Civil Engineering / İnşaat Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/13

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Author: search.filters.author.Hazar, Oğuz

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  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Destratification of Thermally Stratified Water Columns by Air Diffusers
    (Elsevier, 2023) Elçi, Şebnem; Hazar, Oğuz; Bahadıroğlu, Nisa; Karakaya, Derya; Bor, Aslı
    This study aims at improving the understanding in order to optimise an aeration system for artificial destratification to control cyanobacteria growth in the reservoirs. Previous applications for artificial destratification in reservoirs were based on installations based on computational methods, where neither the effect of air bubble size and configuration nor the effect of air density in the bubble plume could be investigated. This study seeks for an optimized design with the help of experimental and numerical analyses. In order to perform experimental studies, a novel water tank enabling the heating/cooling of the water column as desired and a diffuser system were manufactured. During the experimental studies, effect of bubble size, bubble slip velocity, and other parameters of air diffuser on destratification efficiency were investigated. Based on the nondimensional parameters, a new destratification efficiency formula is obtained by the Genetic Algorithm (GA) approach. Additionaly, the hydrodynamics of the water tank during the mixing process by air diffuser was simulated via 3D numerical model and validated with experimental results. The Eulerian multiphase model with the ‘degassing’ boundary condition and k-ω turbulence model are found to be suitable for the purposes of the study. Based on the error analysis of comparisons of the model and observations, the best configuration of air diffuser is proposed, and the numerical model is found to be successful in simulating the destratification of thermally stratified water columns by air diffuser.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Developing Predictive Equations for Water Capturing Performance and Sediment Release Efficiency for Coanda Intakes Using Artificial Intelligence Methods
    (MDPI, 2022) Hazar, Oğuz; Tayfur, Gökmen; Elçi, Şebnem; Singh, Vijay P.
    Estimation of withdrawal water and filtered sediment amounts are important to obtain maximum efficiency from an intake structure. The purpose of this study is to develop empirical equations to predict Water Capturing Performance (WCP) and Sediment Release Efficiency (SRE) for Coanda type intakes. These equations were developed using 216 sets of experimental data. Intakes were tested under six different slopes, six screens, and three water discharges. In SRE experiments, sediment concentration was kept constant. Dimensionless parameters were first developed and then subjected to multicollinearity analysis. Then, nonlinear equations were proposed whose exponents and coefficients were obtained using the Genetic Algorithm method. The equations were calibrated and validated with 70 and 30% of the data, respectively. The validation results revealed that the empirical equations produced low MAE and RMSE and high R2 values for both the WCP and the SRE. Results showed outperformance of the empirical equations against those of MNLR. Sensitivity analysis carried out by the ANNs revealed that the geometric parameters of the intake were comparably more sensitive than the flow characteristics.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Design of Coanda Intakes for Optimum Sediment Release Efficiencies
    (Korean Society of Civil Engineers, 2020) Hazar, Oğuz; Elçi, Şebnem
    When the water has to be diverted from a turbid source having a great amount of suspended materials in it, bottom intake structures such as Coanda and Tyrolean types are preferred. To perform this task, diverted water is captured by a transversal rack, and a gallery located in the control crest is utilized. This study was motivated by a search for the best design where the quality of the diverted water can be increased by screening out most of the sediments in the flow. Current work focuses on the water capture and sediment release efficiencies of both Tyrolean and Coanda type intakes through experimental work. It complements and extends existing experimental studies by considering sediment-laden flow. We used a novel sediment feeding system designed specifically for this study in the experiments. Study results pointed out that when sediment release efficiency is considered, all types of Coanda intakes having different design parameters performed better as compared to Tyrolean intakes. Water capture and sediment release efficiencies are related to parameters used in the experiments including Coanda type, rack angle, void ratio, sediment amount, and flow rate based on the statistical analyses of these parameters. An optimum design is proposed with the maximum sediment release efficiency to prevent clogging during the operation of the intakes. © 2020, Korean Society of Civil Engineers.