Theses supervised by Yrd. Doç. Dr. Mehmet İshak Yüce
12 theses · Gaziantep University
Determination of the rainfall-runoff relationship for Kizilirmak basin
In this study, the Kızılırmak River Basin boundaries were delineated by using Digital Elevation Model (DEM) and Arc-Hydro Tools of ArcGIS. Sub-basin boundaries were obtained by taking available flow measurement stations (FMS) as sub-basins' pour points. The influence area of each rainfall station was determined by thiessen polygons. The calculated runoff coefficient of the main basin was found to be compatible with the literature. The most productive regions of the basin were determined by placing the calculated rainfall-runoff coefficients of sub-basins on the Kızılırmak Basin map. This process was done both for the stations on the main stream of the river and for the tributaries of the river and shown on the map by colorizing. This study aims to find out the rainfall-runoff relationship of the Kızılırmak basin.
Numerical simulation of shallow recirculating flows in sudden enlargements
Investigations on different shapes of harbors at various flow conditions are expected to deliver numerous benefits in designing them, including keeping them clean, reducing the amount of pollutants carried by water flow and decreasing the disposing time of the contaminants. In this study, river harbor-like structures (sudden enlargements) were analyzed by 3-D numerical simulations. Analyses were carried out in an 8 m long, 1 m wide open channel with a sudden enlargement width of 0.5 m. The analyses were performed in three different geometries named as structures A, B and C. In structure A, the sudden enlargement was followed by a sudden contraction with a distance of 1 m in the flow direction. In structure B, the distance between the sudden enlargement and contraction was set to be 2 m, while in structure C there was no contraction after the sudden expansion. The depth of flow ranged from 10 mm to 100 mm. The flow of water and its recirculation in the sudden enlargements were studied by using the shear stress transport (SST) k-ω turbulence closure model. ANSYS FLUENT was employed in the computational fluid dynamic (CFD) simulations. The results of the simulations were compared with the experimental investigations in the literature.
Design of the optimum ogee spillway toe for a maximum energy dissipation
Hydraulic design of a spillway has been one of the most studied subjects in hydraulic engineering. Properly designed, flow condition dependent spillways will be able to release water efficiently and safely from a dam reservoir to the downstream. This study aims to investigate the energy dissipation at the toe of ogee spillway by making an ogee spillway with different end sill models at the downstream by using a commercially available Flow-3D. The case A model was an ogee spillway with rectangular end sill, the case B, C, D and E with a curved end sill with radius of 0.10, 0.15, 0.18 and 0.20 meters, respectively, and the case F which has an inclined end sill. The major amount of energy dissipation occurs at the toe in the region where the hydraulic jump takes place. The hydraulic jump is used to dissipate energy at the downstream. These models were compared to one another to see the corresponding energy loss respectively. To simulate the turbulent flow, the "𝑘−𝜀" turbulence model is done in the numerical modelling. The numerical result shows that the model with curved end sill dissipates more energy than others. In the case F model with inclined end sill, it can be concluded that the hydraulic jump did not occur, the velocity remained high for all cases of discharge and the energy loss is insignificant regarding its form. Therefore, energy loss changes in relation to discharge, most loss occurs at low discharge while in the case of high discharges energy loss decreases. Results indicated numerical methods as convenient and time-saving, with least errors.
Feasibility assessment of small hydropower projects
The most favorable renewable energy production method is small scale hydropower plants. The main parameters needs to be determined in small scale hydropower plants are the installed capacity and cost estimation. Installed capacity and cost estimation are effected by the design flow, gross head, turbines, tunnels, canals, penstocks, and the other variables. All of these variables are analyzed in the feasibility studies to find optimum installed capacity and cost estimation. A computer program named RETScreen, which is generally used in Canada, is capable of evaluating the energy generation, investment and maintenance costs for small scale hydropower projects. In this thesis four different small scale hydropower plants? feasibility studies, which were obtained from State Hydraulic Works (DSI), were compared with the results found by RETScreen. The results achieved by RETScreen were noticed to be very close to the results found in the feasibility studies obtained from DSI. RETScreen was noted to be capable of assessing feasibility studies of small hydropower plants (SHPP) within a relatively short period of time, thus minimizing costs.Key Words: small scale hydropower plants, RETScreen, feasibility study, installed capacity, cost estimation.
Supplying water from göksu basin to gazi̇antep in order to meet future drinking water demand
This study aims to determine the future domestic water requirement and the potential sources for the city of Gaziantep. The future population (2050) of Gaziantep is calculated as 3 million, thus a number of projection methods estimated the need for drinking water of the city. The discharge data obtained from the flow measurement station (FMS) on the Göksu River suggests that the average annual water amount in the river is around 403 million m3 with an average discharge of 12.87m3/s. In Düzbağ Dam, there will be no or very limited energy cost, which makes Düzbağ dam the most suitable project. The capacity of the reservoir was found to be 32 million m3 by Ripple diagram, while it was estimated to be 251 million m3 by the Sequent-Peak method. The height of the dam is expected to be around 160m corresponding to an elevation of 1190 m above sea level; the storage capacity of the reservoir is estimated to be almost 485 million m3 with GIS. In order to determine the ideal flow velocity and the diameter of the water supply line for the total head available, Darcy-Weisbach method was utilized in the calculations. The total head is chosen to be 150 m; therefore the ideal flow velocity and the pipe diameter are estimated to be around 2.6 m/s and 2600 mm respectively.
