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1
Szada-Borzyszkowska, Monika, Wojciech Kacalak, Dariusz Lipiński i Błażej Bałasz. "Analysis of the Erosivity of High-Pressure Pulsating Water Jets Produced in the Self-Excited Drill Head". Materials 14, nr 15 (27.07.2021): 4165. http://dx.doi.org/10.3390/ma14154165.
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The dynamic impact of a water jet with a periodically changing structure can be used in various industries. The paper presents a design solution for a self-excited pulse head. This head can be used in mining for drilling holes and breaking rocks. The design of the head was developed based on computer simulations, which made it possible to learn the mechanism of impulse shaping inside the head. Tests of the water jet produced in the self-excited pulsation head showed the occurrence of periodic changes in its internal structure and pulsation frequency. A significant increase in the dynamic stream pressures was demonstrated for the head working in the water environment compared to the head working in the air environment For example, for nominal medium and highest pressures, this increase is up to 82%, while for the lowest pressures (10 MPa), the pressure force values increase by 46%. It was found that an increase in the nominal water pressure causes a decrease in the frequency of hydrodynamic pulses in the head operating in both the water and air environment.
2
Zhang, Kai, Bo Song i Delan Zhu. "The Development of a Calculation Model for the Instantaneous Pressure Head of Oscillating Water Flow in a Pipeline". Water 11, nr 8 (31.07.2019): 1583. http://dx.doi.org/10.3390/w11081583.
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Sinusoidal oscillating water flow at low pressure can improve the anti-clogging ability of an emitter in drip irrigation or the water distribution of a nozzle in sprinkler irrigation and reduce the cost and energy consumption of the irrigation system. In this study, the characteristics of instantaneous pressure head attenuation of oscillating water flow along a pipeline have been investigated. By using a complex function to solve the continuity equation and the momentum equation of a pipeline with water hammer motion and using the Darcy–Weisbach formula to estimate the head loss, a calculation model for the instantaneous pressure head of oscillating water flow along a pipeline was developed. The measured value of the amplitude of the pressure head and the average instantaneous pressure head in the experiments have been used to verify the corresponding pressure head calculated by the model. The results show that the amplitude of the pressure head and the average instantaneous pressure head decrease linearly along the pipeline. The calculated value of the amplitude of the pressure head and the average instantaneous pressure head are basically close to the corresponding measured pressure head. From the results of all the tests, the maximum relative error of the calculated and measured value of the amplitude of the pressure head along the pipeline was 9.44%. The maximum relative error of the calculated and measured value of the average instantaneous pressure head along the pipeline was 8.37%. Hence, the model can accurately predict the instantaneous pressure head of oscillating water flow along a pipe and provide a theoretical basis for the application of oscillating water flow in irrigation systems and the design of irrigation pipe networks.
3
Bicejova, Luba, i Slavko Pavlenko. "Water Jet Technology Head Vibration due to Water Pressure Change". Advanced Materials Research 1061-1062 (grudzień 2014): 511–14. http://dx.doi.org/10.4028/www.scientific.net/amr.1061-1062.511.
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The following paper analyses effects of pressure values of a high pressure pump on technology head vibrations origin at hydroabrasive erosion in production process. The aim is to focus onto one of possible sources of undesirable vibrations which can be subsequently influencing the cutting surface quality.
4
Miki, K., M. R. Klocke, S. K. Hong i J. A. Krasney. "Interstitial and intravascular pressures in conscious dogs during head-out water immersion". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 257, nr 2 (1.08.1989): R358—R364. http://dx.doi.org/10.1152/ajpregu.1989.257.2.r358.
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Water immersion (WI) causes an increase in plasma volume in humans and dogs. To determine the mechanism for this fluid movement, the transmission of external water hydrostatic pressure to the interstitial and vascular compartments was studied in six conscious dogs. Systemic arterial, central venous, peripheral arterial (ulnar artery) and venous (cephalic vein), pleural, intra-abdominal, and interstitial fluid hydrostatic (by Guyton's capsule and wick catheter method) pressures and external reference water pressure were measured at three different levels of WI: 1) extremities only, 2) midchest, and 3) midcervical levels at 37 degrees C. There was a significant linear relationship between interstitial fluid hydrostatic pressure (X) and external water pressure (Y): (Y = 0.86X + 1.4, r = 0.93 by Guyton's capsule; Y = 0.85X + 2.4, r = 0.93 by wick catheter. However, vascular pressures did not change when dogs were immersed at the level of the extremities. These pressures increased only during WI at the midchest and midcervical levels. Therefore the pressure gradient that develops between the interstitial and intravascular compartments is probably the major reason for the transcapillary fluid shift during WI.
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Chang, Dong Eil, Do Guen Yoo i Joong Hoon Kim. "A Study on the Practical Pressure-Driven Hydraulic Analysis Method Considering Actual Water Supply Characteristics of Water Distribution Network". Sustainability 13, nr 5 (5.03.2021): 2793. http://dx.doi.org/10.3390/su13052793.
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For reliable pressure-driven analysis (PDA) results, it is necessary to reasonably determine an objective head-outflow relationship (HOR) and the required head for each node. So far, no methodology has been proposed to objectively determine two factors based on data of real block. In this study, the HOR was defined using the water supply method, residential environment, and water consumption data within real blocks. The standard minimum residual pressure criteria were reviewed to quickly and rationally determine the required head for each node. To validate the proposed methodology, the HOR and required head application conditions were configured for different scenarios; the available flow rate of nodes and the water supply capacity of the entire block were evaluated based on PDA results. Through the results for each scenario, the HOR definition method was able to provide a reasonable result reflecting the actual block’s conditions, unlike the conventional orifice-type HOR, and the standard minimum residual pressure criteria as the required head was evaluated to be more efficient than the conventional time-consuming method. The HOR uncertainty and the lack of rationality in the selection of the required heads affected the reliability of PDA results; these problems can be solved using the proposed methodology.
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Dobrovolskaya, O. G. "ANALYSIS OF EMERGENCY OPERATION OF WATER PIPELINES". Bulletin of Odessa State Academy of Civil Engineering and Architecture, nr 83 (4.06.2021): 122–29. http://dx.doi.org/10.31650/2415-377x-2021-83-122-129.
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In this work, the influence of individual sections of the water supply network on the dynamics of nodal heads in emergency operating modes is investigated. During accidents in the network sections, the dynamics of the head changes, the supply of water to the network decreases, areas with insufficient heads are formed. The subject of the analyzed stage of research is the influence of individual sections of the network on the location and size of areas with insufficient head. To determine the influence of individual sections of the network on head dynamics, methods of mathematical modeling of flow distribution in the water supply network, methods of hydraulic calculations of water supply networks were used. The results of studies of formation and change of areas with insufficient head taking into account emergency situations for networks with different structure and configuration are presented. The tasks to be performed by the flow management system at the network design stage are defined. Based on the results of the studies, the water supply conditions were evaluated during the formation of areas of insufficient pressure. Proposed algorithm consists of visualization of network structure, simulation of emergency situations, hydraulic calculations of network in normal and emergency operation modes, determination of actual head in network nodes, clarification of location of control nodes, calculation of required head of pumps in emergency operation mode. The proposed method allows you to determine the priority selection of network sections during its reconstruction and restoration. Modeling and analysis of pressure zones in the network allows you to change the number and location of pressure control units depending on the need. The proposed recommendations on flow management can be implemented in the work of utility dispatch services.
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Qin, Yinghong, Haifeng Yang, Zhiheng Deng i Jiang He. "Water Permeability of Pervious Concrete Is Dependent on the Applied Pressure and Testing Methods". Advances in Materials Science and Engineering 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/404136.
