relative errors between the experimental and numerical simulations are only -6.433%, 4.619%, and 7.264%. 3 With a constant inlet flow, the static pressure decreases from inlet to outlet in flow passage. Flow contraction caused by the blockage of the valve wall and the flow impinging on the diaphragm creates a large static pressure gradient in the valve body. 4 After water passes through the narrow flow channel on the valve wall, a cavitation zone and reflux phenomena occur downstream of the valve body. The cavitation zone appears mainly in the 1/3 fluid domain away from the outlet. As the inlet flow increases, the vortex in the downstream of the valve body intensifies and the reflux phenomenon becomes more significant, but the scope of the reflux zone does not increase significantly. 2 After verifying the accuracy of the model, this paper studies the valve body's internal flow characteristics and pressure field distribution under 18 different inlet flow conditions. The model establishes a relationship between the inlet mass flow Q and the head loss ΔP of the valve body. For Reynolds numbers from 37 927-21 5984 and inlet mass flow Q from 2.787-15.428 kg/s, the fitting equation is ΔP = 2 076.31Q - 7 567.49 (R² = 0.964). For Reynolds numbers from 240 097-467 009 and inlet mass flow Q from 17.141-33.273 kg/s, the fitting equation is ΔP = 5 688.02Q - 67 317.39(R² = 0.993). These results are useful for hydraulic calculations in irrigation systems. [ABSTRACT FROM AUTHOR]

Trash racks installed at hydropower plants cause head losses that reduce energy output. Previous research has thoroughly investigated head losses through both experimental and field studies. However, only a limited number of numerical studies have been performed, which have shown significant simplifications in terms of model complexity. In this study, the head loss coefficients ξ of circular bar trash racks (CBTRs) were analyzed using 3D Large Eddy Simulation (LES). Specifically, a single submerged bar oriented perpendicular to the flow direction was studied under homogeneous inflow conditions while (i) the blocking ratio P was varied between 0.043 and 0.444, and (ii) the flow velocity U was varied between 0.3 and 1.0 m/s. The model parameters were selected primarily based on the extensive literature on flow past circular cylinders, particularly at a Reynolds bar number Reb of 3900. To ensure the validity of the parameters, systematic independence tests were performed, including simulations with three and five bars in the computational domain. The results confirmed the suitability of 3D LES as an appropriate tool to determine ξ of CBTRs. In general, ξ decreased continuously with decreasing P and increased with increasing U when Reb ≥ 3981, which is consistent with comparable flow parameters observed in previous studies of flow past circular cylinders. Notably, the study found that the empirical formulas used for comparison tended to underestimate ξ when P was relatively low. Finally, the potential of the presented approach for future applications was discussed in detail. [ABSTRACT FROM AUTHOR]

In this era of scarce and expensive energy, it has become imperative to devise means of reducing energy consumption, particularly in petroleum industries where huge amounts of energy are usually consumed. It is within this context that attempts have been made to reduce the energy consumption during pump-driven fluid transportation by the addition of drag-reducing polymers (DRPs), which mitigate the adverse frictional drag caused by the pipe wall. Hence, this study focused on quantifying the energy savings by the DRPs in dispersed oil-water flow at different Reynolds numbers using twelve DRPs, which possess different combinations of properties such as molecular weight, charge density, and ionic type. The results revealed substantial savings in energy in all cases with the highest saving of about 60.4%. Molecular weight posed a positive and most dominant impact among the three polymer properties investigated. The charge density slightly increased the energy savings at low values while the reverse was the case at high values. Cationic polymers produced slightly better performances than their anionic counterparts of comparable molecular weights and charge densities. Specifically, the energy saving at oil fractions of 0.1 and 0.3 increased from 6.9 to 60.4% and 5 to 51.9%, respectively, indicating the negative impact of the oil fraction. Overall, the use of DRPs has proved to be an efficient and sustainable means of saving substantial amounts of energy required to overcome the frictional drag in pipe flow. [ABSTRACT FROM AUTHOR]

