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Experimental investigation of baffle effect on the flow in a rectangular primary sedimentation tank
, Article Scientia Iranica ; Volume 17, Issue 4 B , 2010 , Pages 241-252 ; 10263098 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
2010
Abstract
In primary sedimentation tanks, short-circuiting enlargement of dead zones and high flow mixing problems are caused by circulation regions (dead zones), which can reduce the optimal sedimentation of particles. For proper design of such tanks, the formation of recirculation zones should be avoided. The provision of a baffle as a geometrical modification of a tank may influence the flow field for better sedimentation. Thus, in this study, velocity measurements were performed by a three-dimensional Acoustic Doppler Velocimeter (ADV) to investigate baffle effects on the velocity distribution in a primary rectangular sedimentation tank, quantitatively. Effects of baffle positioning were also...
Experimental and numerical approach to enlargement and determination of performance of primary sedimentation basin
, Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 2 FORA, Issue PART A , March , 2007 , Pages 265-272 ; 0791842886 (ISBN); 9780791842881 (ISBN) ; Firoozabadi, B ; Sharif University of Technology
2007
Abstract
In the present study, the presence of a baffle and its effect on the hydrodynamics of the flow in a primary settling tank has been investigated experimentally by ADV (Acoustic Doppler Velocimeter). On the other hand, the characteristics of this flow field were simulated by an unsteady two-phase finite volume method, and VOF (Volume of Fluid) model; and results were evaluated by the experimental data. The numerical calculation performed by using k - ε RNG model agrees well with experiments. It depicts the ability of this method in predicting the velocity profile and flow structure. In addition, the optimum position of the baffle to achieve the best performance of the tank was determined by...
Effects of inlet position and baffle configuration on the hydraulic performance of primary settling tanks
, Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 261 FED , 2005 , Pages 613-618 ; 08888116 (ISSN); 0791842193 (ISBN); 9780791842195 (ISBN) ; Tamayol, A ; Ahmadi, G ; ASME Fluids Engineering Division ; Sharif University of Technology
2005
Abstract
Circulation regions always exist in the settling tanks. These regions reduce the tank's performance and decrease effective volume of the tank. Recirculation zones would also result in short-circuiting and high flow mixing problems. Inlet position would also have effect on these, too. Using good baffle configuration may increase performance of settling tanks. One method for comparison of different tanks with each others is to use FTC. In this paper, by using FTC the effects of inlet position and baffle configuration on the hydraulic performance of primary settling tanks are studied. The best position of baffle is also determined. Copyright © 2005 by ASME
Hydrodynamics of secondary settling tanks and increasing their performance using baffles
, Article Journal of Environmental Engineering ; Volume 136, Issue 1 , 2010 , Pages 32-39 ; 07339372 (ISSN) ; Firoozabadi, B ; Ashjari, M. A ; Sharif University of Technology
Abstract
Generally, the flow in settling tanks is stratified, but the effect of buoyancy force on the flow field depends on the inlet concentration of particles and flow bulk velocity. A common approach for increasing settling tanks performance is to use baffles which can reduce effects of the unfavorable phenomena such as short circuiting between inlet and outlet and density currents in primary and secondary settling tanks, respectively. The suitable position of the baffles is related to the importance of buoyancy force. As a result, effects of inlet Reynolds and Froude numbers on the strength of buoyancy force are studied for a secondary settling tank and the results show that neither Reynolds nor...
Numerical Simulation of Sedimentation Tanks Using the LES Model
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Supervisor)
Abstract
In the present study, hydrodynamics and particle sedimentation of a rectangular basin is studied numerically. Results are also validated with experimental data. Two major goals are perused in this work: First comparing LES and RNG k-ϵ turbulence models and second, investigating the accuracy of simulation of particle sedimentation by solving the concentration formula.
In order to achieve these goals, a 2D sedimentation tank is simulated using the RNG k-ϵ model. Velocity and concentration profiles are also plotted. Comparing the results with experimental data reveals that simulating sedimentation by the mentioned method has acceptable accuracy and can be used to predict sedimentation. In...