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Falling head method (FHM) and constant head method (CHM) are, respectively, used to test the water permeability of permeable concrete, using different water heads on the testing samples. The results indicate the apparent permeability of pervious concrete decreasing with the applied water head. The results also demonstrate the permeability measured from the FHM is lower than that from the CHM. The fundamental difference between the CHM and FHM is examined from the theory of fluid flowing through porous media. The testing results suggest that the water permeability of permeable concrete should be reported with the applied pressure and the associated testing method.
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Wester, T. E., A. D. Cherry, N. W. Pollock, J. J. Freiberger, M. J. Natoli, E. A. Schinazi, P. O. Doar i in. "Effects of head and body cooling on hemodynamics during immersed prone exercise at 1 ATA". Journal of Applied Physiology 106, nr 2 (luty 2009): 691–700. http://dx.doi.org/10.1152/japplphysiol.91237.2008.
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Immersion pulmonary edema (IPE) is a condition with sudden onset in divers and swimmers suspected to be due to pulmonary arterial or venous hypertension induced by exercise in cold water, although it does occur even with adequate thermal protection. We tested the hypothesis that cold head immersion could facilitate IPE via a reflex rise in pulmonary vascular pressure due solely to cooling of the head. Ten volunteers were instrumented with ECG and radial and pulmonary artery catheters and studied at 1 atm absolute (ATA) during dry and immersed rest and exercise in thermoneutral (29–31°C) and cold (18–20°C) water. A head tent varied the temperature of the water surrounding the head independently of the trunk and limbs. Heart rate, Fick cardiac output (CO), mean arterial pressure (MAP), mean pulmonary artery pressure (MPAP), pulmonary artery wedge pressure (PAWP), and central venous pressure (CVP) were measured. MPAP, PAWP, and CO were significantly higher in cold pool water ( P ≤ 0.004). Resting MPAP and PAWP values (means ± SD) were 20 ± 2.9/13 ± 3.9 (cold body/cold head), 21 ± 3.1/14 ± 5.2 (cold/warm), 14 ± 1.5/10 ± 2.2 (warm/warm), and 15 ± 1.6/10 ± 2.6 mmHg (warm/cold). Exercise values were higher; cold body immersion augmented the rise in MPAP during exercise. MAP increased during immersion, especially in cold water ( P < 0.0001). Except for a transient additive effect on MAP and MPAP during rapid head cooling, cold water on the head had no effect on vascular pressures. The results support a hemodynamic cause for IPE mediated in part by cooling of the trunk and extremities. This does not support the use of increased head insulation to prevent IPE.
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Boonyaphon, Korakot, Zhenglin Li, Geunyong Kim, Chae Seung Lim i Sung-Jin Kim. "Microfluidic sputum homogenizer driven by water-head pressure". Sensors and Actuators B: Chemical 277 (grudzień 2018): 431–36. http://dx.doi.org/10.1016/j.snb.2018.09.041.
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Cho, H., i G. H. de Rooij. "Pressure head distribution during unstable flow in relation to the formation and dissipation of fingers". Hydrology and Earth System Sciences 6, nr 4 (31.08.2002): 763–71. http://dx.doi.org/10.5194/hess-6-763-2002.
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Abstract. Wetting front instability creates a shallow induction zone from which fingers emerge that rapidly transport water and solutes downwards. How the induction zone affects finger location and spacing is unknown. In the moist subsoil, fingers may well dissipate because the finger tips no longer have to overcome the water entry value. Both flow regions were investigated in a two-dimensional chamber with a fine-over-coarse glass bead porous medium. A capillary fringe was created by upward wetting through capillary rise. Upon ponding with dye-coloured water, fingers emerged, propagated downward and diverged when reaching the capillary fringe. Microtensiometers were installed in the induction zone, the fingers, and in the capillary fringe. In the induction zone, a lateral sinusoidal pressure head developed within minutes. Only in one of two experiments could the observed pressure head pattern be satisfactorily reproduced by a steady-state model assuming uniform induction zone properties and uniform infiltration. Later, fingers emerged below the pressure head minima. The induction zone did not affect finger properties. The pressure head in the induction zone was determined by the depth of the finger tips. The water requirement of the fingers dictated the lateral pressure head gradients. The pressure heads in the capillary fringe supported the hypothesis that the flow stabilised and dissipated there. Keywords: fingered flow, wetting front instability, unsaturated flow, microtensiometers, induction zone, capillary fringe
11
Wang, Yong Shuai, Jing Yang, Xiang Jun Yu i Ke Li. "Temperature Field Analysis of High-Speed Gasoline Engine Cylinder Head Based on Fluid-Solid Coupling". Advanced Materials Research 680 (kwiecień 2013): 327–32. http://dx.doi.org/10.4028/www.scientific.net/amr.680.327.
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As the important part of the internal-combustion engine, cylinder head bears high thermal loads and mechanical loads. In order to analyse the merits or defects of cylinder head cooling system , built the 3-D model of cylinder head, and analysed the heat transfer processes between cylinder head and cooling water by fluid-solid coupled simulation in STAR-CCM+. The pressure nephograms and velocity vector of cooling water in the water jacket, and the whole temperature distributions of cylinder head were acquired. And analysed separately the temperature fields of fire power faces and exhaust passages which were under high heat loads .According to the analysis results , the structrue of cylinder head water jacket was evaluated and corresponding suggestions was put forward.
12
Strijdom, Louis, Vanessa Speight i Heinz Erasmus Jacobs. "An assessment of sub-standard water pressure in South African potable distribution systems". Journal of Water, Sanitation and Hygiene for Development 7, nr 4 (3.10.2017): 557–67. http://dx.doi.org/10.2166/washdev.2017.227.
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Abstract Sub-standard residual water pressures in urban water distribution systems (WDS) are a prevalent phenomenon in developing countries – South Africa being no exception. The phenomenon of sub-standard pressure is poorly understood, with intermittent supply ultimately resulting when there is no residual pressure left in the system. This research addressed the prevalence and extent of sub-standard pressures by using hydraulic models of potable WDS for 71 South African towns, located in 17 different South African municipalities geographically spread over the country. The hydraulic models included 539,388 modelled nodes, which were analysed to determine the number of nodes with sub-standard pressure heads during peak hour flow conditions. The results show that the residual pressure head was <24 m at 16.5% of the model nodes under peak hour flow conditions, with 6.7% of the nodes having pressure heads <12 m. In contrast, the results also report relatively high pressures in certain parts of the systems, far in excess of the minimum requirement, underlining the need for better pressure management at both high and low ranges. It was also noted that the South African design criterion is relatively stringent compared with some other countries and could potentially be relaxed in future.
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Gönczi, Gábor. "Pressure loss reduction of pipe elements". Water Practice and Technology 15, nr 2 (30.04.2020): 489–93. http://dx.doi.org/10.2166/wpt.2020.035.
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Abstract A theoretical research was conducted from 2016 to 2018 which aimed to reduce the head loss of pipe networks in the pump stations. The results were promising and predicted an average head loss reduction by 30%. Afterwards, physical experiments were carried out to test the effectiveness of the new pipe designs. Two new prototype pipe sections were installed into one of our pump stations. The experiment was successful as two unique pipe sections installed in the discharge pipe reduced the head loss of the pump station by 25–26%. According to these results, we can set a target value of 30% head loss reduction at full pump station pipe reconstruction.