Transportation of high-concentration slurry is a specialized field that requires a deep understanding of the rheological behavior of slurry. Fly ash, a fine, powdery residue of pulverized coal combustion in power plants, is transported in pipelines as a slurry with water as a carrier medium and flow-improver additives. The current research aims to compute the rheological properties of the fly ash-water slurry by adding 0.1 to 1 g/mL of Diascorea hispida extract as a natural drag reducer or flow improver. In addition to the effect of D. hispida, other parameters such as temperature, addition of fly ash, and fly ash-bottom ash mixture on the rheological performance of fly ash-water slurry have been investigated. The economic effect of the developed dispersant, D. hispida, has been examined by applying Darby – Melson combined equation by varying the slurry flow rate from 1 m/s to 3 m/s at a fixed 250 mm pipe diameter. The slurry head loss, solids conveying rate, hydraulic power need, and specific power consumption at different . D hispida concentrations were calculated. [ABSTRACT FROM AUTHOR]

The numerical models commonly used for pressurized water distribution networks can also be adapted for modeling underground irrigation networks, which has also been done in this paper. Software packages such as Epanet, Mike Urban, etc. are usually designed for drinking water supply applications thus requiring adaptation of boundary conditions specific to underground irrigation networks. In this case study the hydraulic modelling of the irrigation network was done with the advanced Mike Urban software package. Following the modelling, the sizing of the newly designed pipeline network, the diagrams of pressures, speeds, flows, as well as the evolution in time in various operating scenarios were performed. The investment of the modernization and rehabilitation of OUAI Hotarani was financed currently through the 2023-2027 Strategic Program, intervention DR-25. In our paper we present the current nonfunctional and proposed rehabilitated functional situation of the SPP15 Hotarani irrigation system. Modernization by using new/modern mobile irrigation by sprinkling equipment ensures the operation at superior technical parameters, water, and energy saving. [ABSTRACT FROM AUTHOR]

One of the most basic issues in fluid mechanics is the description of flow in closed flows; more precisely, the calculation of pressure drops and the description of the flow form. Therefore, in this paper, the numerical simulation of the flow through the elbow was presented. This case was used to comprehensively describe the most important phenomena that should be taken into account during closed flows. The elbow was chosen as one of the most frequently used fittings in practice. The simulation was made with ANSYS Fluent, with the use of the turbulent model k-ω, SIMPLE simulation method, and at Reynolds number Re=500−100,000. The minor and major pressure loss were presented and discussed in the paper. The minor loss coefficient at the high Reynolds number was equal to around 0.2, which is close to the value of 0.22 used in engineering calculations. The influence of the Reynolds number on the shift of the stream separation point in the elbow was described. The secondary flow in the elbow was observed and the vortex structure was discussed and shown with the use of the Q-criterion (Q iso surface for level 0.005). This analysis allowed us to better visualize and describe the complex flow structure observed in the investigated case.

Limitations of the operation of down-flow sand filters were investigated without and with dosages of methanol, ethanol, or acetate for denitrification and dosages of ferrous sulphate to remove phosphorous. The dynamic head loss was developed due to clogging by suspended solids (SS) that originated from the secondary sedimentation tanks including sludge overflow and from SS in primary settled wastewater that bypassed the biological step. The dynamic head loss was also developed from clogging by gas bubbles formed during denitrification, not by the SS produced from cell growth. The dynamic head loss in sand filters after 24 h operation without and with denitrification increased by 0.9–1.3 and 2.3–2.4 mH2O, respectively. The total time of operation was prolonged by 50% after one water bumping, by 75% after two bumpings, and by 85% after six or seven bumpings. Operational time for filter cycles was prolonged by 4–5 h by one bumping in the full-scale and pilot-scale filters. The time of operation depended on hydraulic loading. With a carbon source dosage, one filter cycle lasted 20–40 h at 10 m/h and 60 h at 5 m/h in pilot-scale filters, and 15–27 h at 3.3 m/h in full-scale filters. HIGHLIGHTS Head loss in the main filter bed in denitrification was similar to the total head loss in non-denitrifying filters after 24 h.; Pilot-scale study results were confirmed by full-scale studies.; The dynamic head loss was developed from SS or gas clogging.; Bumping could prolong the time of operation but was rejected due to increased filtrate SS concentration.; Operational time defined the functionality of abruptly gas-clogged filters.;

