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  1. Ana Sayfa
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Yazar "Bagatur, Tamer" seçeneğine göre listele

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    Evaluation of Plant Growth with Aerated Irrigation Water Using Venturi Pipe Part
    (Springer Heidelberg, 2014) Bagatur, Tamer
    A venturi pipe part (VPP) allows air bubbles to be inserted into flowing water from air inlet holes and so increases dissolved oxygen (DO) levels in irrigation water. The DO helps the roots absorb nutrients at a faster rate, and can increase a plant's growth rate by up to 30 %. Therefore, the aim of this paper is to evaluate design considerations and experimental results related to characteristics of VPP in air vacuum and aeration process. Optimal flow velocity in venturi inlet is determined between 1 and 4 m/s for aeration process. For starting of air vacuum process, minimum flow velocity is determined as 0.80 m/s. The ratio of the throat diameter of VPP to the inlet diameter of VPP equals to 0.5. Also, the ratio of the air vent diameter of VPP to the throat diameter of VPP equals to 0.3. Volumetric air flowrate decreases with increasing pipe length. In addition, the effect of aerated water on plant growth is tested with a case study. The case study is carried out on growth of the onion (Allium cepa) samples. In result of this test, aerated water is capable for plant growth of the onion (A. cepa) samples. However, it increased the plant's growth rate by 27 %. Thus, irrigation projects can be planned with both VPP (AirJection Irrigation) and subsurface drip irrigation systems.
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    Evaluation of Preaeration with V-Notch Weir and Cascade Structures in Clarifiers
    (Asce-Amer Soc Civil Engineers, 2009) Bagatur, Tamer
    Hydraulic structures, such as stepped cascades and weirs, involve air entrainment (aeration) and oxygen transfer. Therefore, they can increase dissolved oxygen levels. Weir aeration occurs in rivers, fish hatcheries, and wastewater treatment plants. A stepped cascade aerator is another type of aeration structure. A stepped cascade consists of a series of steps or drops, built into the face of the chute. Often, the hydraulic head is naturally available and incurs no operating cost. For the preaeration process, weir and stepped cascade structures can be previously designed for clarifiers where weirs can be used as an aid to aeration process of treatment plants. Therefore, this paper aims to review the design considerations of circular clarifiers with combined weir and stepped cascade structures as a new approach and alternative preaeration system without energy requirement before aeration tank units. The detailed example for preaeration in circular clarifiers with combined weir and stepped cascade structures is presented. Thus, the circular clarifiers with weir and stepped cascade structures as effluent and preaeration strucures can be effectively redesigned with given new design considerations.
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    Experimental Analysis of Flow Characteristics from Different Circular Nozzles at Plunging Water Jets
    (Springer Heidelberg, 2014) Bagatur, Tamer
    A plunging water jet passing through the surrounding air entrains a large amount of air bubbles into a pool and forms a large submerged two-phase (gas-liquid) contacting area. This process is called air-entrainment or aeration by plunging water jets. Numerous studies were conducted with circular nozzles. This paper presents experimental investigation of flow characteristics of truncated and non-truncated circular nozzles. The flow characteristics such as volumetric air entrainment rate, bubble penetration depth and oxygen transfer efficiency are evaluated based on four major parameters which describe air entrainment at the plunge point: the nozzle diameter, jet length, jet velocity, and jet impact angle. In addition, new predictive equations are developed for the flow characteristics of truncated and non-truncated circular nozzles. Experimental results showed that truncated and non-truncated circular nozzles have very different flow characteristics. The truncated circular nozzles indicated a rather high quality with respect to bubble penetration depth, volumetric air entrainment and oxygen transfer. In aeration application, the truncated circular nozzles can be preferred due to different flow characteristics.