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Zhao, Yaping, Jianjun Feng, Zhihua Li, Mengfan Dang i Xingqi Luo. "Analysis of Pressure Fluctuation of Tubular Turbine under Different Application Heads". Sustainability 14, nr 9 (24.04.2022): 5133. http://dx.doi.org/10.3390/su14095133.
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The vigorous development of low-head hydraulic resources and tidal energy with greater stability and predictability is drawing attention to tubular turbines. However, many problems, such as incorrect unit association relationship, insufficient unit output, and severe vibration, occur frequently in tubular turbines, particularly when the water head is low. These phenomena cannot be known through model machine tests and numerical studies. Therefore, this study takes the tubular turbine with different water heads as the research object, in accordance with the actual boundary conditions. The unsteady numerical research for the prototype machine is conducted while considering the free surface in the reservoir area and water gravity. The internal flow characteristics of the tubular turbine with different water heads and the influence of free surface on its performance are analyzed. The research indicates the following: affected by the free surface and the water gravity, the pressure in the entire flow passage of the horizontal tubular turbine increases with the increase in the submerged depth. In addition, the short water diversion section allows the water flow from the reservoir area to still have a certain asymmetry before reaching the runner. During the rotation process of the runner, the surface pressure and torque of the blade have evident periodic fluctuations, and the amplitude of the fluctuations will increase significantly with the decrease in H/D1. Moreover, in the case of small H/D1, the amplitude of pressure pulsation in the draft tube is larger, and concentrated high-frequency pressure pulsation occurs. These factors will lead to the occurrence of material fatigue damage, unstable output, and increased vibration in low-head tubular turbines.
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Zhao, Yaping, Jianjun Feng, Zhihua Li, Mengfan Dang i Xingqi Luo. "Analysis of Pressure Fluctuation of Tubular Turbine under Different Application Heads". Sustainability 14, nr 9 (24.04.2022): 5133. http://dx.doi.org/10.3390/su14095133.
Pełny tekst źródłaStreszczenie:
The vigorous development of low-head hydraulic resources and tidal energy with greater stability and predictability is drawing attention to tubular turbines. However, many problems, such as incorrect unit association relationship, insufficient unit output, and severe vibration, occur frequently in tubular turbines, particularly when the water head is low. These phenomena cannot be known through model machine tests and numerical studies. Therefore, this study takes the tubular turbine with different water heads as the research object, in accordance with the actual boundary conditions. The unsteady numerical research for the prototype machine is conducted while considering the free surface in the reservoir area and water gravity. The internal flow characteristics of the tubular turbine with different water heads and the influence of free surface on its performance are analyzed. The research indicates the following: affected by the free surface and the water gravity, the pressure in the entire flow passage of the horizontal tubular turbine increases with the increase in the submerged depth. In addition, the short water diversion section allows the water flow from the reservoir area to still have a certain asymmetry before reaching the runner. During the rotation process of the runner, the surface pressure and torque of the blade have evident periodic fluctuations, and the amplitude of the fluctuations will increase significantly with the decrease in H/D1. Moreover, in the case of small H/D1, the amplitude of pressure pulsation in the draft tube is larger, and concentrated high-frequency pressure pulsation occurs. These factors will lead to the occurrence of material fatigue damage, unstable output, and increased vibration in low-head tubular turbines.
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Zhao, Yaping, Jianjun Feng, Zhihua Li, Mengfan Dang i Xingqi Luo. "Analysis of Pressure Fluctuation of Tubular Turbine under Different Application Heads". Sustainability 14, nr 9 (24.04.2022): 5133. http://dx.doi.org/10.3390/su14095133.
Pełny tekst źródłaStreszczenie:
The vigorous development of low-head hydraulic resources and tidal energy with greater stability and predictability is drawing attention to tubular turbines. However, many problems, such as incorrect unit association relationship, insufficient unit output, and severe vibration, occur frequently in tubular turbines, particularly when the water head is low. These phenomena cannot be known through model machine tests and numerical studies. Therefore, this study takes the tubular turbine with different water heads as the research object, in accordance with the actual boundary conditions. The unsteady numerical research for the prototype machine is conducted while considering the free surface in the reservoir area and water gravity. The internal flow characteristics of the tubular turbine with different water heads and the influence of free surface on its performance are analyzed. The research indicates the following: affected by the free surface and the water gravity, the pressure in the entire flow passage of the horizontal tubular turbine increases with the increase in the submerged depth. In addition, the short water diversion section allows the water flow from the reservoir area to still have a certain asymmetry before reaching the runner. During the rotation process of the runner, the surface pressure and torque of the blade have evident periodic fluctuations, and the amplitude of the fluctuations will increase significantly with the decrease in H/D1. Moreover, in the case of small H/D1, the amplitude of pressure pulsation in the draft tube is larger, and concentrated high-frequency pressure pulsation occurs. These factors will lead to the occurrence of material fatigue damage, unstable output, and increased vibration in low-head tubular turbines.
17
Massoud, T., i A. Zia. "Dynamic management of water distribution networks based on hydraulic performance analysis of the system". Water Supply 3, nr 1-2 (1.03.2003): 95–102. http://dx.doi.org/10.2166/ws.2003.0091.
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In this paper the hydraulic performance of water distribution networks is evaluated by assessing the head values in demand points and velocities in pipes. To obtain the hydraulic parameters a head-driven simulation method is used. In this method, nodal outflows are not fixed and vary with nodal heads. Considering the possibility of a range of demand variations and mechanical and hydraulic failures in the system, nodal heads and pressure dependent outflows are obtained. Then, by using a mathematical function, the performance of the system is realistically evaluated. As expected, the level of service in the system is decreased when head and velocity values are out of the standard ranges. Also, the reliability of a water distribution network is calculated using the ratio of the pressure-dependent outflows to the demand values considering the probability of pipe failures. Comparing the level of service index and reliability applications on a test network, it can be concluded that the reliability method is not sensitive to high-pressure values in the system. However, in this situation the performance index shows a lower level of service in the network. This means that high reliability values guarantee a good connectivity and enough pressure to satisfy the required nodal outflows, although pressure values higher than the standard codes, which lead to more leaks and bursts, are not acceptable in water supply systems. Therefore, the existing definitions of reliability are not comprehensive enough to realistically evaluate performance of the system. Using the level of service index and the head-driven simulation method, the network performance under different normal and abnormal conditions can be appropriately evaluated for water companies.
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Maria Viola, Ignazio, i Richard G. J. Flay. "Sail Aerodynamics: On-Water Pressure Measurements on a Downwind Sail". Journal of Ship Research 56, nr 04 (1.12.2012): 197–206. http://dx.doi.org/10.5957/jsr.2012.56.4.197.
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Pressures on three horizontal sections of a downwind sail were measured for several wind directions and sail trims. The pressure distributions were compared with wind tunnel tests; similarities and differences were found, the latter as a result of the dynamic effects, which were not modeled in the wind tunnel. A pressure distribution at the head of the spinnaker resembling that from a delta wing was measured at an apparent wind angle of 120°.
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Agunwamba, J. C., O. R. Ekwule i C. C. Nnaji. "Performance evaluation of a municipal water distribution system using WaterCAD and Epanet". Journal of Water, Sanitation and Hygiene for Development 8, nr 3 (18.06.2018): 459–67. http://dx.doi.org/10.2166/washdev.2018.262.