Two options for the transportation of a mixture of lignin and water are considered. One option is to rehabilitate an existing pipeline using the modern sliplining method. In this case, the capacity of the pipeline decreases, which leads to an increase in friction losses. The second option is to lay a new pipeline. The average velocity ensuring two-phase flow without sedimentation is calculated. The proposed options are analyzed. [ABSTRACT FROM AUTHOR]

This study investigated the performance of a granular filtration system (GFS) composed of a rock filter (RF), a rapid sand filter (RSF), and an activated carbon filter (ACF), applied to the post-treatment of an anaerobic reactor effluent. Four filtration rates (FR) were applied to the GFS (in m3·m−2·d−1): 100–60-60, 100–90-90, 200–120-120, and 200–160-160, for RF-RSF-ACF, respectively. A clarified final effluent with low turbidity (~ 10 NTU), solids (~ 6.5 mg TSS.L−1), and organic matter content (~ 40 mg COD.L−1) was obtained when the GFS worked with FR up to 100–90-90 m3·m−2·d−1. For higher FR, the effluent quality was a little poorer. Principal component analysis showed when the RSF operated at 120 or 160 m3·m−2·d−1, it presented an effluent with higher turbidity which did not affect negatively the ACF performance. The hydraulic load limits in the RSF were reached in periods of 45, 30, and 24.5 h for the FR of 60, 120, and 160 m3·m−2·d−1, respectively, and head loss analysis depicted a more distributed solid retention through the sand depth with the lower FR. Thus, the results revealed that the RF-RSF-ACS system is a promising alternative for effluent polishing of anaerobic reactor, especially when the FR is set at 90 m3·m−2·d−1 or even higher. [ABSTRACT FROM AUTHOR]

Y-type mesh filters have been widely used in the micro-irrigation systems. A better hydraulic performance is highly required for the stable operation during irrigation. In this study, the standard k-model was adopted to simulate the internal flow field of different filters using the computational fluid dynamics with multi-angle analysis. A series of simulation tests were carried out under three types of filter screen shapes (square, circular and diamond) and three angles of cylinder arc (0°, 15°, and 30°). Specifically, a systematic analysis was implemented on the hydraulic characteristics of the internal pressure drop coefficient, the flow distribution on the surface of the filter element, the internal flow field, and the pressure distribution. Physical tests were also conducted to verify the numerical simulation. The results show that: There was 9% average difference in the head loss coefficient between the physical test and the numerical simulation, indicating the better reliability of the numerical simulation. The head loss of the filter was concentrated on the outlet side of the screen, which was accounted for 85% of the total head loss. A stagnant zone of water flow was formed inside the plug, where the velocity was very low without the water flowing back. The smallest pressure was found in the center of the filter chamber from the center to the surrounding area. There was also an increase in the minimal pressure in a stepwise manner from the center to the periphery. Among them, the circular mesh filter shared the largest head loss coefficient, followed by the square mesh filter, and the smallest was found in the diamond mesh filter. The pressure dropped at the mesh, and the total pressure dropped to change, as the shape of the mesh changed. But there was no variation in the value and distribution of the maximum and minimum pressure in the chamber. It infers that the shape of the mesh posed a greater influence on the distribution of the overflow rate on the mesh surface of the filter. The highest proportion of medium-rate overflow area was 47.5% in the square mesh filters, followed by the circular shape, and the smallest medium-rate overflow area of diamond shape was only 26.5%. The head loss of the filter gradually decreased with the increase of the arc angle of the cartridge. The pressure drop coefficient at 35° decreased by 73.15%, compared with 0°. There was also the much more uniform distribution of the flow rate on the mesh surface with the increase of the angle, in which the area of the medium speed overflow area at 35° increased by 71.48%, compared with 0°, indicating the outstandingly improved hydraulic performance. There was the significant decrease in the internal and external pressure difference at the middle and upper section of the screen on the outlet side with the increase of the arc angle of the cartridge, particularly for the differences between 35° and 0°. The difference of the pressure drop between 35° and 0° was 2.97 times. Therefore, an optimal filter can be selected with a square cylinder arc angle of 30°in the actual micro-irrigation system, in order to improve the hydraulic performance and service life of the filter with the gentle internal flow field and uniform flow distribution on the mesh surface. [ABSTRACT FROM AUTHOR]

