scholarly journals Sediment Flushing from Reservoir and Ecological Impacts

10.29007/1fsv ◽  
2018 ◽  
Author(s):  
Giuseppe Roberto Pisaturo ◽  
Maurizio Righetti
Keyword(s):  
Flow Rate ◽  
Sediment Concentration ◽  
Ecological Impacts ◽  
Cfd Model ◽  
Erosion And Deposition ◽  
Event Duration ◽  
Reservoir Volume ◽  
Sediment Flushing ◽  
The University ◽  
Lower Flow Rate

Dams cause a sediment transport trapping phenomenon and the effects can be the reduction of reservoirs operations, the decreasing of the storage, a channel erosion of the downstream watercourse and habitats pauperization. A possible method used to preserve the reservoir volume and the sediment continuity downstream the dam is to operate sediment flushing. In this work, the sediment flushing phenomena and its impact on morphology and ecology is investigated. In particular two possible flushing strategies are proposed. The two strategies differ for the flow rate, sediment concentration and event duration. The results are obtained using an original CFD model developed at the University of Trento. The CFD model has the possibility to simulate the erosion and deposition phenomena and to calculate the severity of the ill effects (SEV parameter) for juvenile and adult Salmonids. The results showed that the two strategies have very different effects on morphology and habitat. The strategy that involve lower flow rate and concentration with higher event duration, seems to minimize the deposition phenomena and the effects on the habitat.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

scholarly journals The method for recalibration of thoron concentration reading of RAD7 and obtaining the thoron exhalation rate from soil surface

2013 ◽  
Vol 28 (1) ◽  
pp. 92-96 ◽  
Author(s):  
Yanliang Tan ◽  
Detao Xiao
Keyword(s):  
Flow Rate ◽  
South China ◽  
Soil Surface ◽  
Field Conditions ◽  
Radon Exhalation Rate ◽  
Exhalation Rate ◽  
Air Flow Rate ◽  
Rapid Decay ◽  
The University ◽  
Chamber Technique

Thoron exhalation rate can be obtained through the combination of the ?accumulation chamber? technique and RAD7. Thoron?s rapid decay causes the intake path and the air flow rate to become important factors in calibration. In field conditions, since the flow rate of the internal pump in RAD7 will change as the voltage of the battery decreases, the big drying tube is more suitable for a long measurement than the small drying tube. We developed the method for recalibration of the thoron concentration reading of RAD7 based on the calibration factor for 222Rn, and obtained the thoron exhalation rate from soil surface near by the Radon Laboratory of the University of South China. This method can be applied to develop and improve instruments for measuring the radon exhalation rate.

scholarly journals CARACTERIZAÇÃO HIDRÁULICA DE GOTEJADORES AUTOCOMPENSANTES EXPOSTOS À APLICAÇÃO DINÂMICA DE CLORO LIVRE (Parte II)

Irriga ◽  
2008 ◽  
Vol 13 (3) ◽  
pp. 411-425
Author(s):  
Rubens Duarte Coelho ◽  
Marconi Batista Teixeira ◽  
Ralini Ferreira de Melo ◽  
Meiby Carneiro de Paulo
Keyword(s):  
Flow Rate ◽  
Gravimetric Method ◽  
Sao Paulo ◽  
Free Chlorine ◽  
São Paulo ◽  
Rate Reduction ◽  
Linear Effect ◽  
The University ◽  
Effect Of Chlorine