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Abstract Population explosion in urban settings usually exerts enormous pressure on existing water supply systems. The result is that overall water demand is usually not satisfied. This study evaluated the performance of Wadata sub-zone water distribution system with respect to pressure, velocity, hydraulic head loss and nodal demands using WaterCAD and Epanet. There was no statistical difference between the results of Epanet and WaterCAD, however, Epanet produced slightly higher results of pressure and velocity in about 60% of all cases examined. About 19 percent (18.52%) of the total number of nodes analyzed had negative pressures while 69 percent (69%) of the nodes had pressures less than the adopted pressure for the analysis. These negative pressures indicate that there is inadequate head within the distribution network for water conveyance to all the sections. About 88 percent (87.7%) of flow velocities in the pipes were within the adopted velocity while around 12 percent (12.3%) of the velocities exceeded the adopted velocity. These excess velocities are partly responsible for the leakages and pipe bursts observed at some points within the system. The results in this study revealed that the performance of the water distribution system of Wadata sub-zone under current demand is inefficient.
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Christie, J. L., L. M. Sheldahl, F. E. Tristani, L. S. Wann, K. B. Sagar, S. G. Levandoski, M. J. Ptacin, K. A. Sobocinski i R. D. Morris. "Cardiovascular regulation during head-out water immersion exercise". Journal of Applied Physiology 69, nr 2 (1.08.1990): 657–64. http://dx.doi.org/10.1152/jappl.1990.69.2.657.
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Head-out water immersion is known to increase cardiac filling pressure and volume in humans at rest. The purpose of the present study was to assess whether these alterations persist during dynamic exercise. Ten men performed upright cycling exercise on land and in water to the suprasternal notch at work loads corresponding to 40, 60, 80, and 100% maximal O2 consumption (VO2max). A Swan-Ganz catheter was used to measure right atrial pressure (PAP), pulmonary arterial pressure (PAP), and cardiac index (CI). Left ventricular end-diastolic (LVED) and end-systolic (LVES) volume indexes were assessed with echocardiography. VO2max did not differ between land and water. RAP, PAP, CI, stroke index, and LVED and LVES volume indexes were significantly greater (P less than 0.05) during exercise in water than on land. Stroke index did not change significantly from rest to exercise in water but increased (P less than 0.05) on land. Arterial systolic blood pressure did not differ between land and water at rest or during exercise. Heart rates were significantly lower (P less than 0.05) in water only during the two highest work intensities. The results indicate that indexes of cardiac preload are greater during exercise in water than on land.
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Siew, Calvin, i Tiku T. Tanyimboh. "Practical application of the head dependent gradient method for water distribution networks". Water Supply 11, nr 4 (1.09.2011): 444–50. http://dx.doi.org/10.2166/ws.2011.065.
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Critical pressure-deficient operating conditions frequently occur in water distribution networks. Head driven analysis (HDA) of water distribution networks allows for the pressure-dependent nature of nodal flows and, therefore, yields the actual nodal flows and heads for both normal and subnormal pressure conditions. Hence, HDA simulation models are more practical than demand driven analysis models that assume that all demands are satisfied in full even under pressure-deficient conditions. This paper describes an approach in which a new pressure-dependent demand function that has no discontinuities has been incorporated in the Gradient Method. The procedure has been tested extensively and demonstrated to be capable of effectively simulating both normal and pressure-deficient operating conditions. The algorithm's convergence is smooth and rapid thanks to a line search and backtracking procedure that ensures progress towards the solution in each iteration. The results presented herein would appear to confirm that the proposed method is robust and efficient. Results for a real network are also included.
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de Rooij, G. H. "Thermodynamics of the hydraulic head, pressure head, and gravitational head in subsurface hydrology, and principles for their spatial averaging". Hydrology and Earth System Sciences Discussions 5, nr 3 (9.05.2008): 1137–57. http://dx.doi.org/10.5194/hessd-5-1137-2008.
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Abstract. In order to establish a thermodynamic justification of the theoretical relationship between the hydraulic, pressure/matric, and gravitational head in subsurface hydrology, the thermodynamic literature pertaining to subsurface flow processes is reviewed. The incompressibility of liquids negates a thermodynamic definition of pressure, which gives rise to several inconsistencies in pore scale theories. At larger scales, the gravitational potential and fluid pressure are treated as additive potentials. This superposition principle is replicated in the well-established relationship between the various heads according to subsurface hydrological theory. The necessary requirement that the superposition be maintained across scales is combined with conservation of energy during volume integration to establish consistent upscaling equations for the various heads. The power of these upscaling equations is demonstrated by the derivation of an upscaled water content-matric head relationship and the resolution of an apparent paradox reported in the literature that is shown to have arisen from a violation of the superposition principle.
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Zhonghao, Mao, Guan Guanghua, Yang Zhonghua i Zhong Ke. "Linear model of water movements for large-scale inverted siphon in water distribution system". Journal of Hydroinformatics 21, nr 6 (14.10.2019): 1048–63. http://dx.doi.org/10.2166/hydro.2019.053.
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Abstract This paper proposes a linear model that relates the pressure head variations at the downstream end of an inverted siphon to the flow rate variations at two ends. It divides the pressure head variations in the inverted siphon into low-frequency part and high-frequency part. The two parts are caused by the deformation of the siphon wall and the reflection of acoustic wave, respectively. In order to build a simplified relation between wall deformation and low-frequency pressure head variations, the Preissmann slot method (PSM) is adopted in this paper. The linear model can also be used in other forms of structures, such as pipes and tunnels, where a pressurized flow condition is present. In comparison with simulation results using the finite volume method, the linear model shows an L2 norm of 0.177 for a large-scale inverted siphon and 0.044 for a PVC pipe. To this end, the linear model is adopted to model a large-scale inverted siphon in a virtual water delivery system. Simulation results show that the inverted siphon can reduce water fluctuations. An equation to quantify this effect is proposed based on the linear model.
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Zhang, Zhiqiang, Binke Chen i Qingnan Lan. "Experimental Investigation of Load-Bearing Mechanism of Underwater Mined-Tunnel Lining". Journal of Marine Science and Engineering 9, nr 6 (4.06.2021): 627. http://dx.doi.org/10.3390/jmse9060627.
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A series of model tests were performed to investigate the load-bearing mechanism of a mined railway tunnel lining under water pressure. To investigate the load-bearing characteristics of different types of linings, a fully closed water pressure exerting device for a noncircular section tunnel was invented. A large-scale model test (1:30) under combined water and soil pressures was conducted to investigate the mechanical characteristics, deformation, stress distribution, crack development process, and failure mode of the underwater mined-tunnel lining. The test results indicated that for the high-speed railway tunnel of Class IV surrounding rock with a design speed of 350 km/h, both the drainage lining and the waterproof lining were controlled by a small eccentric compression under the two test conditions. One had only water pressure, and the other had a variable water pressure and constant soil pressure. The key sections for controlling instability were the bottom of the wall and the inverted arch. The ultimate water head of the drainage lining was 49 m, and the ultimate water head of the waterproof lining was 78 m. In comparison with the drainage lining, the waterproof lining could significantly improve the water-pressure resistance. Thus, design loads of 30 and 60 m are recommended for the drainage and waterproof lining structures, respectively.
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Lassabatere, Laurent, Pierre-Emmanuel Peyneau, Deniz Yilmaz, Joseph Pollacco, Jesús Fernández-Gálvez, Borja Latorre, David Moret-Fernández i in. "Mixed formulation for an easy and robust numerical computation of sorptivity". Hydrology and Earth System Sciences 27, nr 4 (24.02.2023): 895–915. http://dx.doi.org/10.5194/hess-27-895-2023.
