Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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2008 - 200912010 - 20152

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Subject: search.filters.subject.Sediment transport--Mathematical models

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Now showing 1 - 3 of 3
  • Master Thesis
    Modification of a Computational Fluid Dynamics Model (ansys-Fluent) for the Purpose of River Flow and Sediment Transport Modeling
    (Izmir Institute of Technology, 2015) Ekmekçi, Hüseyin Burak; Elçi, Şebnem
    Precise estimation of the sediment transport and settling velocity of particle in turbulent flows is required for many engineering applications including modeling of the transport of suspended sediments and the transport of particle pollutants. This study presents an approach for modification of an existing CFD Model for sediment transport in turbulent flow based on field measurements. In the first part, synchronized 3-D velocity and temperature time series were monitored at Büyük Menderes River in Turkey where the data were utilized to characterize the turbulence characteristics and model particle – fluid interaction. Sieve and hydrometer analysis were obtained from earlier studies to understand and modify sediment transport under different conditions via ANSYS Fluent programme. The second part of the study involved numerical modeling of hydrodynamics via 3D CFD model in the selected portion of a river body through use of field measurements conducted at the study site. The k-ω turbulence model found to be the best suited when such flow around a structure as piers or flow through a water intake is considered. Effect of particle size, concentration and modeling approach for particle motion are also investigated and Rossin Rammler Logarithmic Distribution and multiphase modeling approach was the most appropriate methods. This study involved development of an approach to modify drag force on sediment particles using turbulence characteristics in the Fluent solver as well.
  • Master Thesis
    Numerical Modeling of Unsteady and Non-Equilibrium Sediment Transport in Rivers
    (Izmir Institute of Technology, 2008) Bor, Aslı; Tayfur, Gökmen
    Management of soil and water resources is one of the most critical environmental issues facing many countries. For that reason, dams, artificial channels and other water structures have been constructed. Management of these structures encounters fundamental problems: one of these problems is sediment transport.Theoretical and numerical modeling of sediment transport has been studied by many researchers. Several empirical formulations of transported suspended load, bed load and total load have been developed for uniform flow conditions. Equilibrium sediment transport under unsteady flow conditions has been just recently numerically studied. The main goal of this study is to develop one dimensional unsteady and nonequilibrium numerical sediment transport models for alluvial channels.Within the scope of this study, first mathematical models based on the kinematic, diffusion and dynamic wave approach are developed under unsteady and equilibrium flow conditions. The transient bed profiles in alluvial channels are simulated for several hypothetical cases involving different particle velocity and particle fall velocity formulations and sediment concentration characteristics. Three bed load formulations are compared under kinematic and diffusion wave models. Kinematic wave model was also successfully tested by laboratory flume data. Secondly, a mathematical model developed based on kinematic wave theory under unsteady and nonequilibrium conditions. The model satisfactorily simulated transient bed forms observed in laboratory experiments. Finally, nonuniform sediment transport model was developed under unsteady and nonequilibrium flow based on diffusion wave approach.The results implied that the sediment with mean particle diameter and the sediments with nonuniform particle diameters gave different solutions under unsteady flow conditions.
  • Master Thesis
    Assessment of Impact of Reservoir's Contaminated Bottom Sediments on Surfacewater Quality by Sediment-Water Interaction Model
    (Izmir Institute of Technology, 2011) Şimşek, Sinem Elif; Elçi, Şebnem
    In this study, an approach for the assessment of the life-long impact of submersed contaminated bottom sediments in projected reservoirs on surface water quality is presented. A sediment-water interaction model designed to simulate contaminants in the sediments and in the overlying water column is developed and the impact of contaminated bottom sediments on water quality is investigated under different scenarios. One goal of this study is to investigate the contribution of contaminated soils underlying the reservoir compared to the contaminants transported by surface and groundwater influx. The proposed study predicts the long term impact of the selected site on water quality before the construction of the dam. The sediment-water interaction model developed in this study consists of three main layers: water column which can be specified as well mixed or stratified according to the temperature profile in the vertical column, a mixed sediment layer and a deep sediments layer. In the model, mass balance equations for contaminants are solved for the water column and the mixed sediment layer.This study further presents the projection of possible contamination in a reservoir based on the analysis of the soil samples collected from the reservoir bottom before the filling of the reservoir. Reverse modeling approach for the prediction of contaminant concentration in the water column originating from the bottom sediments is applied. Transfer of five heavy metals; Copper, Zinc, Chromium, Nickel, and Lead existing in bottom sediments of Çamlı Basin to the reservoir water is modeled.