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    Improving the durability of pumice-fly ash based geopolymer concrete with calcium aluminate cement
    (Elsevier, 2022) Karaaslan, Cemal; Yener, Engin; Bagatur, Tamer; Polat, Riza
    This study aims to improve the durability of pumice (70 wt%) and fly ash (30 wt%) based geo-polymer concretes (PGCs) by replacing pumice with calcium aluminate cement (CAC) up to 20 wt % of the total powder binder. In this context, durability characteristics (wetting-drying, freeze-thaw, sulfuric acid, resistance to water-penetration, and abrasion) and microstructure (by performing XRD, FTIR, and SEM-EDS analyses) of PGCs were examined and compared with Portland cement-based concrete (PCC) to control. As a result, CAC substitution of 20% increased the 28-day compressive strength of PGC from 20.0 MPa to 70.0 MPa. The abrasion resistance of PGCs was better than that of PCC, regardless of CAC replacement levels. Since PGC without CAC is highly permeable, wetting-drying cycles, freeze-thaw action, and sulfuric acid attack reduced the strength of this concrete by easily leaching the weakly bound Na cations in the geopolymer matrix and forming -OH and H-O-H type bonds. On the other hand, C-A-S-H type gels formed in PGC with 20% CAC reduced the water penetration depth up to 33 mm by reducing the permeability. In addition, upon 20 wetting-drying and 100 freeze-thaw cycles, compressive strength losses with the CAC replacement level increasing from 0% to 20% decreased from 36.7% to 1.4% and from 43.4% to 4.6%, respectively. Exposure to 5% sulfuric acid solution for 120 days resulted in 0.5% and 16.6% weight loss and 47.4% and 72.6% compressive strength loss in PGCs and PCC, respectively.
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    Influence of Chute Slope on Oxygen Content in Stepped Waterways
    (Gazi Univ, 2009) Baylar, Ahmet; Emiroglu, M. Emin; Bagatur, Tamer
    Water quality and its enhancement have a close connection with the presence of dissolved oxygen. In fact, the oxygen concentration in surface waters is a prime indicator of the water quality for human use as well as for the aquatic biota. The physical process of oxygen transfer or oxygen absorption from the atmosphere acts to replenish the used oxygen. This process is termed re-aeration or aeration. Aeration enhancement by macro-roughness is well-known in water treatment, and one form is the aeration cascade. The macro-roughness of the steps significantly reduces flow velocities and leads to flow aeration along the stepped cascade. This paper seeks influence of channel slope on oxygen content in stepped cascade aerators. It is demonstrated that the aeration efficiency of the stepped cascade aerators increases with increasing channel slope.
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    Modified Newton-Raphson solution for dispersion equation of transition water waves
    (Coastal Education & Research Foundation, 2007) Bagatur, Tamer
    Modified Newton-Raphson solution for dispersion equation of transition water waves is proposed for practical applications. The wave dispersion equation is a nonlinear equation. Therefore, one has to apply a time-consuming trialand-error method. However, it may be solved by utilizing an iterative technique commonly referred to as Newton-Raphson (NR) iteration technique and Chebyshev approximation, which are used to solve the system of nonlinear equations. Chebyshev approximation has the advantage of requiring less iteration. In this study, a numerical solution model based on utilizing modified NR technique with Chebyshev approximation to determine value of the wave number (k) is developed. It is shown how iteration problems can be solved by modified NR technique with Chebyshev approximation. This computational model is applied by computer programs that have visual basic (VBA) code prepared under the Microsoft Excel Macro. The wave dispersion equation for transition water waves were solved by modified NR technique with Chebyshev approximation implemented in the computer programs prepared with VBA computer language. An example for the given numerical solution model is presented.
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    NUMERICAL ANALYSIS OF A TURBULENT PLUNGING WATER JET
    (Begell House Inc, 2024) Can, Omer F.; Bagatur, Tamer; Celik, Nevin
    In the present study, we employed multiphase computational fluid dynamics analysis to investigate the mechanisms of air entrainment by plunging liquid jets. The ANSY-CFX commercial software program, which is based on finiteelement analysis, was used in the numerical simulations. The effects of the exit velocity of the jet on the velocity distribution in the pool, bubble depth, and volumetric fraction of air were the extracted results of the simulations. In this article, we conducted verification analyses to compare the results obtained from our numerical runs to the results of a previously published experimental study. Good agreement was achieved between the numerical simulations and the experimental study.
