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sediment-transport
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Numerical Modeling of Sediment Transport in Souza Gheshm Island
, M.Sc. Thesis Sharif University of Technology ; Raie, Mohammad (Supervisor) ; Ataei Ashtiani, Behzad (Supervisor)
Abstract
Complicated theories dominated toward interacting of coastal regions resulted from its nature. Besides of that interference of human activities for acquiring beneficial aspects of shorelines causes environmental considerations to be challenged. One of the main factors for resolving this challenge is to obtain adequate information from hydrodynamic process and sediment regime. In spite of scientific researches that carried out along past three decades for understanding the exact mechanism of along shore sediment transport, it was not fully developed. One of the main reasons of uncertainty for forecasting the sediment regime regarded not exact knowledge of how sediment act in different...
Simulating Sediment Transportation (Scour) Under Pipelines
,
M.Sc. Thesis
Sharif University of Technology
;
Abbaspour, Madjid
(Supervisor)
Abstract
Regarding to significant role of marine pipelines in transferring oil, water and other products, a research was carried out to study the sediment transportation (Scouring) under pipelines which threaten pipelines. Interaction between fluid phase (flow field), structure phase (pipe) and sediment, determine scour profile shape and specifications of each phase which can change scour depth. In this research Flow-3D software was used to simulate scouring process under cylinder. First the flow field around cylinder near wall was studied and the scour depth under direct and oscillating flow was simulated. In addition, in next pace, the number of pipes and their distance were varied to measure...
Investigating Engineering Solutions to Preserve Goragan Bay:Dreding Ashouradeh Channel
, M.Sc. Thesis Sharif University of Technology ; Raie, Mohammad (Supervisor)
Abstract
Gorgan Bay, registered as a biosphere reserve, has environmental value in the country and the world. The bay is separated from the Caspian Sea by sedimentation in the sandy spit of Miankaleh. Due to the declining water level of the Caspian Sea and the possibility of hydraulic connection disruption and closure of its openings, this water body may face many problems in the future. Main problems are the increase in water retention time and, consequently, the decrease in water quality and the problem of local access during the seasons when the water level drops. In this study, engineering solutions have been studied in proportional with the current conditions of the Gorgan Gulf, which include...
Analysis of threshold and incipient conditions for sediment movement
, Article Coastal Engineering ; Volume 55, Issue 5 , 2008 , Pages 423-430 ; 03783839 (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
2008
Abstract
Prediction of threshold conditions and incipient motion is the essential issue for the study of sediment transport. This work compares existing empirical threshold curves proposed for Shields diagram, a method based on the concept of probability of sediment movement, and an empirical method based on movability number. These methods are used to predict the incipient motion conditions for experimental runs taken from various studies. Most of the experimental data, used in this work, have not been used before in derivation of alternative formulations for Shields diagram and other methods. The empirical threshold curves based on the Shields entrainment function was the least successful at...
Investigating Sediment Transport in Deep Reservoirs Using the 3D Numerical Model MIKE3
, M.Sc. Thesis Sharif University of Technology ; Shamsai, Abolfazl (Supervisor) ; Ghaemial, Mohsen (Supervisor)
Abstract
Nowadays, in the world and our country, Iran, sediment transport and the phenomenon of sedimentation are of great importance. The entry of water flow with suspended sediments into the dam reservoir by floods with different return periods during the initial period of dam construction causes a considerable part of the helpful volume of the reservoir to be filled with sediments. As a result, the discharge of these sediments and the methods that exist in this field should be studied so that a large volume of reservoir water is not wasted during the discharge of these sediments. In this research, the opening time and extent of the bottom outlets of Qeshlaq Dam when the flood enters the reservoir...
Experimental investigation of the effect of obstacles on the behavior of turbidity currents
, Article Canadian Journal of Civil Engineering ; Volume 40, Issue 4 , 2013 , Pages 343-352 ; 03151468 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
2013
Abstract
Turbidity current is produced when a particle-laden fluid flows under lighter ambient fresh fluid. The streaming of particle-laden fluid is called a turbidity current and this kind of current is an important mechanism for sediment transportation in lakes and oceans. In the present research, the main concentration is on the effect of obstacle with an isosceles right triangular cross section on the behavior of turbidity current. A series of laboratory experiments were carried out with various obstacle heights and different inlet densimetric Froude numbers. In each experiment, velocity profiles upstream and downstream of the obstacle were measured, using an acoustic Doppler velocimeter. Kaolin...
Experimental study of obstacle effect on sediment transport of turbidity currents
, 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
Abstract
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...
Effect of an obstacle on the depositional behaviour of turbidity currents
, 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
Abstract
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...
Experimental study on the interfacial instability of particle-laden stratified shear flows
, 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
Abstract
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;...
3-D simulation of sedimentation in turbidity currents
, 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
Abstract
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...
Effects of density currents on sedimentation in reservoirs
, Article Scientia Iranica ; Volume 14, Issue 5 , 2007 , Pages 395-404 ; 10263098 (ISSN) ; Shamsai, A ; Sharif University of Technology
Sharif University of Technology
2007
Abstract
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...