In order to achieve these goals, a 2D sedimentation tank is simulated using the RNG k-ϵ model. Velocity and concentration profiles are also plotted. Comparing the results with experimental data reveals that simulating sedimentation by the mentioned method has acceptable accuracy and can be used to predict sedimentation. In...
Numerical Assessment of Optimum Baffle Configuration and Hydrodynamics of Settling Tanks
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor)
Abstract
Sedimentation tanks are channels designed for sedimentation of suspended solids in water. These tanks are one of the most important parts of water treatment plants and their performance directly affects the functionality of water treatment plants. Therefore, researchers have tried to find better designs of sedimentation tanks. Among several design methods have been presented, modification of the geometry of tanks by installing baffles is one of the most effective and economic methods. According to the importance of performance improvement of industrial sedimentation tanks as well as the diversity in reported results, development and completion of previous studies seem to be necessary. In...
UWB spectrally-encoded spread-time CDMA in the presence of multiple Gaussian interferences: RAKE receiver and three-level codes
, Article IEEE Transactions on Communications ; Volume 56, Issue 12 , December , 2008 , Pages 2178-2189 ; 00906778 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2008
Abstract
In this paper we study and analyze the performance of the RAKE receiver for a typical Ultrawideband (UWB) Spectrally-Encoded Spread-Time (ST) CDMA in the presence of multiple Gaussian Interference (GI) signals. We demonstrate that by combining useful properties of three-level codes, i.e., codes with values of - 1, 0, +1, and RAKE receiver, we can introduce a new strategy in which it can result in superior performance when compared to previous results. In particular, following a discussion on three-level codes we can show that RAKE receiver with optimum multiplicative weights achieves a better performance when compared with simple two-level codes. With the help of an example we show various...
Effects of turbulent models and baffle position on the hydrodynamics of settling tanks
, Article Scientia Iranica ; Volume 13, Issue 3 , 2006 , Pages 255-260 ; 10263098 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Sharif University of Technology
2006
Abstract
In this paper, the numerical results of hydrodynamic modeling of primary settling tanks are presented. The flow field is assumed to be incompressible and non-buoyant. The effects of two different types of turbulence model, standard κ - ε and RNG, are compared with each other. The effects of an inlet baffle on the hydrodynamics of settling tanks are also studied. Results are obtained for the primary settling tank of the city of Sarnia, Ontario, Canada. The effects of the existence and position of another interior baffle in the settling tanks are also studied. Results in the different parts are compared with experimental and numerical data and showed good agreement. Comparison between two...
Experiments and numerical modeling of baffle configuration effects on the performance of sedimentation tanks
, Article Canadian Journal of Civil Engineering ; Volume 40, Issue 2 , 2013 , Pages 140-150 ; 03151468 (ISSN) ; Bakhtyar, R ; Firoozabadi, B ; Barry, D. A ; Sharif University of Technology
2013
Abstract
The hydraulic efficiency of sedimentation basins is reduced by short-circuiting, circulation zones and bottom particleladen jets. Baffles are used to improve the sediment tank performance. In this study, laboratory experiments were used to examine the hydrodynamics of several baffle configurations. An accompanying numerical analysis was performed based on the 2-D Reynolds-averaged Navier-Stokes equations along with the k-ε turbulence closure model. The numerical model was supplemented with the volume-of-fluid technique, and the advection-diffusion equation to simulate the dynamics of particle-laden flow. Model predictions compared well with the experimental data. An empirical function was...