The large head loss of the disc filter has always been one of its main limiting factors, which may affect its working efficiency and service life. Disc flow channel structure is an important factor affecting the performance of the disc filter. In this context, to reduce the head loss of the disc filter while ensuring the filtration effect, a new type of disc filter with a discrete channel structure was designed. Its performance in terms of head loss, sediment retention, uniformity of sediment distribution, and particle-size distribution in the runner was compared with that of a traditional linear channel disc filter. The results showed that the head loss of the new disc filter under the condition of clear water was 33.5%–50% lower than that of the traditional disc filter. Moreover, in sandy water, the head loss was 18.85%–47.07% lower than that of the traditional disc filter. Compared with the traditional disc filter, the average sediment retention and sediment uniformity ημ of the disc filter with discrete channels were increased by 6.32% and 1.5–2.5 times, respectively, when the flow rate was 1.5 m3/h. Considering the head loss, sediment retention, uniformity of sediment distribution, and other indicators, the hydraulic performance of the disc filter with a discrete channel is better than that of a traditional disc filter, and the filtration performance is slightly improved. The research results can provide a reference for the design and structural optimization of disc filter. [ABSTRACT FROM AUTHOR]

【Objective】 Flume is a device to measure water flow in open channels. The purpose of this paper is to propose a bionic technology to optimize wing-shaped flume in attempts to reduce the head loss across the flume and improve the critical submergence degree for channels in areas with small topographic gradient. 【Method】 The experiments compared 15 flow conditions. The change in water levels from the inlet to the outlet of the flumes was measured. These enabled us to analyze the hydraulic parameters including water head loss, backwater height, Frude number and critical gradient, and to compare the performance of the original wing-shaped flume and the optimized imitation pigeon wing section curve type flume. 【Result】 The average error of the optimized imitation pigeon wing section curve type flume is 1.28%, meeting the requirements. Compared with the original wing-shaped flume, the critical submergence degree working condition, the average backwater height and the average head loss of the optimized flume are reduced by 7.46% and 5.81% respectively, the flow in the upstream became smoother with the Fr

Valves are widely used in several areas, and their application in building installations is common, e.g., as shower control valves. Rapid technological advances have resulted in improvements to valve performance, reducing water and energy consumption. Removing parts external to the masonry improves space use and ergonomics in valve operation. Front access to the internal parts of a valve facilitates maintenance. The objective of this study is to present a new model of hydraulic valve for building installations, designed to decrease head loss, increase controllability, and eliminate parts outside the masonry. Three geometries were initially designed using SolidWorks, and a CFD model was used to specify the pressures at the inlet and outlet of the analyzed sections. As a result, the third valve geometry presented a pressure drop coefficient when 100% open that was roughly one third of that typically seen in globe valves. The pumps and the reduction in head loss implied that lower power was required, and therefore its energy consumption was low. Gains in controllability were also observed, as it did not reach high flows for small openings. When used on a large scale, these attributes would prevent the valves from wasting natural resources. [ABSTRACT FROM AUTHOR]

