Master Degree / Yüksek Lisans Tezleri

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

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Subject: search.filters.subject.Numerical model

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  • Master Thesis
    Numerical Modeling of the Filter Sand Performance in Embankment Dam Under Static and Dynamic Conditions
    (01. Izmir Institute of Technology, 2023) Karaoğlu, Aybüke; Ecemiş Zeren, Nurhan
    The filter material in embankment dams is a crucial part of the dam due to protecting the core material (usually clay) against internal erosion. Internal erosion is defined as the transportation of core material particles to the filter material by seepage flow. It is the main reason for the deformation and loss of resistance in the body and foundation of a dam. Therefore, it is a serious threat risk to embankment dams. To prevent internal erosion, it is necessary to accurately evaluate the interaction between water-filter material-core material during the dam's design and operation stages. A suitable filter material should be able to control and block cracks that can form in the core material. Terzaghi (1925) did the first research on filter material and proposed a criterion based on the particle size of a clay. Another detailed study was conducted by Sherard et al. (1989) who developed an experiment called No Erosion Filter Test (NEF Test) to comprehend the relationship between filter and core materials. NEF Test is seen as the most proper method to determine the critical filter which leans on the impermeable core material in the downstream side of an embankment dam. In the NEF test, the most severe condition that can occur is represented as an erosive leak from the core material to the filter material. Within the scope of this study, the internal erosion of the backfill used in the dam is studied through outflow rate and deformations in the base sample (clay). First, the samples taken from two embankment dams in Izmir (Kalabak Dam and Rahman Dam) were brought to the geotechnical laboratory of Izmir Institute of Technology (IZTECH), and the filter material was mixed with fine materials (silt) in different contents. A series of NEF Tests were performed in the IZTECH-geotechnical laboratory on the filter and core samples of Kalabak Dam within a TUBITAK Project No. 221M071 (Ecemis, 2023). Then, the performed NEF Tests were modeled by the finite difference method (FDM) using the Itasca-FLAC3D software. Finally, the outcomes of the numerical models were compared to experimental results. Numerical models had a good agreement to decide whether filter sand performance is successful or not.
  • Master Thesis
    Numerical Modeling of the Artificial Destratification of the Thermally Stratified Water Column by Air Diffusers
    (01. Izmir Institute of Technology, 2021) Bahadıroğlu, Nisa; Elçi, Şebnem
    Reservoirs have essential roles in water management due to the large areas of use. In a reservoir, the structure of the temperature profile in the vertical water column mainly controls the vertical distribution of heat, dissolved substances, and nutrients. Thermal stratification in the water column can lead to an anoxic and poor quality water source. Artificial destratification has been widely used to improve water quality in thermally stratified water sources. This study focuses on the numerical modeling of artificial destratification of thermally stratified water columns by air diffusers to improve the water quality of reservoirs. Firstly, destratification experiments were performed to verify the numerical models. In the experiments, the effects of air diffuser hole diameter, air flow rate, and the number and configuration of holes on the diffuser on destratification time and efficiency were observed. The second part of the study comprised the numerical modeling of hydrodynamics during the destratification of thermally stratified water columns by air diffusers. ANSYS Fluent software is utilized for the simulation of the hydrodynamic processes. Model options for multiphase flows, boundary conditions, and turbulence; and their comparison with experimental studies are discussed. The Eulerian multiphase model and k-ω turbulence model were found to be suitable for this study. In the final part, the numerical model was verified with the experiments. Based on the error analysis of comparisons of the model and observations, the best configuration of air diffuser is proposed, and the numerical model was found to be successful in simulating the destratification of thermally stratified water columns by air diffuser.