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Abstract. Sorptivity is one of the most important parameters for the quantification of water infiltration into soils. Parlange (1975) proposed a specific formulation to derive sorptivity as a function of the soil water retention and hydraulic conductivity functions, as well as initial and final soil water contents. However, this formulation requires the integration of a function involving hydraulic diffusivity, which may be undefined or present numerical difficulties that cause numerical misestimations. In this study, we propose a mixed formulation that scales sorptivity and splits the integrals into two parts: the first term involves the scaled degree of saturation, while the second involves the scaled water pressure head. The new mixed formulation is shown to be robust and well-suited to any type of hydraulic function – even with infinite hydraulic diffusivity or positive air-entry water pressure heads – and any boundary condition, including infinite initial water pressure head, h→-∞. Lastly, we show the benefits of using the proposed formulation for modeling water into soil with analytical models that use sorptivity.
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Ni, Weixiang, Jian Zhang i Sheng Chen. "Optimal Location of Energy Dissipation Box in Long Distance and High Drop Gravitational Water Supply System". Water 13, nr 4 (10.02.2021): 461. http://dx.doi.org/10.3390/w13040461.
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In the long-distance and high-drop gravitational water supply systems, the water level difference between the upstream and downstream is large. Thus, it is necessary to ensure energy dissipation and pressure head reduction to reduce the pipeline pressure head. The energy dissipation box is a new type of energy dissipation and pressure head reduction device, which is widely used in the gravitational flow transition systems. At present, there is still a dearth of systematic knowledge about the performance of energy dissipation boxes. In this paper, a relationship between the location of the energy dissipation box and the pressure head amplitude is established, a theoretical optimal location equation of the energy dissipation box is derived, and numerical simulations using an engineering example are carried out for verification. The protective effects of an energy dissipation box placed at the theoretical optimal location and an upstream location are compared. The results indicate that for the same valve action time, the optimal position allows effectively reducing the total volume of energy dissipation box. The oscillation amplitudes of the water level in the box and the pressure head behind the box are markedly reduced. Under the condition that the water level oscillation of the energy dissipation box is almost the same, the optimal location offers better pressure head reduction protection performance than the upstream location.
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Alsaydalani, M. O. A. "Simulation of Pressure Head and Chlorine Decay in a Water Distribution Network: A Case Study". Open Civil Engineering Journal 13, nr 1 (30.06.2019): 58–68. http://dx.doi.org/10.2174/1874149501913010058.
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Background: The main issue in the operation of water distribution systems arises from the pressure deficiency resulting from events such as loss from leaks and bursts and loss of hydraulic capacity due to deterioration of aging water pipes. Such conditions affect the hydraulic performance of the system and the quality of water. Objective This paper investigates the hydraulic and water quality behavior of a selected water distribution network in Makkah city using the EPANET software. Methodology: The system was simulated under different hydraulic conditions including a loss of hydraulic capacity with pipe age and the presence of 30% leakage in the network over varying time conditions by employing extended period simulation models. Results and Conclusion: The results show that increasing pipe roughness with pipe age resulted in significantly low-pressure heads at the end of the network-particularly during peak demand hours. It also resulted in an increase in the rate of chlorine decay. Leakage in the network significantly affects the pressure head, resulting in pressure deficiency at some points in the network to below the minimum requirement during regular operation. The highest leakage rate occurs at periods of low demand where the pressure head in the network is high.
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Zhao, Yaping, Yanrong Li, Jianjun Feng, Mengfan Dang, Yajing Ren i Xingqi Luo. "Vibration Characteristics of a Tubular Turbine Prototype at Different Heads with Considering Free Surface and Water Gravity". Water 15, nr 4 (17.02.2023): 791. http://dx.doi.org/10.3390/w15040791.
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Tubular turbines are widely used in low water head and tidal power development due to their straight flow path, simple structure, and wide efficient area. However, the severe vibration during actual operation greatly affects the safe operation of the tubular turbine. This study performs a numerical calculation of the tubular turbine, which meets the actual machine conditions considering the free surface and water gravity; compares and analyzes the flow characteristics and pressure fluctuation spectrum characteristics in the tubular turbine under different water heads; and verifies the comparison with the actual machine test results to explore the vibration characteristics and vibration mechanism of the tubular turbine. Research results show that a large pressure difference is observed between the top and bottom of the runner chamber, and the runner needs to experience large periodic pressure fluctuations during rotation due to the combined effect of hydrostatic pressure and hydrodynamic pressure. Under different water heads, obvious flow turbulence and high turbulent kinetic energy areas are observed in the runner and draft tube due to the influence of the shape of the blade wake vortex. The vibration in the tubular turbine is mainly concentrated in the runner and draft tube and influenced by the water gravity and the runner structure of the transverse cantilever beam. The amplitude of pressure fluctuation is the largest when the frequency inside the runner is the blade passing frequency at each water head, so the maximum vibration position is located at the runner. The research results serve as a guide for the design and operation of the horizontal tubular turbine.
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Bicejova, Luba, i Stanislav Fabian. "Analysis of Technological Head Working Pressure, Tilt Angle and Shift Impact to its Vibrations Using AWJ Technology". Applied Mechanics and Materials 616 (sierpień 2014): 159–66. http://dx.doi.org/10.4028/www.scientific.net/amm.616.159.
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The paper deals with an experimental analysis of a technological head tilt angle impact to vibration generation. The search of the technological head tilt influence is performed for three technological head shift speeds and for three abrasive water medium pressure values. From graphic records showing relation of vibration acceleration amplitude to its frequency, a group of 9 comparative frequency envelope graphs for two tilt angles and three technological medium analyzed pressures for each of three speeds of the head shift is created. On the base of the frequency envelope comparative graphs a discussion and formulated conclusion are stated. The paper presents a thematically integrated part of the thesis and complements recent knowledge on water jet technology manufacturing system working condition diagnosis.
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Tao, Hongfei, Pingping Shen, Qiao Li, Youwei Jiang, Wenxin Yang i Jianqun Wei. "Research on head loss of pre-pump micro-pressure filter under clean water conditions". Water Supply 22, nr 3 (22.11.2021): 3271–82. http://dx.doi.org/10.2166/ws.2021.402.
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Abstract 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.
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Jacinto, Ana Carolina Pires, Leonardo Paula de Souza, Adriana Tiemi Nakamura, Fábio Janoni Carvalho, Edson Simão, João Luis Zocoler i Celso Luis Bergo. "Idioblasts formation and essential oil production in irrigated Piper aduncum". Pesquisa Agropecuária Tropical 48, nr 4 (październik 2018): 447–52. http://dx.doi.org/10.1590/1983-40632018v4853165.
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ABSTRACT The growing of Piper aduncum for essential oil extraction has increased, but there is a lack of basic information about its management and cultivation, which allows the productivity and quality of the oil, in order to attend the market demands. This study aimed to evaluate the relation between the production of essential oils from P. aduncum and soil water pressure heads (20 kPa, 40 kPa, 60 kPa, 100 kPa and non-irrigated). The assessment comprised the quantification of idioblasts and the production of essential oil extracted from leaves of cultivated plants. The variation in the soil water pressure head alters the amount of idioblasts in P. aduncum leaves, with impacts on the essential oil production. A soil water pressure head range of 20-60 kPa is sufficient for this species to express the highest amount of idioblasts and the highest level of essential oil production. The species adapts itself to different water availability conditions in the soil. Under stress conditions, due to water deficit or excess, the production of essential oil is reduced.
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Liu, Chengming, Tao Chen, Wenzhe Kang, Jianjun Kang, Lingjiu Zhou, Ran Tao i Zhengwei Wang. "Study on Pressure Pulsation and Force Characteristics of Kaplan Turbine". Water 15, nr 13 (30.06.2023): 2421. http://dx.doi.org/10.3390/w15132421.
