39 research outputs found
Mitigating Thermal Stratification in Lakes/Reservoirs Through Wind-Powered Air Diffusers
No full textThermal stratification can cause various water quality issues in large water bodies. To address this, a new wind-powered artificial mixing system is designed and experimentally tested for various Savonius rotor combinations (three-stage and four-stage rotors). These turbines directly utilize wind energy to draw air into the water column for aeration, bypassing the need for electrical conversion. The rotor performances were tested in terms of power and torque coefficients. Additionally, these rotors were tested for artificial mixing efficiencies in a specially designed water tank that can mimic thermal stratification typically observed in an actual water supply reservoir. Among the rotors, the three-stage rotor with a 60 degrees phase shift was found to exhibit superior power and torque coefficients, achieving a power efficiency value of 0.14. As for the mixing efficiency, the four-stage rotor with a 45 degrees phase shift excelled in mixing efficiency, reaching 95%.Practitioner Points A new wind-powered artificial mixing system is designed and tested for various Savonius rotor combinations. While keeping the total rotor height constant, the three-stage Savonius rotor class shows superior performance against the four-stage Savonius rotor class in terms of power and torque efficiency. Apart from the rotor performance results, the four-stage Savonius rotors show greater artificial mixing efficiency than the three-stage Savonius rotors. Single-pump/diffuser artificial destratification system exhibits better mixing efficiency than multiple-pump/diffuser systems. A new wind-powered artificial mixing system is designed and tested for various Savonius rotor combinations. The three-stage 60 degrees phase shift Savonius rotor demonstrated the best performance of turbine efficiency. The four-stage Savonius rotor with a 45 degrees phase shift connected to a single-pump system achieved the highest destratification efficiency at 95%. imag
Effects of Selective Withdrawal on Hydrodynamics of a Stratified Reservoir
No full textIn water supply reservoirs, selective withdrawal is commonly implemented to control released water temperature for quality purposes. This study investigated the effects of selective withdrawal on hydrodynamics of a stratified reservoir through numerical modeling and analytical analysis. A 3-D hydrodynamic model was applied where observations of water temperature time series recorded every 30 min at the thermocline and measured temperature profiles along the water column were used to validate the numerical model. The effect of selective withdrawal from four outlets located along the water intake structure of Tahtali Reservoir in Turkey on water temperatures was investigated and the effects on thermal stratification structure were discussed. Withdrawal of the water at the bottom outlet was found to be the most effective choice encouraging the mixing of the water column and thus reducing anoxia. The results of this study can be used to guide the further investigations in stratified lakes for better management practices
Modeling of Hydrodynamic Circulation and Cohesive Sediment Transport and Prediction of Shoreline Erosion in Hartwell Lake, SC/GA
No full textThis dissertation addresses hydrodynamics, sediment transport and shoreline erosion within the main pool of Hartwell Lake, a U.S. Army Corps of Engineers reservoir built on the Savannah River, between Anderson, South Carolina, and Hartwell, Georgia, USA. A U.S. Environmental Protection Agency (EPA) Superfund site is located on a tributary of Hartwell Lake because of high concentrations of polychlorinated biphenyls (PCBs) in the lake sediments. PCBs are hydrophobic and typically bond to fine-grained sediments, such as silts and clays. The primary goal of the study was to document, through field measurements, and model, using a 3-D numerical model of flow and sediment transport, the fate of sediments within the main pool of Hartwell Lake.
To document forty years of sedimentation within the reservoir, bathymetric survey data were collected in Hartwell Lake during the period, February 10-14, 2003. The bathymetric surveys revealed that deposition was, in places, up to two meters thickness in forty years. During the field campaign, flow velocity measurements were made primarily to provide a check on the magnitude of the velocities predicted by the numerical model used in the study. Shoreline surveys provided data for the modeling procedure for shoreline change. This in turn facilitated specification of the sediment flux into the domain via shoreline erosion.
Hartwell Lake is located near the southern terminus of the Appalachian mountain chain in the Piedmont region. Sediments contain high fractions of silt and clay. Hartwell Lake has a shoreline length of 1548 km, and erosion of lake shorelines has been a significant problem for many homeowners. As of September 2002, there were 1123 permitted riprap installations, and 393 permitted retaining walls, for a total of 1516 erosion control structures along the lakeshores (source: USACE Hartwell Office), an indication of the magnitude of the erosion problem.
