Search for: turbidity
Total 45 records
Article Journal of Hydraulic Research ; Volume 41, Issue 6 , 2003 , Pages 623-630 ; 00221686 (ISSN) ; Farhanieh, B ; Rad, M ; Sharif University of Technology
International Association of Hydraulic Engineering Research 2003
Motion of turbid density currents laden fine solid particles, released on sloping bed and under still bodies of clear water, are numerically investigated. The equations of mass, momentum and diffusion for unsteady, laminar flow are solved at the same time in the fixed Cartesian directions, on a non-staggered grid using finite volume scheme. The velocity-pressure coupling is handled by SIMPLEC method. Turbidity currents with uniform velocity and concentration enter the channel via a sluice gate into a lighter ambient fluid and move forward down-slope. At the front of this flow, a vortex forms and grows while moving downstream. Comparison of the computed height of turbidity current with the...
Article Journal of Applied Fluid Mechanics ; Volume 3, Issue 1 , 2010 , Pages 63-73 ; 17353572 (ISSN) ; Afshin, H ; Bagherpour, A ; Sharif University of Technology
The present study investigates the turbulence characteristic of turbidity current experimentally. The three-dimensional Acoustic-Doppler Velocimeter (ADV) was used to measure the instantaneous velocity and characteristics of the turbulent flow. The experiments were conducted in a three-dimensional channel for different discharge flows, concentrations, and bed slopes. Results are expressed at various distances from the inlet, for all flow rates, slopes and concentrations as the distribution of turbulence energy, Reynolds stress and the turbulent intensity. It was concluded that the maximum turbulence intensity happens in both the interface and near the wall. Also, it was observed that the...
Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of 'near-wall' k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v2̄-f model which show similarity. Also results show good agreement with experimental data...
Article Journal of Hydraulic Research ; Volume 56, Issue 5 , 2018 , Pages 618-629 ; 00221686 (ISSN) ; Iranshahi, M ; Ghodsian, M ; Firoozabadi, B ; Sharif University of Technology
Taylor and Francis Ltd 2018
The effects of an obstacle on the suspended load transport rate of supercritical turbidity currents were investigated experimentally. A Vectrino velocity meter was used to measure velocity and sediment concentration profiles. The effects of important parameters including inlet discharge, mean inlet sediment concentration and obstacle height on suspended load transport rate were investigated. In the upstream velocity profiles, the obstacle generates the reflected and the interface regions in addition to the wall and the jet regions. The average amount of suspended load transport rate downstream of the obstacle decreases to about 92%. This confirms the depositional behaviour of turbidity...
Study of Light Propagation in Biological Tissues by Means of the Monte Carlo Simulation and Diffusion Method, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad ; Ansari, Mohammad Ali
The tissue characteristics are important for all kinds of medical laser applications in order to understand the interaction mechanisms between light and tissue. Knowledge about light transport in tissue is essential for cancer treatment and cancer diagnostic techniques. By having the diffused reflectance of a tissue we can determine its optical characteristics. In this thesis we have solved the inverse process. That is, we compute the diffused reflectance of a turbid media with pre-determined optical parameters. This problem can be solved using two methods: Monte Carlo simulation and diffusion method. Since Monte Carlo simulation is computationally very expensive, it is not used in medical...
Artificial neural network modeling for predict performance of pressure filters in a water treatment plant, Article Desalination and Water Treatment ; Volume 39, Issue 1-3 , Feb , 2012 , Pages 192-198 ; 19443994 (ISSN) ; Gholikandi, G. B ; Hazrati, H ; Sharif University of Technology
Taylor and Francis Inc 2012
Pressure filters are popular in small municipal water treatment plants. One of the principles for designing and using the various units of water treatment plants is the ability of assigning and predicting the performance of those units under different and various conditions that could be verified by making pilot scale tests and could be modeled by means of available programs and software such as artificial neural network. The goals of this study that was conducted to predict pressure filter efficiency are: (1) evaluations of pressure filter efficiency for turbidity removal under different conditions such as turbidity of raw water, filtration rate and filter pressure changes; (2) statistical...
An artificial neural network model for the prediction of pressure filters performance and determination of optimum turbidity for coli-form and total bacteria removal, Article Journal of Environmental Studies ; Volume 37, Issue 60 , 2012 , Pages 129-136 ; 10258620 (ISSN) ; Hazrati, H ; Rostamian, H ; Sharif University of Technology
In water treatment processes, because of complicated and nonlinear relationships between a number of physical, chemical and operational parameters, using analytical models with the ability to capture underlying relationships using examples of the desired input-output mapping is quite suitable. Artificial Neural Networks (ANN) has been increasingly applied in the area of environmental and water resources engineering. The main advantage of Artificial Neural Networks over physical-based models is that they are data-driven. The purpose of this research is to study the performance of pressure filters on turbidity removal from water according to several parameters such as turbidity, filtration...