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With the continuous increase in the size and power generation of turbines, the operational characteristics of turbines under off-design conditions are gradually receiving attention. In this paper, the Reynolds time-averaged method (RANS) is applied to the unsteady calculation of three different flow rate of a large Kaplan turbine under three heads: high head, rated head and low head. The focus is on the internal flow pattern of the turbine and the hydraulic excitation characteristics under low flow conditions. The unsteady characteristics of pressure pulsation, axial force of runner, radial force of runner and hydraulic torques along blade shank (τb) for six blades are analyzed. The results show that the pressure pulsation in the vaneless space is larger under low flow conditions, and frequencies of 0.33–1 fn ( fn is the rotating frequency of the runner) can be observed at monitoring points at different heights in the vaneless space. The analysis of the flow field under low flow conditions reveals the presence of larger scale vortices in the vaneless space. The position and intensity of vortices fluctuate periodically and cause larger amplitude pressure fluctuations. The frequency of 0.33–1 fn can also be observed for axial force, radial force, and τb for six blades due to the influence of vortices in the vaneless space. The low-frequency pulsations of pressure, force and τb are much greater under the low head and high head condition than that under rated head condition. The amplitude of pulsation of various parameters is the smallest under the low flow and rated head compared to that under the low flow conditions of other heads. The flow passage under low head is more influenced by the flow rate. Low-frequency pulsations occur under both the low flow and medium flow conditions. The asymmetry of the flow in the vaneless space causes unbalanced force and hydraulic instability of the runner, which seriously threatens the safe and stable operation of the turbine.
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Pei, Hai-lin, Xue-yi Qi, Hui Li, Jian-hui Li i Ze-yu Pei. "Fault Caused by Water Pressure in the Head-Cover Chamber". Journal of Hydrodynamics 18, nr 3 (czerwiec 2006): 280–86. http://dx.doi.org/10.1016/s1001-6058(06)60004-8.
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Wang, Lin, Kaihang Han, Tingwei Xie i Jianjun Luo. "Calculation of Limit Support Pressure for EPB Shield Tunnel Face in Water-Rich Sand". Symmetry 11, nr 9 (2.09.2019): 1102. http://dx.doi.org/10.3390/sym11091102.
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With the rapid development of the tunnels constructed under the rivers and seas, the research on face stability of shield tunnel in water-rich sand has important theoretical value and engineering application significance. In addition to the loads exerted by overlaying strata, the tunnels constructed in water-rich strata are usually subjected to high hydrostatic pressure or seepage forces, which are apt to cause the ground collapse of the shield tunnel face. The distribution of hydraulic head field around the tunnel face is critical to assess the impacts of the seepage forces on the tunnel face stability. This paper investigates the axisymmetric problem of the face stability of the shield tunnel under a seepage condition within the framework of limit equilibrium analysis. First, numerical simulations are carried out in this paper to analyze the distribution rules of total hydraulic head and pore water pressure near the tunnel face of the shield tunnel under the condition of stable seepage with different cover depths. Then, based on the distribution rules of total hydraulic head, new formulas for predicting the total hydraulic head along the horizontal and vertical directions are proposed and compared with the numerical simulations in this paper and existing approximate analytical solutions. Second, the classical axisymmetric limit equilibrium model is revised by incorporating the new approximate analytical solutions of hydraulic head field to determine the failure modes and the limit support pressures with a numerical optimization procedure. Lastly, the comparisons of the results obtained from the theoretical analysis model in this paper and the existing approaches are conducted, which shows that the failure mechanism proposed in this paper could provide relatively satisfactory results for the limit support pressures applied to the tunnel face.
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Liou, Chyr Pyng. "Maximum Pressure Head Due to Linear Valve Closure". Journal of Fluids Engineering 113, nr 4 (1.12.1991): 643–47. http://dx.doi.org/10.1115/1.2926528.
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The maximum pressure head resulting from one-speed closure of wide open valves is investigated. The dimensionless variables formulated in this study make the subtle effect of the initial valve head loss explicit and separate from that of the pipe frictional head loss. The maximum head is related to initial pipe frictional head loss, the initial valve head loss, the inherent flow characteristic of the valve, and the closure period by plots of dimensionless variables. The trends of the variation of the maximum pressure head are discussed. An example is used to illustrate the usage of the plots, and to show the advantage of having a global perspective of the phenomenon in the selection and sizing of valves from the water hammer point of view.
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Li, Yu-Qi, Kai-Wen Wang, Ke-Li Zhang, Ze-Wei Zhou i Xiao-Hua Yang. "Spatial and temporal distributions of migration in bio-retention systems". Thermal Science 18, nr 5 (2014): 1557–62. http://dx.doi.org/10.2298/tsci1405557l.
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Urban bio-retention system is meaningful in reducing rainfall runoff and enhancing infiltration capacity. But the moisture migration in bio-retention systems are not clear under climate change. The spatial and temporal distribution of moisture under different rainfall events in bio-retention systems are studied in this paper based on experimental data in Beijing. Richards model is introduced to simulate the spatial and temporal distribution of moisture including pressure head, hydraulic head and water content under different initial and boundary conditions. As a result, we found that from the depth of the node to the lower boundary, the values of pressure head and hydraulic head increase with depth and decrease with time, while the values of water content represent opposite trends relative to the distribution of pressure head and hydraulic head in bio-retention systems.
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Karney, Bryan W., i Eugen Ruus. "Charts for water hammer in pipelines resulting from valve closure from full opening only". Canadian Journal of Civil Engineering 12, nr 2 (1.06.1985): 241–64. http://dx.doi.org/10.1139/l85-027.
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Maximum pressure head rises, which result from total closure of the valve from an initially fully open position, are calculated and plotted for the valve end and for the midpoint of a simple pipeline. Uniform, equal-percentage, optimum, and parabolic closure arrangements are analysed. Basic parameters such as pipeline constant, relative closure time, and pipe wall friction are considered with closures from full valve opening only. The results of this paper can be used to draw the maximum hydraulic grade line along the pipe with good accuracy for the closure arrangements considered. It is found that the equal-percentage closure arrangement yields consistently less pressure head rise than does the parabolic closure arrangement. Further, the optimum closure arrangement yields consistently less head rise than the equal-percentage one. Uniform closure produces pressure head rise that usually lies between those produced by the parabolic and the equal-percentage closure arrangements, except for the range of low pressure head rise combined with low or zero friction, where the rise due to uniform closure approaches that produced by optimum closure.
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Yang, Jianxin, Jun Hu, Yuwei Wu i Boyang Zhang. "Numerical Simulation of Seepage and Stability of Tailing Dams: A Case Study in Ledong, China". Sustainability 14, nr 19 (29.09.2022): 12393. http://dx.doi.org/10.3390/su141912393.
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Tailings dams are built to safely store tailings and to protect the natural environment from damage. However, tailings dam accidents occur frequently, endangering the safety of life and property, and causing pollution to the environment. Many tailings dam accidents are caused by seepage. As such, this study takes the No. II tailings dam of Ledong Baolun Gold Mine in Hainan Province as an example and builds a two-dimensional finite element model to simulate the seepage field. The effects of normal-water-level and high-water-level conditions on the total head, pressure head, and wetting line of the main and auxiliary dams were compared. The results show that higher water levels in both the main dam and the auxiliary dam lead to a higher pressure head at the top of the dam, lower pressure head at the bottom of the dam, higher total pressure head, and at the same time, a higher wetting line, and greater destabilization. In this study, the seepage deformation failure of the main dam and the auxiliary dam, in both cases, does not occur.