CARACTERIZAÇÃO HIDRÁULICA DE GOTEJADORES AUTOCOMPENSANTES EXPOSTOS À APLICAÇÃO DINÂMICA DE CLORO LIVRE (Parte II)  Rubens Duarte Coelho1; Marconi Batista Teixeira1; Ralini Ferreira de Mélo1; Meiby Carneiro de Paula21Departamento de Engenharia Rural, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, SP,  [email protected] genético e reprodução animal, IAPAR – Estação Experimental da Faz. Modelo, Ponta Grossa, PR  1 RESUMO Este trabalho teve como objetivo avaliar a caracterização hidráulica de 14 modelos de gotejadores autocompensantes, quanto ao efeito do cloro na redução de vazão, causada pela aplicação dinâmica de 100 mg L-1 de cloro livre, e o efeito linear de redução de vazão para dosagens e tempos de aplicação calculados a partir da dosagem padrão de 100 mg L-1 de cloro livre. Utilizou-se uma bancada de ensaios em estrutura metálica com 11,0 m x 4,0 m, instalada no Laboratório de Irrigação do DER– ESALQ/USP. Semanalmente, foi feita a coleta de água utilizando o método gravimétrico para todos os emissores presentes na linha gotejadora de cada um dos modelos estudados. Os modelos de gotejadores ensaiados apresentaram sensibilidade variável à aplicação de cloro livre. Ocorreu um decréscimo de 10 a 20% em média da vazão (L h-1) para a maior parte dos emissores, com exceção do modelo E que apresentou aproximadamente 90% de redução de vazão com 2688 h de funcionamento e redução drástica de vazão na ordem de 100% em virtude do bloqueio total do orifício para o emissor I. Embora o efeito da dosagem de cloro tenha sido linear, não se observaram alterações na vazão dos gotejadores com a aplicação de 10 mg L-1 de cloro livre. UNITERMOS: cloração, emissores autocompensantes, entupimento de emissores.  COELHO, R. D.; TEIXEIRA, M. B.; MÉLO, R. F. de; PAULA, M. C. de. HYDRAULIC CHARACTERIZATION OF COMPENSATING EMITTERS EXPOSED TO FREE CHLORINE DYNAMIC APPLICATION (PART II)  2 ABSTRACT The objective of this work was to evaluate the hydraulic characterization of 14 compensating emitters regarding the effect of chlorine on the reduction of the flow rate and the linear effect of flow rate reduction at different times and dosages. The reduction of the flow rate was caused by the dynamic application of 100 mg L-1 of free chlorine. The experiment was carried out under laboratory conditions in a metal bench (11.0 m x 4,.0 m) at the University of São Paulo Brazil. Emitter flow was evaluated weekly using the gravimetric method. The studied emitter models presented varying sensitivity to the application of free chlorine. An average reduction of 10 to 20% in the flow rate (L h-1) for most   emitters was observed. The “E” model presented a reduction of 90% in the flow rate over 2,688 operation hours. The “I” model presented a sharp reduction of flow rate on the order of 100% (total clogging). Although the linear effect of chlorine dosage was present in all models, changes in the flow rate among the emitters during chlorine application of 10 mg L-1 were not observed. KEY WORDS: chlorination, compensating emitters, emitter clogging. 

scholarly journals A Systematic Study of Ammonia Recovery from Anaerobic Digestate Using Membrane-Based Separation

Membranes ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 19
Author(s):  
Fanny Rivera ◽  
Raúl Muñoz ◽  
Pedro Prádanos ◽  
Antonio Hernández ◽  
Laura Palacio
Keyword(s):  
Flow Rate ◽  
Membrane Surface ◽  
H2so4 Solution ◽  
Membrane Area ◽  
Recirculation Flow ◽  
Force Microscopy ◽  
Reservoir Volume ◽  
Atomic Force ◽  
Flat Sheet ◽  
Ammonia Recovery

Ammonia recovery from synthetic and real anaerobic digestates was accomplished using hydrophobic flat sheet membranes operated with H2SO4 solutions to convert ammonia into ammonium sulphate. The influence of the membrane material, flow rate (0.007, 0.015, 0.030 and 0.045 m3 h−1) and pH (7.6, 8.9, 10 and 11) of the digestate on ammonia recovery was investigated. The process was carried out with a flat sheet configuration at a temperature of 35 °C and with a 1 M, or 0.005 M, H2SO4 solution on the other side of the membrane. Polytetrafluoroethylene membranes with a nominal pore radius of 0.22 µm provided ammonia recoveries from synthetic and real digestates of 84.6% ± 1.0% and 71.6% ± 0.3%, respectively, for a membrane area of 8.6 × 10−4 m2 and a reservoir volume of 0.5 L, in 3.5 h with a 1 M H2SO4 solution and a recirculation flow on the feed side of the membrane of 0.030 m3 h−1. NH3 recovery followed first order kinetics and was faster at higher pHs of the H2SO4 solution and recirculation flow rate on the membrane feed side. Fouling resulted in changes in membrane surface morphology and pore size, which were confirmed by Atomic Force Microscopy and Air Displacement Porometry.

Radial Impeller Forces Using CFD: Part II — A Comparison Between Compressible and Incompressible Flows

2002 ◽  
Author(s):  
Daniel O. Baun ◽  
Ronald D. Flack
Keyword(s):  
Mach Number ◽  
Flow Rate ◽  
Incompressible Flows ◽  
Lateral Force ◽  
Magnetic Bearing ◽  
Flow Coefficient ◽  
Low Flow ◽  
Working Fluid ◽  
Centrifugal Impeller ◽  
Cfd Model

Lateral centrifugal impeller forces are calculated using the CFD model developed in Part I of this paper. The impeller forces are evaluated by integrating the pressure and momentum profiles at both the impeller inlet and exit planes. Direct impeller lateral force measurements were made using a magnetic bearing supported pump rotor. Comparisons between the simulated and measured forces are first made for both average and transient impeller forces with water as the working fluid. Air was then substituted as the working fluid in the validated CFD model and the effect of impeller Mach number and Reynolds number on the static impeller lateral forces was investigated. The non-dimensional lateral impeller force characteristics as a function of normalized flow coefficient are similar in character between the incompressible and compressible case. At the matching point flow coefficient the non-dimensional impeller force magnitude was the same for all compressible and incompressible simulations. For any normalized flow rate other than the matching point flow rate, the magnitude of the non-dimensional impeller force increased as the Mach number increased. As the choke condition was approached the magnitude of the impeller force increased exponentially. As the Mach number increased the transition of the force orientation vector from the low flow asymptote to the high flow asymptote occurred over a progressively smaller range of flows.