Greywater treatment and reuse is getting increasing attention all over the world, and sand filters are one of the on-site greywater treatment alternatives. Effects of media size, media depth and flow rates on the performance of the continuously operated saturated sand filters treating greywater were evaluated in this study. River sand of three different media sizes 0.30-0.60 (fine), 0.60-0.85 (medium), and 0.85-1.18 (coarse) mm was used and sand filters with the same media size were constructed and operated at flow rates of 10 (320 L/m2/day), 20 and 30 L/d. Fine sand media filter operated at a hydraulic loading rate of 320 L/m2/day gave the best performance with 99, 94 and 95% removal of turbidity, BOD and COD, respectively. NH4-N, PO4-P and FC were reduced by 84, 99% and 1.65 log, respectively. An optimization study showed an optimum sand size of 0.68 mm and a hydraulic loading rate of 470 L/m2/day. [ABSTRACT FROM AUTHOR]

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Trash racks installed at hydropower plants cause head losses that reduce energy output. Previous research has thoroughly investigated head losses through both experimental and field studies. However, only a limited number of numerical studies have been performed, which have shown significant simplifications in terms of model complexity. In this study, the head loss coefficients ξ of circular bar trash racks (CBTRs) were analyzed using 3D Large Eddy Simulation (LES). Specifically, a single submerged bar oriented perpendicular to the flow direction was studied under homogeneous inflow conditions while (i) the blocking ratio P was varied between 0.043 and 0.444, and (ii) the flow velocity U was varied between 0.3 and 1.0 m/s. The model parameters were selected primarily based on the extensive literature on flow past circular cylinders, particularly at a Reynolds bar number Reb of 3900. To ensure the validity of the parameters, systematic independence tests were performed, including simulations with three and five bars in the computational domain. The results confirmed the suitability of 3D LES as an appropriate tool to determine ξ of CBTRs. In general, ξ decreased continuously with decreasing P and increased with increasing U when Reb ≥ 3981, which is consistent with comparable flow parameters observed in previous studies of flow past circular cylinders. Notably, the study found that the empirical formulas used for comparison tended to underestimate ξ when P was relatively low. Finally, the potential of the presented approach for future applications was discussed in detail.

The effects of stormwater discharges on receiving aquatic environments and the need for their purification were highlighted by an EU court in May 2020. The ruling stated the need for removal of dissolved pollutants, which justifies field studies for development of far-reaching methods for runoff treatment. In this study, a standard sand was used as medium for road runoff filtration and removal of dissolved and particle-bound (

Dual media sand filters at Henriksdal WWTP began to show high head loss after five years of operation, especially during the fluidization for sorting the filter bed after backwashing. At that time, the filters were still clean and the dynamic head loss, due to clogging of the filters with suspended solids during a cycle of operation, had its lowest value. Dynamic head loss over the lower sand layer surface in the dual media sand filter was detected in some filter cycles of operation. The initial head loss in the filters has increased over the years. This type of head loss is constant during a cycle of operation and increases only slowly with time. It is due to different factors, as precipitation of ferric oxide hydroxide in the nozzle slots and on the grains in the filter bed, and accumulation of filter bed grains below the filter bottom. Different measures were tested to reduce or eliminate the initial head loss in the filters. Results from frequency diagrams showed that changing nozzles and removing of filter bed material from below the filter bottom were the most favourable actions. Backwashing more frequently and with more sequences also reduced the initial head loss. HIGHLIGHTS Initial head loss from inorganic clogging developed by filtration of wastewater.; Measures taken decreased the initial head loss by 0.10–0.31 mH2O.; Sand filter nozzles were changed every 12th year in average.; Dynamic head loss developed from organic clogging during each filtration cycle.; Initial head losses were zero–0.67 mH2O before undertaken measures.;