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Ma, Yanna, Zhenyu Wang i Dan Wang. "The Safe Load-Bearing Capacity of Railway Tunnel Linings under High-Pressure and Water-Rich Conditions". Buildings 13, nr 9 (25.08.2023): 2154. http://dx.doi.org/10.3390/buildings13092154.
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High water pressure has been identified as the direct cause of water seepage problems in tunnels. Consequently, it is imperative to ascertain the safety load-bearing limits of tunnel linings in high-pressure, water-rich strata. In this study, FLAC3D (V5.0) numerical simulation software was employed to establish seepage models of tunnels under high-pressure, water-rich conditions, taking an actual engineering project as a reference. The hydrostatic pressure on tunnel linings under various conditions, including different permeability coefficients of the surrounding rock, grouting rings, levels of the water table, and coordinates of lining positions, was computed. By extracting the results of these simulations, correlations between lining water pressure and various parameters were analyzed, and preliminary hydrostatic pressure calculation formulas were deduced. Through regression analysis using SPSS (19.0) software, a general calculation formula for lining water pressure was derived. Given similar surrounding rock conditions, it was revealed that railway tunnel lining types adhere to a universal standard. The calculation formula for lining water pressure, when integrated with lithostatic pressure in the seepage model, facilitates the computation of the maximum pressure head that the tunnel lining can withstand under different conditions. A tabulation summarizing safe water head heights under various conditions is also presented, which enables rapid consultation of the safe load-bearing range of tunnel lining under corresponding conditions. This study provides a new calculation method for the lining water pressure of a water-rich railway tunnel, filling the literature gap. The safe tunnel head query table provides a new research approach for the design of water-rich tunnels. The research method in this article is rare in the literature, and the research approach has obvious innovations. The findings of this study have the potential to provide a theoretical foundation and data reference for the structural design of tunnel linings and the remediation of related issues.
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Hammami, Moncef, Khemaies Zayani i Hédi Ben Ali. "Required Lateral Inlet Pressure Head for Automated Subsurface Drip Irrigation Management". International Journal of Agronomy 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/162354.
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Subsurface drip irrigation (SDI) is one of the most promising irrigation systems. It is based on small and frequent water supplies. Because SDI emitters are buried, their discharges are dependent on the water status at the vicinity of the outlets. This paper was targeted to design the SDI laterals accounting for the soil water-retention characteristics and the roots water extraction. The proposed approach provides systematic triggering and cut-off of irrigation events based on fixed water suctions in the vadose zone. In doing so, the soil water content is maintained at an optimal threshold ascertaining the best plant growth. Knowing the soil water-retention curve, the appropriate water suction for the plant growth, and the emitter discharge-pressure head relationship, the developed method allows the computation of the required hydraulics of the lateral (e.g., inlet pressure head, inside diameter, etc.). The proposed approach is a helpful tool for best SDI systems design and appropriate water management. An illustrative example is presented for SDI laterals’ design on tomato crop.
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A. Al-Hemiri, Adel, Ghazwan A. Mohammed i Ghazi F. Naser. "Energy Generation from Static Water Head Developed By Forward Osmosis". Iraqi Journal of Chemical and Petroleum Engineering 12, nr 4 (30.12.2011): 1–4. http://dx.doi.org/10.31699/ijcpe.2011.4.1.
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In this work, the possibility of utilizing osmosis phenomenon to produce energy as a type of the renewable energy using Thin Film Composite Ultra Low Pressure membrane TFC-ULP was studied. Where by forward osmosis water passes through the membrane toward the concentrated brine solution, this will lead to raise the head of the high brine solution. This developed static head may be used to produce energy. The aim of the present work is to study the static head developed and the flux on the high brine water solution side when using forward and reverse osmosis membranes for an initial concentration range from 35-300 g/l for each type of membrane used at room temperature and pressure conditions, and finally calculating the maximum possible power generated from developed static head.
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Ruus, Eugen, i Bryan Karney. "Charts for water hammer in high head pump discharge lines resulting from pump failure and check valve closure". Canadian Journal of Civil Engineering 12, nr 1 (1.03.1985): 137–49. http://dx.doi.org/10.1139/l85-014.
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Maximum pressure head drops and rises resulting from pump failure and subsequent check valve closure are calculated and plotted for a simple pump discharge line at pump end, midpoint, and three-quarter point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, and pump inertia constant are accounted for in the analyses. Computer studies indicate that pipe friction, pipeline constant, and pump inertia have a major effect on pressure head drops and rises.Studies indicate further that whereas for large pump inertia the pressure head rise or drop at the midpoint is only moderately larger than one-half of the rise or drop at pump end, for small pump inertia this difference is much greater. For very small pump inertia, the pressure head drop or rise at midpoint approaches the values at pump end. This increase in pressure head drop and rise for very small pump inertia is even more pronounced at the three-quarter point.
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Zhang, Bo, Ping Zhang, Zhao Zhang, Shaobo Yang, Chengli Wang i Fanming Zeng. "Numerical Simulation of Flow Field Characteristics of The Cooling Water Jacket of A Marine Diesel Engine". E3S Web of Conferences 261 (2021): 02040. http://dx.doi.org/10.1051/e3sconf/202126102040.
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In order to evaluate the flow field characteristics of a marine diesel engine cooling water jacket, and provide a theoretical basis for further optimizing the water jacket structure. A computational fluid dynamics (CFD) method was used to calculate the three-dimensional flow field of the water jacket. Based on the CFD simulation model of the engine water jacket, the analysis of pressure field, velocity field, streamline distribution and flow uniformity of water jacket of diesel engine under rated condition were carried out. The results show that: the total pressure loss of water jacket is 30.3 kPa, in which the pressure loss of cylinder block is 8.4 kPa, and the one of cylinder head and outlet manifold is 21.9 kPa, which indicates that the flow resistance design of the cylinder block and head is reasonable; the flow rate of coolant in the nose zone of cylinder head is above 1.5 m/s, which meets the cooling demand of cylinder head; the cooling water flows circumferentially in the engine block water jacket, and the flow dead zones are easily formed by the mutual extrusion and collision of the water flows; the outlet of the cylinder head water jacket is connected with the outlet manifold at right angle, which leads to large energy loss of the flow field; the maximum non-uniformity of flow rate of water jacket of each cylinder is 5.85%, which can be further optimized by adjusting the position of water jacket inlet.
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Riha, Zdenek, Michal Zelenak, Kamil Soucek i Antonin Hlavacek. "Flow Field Analysis Inside and at the Outlet of the Abrasive Head". Materials 14, nr 14 (14.07.2021): 3919. http://dx.doi.org/10.3390/ma14143919.
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This paper focuses on the investigation of a multiphase flow of water, air, and abrasive particles inside and at the outlet of the abrasive head with the help of computational fluid dynamics calculations and measurements. A standard abrasive head with a water nozzle hole diameter of 0.33 mm (0.013”) and an abrasive nozzle cylindrical hole diameter of 1.02 mm (0.04”) were used for numerical modelling and practical testing. The computed tomography provided an exact 3D geometrical model of the cutting head that was used for the creation of the model. Velocity fields of abrasive particles at the outlet of the abrasive head were measured and analysed using particle tracking velocimetry and, consequently, compared with the calculated results. The calculation model took the distribution of the abrasive particle diameters with the help of the Rosin-Rammler function in intervals of diameters from 150 to 400 mm. In the present study, four levels of water pressure (105, 194, 302, 406 MPa) and four levels of abrasive mass flow rate (100, 200, 300, 400 kg/min) were combined. The values of water pressures and hydraulic powers measured at the abrasive head inlet were used as boundary conditions for numerical modelling. The hydraulic characteristics of the water jet were created from the measured and calculated data. The calculated pressure distribution in the cylindrical part of the abrasive nozzle was compared with studies by other authors. The details of the experiments and calculations are presented in this paper.