Viscous wave interaction due to motion of a surface wave over a sediment bed
, Article Journal of Offshore Mechanics and Arctic Engineering ; Volume 128, Issue 4 , 2006 , Pages 276-279 ; 08927219 (ISSN) ; Lawrence, G. A ; Sharif University of Technology
2006
Abstract
The results of a flume experiment and a theoretical study of surface wave motion over a fluidized bed are presented. It is shown that a resonant wave interaction between a surface wave and two interfacial waves at the interface of the fresh water and the fluidized bed is a strong mechanism for instability of the interface and the subsequent mixing of the layers. The interfacial waves are subharmonic to the surface wave and form a standing wave at the interface. The interaction is investigated theoretically using a viscous interaction analysis. It is shown that surface wave height and viscous effects are the determining factors in the instability mechanism. The results indicate that the net...
Effect of selected parameters on the depositional behaviour of turbidity currents
, Article Journal of Hydraulic Research ; Volume 50, Issue 1 , Dec , 2012 , Pages 60-69 ; 00221686 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
2012
Abstract
Turbidity currents containing kaolin particles were studied experimentally in a channel and the velocity and concentration profiles were measured using an acoustic Doppler velocimeter. These experiments were performed to investigate the depositional behaviour of turbidity currents. The suspended sediment flux was evaluated by experimental and analytical methods and the results of these two methods were in a good agreement. To evaluate the suspended sediment flux, it was necessary to recognize the suspended sediment zone from the upper shear layer region and near the bed depositional area as well. The method of determination of these areas is discussed. The effects of important parameters...
Experimental observation of the flow structure of turbidity currents
, Article Journal of Hydraulic Research ; Volume 49, Issue 2 , 2011 , Pages 168-177 ; 00221686 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
Abstract
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...
Experimental investigation of the effect of inlet concentration on the behavior of turbidity currents in the presence of two consecutive obstacles
, Article Journal of Waterway, Port, Coastal and Ocean Engineering ; Volume 143, Issue 2 , 2017 ; 0733950X (ISSN) ; Afshin, H ; Firoozabadi, B ; Farizan, A ; Sharif University of Technology
American Society of Civil Engineers (ASCE)
2017
Abstract
Turbidity currents are often the main processes of sediment transport in deep waters and reservoirs. To prevent sedimentation in critical locations, various methods, such as placing solid obstacles in the path of these flows, have been proposed. In the present study, the effect of inlet concentration on the behavior of turbidity currents in the presence of two consecutive triangular obstacles was investigated experimentally. For this purpose, a series of laboratory experiments were conducted with various inlet concentrations. In each experiment, velocity and concentration profiles were measured using an acoustic Doppler velocimeter. The velocity of the current head and local Froude number...
Effect of an obstacle on the depositional behaviour of turbidity currents
, Article Journal of Hydraulic Research ; Volume 57, Issue 1 , 2019 , Pages 75-89 ; 00221686 (ISSN) ; Yaghoubi, S ; Firoozabadi, B ; Afshin, H ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
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...
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
2006
Abstract
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...
Experiments on turbidity current regimes in a straight open channel
, Article World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress, 22 May 2011 through 26 May 2011 ; May , 2011 , Pages 4047-4064 ; 9780784411735 (ISBN) ; Ayyoubzadeh, S. A ; Firoozabadi, B ; Kordi, E ; Sharif University of Technology
2011
Abstract
The present study has been conducted to investigate the effect of inlet flow regimes on vertical velocity and concentration profiles of the turbidity current. Experiments carried out on small scale channel and Kaolin with a density of 2.65 kg/m3 and a mean particle diameter of 4.5 μm, was used to generate the currents. Velocities were obtained at a rate of 10 Hz using an acoustic Doppler velocimeter. Using the siphon sampling approach, the acoustic backscattering intensity was calibrated and concentration was determined using a backscattering analysis. Results showed that the ratio of maximum velocity height to the height of the current was around 0.4-0.5 in sub- and super-critical regimes....
The power of environmental observatories for advancing multidisciplinary research, outreach, and decision support: the case of the minnesota river basin
, Article Water Resources Research ; Volume 55, Issue 4 , 2019 , Pages 3576-3592 ; 00431397 (ISSN) ; Dolph, C ; Baker, A ; Bevis, M ; Cho, S. J ; Czuba, J. A ; Dalzell, B ; Danesh Yazdi, M ; Hansen, A. T ; Kelly, S ; Lang, Z ; Schwenk, J ; Belmont, P ; Finlay, J. C ; Kumar, P ; Rabotyagov, S ; Roehrig, G ; Wilcock, P ; Foufoula Georgiou, E ; Sharif University of Technology
Blackwell Publishing Ltd
2019
Abstract
Observatory-scale data collection efforts allow unprecedented opportunities for integrative, multidisciplinary investigations in large, complex watersheds, which can affect management decisions and policy. Through the National Science Foundation-funded REACH (REsilience under Accelerated CHange) project, in collaboration with the Intensively Managed Landscapes-Critical Zone Observatory, we have collected a series of multidisciplinary data sets throughout the Minnesota River Basin in south-central Minnesota, USA, a 43,400-km2 tributary to the Upper Mississippi River. Postglacial incision within the Minnesota River valley created an erosional landscape highly responsive to hydrologic change,...