Synchronous measurements of the velocity and concentration in low density turbidity currents using an Acoustic Doppler Velocimeter, Article Flow Measurement and Instrumentation ; Volume 17, Issue 1 , 2006 , Pages 59-68 ; 09555986 (ISSN) ; Shamsai, A ; Ataie Ashtiani, B ; Sharif University of Technology
Low density turbidity currents have been investigated in a laboratory flume. An Acoustic Doppler Velocimeter (ADV) was used to measure the velocity. The dimensionless velocity profiles were compared with previous studies to check the accuracy of acoustic measuring techniques for turbidity currents. Successful use of the ADV to measure the current velocity has led to interest in the technique of using acoustic sensors to estimate concentrations. Acoustic backscattering analyses are used for estimating the sediment concentration in turbidity currents. With this approach, concentration measurements can be reasonably well represented by a similarity profile. Using this technique, an accurate...
Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Firoozabadi, B ; Ghasvari Jahromi, H ; Moosavi Hekmati, S. M. H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME) 2006
Flows generated by density differences are called gravity or density currents which are generic features of many environmental flows. These currents are classified as the conservative and non-conservative flows whether the buoyancy flux is conserved or changed respectively. In this paper, a low Reynolds k-ε turbulence model is used to simulate three dimensional density and turbidity currents. Also, a series of experiments were conducted in a straight channel to study the characteristics of the non-conservative density current. In experiments, Kaolin was used as the suspended material. Comparisons are made between conservative and non-conservative's height, concentration and velocity profiles...
Stabilization of the suspension of zirconia microparticle using the nanoparticle halos mechanism: zeta potential effect, Article Journal of Dispersion Science and Technology ; Volume 37, Issue 1 , 2016 , Pages 6-13 ; 01932691 (ISSN) ; Saidi, M.H ; Zabetian, M ; Sharif University of Technology
Taylor and Francis Inc 2016
An experimental study has been conducted to investigate the effect of silica nanoparticle halos on the stability of the zirconia aqueous suspension. The results of turbidity measurements showed that addition of nanoparticles to the suspension increases the stability of the zirconia suspension for all pH values. The achieved stability refers to the formation of nanoparticle halos around the microparticles that can be observed by scanning electron microscopy (SEM) imaging. The best stabilization is achievable when zirconia microparticles are at the isoelectric point. The minimum stabilization occurs when microparticles have relatively high zeta potential and the force between micro and...
Article Journal of Hydraulic Research ; 2018 , Pages 1-15 ; 00221686 (ISSN) ; Yaghoubi, S ; Firoozabadi, B ; Afshin, H ; Sharif University of Technology
Taylor and Francis Ltd 2018
Turbidity currents are responsible for much of the sedimentation in reservoirs. In order to control these flows, various methods such as placing an obstacle in their path have been proposed. In this study, the effect of inlet sediment concentration and obstacle height on the behaviour of turbidity currents is investigated experimentally. For this purpose, some experiments were carried out with different inlet concentrations and various obstacle heights. Velocity and concentration profiles were measured using an acoustic Doppler velocimeter. To examine the depositional behaviour of turbidity current, suspended sediment flux was calculated using velocity and concentration profiles of the...
Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 40, Issue 4 , April , 2018 ; 16785878 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Springer Verlag 2018
Turbidity currents are one of the more frequently observed types of stratified flows. In these currents, the density difference is created as a result of suspended particles. The interfacial instability of turbidity current is studied experimentally in the present research. Both Kelvin–Helmholtz and (asymmetric) Holmboe instabilities are observed during the experiments; the first one was downstream, and the second one was upstream of the obstacle. Kelvin–Helmholtz instability is observed by approximately zero (phase) speed with respect to the mean flow. With the aim of measuring spectral distribution of velocity fluctuations, the effects of some parameters are studied on interfacial waves;...