This paper study the influence of roughness of the tank base in the formation of air core vortex when liquid inside the cylindrical tank is rotated and subsequently drained. The vortex air core formation in drain tanks can lead to the blockage of drain port and can result in reduced discharge of draining liquid as an immediate consequence. The formation of such a vortex in propellant tanks of spacecraft and rockets will lead to underutilization of propellants and can adversely affect the performance of rocket engines. Ingestion of air core vortex in metal casting process can affect the mechanical properties of casted metal. Hence, suppression of air core vortex is inevitable in the fields of aerospace, metal casting and other hydraulic engineering systems. Current study makes use of roughness of the tank base to suppress vortexing which is the first of its kind and therefore, novel. Experimental investigations have been carried out at several values of roughness height and initial fluid rotation to study the characteristics of air core vortex. It is found that at the highest value of initial rotation provided to the liquid, air core vortexing can be subdued up to 25% by making use of base roughness. Current study also recommends drain tank manufacturers not to smoothen the tank base surface spending time at extra cost. In addition, applying roughness on the tank base will further weaken the formation of air core vortex, in the light of this study. [ABSTRACT FROM AUTHOR]

Sluice gates are commonly used to measure water discharge and to adjust the water level in open canals. Estimation of head loss (ΔE) and discharge coefficients (Cd) for a sluice gate is essential for the design of open canals. Depending on the downstream water level, free or submerged flow conditions may occur. Although there have been some investigations on Cd for sluice gates, a comprehensive literature review shows that there are no studies of ΔE (to the best knowledge of the authors). Knowledge of ΔE is necessary for the design of intakes and irrigation canal inverts. This study investigates ΔE and Cd using scaled experimentation. Results show that ΔE for free flow is greater than that for submerged flow conditions. Meanwhile, discharge coefficients in a free flow are greater than those under submerged flow conditions. Relative energy losses (ΔE) have a minimum value of 0.271 and a maximum value of 0.604. These high energy losses cannot be ignored in intake structures and canal-designing processes, and their impact on minor canal inverts receiving water from main canals should be considered. Application of multiple nonlinear regression (MNR) models is presented for predicting ΔE and Cd. The MNR method yields accurate predictions. [ABSTRACT FROM AUTHOR]

In this study, the energy dissipation of flow over the triangular and trapezoidal labyrinth weirs with one and two key cycles was investigated. The magnification ratios (MR) of models were 1.57, 2.57, 3.57, and 4.57. Results declared that the labyrinth weirs can dissipate the energy of flow between 85% and 70% considering the range of the relative head (ho/P) between 0.10 and 1.0. The lowest efficiency of labyrinth weirs concerning energy dissipation occurs when the ho/P is about 0.25. For values less than 0.60 of ho/P, by increasing MR, the performance of models is decreased. For values less than 0.30 of ho/P, the performance of the trapezoidal plan crest is about 10 percent lower than the crest with a triangular plan. For values greater than 0.30 of ho/P, the performances of labyrinth weir models are identical and are about 75%.

Filters are important pieces of equipment to ensure the normal operation of micro-irrigation systems, and the head loss is a key indicator to evaluate their hydraulic performances. To reduce the head loss and energy consumption, a new type of filter for treating surface water – the pre-pump micro-pressure filter was proposed. The pre-pump micro-pressure filter was studied, and physical model tests on the flow rate, water separator type, and filter screen area were conducted under clean water conditions. Statistical and dimensional analysis methods were used to analyze the test results. Our results showed that the order of the factors affecting the head loss of the filter was flow rate > water separator type > filter screen area. The various water separator types showed no significant differences in terms of head loss, while the different flow rates showed significant differences. A head loss prediction model was constructed, and the coefficient of determination R2 reached 0.987. Our results can provide technical support for new filter development and enrich the theory of micro-pressure filtration. HIGHLIGHTS The predicted head loss of pre-pump micro-pressure filter has a high regression coefficient. The average relative error of the predicted value is 6.07%, which shows that the calculation equation is an ideal head loss prediction model.; The order of the factors affecting the head loss of the filter is as follows: flow rate > water separator type > filter screen area.;