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    Prediction of Flood Frequency Factor for Gumbel Distribution Using Regression and GEP Model
    (Springer Heidelberg, 2017) Onen, Fevzi; Bagatur, Tamer
    Floods are the most common natural disasters that affect societies around the world. One of the major problems in water resources engineering design is the estimation of maximum flood discharges. These estimations are determined to assign hydrological and hydraulic dimensions to bridges, sewers, dam, spillway, protection embankments, weirs, detention ponds and diversion canals. Accurate estimation of flood frequency discharge increases safety of the hydraulic structures. In probability theory and statistics, flood frequency analysis is used to obtain the probability distribution of floods. The distribution models can be summarized the generalized extreme value, Gumbel or extreme value type 1, Log-Normal and the Log Pearson type III distributions. The Gumbel distribution provides the best fit according to the extreme value analysis studies. This study concentrates on prediction of flood frequency factor (K) for the Gumbel distribution using gene expression programming (GEP) and regression model. Some prediction models are presented for determining of flood frequency factor (K). The proposed regression model (Model 4) and GEP model (Model 7) give a fast and practical way of estimating the flood frequency factor. Thus, Gumbel's method has been simplified in such a predictive model that one can obtain the magnitude of a given return period for flood discharges without recourse to looking at a table. The performance of the prediction models was evaluated with an illustrative example for 2, 5, 10, 20, 50, 100, 200, 250, 500 and 1000 years flood.
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    Prediction of Flow and Oxygen Transfer by a Plunging Water Jets with Genetic Expression Programming (GEP) Models
    (Springer Heidelberg, 2014) Bagatur, Tamer; Onen, Fevzi
    A plunging water jet passing through the surrounding air entrains a large amount of air bubbles into a pool and forms a large submerged two-phase (gas-liquid) contacting area. This process is called air entrainment or aeration by a plunging water jets. In this study, the flow characteristics such as volumetric air entrainment rate, bubble penetration depth and oxygen transfer efficiency are evaluated based on five major parameters which describe air entrainment at the plunge point: the nozzle diameter, jet length, jet velocity, nozzle length-to-diameter ratio and jet impact angle. This paper presents gene expression programming (GEP) model, which is an extension to genetic programming, as an alternative approach to modeling of the flow characteristics such as the bubble penetration depth, air entrainment rate and oxygen transfer efficiency by plunging water jets. New formulations for prediction of the flow characteristics in the plunging water jet system are developed using GEP and regression models.
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    Öğe
    Prediction of oxygen content of nappe, transition, and skimming flow regimes in stepped-channel chutes
    (Ice Publishing, 2007) Baylar, Ahmet; Bagatur, Tamer; Emiroglu, M. Emin
    In a stepped-channel chute, the chute face is provided with a series of steps, from near the crest to the toe. Like many other high-speed flow configurations in hydraulic engineering, stepped-channel chute flows are characterized by the large amount of self-entrained air. Air entrainment on stepped-channel chutes is also recognized for its contribution to the oxygen transfer. The flow conditions in stepped-channel chutes have been classified into nappe flows, transition flows, and skimming flows. In this study, the aeration efficiency of stepped-channel chutes was investigated, and in particular, the effect of varying flow regimes. The results indicated that the nappe flow regime led to the larger aeration efficiency than the other flow regimes. Moreover, the mass transfer equations were developed to predict the aeration efficiency of the stepped-channel chutes in terms of dissolved oxygen. There is good agreement between the measured aeration efficiency values and the values computed from the predictive equations.
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    A predictive model on air entrainment by plunging water jets using GEP and ANN
    (Korean Society Of Civil Engineers-Ksce, 2014) Bagatur, Tamer; Onen, Fevzi
    Plunging water jet flow situations are frequently encountered in nature and environmental engineering. A plunging liquid jet has the ability to provide vigorous gas-liquid mixing and dispersion of small bubbles in the liquid, and enhances mass transfer rate by producing larger gas-liquid interfacial area. This process is called air-entrainment or aeration by a plunging water jet. Advances in field of Artificial Intelligence (AI) offer opportunities of utilizing new algorithms and models. This study presents Artificial Neural Network (ANN) and Gene-Expression Programming (GEP) model, which is an extension to genetic programming, as an alternative approach to modeling of volumetric air entrainment rate by plunging water jets. A new formulation for prediction of volumetric air entrainment rate by plunging water jets using GEP is developed. The GEP-based formulation and ANN approach are compared with experimental results, Multiple Linear/Nonlinear Regressions (MLR/NMLR) and other equations. The results have shown that the both ANN and GEP are found to be able to learn the relation between volumetric air entrainment rate and basic water jet properties. Additionally, sensitivity analysis is performed and it is found that nozzle diameter is the most effective parameter on the volumetric air entrainment rate among water jet velocity, jet length and jet impact angle.