Impingement of liquid jets at atmospheric and elevated pressures: an observational study using paired water jets or water and methylcyclohexane jets

2010 ◽  
Vol 466 (2124) ◽  
pp. 3501-3526 ◽  
Author(s):  
Naohiro Yasuda ◽  
Koji Yamamura ◽  
Yasuhiko H. Mori
Keyword(s):  
Flow Rate ◽  
Jet Impingement ◽  
Normal Pressure ◽  
Liquid Jets ◽  
Immiscible Liquids ◽  
Lower Flow ◽  
Elevated Pressures ◽  
System Pressure ◽  
Sheet Breakup ◽  
Lower Flow Rate

We have observed the impingement of two cylindrical liquid jets of either the same liquid, water, or two mutually immiscible liquids, water and methylcyclohexane (MCH), in either air under normal pressure (0.101 MPa) or nitrogen gas under elevated pressures up to 4.0 MPa. The flow rates of the two jets were adjusted such that they had equal axial momentum. Irrespective of the system pressure, we distinguished two characteristic regimes: the lower flow-rate regime, in which the jet impingement formed a regularly shaped planar sheet, and a higher flow-rate regime, in which a wrinkled sheet repeated azimuthal breakup. The transition from the former to the latter regime occurred at a lower flow rate for the water–MCH impingement than for the water–water impingement. An increase in the system pressure tended to shrink the liquid sheets, to promote the transition to the sheet-breakup regime and to intensify the liquid atomization. The formation of water–MCH compound droplets by the water–MCH impingement was confirmed visually.

Experimentally Validated Computational Fluid Dynamics Model for Data Center With Active Tiles

2018 ◽  
Vol 140 (1) ◽  
Author(s):  
Jayati Athavale ◽  
Yogendra Joshi ◽  
Minami Yoda
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Data Center ◽  
Hot Spot ◽  
Volume Flow Rate ◽  
Optimal Number ◽  
Inlet Temperature ◽  
Cfd Model ◽  
Level Model

Abstract This paper presents an experimentally validated room-level computational fluid dynamics (CFD) model for raised-floor data center configurations employing active tiles. Active tiles are perforated floor tiles with integrated fans, which increase the local volume flow rate by redistributing the cold air supplied by the computer room air conditioning (CRAC) unit to the under-floor plenum. The numerical model of the data center room consists of one cold aisle with 12 racks arranged on both sides and three CRAC units sited around the periphery of the room. The commercial CFD software package futurefacilities6sigmadcx is used to develop the model for three configurations: (a) an aisle populated with ten (i.e., all) passive tiles; (b) a single active tile and nine passive tiles in the cold aisle; and (c) an aisle populated with all active tiles. The predictions from the CFD model are found to be in good agreement with the experimental data, with an average discrepancy between the measured and computed values for total flow rate and rack inlet temperature less than 4% and 1.7 °C, respectively. The validated models were then used to simulate steady-state and transient scenarios following cooling failure. This physics-based and experimentally validated room-level model can be used for temperature and flow distributions prediction and identifying optimal number and locations of active tiles for hot spot mitigation in data centers.

Study on the effect of pore-scale heterogeneity and flow rate during repetitive two-phase fluid flow in microfluidic porous media

2021 ◽  
pp. petgeo2020-062
Author(s):  
Jingtao Zhang ◽  
Haipeng Zhang ◽  
Donghee Lee ◽  
Sangjin Ryu ◽  
Seunghee Kim
Keyword(s):  
Porous Media ◽  
Fluid Flow ◽  
Flow Rate ◽  
Sweep Efficiency ◽  
Residual Saturation ◽  
Flow Rates ◽  
Content Type ◽  
Lower Flow ◽  
Supplementary Material ◽  
Lower Flow Rate

