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Experimental and simulation of a novel hydrocyclone-tubular membrane as overflow pipe

SEPARATION AND PURIFICATION TECHNOLOGY 2018年 198卷 60-67页

作者： Wang, Chu-Chiao Wu, Rome-Ming Tamkang Univ Dept Chem & Mat Engn 151 Ying Chuan Rd Tamsui 25137 Taipei County Taiwan Tamkang Univ Energy & Optoelect Mat Res Ctr 151 Ying Chuan Rd Tamsui 25137 Taipei County Taiwan

This study proposes a new type of hydrocyclone. Through the testing of a simulation and experiment, if the overflow section at the hydrocyclone is changed to a tubular membrane, the fluid near the overflow pipe will be allowed to pass through and particles will be filtered out. Therefore, the turbulence surrounding the overflow exit can be weakened. The flow of the overflow can be increased, and its clarity can be raised. This is extremely valuable for the recycling of precious liquids and it can otherwise serve as a grading hydrocyclone. Complex flow field inside the hydrocyclone and hydrodynamic study is done with the help of commercial Fluent software. The pressure and the axial velocity decreases form the hydrocyclone wall towards the center. (C) 2017 Elsevier B.V. All rights reserved.

关键词： overflow Membrane Multiphase DPM CFD

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Dynamics of settling-driven convection beneath a sediment-laden buoyant overflow: Implications for the length-scale of deposition in lakes and the coastal ocean

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SEDIMENTOLOGY 2020年第1期67卷 699-720页

作者： Jazi, Shahrzad Davarpanah Wells, Mathew G. Univ Toronto Dept Phys & Environm Sci 1065 Mil Trail Toronto ON M1C 1A4 Canada

A series of laboratory experiments was conducted in order to determine how settling-driven convection influences the length-scale over which the majority of particles settle beneath a buoyant sediment-laden plume spreading over a denser saline layer. This system is analogous to sediment-laden river water spreading into a lake or the coastal ocean. The key dimensionless parameter that controls the settling dynamics of such flows is the density ratio, defined as the ratio of density differences due to the added salt and sediment. For a buoyant plume, this ratio has to be greater than unity, so that the experiments in the current study were performed for density ratios between one and five. When density ratio was close to one, settling-driven convection was vigorous and the length-scale over which sedimentation occurred was very small. A strong secondary turbidity current was generated in this case. On the other hand, for larger values of density ratio, the predicted length-scale over which a secondary plume was generated increased in proportion to the density ratio. A complete mathematical expression for this length-scale was developed using recent theory that described the timescale over which settling-driven convection evolved. The theoretically predicted propagation length-scale showed very good quantitative agreement with laboratory experiments. The use of the dimensionless density ratio allows the expression to predict which sediment-laden river plumes in lakes and the coastal ocean could quickly form secondary turbidity currents.

关键词： Density ratio overflow sediment-laden gravity current settling-driven convection Stokes settling velocity turbidity currents

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A dynamic, embedded Lagrangian model for ocean climate models, Part II: Idealised overflow tests

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OCEAN MODELLING 2012年 59-60卷 60-76页

作者： Bates, Michael L. Griffies, Stephen M. England, Matthew H. MIT Dept Earth Atmospher & Planetary Sci Cambridge MA 02139 USA Univ New S Wales Climate Change Res Ctr Sydney NSW Australia NOAA Geophys Fluid Dynam Lab Princeton NJ 08542 USA

Dense gravity current overflows occur in several regions throughout the world and are an important process in the meridional overturning circulation. overflows are poorly represented in coarse resolution level coordinate ocean climate models. Here, the embedded Lagrangian model formulated in the companion paper of Bates et al. (2012) is used in two idealised test cases to examine the effect on the representation of dense gravity driven plumes, as well as the effect on the circulation of the bulk ocean in the Eulerian model. The results are compared with simulations with no parameterisation for overflows, as well as simulations that use traditional hydrostatic overflow schemes. The use of Lagrangian "blobs" is shown to improve three key characteristics that are poorly represented in coarse resolution level coordinate models: (1) the depth of the plume, (2) the along slope velocity of the plume, and (3) the response of the bulk ocean to the bottom boundary layer. These improvements are associated with the more appropriate set of dynamics satisfied by the blobs, leading to a more physically sound representation. Experiments are also conducted to examine sensitivity to blob parameters. The blob parameters are examined over a large parameter space. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Numerical model overflow Density flow Embedded Lagrangian model Blobs