To quantify the erosion rate of the shorelines, an approach that relates erosion rates to wind wave forces was developed. A simplified representation of the shape of beach profiles is employed. Historical shoreline change rates were quantified by comparing available digital aerial photos taken in different years, and the erosion prediction model was calibrated using these computed erosion rates.
Sediments derived from shoreline erosion were introduced to the model as an additional source along the model boundary, and the fate of the eroding sediments was investigated via numerical modeling.Ph.D
Prediction of Reservoir Shoreline Erosion
No full textProceedings of the 2003 Georgia Water Resources Conference, held April 23-24, 2003, at the University of Georgia.This paper describes the development and application of a new method for predicting wave-induced shoreline erosion on a reservoir. A method that relates erosion rates to winds, water levels, fetch distances, and a simplified representation of the shape of beach profiles was developed and applied to the shores of Hartwell Lake, South Carolina/Georgia, a U.S. Army Corps of Engineers (USACE) hydropower and flood control reservoir. Historical shoreline change rates were quantified by comparing available digital aerial photos from different years, and the erosion prediction model was calibrated using these computed erosion rates. This paper also discusses the differences between the newly developed method and the existing approaches in the literature. Application of the shoreline erosion methodology to the Western Carolina Sailing Club in Anderson County, SC is also described in this paper
Observational and Numerical Methods for Quantifying and Modeling of Turbulence in a Stratified Reservoir
No full textThe interplay between stratification and shear in lakes controls the vertical mixing, which is the most important mechanism affecting the transport of heat, salt, momentum and suspended and dissolved substances. This study attempts to quantify and characterize the turbulence from direct measurements conducted in a reservoir. A 3D numerical model is used to investigate the water column hydrodynamics for the duration of measurements and the performance of various turbulence models used in the CFD model are investigated via simulation of mixing in the reservoir. The drawdown curves produced by the turbulence models are formulized through linear equations. Although, use of different turbulence models do not have significant effects on the flow hydrodynamics away from the intake structure; significant effects especially on turbulence kinetic energy production are observed at the orifice. Therefore, for simulation of withdrawal flow, either use of shear stress transport (SST) k-omega models solving equations all the way to the wall or k-epsilon models with the nonequilibrium wall function is recommended to account for the changes in the pressure gradient. In this study, the methods using quantified turbulent characteristics of the flow to reformulate the Stokes’ settling velocity to be applied in turbulent flows are also investigated. An approach to predict setting velocity in turbulent flows that utilizes acoustic Doppler instruments for quantification of turbulent characteristics is presented. Modification of the Stokes’ settling velocity with the nondimensionalized turbulent kinetic energy production profiles lead better results than other turbulence characteristics (buoyancy flux and by Richardson number flux) widely used in characterizing turbulent mixing
ANALYZING THE EFFECT OF ANTECEDENTS OF TURNOVER INTENTION ACCORDING TO GENERATIONS
No full textThere are many predictors that determine the turnover intention of employees. Among these predictors, mobbing behaviour can be disruptive in the workplace since workplace deviance is a matter which most organizations wrestle today. Organizational commitment is an important variant for employees to achieve organizational success whereas ethical climate is the picture of an organization which demonstrates its' moral philosophy. This study examines the main effects of ethical climate, mobbing, and organizational commitment in predicting turnover intention among the sample of 166 employees, working in a municipality, particularly in Istanbul province, Turkey. The findings indicate that mobbing affect turnover intention positively, while ethical climate has no effect in estimating turnover intention. Study results also suggest that commitment (continuance and affective) is also found to be negatively related to turnover intention of employees. In addition, for Generation-X members, continuance commitment and for Generation-Y members, affective commitment has a significant effect on turnover intention. (C) 2019 Published by Future Academy www.FutureAcademy.org .U
Hydrokinetic Power Potential Assessment of the Çoruh River Basin