Various energy recovery, storage, conversion, and environmental operations may involve repetitive fluid injection and, thus, cyclic drainage-imbibition processes. We conducted an experimental study for which polydimethylsiloxane (PDMS)-based micromodels were fabricated with three different levels of pore-space heterogeneity (coefficient of variation, where COV = 0, 0.25, and 0.5) to represent consolidated and/or partially consolidated sandstones. A total of ten injection-withdrawal cycles were applied to each micromodel at two different flow rates (0.01 and 0.1 mL/min). The experimental results were analyzed in terms of flow morphology, sweep efficiency, residual saturation, the connection of fluids, and the pressure gradient. The pattern of the invasion and displacement of nonwetting fluid converged more readily in the homogeneous model (COV = 0) as the repetitive drainage-imbibition process continued. The overall sweep efficiency converged between 0.4 and 0.6 at all tested flow rates, regardless of different flow rates and COV in this study. In contrast, the effective sweep efficiency was observed to increase with higher COV at the lower flow rate, while that trend became the opposite at the higher flow rate. Similarly, the residual saturation of the nonwetting fluid was largest at COV = 0 for the lower flow rate, but it was the opposite for the higher flow rate case. However, the Minkowski functionals for the boundary length and connectedness of the nonwetting fluid remained quite constant during repetitive fluid flow. Implications of the study results for porous media-compressed air energy storage (PM-CAES) are discussed as a complementary analysis at the end of this manuscript.Supplementary material: Figures S1 and S2 https://doi.org/10.6084/m9.figshare.c.5276814.Thematic collection: This article is part of the Energy Geoscience Series collection available at: https://www.lyellcollection.org/cc/energy-geoscience-series

scholarly journals River Channel Relocation: Problems and Prospects

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1360 ◽  
Author(s):  
Alissa Flatley ◽  
Ian Rutherfurd ◽  
Ross Hardie
Keyword(s):  
Ecological Impacts ◽  
Future Research ◽  
Erosion And Deposition ◽  
Channel Change ◽  
Specific Category ◽  
Wide Range ◽  
Key Issues ◽  
And Performance ◽  
Vegetation Loss

River relocation is the diversion of a river into an entirely new channel for part of their length (often called river diversions). Relocations have been common through history and have been carried out for a wide range of purposes, but most commonly to construct infrastructure and for mining. However, they have not been considered as a specific category of anthropogenic channel change. Relocated channels present a consistent set of physical and ecological challenges, often related to accelerated erosion and deposition. We present a new classification of river relocation, and present a series of case studies that highlight some of the key issues with river relocation construction and performance. Primary changes to the channel dimensions and materials, alongside changes to flow velocity or channel capacity, can lead to a consistent set of problems, and lead to further secondary and tertiary issues, such as heightened erosion or deposition, hanging tributaries, vegetation loss, water quality issues, and associated ecological impacts. Occasionally, relocated channels can suffer engineering failure, such as overtopping or complete channel collapse during floods. Older river relocation channels were constructed to minimise cost and carry large floods, and were straight and trapezoidal. In some countries, modern relocated channels represent an exciting new challenge in that they are now designed to replicate natural rivers, the success of which depends on understanding the characteristics, heterogeneity, and mechanisms at work within the natural channel. We discuss shortcomings in current practice for river relocation and highlight areas for future research for successful rehabilitation of relocated rivers.

scholarly journals Siltation and Desilting Practices in A Runoff Reservoir on Heavy Sediment-Laden River

2018 ◽  
Vol 246 ◽  
pp. 01062
Author(s):  
Dangwei Wang ◽  
Anjun Deng ◽  
Zuwen Ji ◽  
Hongling Shi
Keyword(s):  
Flow Rate ◽  
Sediment Concentration ◽  
Reservoir Capacity ◽  
Power Station ◽  
Flood Season ◽  
Medium Flow ◽  
Key Factor ◽  
Diversion Channel ◽  
Dam Site ◽  
Sediment Deposit

Sediment deposition in the reservoir of run-of-the-river power station is severe, in this paper we take upper Marsyangdi reservoir as an example to analyze sedimentation and desilting process according field data measured from September 2016 when the reservoir had just been impounded in order to find strategy for managing reservoir sedimentation. The ratio of Upper Marsyangdi reservoir capacity and volume of sediment into the reservoir is about 0.2. The reservoir arrived silt-stable in a year after impoundment with a depth of 12m deposition at the dam site. Most of sediment deposit in the periods that at the initial and the end of flood reason and it is found the flow rate is the key factor influencing trap efficiency because that due to damming velocity of medium flow decreased significantly compared to natural condition which caused numerous deposition. Based on result of analysis of deposition the desilting condition is determined. Empty flushing is proposed to release deposition after flood season when flow rate is greater than 100m3/s and the new capacity will last to next flood season. In order to reduce sediment concentration into diversion channel a desilting should be done in flood season when flow rate is larger than 200m3/s and flow rate for impound should not be more than 1/10 of that into reservoir which can avoid deposition during impoundment near dam site.

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