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Seasonal barotropic modulation of the deep-water overflow through the Faroe Bank Channel

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2006年第12期36卷 2328-2339页

作者： Lake, Irene Lundberg, Peter Stockholm Univ Dept Meteorol Phys Oceanog S-10691 Stockholm Sweden

As a joint Nordic project, an upward-looking ADCP has been maintained at the sill of the Faroe Bank Channel from 1995 onward. Records from a period in 1998 with three current meters deployed across the channel were used to demonstrate that the Faroe Bank Channel deep-water transport from the Norwegian Sea into the North Atlantic Ocean proper can be reasonably well estimated from one centrally located ADCP. The long-term average of this transport over the period 1995-2001 was found to be 2.1 Sv ( Sv 10(6) m(-3) s(-1)). The transport record demonstrates a pronounced seasonality. Satellite altimetry shows that this is caused by the northbound Atlantic surface water inflow giving rise to a barotropic modulation of the deep-water flow through the Faroe-Shetland Channel and the southern reaches of the Norwegian Sea.

关键词： Norwegian Sea transport positive pressure acoustic doppler current profiling Faroe North Atlantic overflow

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CFD Modeling of Solid Separation in Three Combined Sewer overflow Chambers

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JOURNAL OF ENVIRONMENTAL ENGINEERING-ASCE 2009年第9期135卷 776-787页

作者： Dufresne, Matthieu Vazquez, Jose Terfous, Abdelali Ghenaim, Abdellah Poulet, Jean-Bernard Inst Natl Sci Appl Lab Genie Concept F-67084 Strasbourg France Ecole Natl Genie Eau & Environm Strasbourg F-67070 Strasbourg France

The knowledge of solid behavior in combined sewer overflow (CSO) chambers is a great challenge for the protection of receiving watercourses. Moreover, great attention must be given to the occurrence of deposits on the bed of the chamber because they may lead to operation problems. In this paper, we investigate the capability of a particle tracking approach to determine the solid separation in CSO chambers. This is done by comparing simulations and experimental data collected in three small-scale models, as reported by Kehrwiller 1995. The trap, reflect, and bed shear stress (BSS) boundary conditions are compared. We propose to use the Shields relationship for evaluating the critical BSS. Finally, we propose a methodology for predicting the solid separation in CSO chambers using computational fluid dynamics.

关键词： Combined sewers overflow Computational fluid dynamics technique Separation Solids Shear stress

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METHODS FOR CALCULATION OF ANNUAL AND EXTREME overflow EVENTS FROM COMBINED SEWER SYSTEMS

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WATER SCIENCE AND TECHNOLOGY 1984年第8-9期16卷 311-325页

作者： JOHANSEN, NB HARREMOES, P JENSEN, M Department of Environmental Engineering Technical University of Denmark DK 2800 Lyngby Denmark

overflow from combined systems constitute an increasing source of pollution of receiving waters, as compared to daily wastewater discharges which undergo treatment to a still higher extent. The receiving water problems from overflows are significant both in a long term scale (mean annual load) and in a short term scale (extreme event load). A method for computation of both annual and extreme load is presented. It is based on historical rain series and the use of a time-area model and simple pollutant mixing model in runoff calculation. Statistical calculations for both mean annual load and extreme events have been applied to the computed overflow series. Based on the computerized method simple manual calculations methods have been developed, resulting in graphs and tables for annual load and extreme load.

关键词： Historical rainseries urban runoff combined system overflow basin pollution time-area method

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Process dynamics for overflow devices of rectangular, circular, parabolic and triangular shape - loss prevention applications

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JOURNAL OF LOSS PREVENTION IN THE PROCESS INDUSTRIES 1997年第4期10卷 229-235页

作者： Kadlubowski, BM Brown, JM Forney, LJ Sommerfeld, JT School of Chemical Engineering Georgia Institute of Technology Atlanta GA 30332 USA

The problem of unsteady-state liquid flow across overflow devices of various shapes has been investigated. Dimensionless efflux times to evacuate a given amount of liquid from an upstream vessel or basin through an overflow conduit or weir as a function of dimensionless height of the liquid crest were computed for four specific overflow device shapes: rectangular, circular, parabolic and triangular. Analytical expressions were developed for this purpose in all cases except circular. Generalized comparison charts were developed for the cases of (1) equal flow areas of the overflow devices and (2) equal maximum flow capacities. Two examples illustrating application of the equations and charts developed in this paper to loss prevention scenarios are also presented. (C) 1997 Elsevier Science Ltd. All rights reserved.