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    Synergic effect of fly ash and calcium aluminate cement on the properties of pumice-based geopolymer mortar
    (Elsevier Sci Ltd, 2022) Karaaslan, Cemal; Yener, Engin; Bagatur, Tamer; Polat, Riza; Gul, Rustem; Alma, Mehmet Hakki
    This paper reveals the synergic effect of fly ash (FA) and calcium aluminate cement (CAC) on the properties of pumice-based geopolymer mortars. Geopolymer mortar samples produced by replacing 0, 10, 20, and 30% of the pumice with FA and/or CAC are cured at ambient temperature, and 60C degrees. Physical properties, compressive strength (7, 28, and 90-days), durability, and microstructure of these samples are investigated in this study. While CAC and heat curing greatly reduce the setting time, FA has a limited effect on the setting time. However, both FA and CAC significantly increase the workability of the mortar mix. By replacing the optimum amount of the pumice with FA and CAC, the 7-day compressive strength of heat-cured geopolymer mortars can achieve 68.0 MPa. On the other hand, CAC significantly increases the compressive strength of the geopolymer mortars and their resistance to the wetting-drying and seawater. In addition, the FA has a limited effect on the enhancement of the mechanical properties and durability of the geopolymer mortars. Efflorescence is slightly reduced by FA and CAC additives, however, is greatly reduced by heat curing. The SEM/EDS show that CAC creates C-A-S-H gel and together with FA they reduce cracks and voids in the geopolymer matrix. The findings reveal that the properties of both fresh and hardened geopolymer mortars can be improved by replacing pumice with a suitable amount of FA and CAC.
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    Testing of Microhydropower Generation from a Sprinkler Irrigation System
    (Asce-Amer Soc Civil Engineers, 2012) Bagatur, Tamer
    Sprinkler irrigation is one of the advanced water-saving irrigation technologies, which has a significant effect for the development of agriculture. Sprinklers are designed to rotate in a circle. In practice, sprinklers can also be used to generate electric power by attaching a generator (dynamo) to its rotating head. Thus, the sprinklers can be converted into a turbine. Hydropower generation from a sprinkler system is theoretically discussed in textbooks on fluid mechanics. Therefore, the aim of this paper is to evaluate theoretical considerations and experimental results of hydropower generation from a sprinkler system. In this study, hydropower generation from a sprinkler system is simply tested with a practical application. The results indicate that a sprinkler irrigation device is capable for hydropower generation, i.e., electrical energy can be produced using sprinkler devices. Hence, the generated energy can be used for energy requirements (e.g., remote-controlled electric sprinkler, lighting, and other uses). If sprinkler devices are technological redesigned for both irrigation and power generation, they will generate low-cost electricity for energy requirements. Also, hydropower can be produced from sprinkler head series in center pivot sprinkler irrigation type. DOI: 10.1061/(ASCE)IR.1943-4774.0000428. (C) 2012 American Society of Civil Engineers.
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    Testing of System Performance for Different Aerator Configuration Using Venturi
    (2018) Bagatur, Tamer; Kayaalp, Necati; Onen, Fevzi
    Abstract: A venturi tube or pipe part or device allows air bubbles to be inserted into flowing water from air inletholes and so increases dissolved oxygen (DO) levels in water. Therefore, the aim of this paper is to evaluatesystem design and experimental results related to configuration of venturi tube in air vacuum and aerationprocess. Different aerator modules constructed using venturi tubes connected in either single or double in parallel(with single or double outlet pipe line) were evaluated and compared for their air flowrate, vacuum capacity,oxygen transfer coefficients (OTC), standard oxygen transfer rate (SOTR), and standard oxygenation efficiency(SOE) determined by clean water tests. The experimental results indicated that the double parallel design(connected to a single outlet pipe line) generally performed better than the single and double parallel (connectedto a double outlet pipe line) design in terms of transferring oxygen into water.

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