Biomass Separation in Moving Bed Biofilm Reactors (MBBR) by Natural And Innovative Filters
, M.Sc. Thesis Sharif University of Technology ; Borgheei, Mahdi (Supervisor)
Abstract
The application of membranes for separate of particles in mainly microbial flacs , are fast growing in biological treatment systems. Membrane bioreactors are now considered as one of the major new processes in wastewater treatment. However , membranes are expensive and costly. This study is carried out to test an innovative , locally made filters for separation of flocs in an MBBR reactor. This innovative filter is replacing a traditional settling tank. This type of filters is made very cheaply and has important advantages in installing and operation. Experiments were carried out in a laboratory scale MBBR unit. A filter unit consisting of 3 innovative filter tubes were placed and the...
Experimental investigation of effects of baffle configurations on the performance of a secondary sedimentation tank
, Article Scientia Iranica ; Volume 18, Issue 4 B , August , 2011 , Pages 938-949 ; 10263098 (ISSN) ; Firoozabadi, B ; Afshin, H ; Sharif University of Technology
2011
Abstract
Sedimentation tanks are designed for the settling of floated solids in water. These tanks are one of the most important parts of water treatment plants and their performance directly affects the functionality of these plants. One challenging method for increasing the performance of sedimentation tanks is to use baffles. A useful baffle should be installed in a suitable place with a proper height. In this work, an experimental study of particle-laden flow in a rectangular sedimentation tank has been performed and kaolin is used as solid particles. The effects of baffle configurations on the velocity and concentration profiles along the tank were studied. Sedimentation tank performance was...
Prediction of hydraulic efficiency of primary rectangular settling tanks using the non-linear k - ε turbulence model
, Article Scientia Iranica ; Volume 17, Issue 3 B , 2010 , Pages 167-178 ; 10263098 (ISSN) ; Ashjari, M. A ; Sharif University of Technology
2010
Abstract
Circulation is created in some parts of settling tanks. It can increase the mixing level, decrease the effective settling, and create a short circuiting from the inlet to the outlet. All above-mentioned phenomena act in such a way to decrease the tank's hydraulic efficiency, which quantitatively shows how flow within the tank is uniform and quiet. So, the main objective of the tank design process is to avoid forming the circulation zone, which is known as the dead zone. Prediction of the flow field and size of the recirculation zone is the first step in the design of settling tanks. In the present paper, the non-linear k - ε turbulence model is used for predicting the length of the...
Performance analysis of an internally coded time-hopping spread-time CDMA system in the presence of interference
, Article 2008 5th IEEE Consumer Communications and Networking Conference, CCNC 2008, Las Vegas, NV, 10 January 2008 through 12 January 2008 ; 2008 , Pages 430-434 ; 9781424414574 (ISBN) ; Nasiri Kenari, M ; Sharif University of Technology
2008
Abstract
In this paper, we consider the internally coded time-hopping spread-time multiple access scheme introduced in [1]. We evaluate the performance of the correlator receiver followed by the Viterbi algorithm in fading channel. We analyze the effect of multiple access interference (MAI) and narrowband interference (NBI). We also provide simulation results and further evaluate the performance of the system for the ultra wide band (UWB) application with the UWB channel model specified by the IEEE 802.15.4a group. For comparison, we consider the conventional ST-CDMA system. The results indicate that our method has much better performance while it has the same bandwidth and spectral efficiency as the...
Multiple-access performance analysis of combined time-hopping and spread-time CDMA system in the presence of narrowband interference
, Article IEEE Transactions on Vehicular Technology ; Volume 58, Issue 3 , 2009 , Pages 1315-1328 ; 00189545 (ISSN) ; Nasiri Kenari, M ; Sharif University of Technology
2009
Abstract
We consider a combined time-hopping (TH) and spread-time (ST) multiple-access technique that uses an internal code. In this method, the duration of each bit is divided into Ns frames. The outputs of the encoder and a pseudorandom (PN) sequence specify the number of the frame in which the data bit is transmitted in ST code-division multiple-access (ST-CDMA) form using the second PN sequence. We consider the correlator receiver, followed by the channel decoder. We obtain the performance of the combined method in additive white Gaussian noise (AWGN) and fading channels in the presence of multiple-access interference (MAI) and narrowband interference (NBI). We also consider the conventional...