No full textHydrokinetic power contributes to energy security by a sustainable and predictable power source, and its decentralized nature fosters economic development in local communities. Unlike large-scale hydropower projects, hydrokinetic power has lower environmental impacts, promoting technological innovation and supporting the transition to cleaner energy systems. Furthermore, it pledges to guarantee electricity in isolated regions where traditional power systems are not suited, enhancing energy accessibility. This study presents a method that combines the Soil and Water Assessment Tool (SWAT) with the Hydrologic Engineering Center's River Analysis System (HEC-RAS) to forecast the hydrokinetic power capacity of a basin. The research site chosen is the ; Ccedil;oruh River, a transboundary river basin with unavailable publicly accessible flow data. This method approximates the flow data utilizing the SWAT model, which relies on hydrological factors. Following the prediction of the flow data in the basin, the HECRAS model simulates the river's hydraulic conditions to estimate hydrokinetic energy potential. This integrated methodology provides a framework for optimizing hydrokinetic resources in diverse settings, guiding resource management, and sustainable energy planning. This study calculated theoretical hydrokinetic energy potential by considering flow velocity values. Results of the study indicated that the average flow velocity in the ; Ccedil;oruh basin reaches its maximum value of 0.99 m/s in spring and its minimum value of 0.69 m/s in summer, respectively. Based on the seasonal analysis of the integrated approach, the highest maximum theoretical hydrokinetic power density in the basin reaches 26 kW/m2 during the spring and in subbasins 5, 7, and 8. The average theoretical hydrokinetic power density is calculated as 0.28 kW/m2. Finally, the study presents several potential locations along the ; Ccedil;oruh River through GIS mapping, where small-scale hydrokinetic turbines could be installed as a viable option
Observational and Numerical Methods for Quantifying and Modeling of Turbulence in a Stratified Reservoir
No full textThe brexit negotiations: The next battleground for French-U.K. relations
No full textIn March 2017, following the successful referendum in the UK to leave the European Union in June of 2016, negotiations began to discuss the policies regarding the official exit of the United Kingdom with Theresa May’s declaration of Article 50. In recent developments associated with the Brexit negotiations, more ties have been seen between the UK and France than other member-states of the EU. Given the long history between France and the UK, it is clear that the Brexit negotiations have become the next battleground for UK-French unrest. This essay responds to the strength of the theory of intergovernmentalism within the context of the Brexit negotiations and how the leadership role established by France in the wake of Brexit is a phenomenon based on their economic interests, a desire to advance their position as an international actor, and their deep-rooted, historical discontent for one another. Through analyzing a series of most-read newspapers from both countries, the research has shown the battleground of French-UK relations as taking place in these three categories with national interests being more pertinent in the Brexit negotiations than international relations.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-05-01The student, Emilee McArdle, accepted the attached license on 2018-04-19 at 11:28.The student, Emilee McArdle, submitted this Thesis for approval on 2018-04-19 at 13:20.This Thesis was approved for publication on 2018-04-19 at 15:24.DSpace SAF Submission Ingestion Package generated from Vireo submission #12377 on 2018-08-31 at 17:21:02Made available in DSpace on 2018-09-04T20:36:48Z (GMT). No. of bitstreams: 2
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ANALYZING THE EFFECT OF ANTECEDENTS OF TURNOVER INTENTION ACCORDING TO GENERATIONS
No full textThere are many predictors that determine the turnover intention of employees. Among these predictors, mobbing behaviour can be disruptive in the workplace since workplace deviance is a matter which most organizations wrestle today. Organizational commitment is an important variant for employees to achieve organizational success whereas ethical climate is the picture of an organization which demonstrates its' moral philosophy. This study examines the main effects of ethical climate, mobbing, and organizational commitment in predicting turnover intention among the sample of 166 employees, working in a municipality, particularly in Istanbul province, Turkey. The findings indicate that mobbing affect turnover intention positively, while ethical climate has no effect in estimating turnover intention. Study results also suggest that commitment (continuance and affective) is also found to be negatively related to turnover intention of employees. In addition, for Generation-X members, continuance commitment and for Generation-Y members, affective commitment has a significant effect on turnover intention. (C) 2019 Published by Future Academy www.FutureAcademy.org .U