Article Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 28 January 2018 through 1 February 2018 ; Volume 10494 , 2018 ; 16057422 (ISSN); 9781510614734 (ISBN) ; Salimi, F ; Mohammadian, N ; Fatima, A ; Rahimi Tabar, M. R ; Nasiri Avanaki, M. R ; SENO Medical Instruments, Inc.; The Society of Photo-Optical Instrumentation Engineers (SPIE) ; Sharif University of Technology
In this research, we present the results of applying simulated annealing (SA) which is a heuristic optimization algorithm for focusing light through a turbid media. The performance of this algorithm on both phase optimization and amplitude optimization has been demonstrated. A guideline to set up the SA parameters is also suggested. The performance of SA algorithm in different levels of measurement noise has been also explored. The results showed that the SA algorithm performs effectively in measurement noises as high as 0.3(I0). © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only
Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 8 , 2007 , Pages 503-517 ; 0791843025 (ISBN) ; Firoozabadi, B ; Ghasvari Jahromi, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME) 2007
The gravity currents on the inclined boundaries are formed when the inflow fluid has a density difference with the ambient fluid and a tangential component of gravity becomes the driving force. If the density difference arises from the suspended particles, the currents are known as particle-laden density currents, or turbidity currents in which the local density depends on the concentration of particles. A low Reynolds k- Turbulent model is used to simulate three dimensional turbidity currents. Also some laboratory tests were conducted to study the 3D flow resulting from the release of particle laden density currents on a sloping surface in a channel of freshwater via a sluice gate. Kaolin...
Article Scientia Iranica ; Volume 14, Issue 5 , 2007 , Pages 395-404 ; 10263098 (ISSN) ; Shamsai, A ; Sharif University of Technology
Sharif University of Technology 2007
The development of density or turbidity currents causes serious problems for environmental hydraulics in reservoirs. The stream entered to a reservoir can carry sediments, nutrients and chemicals as density or turbidity currents. The fate of sediment and other substances transported by the current depends on the characteristics of the turbidity current itself, i.e. the velocity of fluid, the amount of mixing with reservoir water and the rates of sediment deposition and resuspension. These are important factors for water quality in reservoirs. A two-dimensional, depth-averaged, finite-volume numerical model is developed to study density currents, driven by non-cohesive sediments. The model...
Article International Journal of Environmental Science and Technology ; Volume 4, Issue 4 , 2007 , Pages 505-512 ; 17351472 (ISSN) ; Torabian, A ; Borghei, M ; Hassani, A. H ; Sharif University of Technology
There is a need to find cheaper and simpler techniques for rural water filtration system in developing countries. Using a filter made of blocks for the water treatment enables one to make vertical filters. It is expected that the amount of land utilized would decrease by more than 70 % if vertical filters were used. The operation and washing would be simpler than using horizontal sand filters as filters made of blocks would be used instead. The feasibility study focused on finding adequate materials, compositions and methods of making a block with enough resistance to water pressure, sufficient porosity for water transformation, and using inexpensive, readily available materials. A pilot...
Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Firoozabadi, B ; Sharif University of Technology
American Society of Mechanical Engineers (ASME) 2006
Dense underflows are continuous currents which move down-slope due to the fact that their density is heavier than that ambient water. In this work, 2-D and 3-D density current in a channel were investigated by a set of experimental studies and the data were used to simulate the density current. The velocity components were measured using Acoustic Doppler Velocimetry (ADV). The height of density current (current's depth) was also measured. In this study, the density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. A low-Reynolds number turbulent model (Launder and Sharma, 1974) has been applied to...
Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 1 SYPMOSIA , 2006 , Pages 1763-1770 ; 0791847500 (ISBN); 9780791847503 (ISBN) ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
American Society of Mechanical Engineers 2006
Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of 'near-wall' k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v̄2 - f model which show similarity. Also results show good agreement with experimental data...
Article Journal of Hydraulic Research ; Volume 49, Issue 2 , 2011 , Pages 168-177 ; 00221686 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
The structure of turbidity currents released on a sloping bed below fresh water is investigated. Kaolin is used as a suspended material. Laboratory observations indicate that if a dense layer moves through the channel, the current thickness increases due to a hydraulic jump. This phenomenon occurs under special inlet conditions and has a significant effect on the current structure including velocity profile, current height and bed shear stress. Flows with different inlet Froude numbers based on various inlet concentrations behave more distinctly than those based on different inlet opening heights. Laboratory experiments indicate that an increase in the inlet Froude number causes an increase...
M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein ; Firoozabadi, Bahar
Density currents, caused by the intrusion of dense fluids under lighter ambient fluids, frequently occur in both natural and industrial situations. As a result of the density differences, the driving force can arise from soluble substances, temperature differences, etc. If the driving force comes from suspended particles including silt and mud, the currents are called turbidity currents. Due to the variation in concentration and the consequent driving force along the flow path, turbidity currents are significantly more complicated than saline currents. These currents play the most important role in sedimentation in lakes, seas and oceans. In addition, turbidity currents are the main factor...