关键词： circular dynamics overflow parabolic rectangular triangular weirs

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Parsimonious Model for Combined Sewer overflow Pollution

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JOURNAL OF ENVIRONMENTAL ENGINEERING-ASCE 2010年第3期136卷 316-325页

作者： Willems, Patrick Katholieke Univ Leuven Hydraul Lab BE-3001 Louvain Belgium Vrije Univ Brussels Dept Hydrol & Hydraul Engn BE-1050 Brussels Belgium

The reservoir concept for flow modeling has been generalized for the purpose of the parsimonious modeling of combined sewer overflow pollution. Conceptual models have been used for the buildup and washoff of pollutants on the paved surfaces, and the transport of these pollutants in the sewer system (advection, dispersion, sedimentation, and resuspension). For the parsimonious modeling of the water quality of the sewage in the effluent of the combined sewer system, the conceptual submodels of these different processes were lumped into one single model equation. When ancillary structures such as a storage sedimentation tank are present at the combined sewer overflow, the additional effect of advection, dispersion, storage, and sedimentation is considered in a similar parsimonious conceptual way. Such a parsimonious model aims to reduce the model complexity, and therefore the number of calibration parameters. In most practical cases of urban drainage modeling, water quality data are extremely limited and consequently only a small number of parameter values can be identified from the data. The proposed model is tested on the basis of 10-min and hourly concentration measurements for total suspended solids, settleable solids, biochemical oxygen demand, and ammonia at the outlet of the combined sewer system of the village of Dessel (Belgium), which were available in this case only for six overflow events.

关键词： Combined sewers Models overflow Pollutants Water quality Reservoirs

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Using overflow in a swash plate compressor for automotive air conditioning system

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY 2012年第A4期226卷 564-579页

作者： Zhang, Y. Wang, W. Shanghai Jiao Tong Univ Inst Refrigerat & Cryogen Shanghai 200240 Peoples R China

Given current environment protection problems, improvement of energy utilization efficiency is a major focus of compressor research. overflow, a method in which the high-pressure gas in the clearance volume is fully used, is introduced in the design of a swash plate compressor. The coefficient of performance (COP) of the swash plate compressor with overflow channel has a certain decrease compared with the conventional compressor, but the volumetric efficiency and the cooling capacity of a swash plate compressor with overflow channel are visibly more improved than those of a conventional compressor in terms of the same operation and dimension parameters. The overflow has beneficial effect on miniaturizing the swash plate compressor. The intake and exhaust times considerably improve after the overflow channel is incorporated into the swash plate compressor. This, in turn, substantially enhances cooling capacity of the theoretical results from 869 to 953 W, an improvement by about 10 per cent in this article;however, COP decreases by about 3.7 per cent.

关键词： swash plate compressor overflow relative clearance volume volumetric efficiency cylinder displacement coefficient of performance

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Modeling and analysis of hierarchical cellular networks with bidirectional overflow and take-back strategies under generally distributed cell residence times

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TELECOMMUNICATION SYSTEMS 2006年第1期32卷 71-91页

作者： Tang, Shensheng Li, Wei Univ Toledo Dept Elect Engn & Comp Sci Toledo OH 43606 USA

The rapid growth of wireless services and mobile users drives a great interest in cellular networks with a hierarchical structure. Hierarchical cellular networks (HCNs) can provide high system capacity, efficient channel utilization and inherent load-balancing capability. In this paper, we develop an analytical model and a performance analysis method for a two-layer HCN with bidirectional overflow and take-back strategies. Mobile users are divided into two classes. The call requests (including new and handoff calls) of fast and slow users are preferably assigned to the macrolayer and microlayer, respectively. A call from a fast user or slow user can overflow to its non-preferable layer if there is no channel available. The successful overflow call can be taken back to its preferable layer if a channel becomes available. Since the commonly used exponentially distributed assumption for cell residence time and then the channel occupancy time does not hold for emerging mobile networks, we model various cell residence times by general distributions to adapt to more flexible mobility environments. The channel occupancy times are derived in terms of the Laplace transforms of various cell residence times. The handoff rates, overflow rates and take-back rates of each layer are also derived in terms of the new call arrival rates and related probabilities. The stationary probabilities (and then the performance measures) are determined on the basis of the theory of multi-dimensional loss systems.

关键词： hierarchical cellular networks handoff overflow take-back cell residence time channel occupancy time

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