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Zhang, Yuquan, Yanhe Xu, Yuan Zheng, E. Fernandez Rodriguez, Huiwen Liu i Jun Feng. "Analysis on Guide Vane Closure Schemes of High-Head Pumped Storage Unit during Pump Outage Condition". Mathematical Problems in Engineering 2019 (31.12.2019): 1–11. http://dx.doi.org/10.1155/2019/8262074.
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When the pumping operation of pumped storage unit suffers from power outage, the hydraulic transient poses a serious threat to the safe operation of the unit and its pressure pipeline system. For high-head pumped storage power station (PSPS), the water hammer pressure (WHP) and rotational speed rise ratio (RSRR) of each hydraulic unit will be increased during the pump outage condition. In order to limit the fluctuation of rotational speed and WHP in power-off condition, optimizing and choosing a reasonable guide vane closure scheme (GVCS) is an economic and efficient means to improve the dynamic characteristics of pumped storage unit. On the basis of the calculation model of the transition process of single tube-double unit type of a high-head PSPS, an optimization model of GVCS balancing WHP and RSRR objectives is established. Furthermore, the two-stage broken line and three-stage delayed GVCSs are applied to the pump outage condition, and the nondominated sorting genetic algorithm-II (NSGA-II) is introduced to calculate the optimal solution set under different water heads and different closure schemes. For four typical water heads, the multiobjective optimization results of the closure law show that the two-stage broken line law has a better Pareto front under high water head, while the three-stage delayed law has a better performance under low water head. Furthermore, through the results of transition process of typical schemes, the adaptability of GVCS and water head is analyzed. The method proposed in this paper can make the RSRR not more than −0.89, and the three-stage delayed law can even make the RSRR only −0.01. Methods of this paper provide a theoretical basis for optimum guide vane closure mode setting of PSPS.
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Langford, Mathew, Jean-Luc Daviau i David Z. Zhu. "Design of a centralized regional water distribution system: a case study in the County of Paintearth No. 18, Alberta, Canada". Canadian Journal of Civil Engineering 39, nr 7 (lipiec 2012): 801–11. http://dx.doi.org/10.1139/l2012-066.
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Water supply to rural communities has historically been difficult. The sparse population distribution results in large infrastructure cost per capita compared to larger urban municipalities. The challenge is to deliver this water efficiently and minimize the corresponding increase in wastewater. Urban water systems supply both fire flow and drinking water at high pressures in large pipes. One solution for rural areas is supplying only potable water using small pipes that are supplied in long spools and that can be ploughed-in, a novel method of direct-bury. This water is delivered to private cisterns at low pressure, extending the range of the system for the same input energy level. Pressure control valves are used to keep pressure positive at high points to safeguard water quality. Modelling is particularly important in rural systems, where extensive pipeline distances and elevation difference result in significant head losses and areas of high local pressure.
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Baiamonte, Giorgio. "Dual-Diameter Laterals in Center-Pivot Irrigation System". Water 14, nr 15 (23.07.2022): 2292. http://dx.doi.org/10.3390/w14152292.
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Design strategies to enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Concerning Center-Pivot Irrigation Systems, different design procedures aimed at optimizing water use efficiency have been proposed. Recently, following a gradually decreasing sprinkler spacing along the pivot lateral with constant diameter and sprinkler flow rate, a new design method providing a uniform water application rate has been introduced. However, no suggestions were given to design multiple-diameter laterals characterized by different values of the inside pipe diameter. In this paper, first the previous design procedure is briefly summarized. Then, for the dual-diameter center pivot laterals a design procedure is presented, which makes it possible to determine pipe diameters that always provide sprinkler pressure heads within an admitted range. The results showed that for the assigned input parameters, many suitable solutions can be selected. The lateral pressure head distributions were compared to those derived by the common numerical step by step solutions, validating the suggested simplified procedure. An error analysis was performed, showing that the relative error, in pressure heads, RE, was less than 2.3%. If imposing the mean weight diameter, Dm, equal to its minimum value, the optimal pressure head tolerance of the outer lateral, δI, amounting to about 2%, with the RE in pressure heads being less than 0.4%, which makes the suggested procedure very accurate. Several applications were performed, compared, and discussed.
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Yang, Bo. "The Experimental Research of Stabilize Water Delivery on Varying Water Head and Non Pressure Water Tunnel". Applied Mechanics and Materials 353-356 (sierpień 2013): 2468–72. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.2468.
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The simple and efficient facilities of steady flow and wave elimination-flow-stabilizing plate and wave-eliminating barrier were introduced to study strong water surface fluctuation existing in free flow tunnel in Aan water project, through comparative trial and fluctuation analysis, it could be found that the introduction of steady-flow and wave-elimination facilities could stabilize the flow pattern of free flow tunnel.
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CHERNYKH, O. N. "Some aspects of organizing the protection of fish from going into water intake facilities". Prirodoobustrojstvo, nr 3 (2022): 65–70. http://dx.doi.org/10.26897/1997-6011-2022-3-65-70.
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The results of laboratory studies of water intake structures of engineering-ecological type with devices that prevent fi sh from entering the water intake windows are presented. When they work in the water intake zone, optimal hydraulic conditions are created that contribute to the guaranteed fish diversion. Three versions of the protective device were studied: single heads of cylindrical and bull types, as well as a structure with a series of fi ve bull-type heads installed obliquely in the direction of the flow. Studies of the influence of the hydraulic structure and hydrodynamic characteristics of the fl ow on the entry of fish into the water intake were carried out in a mirror tray with a change in the water intake in the range of 17…52 l/s. The experiments involved juveniles of different breeds with a size of 35…45 mm. The kinematics turned out to be partly expected: with an increase in water withdrawal, the degree of flow concentration increased. Experiments have shown that when installing a series of water intake heads, the possibility of fish getting into the zone of water intake windows increases compared with the installation of single heads. When placing single heads, the maximum negative velocities in the zone of the water intake window and the distance at which they are observed behind the bull head are signifi cantly higher. As a result of the analysis of hydro biological studies, it was found that the capaability of fish to leave the zone of influence of water intake decreases sharply with an increase in the amount of water withdrawal (outcome III). With a single cylindrical head, the intensity of pressure pulsation is approximately by 18% greater than with a bull head. A series of water intake heads arranged obliquely in a checkered order has higher fish protection properties.
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Watanabe, Kunio, Tetsuya Kito, Tomomi Wake i Masaru Sakai. "Freezing experiments on unsaturated sand, loam and silt loam". Annals of Glaciology 52, nr 58 (2011): 37–43. http://dx.doi.org/10.3189/172756411797252220.
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AbstarctEstimating soil-water flow during ground freezing is important for understanding factors affecting spring farming, soil microbial activity below the frozen soil, and permafrost thawing behavior. In this study, we performed a column freezing experiment using three different unsaturated soils (sand, loam and silt loam) to obtain a detailed dataset of temperature, water-content and pressure-head change under freezing conditions. The liquid water content and pressure head in the three soils decreased with decreasing temperature. Three soil temperature stages were found: unfrozen, stagnating near 0˚C and frozen. The temperature and duration of the stagnation stage differed among the soil types. The changes in liquid water content and pressure head during the freezing process were highly dependent on the soil-water retention curve. Water flowed through the frozen area in silt loam and sand, but no water flux was observed in the frozen loam. The freezing soil columns tended to contain more liquid water than estimated from retention curves measured at room temperature, especially at the early stage of freezing.