Analysis of Hydraulic Transients in Pipelines Due to Sudden, Linear and Stepwise Valve Closure
Hydraulic transient is a flow condition in which the flow velocity and pressure change rapidly with time. Changing in status of a flow control component (for example, a valve closing or pump stop) cause to the occurrence of transient in the system. There are many methods to analyze transient, in this study, hydraulic transient in a simple pipeline was considered by using the method of characteristics. For this aim a model with two reservoirs, each connected to one end of the pipeline was assumed. The pipeline conveys water from the upstream reservoir to the downstream one. A butterfly valve was set at the downstream end of the pipe. As soon as the valve is closed, either suddenly, linearly or in a stepwise manner, the pressure at the upstream end of the hydraulic line is expected to be constant while the velocity of flow at the valve is expected to be zero. Two pipelines with different materials, namely; stainless steel pipe and ductile pipe were employed in the study. A MATLAB code was developed in order to do the analyses. It was detected that the stepwise valve closure can decrease transients significantly than the sudden and linear valve closure operations. There are two important factors which are the water velocity and the frictional coefficient that have significant effect on the hydraulic transient. The value of transient pressure in ductile pipe is less than it is in stainless steel pipe because of the higher frictional factor. Keywords: Hydraulic transient, pipeline, method of characteristics, sudden closure, linear closure, stepwise closure.
Seyhan nehrinin hidrolik geometrisinin belirlenmesi
Cross-section of rivers vary with time due to the dynamic structure of hydraulic geometry. The hydraulic geometry parameters of rivers including the width, depth and velocity are related to its discharge as simple power functions at a given cross-section. The characteristics of a river can be determined by using the hydraulic geometry parameters. The aim of this study is to determine the downstream and at-a-station hydraulic geometry parameters of Seyhan River. The hydraulic geometry parameters were estimated by employing the daily discharge values and the cross-sectional data of seven flow measurement stations located on the main river and its tributaries. The results of the analyses show that both the summation of the exponents and the multiplication of the coefficients are almost unity. These outcomes are expected to be helpful in developing water resources projects in the basin.
Flow field around hydrokinetic turbines
In the search for clean, renewable and sustainable energy, the hydrokinetic energy which is harnessed from moving water of rivers, streams and oceans is being studied as a predictable and environmentally benign source. Compare to conventional hydropower turbines, hydrokinetic turbines are new technology in electricity generation and need to be improved from efficiency point of view. In this study, a vertical axis cross-flow hydrokinetic turbine, namely, a modified form of Savonius turbine was investigated. The working principles of cross-flow hydrokinetic turbines are different from those of commonly used horizontal axis turbines. The advantages of this type of turbines are; independency from the current direction including reversibility, stacking and self-starting without complex pitching mechanisms. The turbine has been simulated in a three dimensional and fully developed rectangular open channel flow. Computational fluid dynamics (CFD) simulation of the hydrokinetic turbine was performed by computationally solving the Reynolds-Averaged Navier-Stokes Equations (RANS). In computational studies ANSYS FLUENT, which is commercially available software was employed. CFD can be used to support turbine design and performance over a wide range of parameters to minimize the number of prototypes which are used for optimization and experimental studies. CFD can also provide a cost-effective way of evaluating detailed full scale effects, such as mooring lines or local bottom bathymetry features, on both turbine performance and environmental assessment. Keywords: Computational Fluid Dynamics, Hydrokinetic Turbines, Kinetic Energy, Renewable Energy, ANSYS FLUENT
Flow field around vertical axis cross-flow hydrokinetic turbines
Renewable energy sources, most notably, wind energy, solar energy and small scale hydropower schemes have undergone major development lately. However the intermittency and weather dependency of solar and wind energies pose a challenge. Another form of renewable energy which has attracted great interest in recent times is hydrokinetic energy. Hydrokinetic energy is harnessed from flow waters of river streams, tidal flows or ocean currents. This energy resource has a great potential to be exploited on a large scale because of its predictability and intensity. It is most likely to be one of the new and clean energy alternatives for the 21st century. In this study, a vertical axis cross-flow hydrokinetic turbine, namely a modified form of Lucid Energy Technology (LET) Gorlov Helical Turbine (GHT) was investigated. The working principles of vertical axis cross-flow hydrokinetic turbines are different from those of commonly used horizontal axis ones. The advantages of this type of turbines are; independency from the current direction including reversibility, stacking and self-starting without complex pitching mechanisms. The turbine has been simulated in a three dimensional and fully developed rectangular open channel flow. Computational fluid dynamics (CFD) simulation of the hydrokinetic turbine was performed by computationally solving the Reynolds-Averaged Navier-Stokes Equations (RANS). In computational studies ANSYS FLUENT, commercially available software was employed. The flow field was studied with the turbine being positioned at two different depths, while the depth and the velocity of the open channel flow were kept constant. The results have shown that placing the turbine closer to the bed of channel causes an increase in water velocity near the free surface. Although the water velocity near the channel bed seems to be decreasing, the turbulence flow takes place just behind the turbine and the burst of the flow directlybelow the turbine are expected to cause scouring and increase turbidity levels. Keywords: Computational Fluid Dynamics, Hydrokinetic Turbines, Kinetic Energy, Renewable Energy, ANSYS FLUENT
İçme suyu dağıtım şebeke modelinin gelişmekte: Örnek çalışma
The distribution networks are used to supply high quality drinking water with a stable quantity and pressure. In this study, a segment of Erbil city drinking water distribution network was modeled by using the documented data and the data collected from the field. A trial-and-error procedure was used to calibrate the model parameters in order to obtain realistic results. The model calibration and validation was carried out by comparing the measured and the simulated, pressure and the chlorine residual concentrations. The measured data was obtained from a number of points on the water distribution network at different times. During the calibration process, the model was evaluated for the average absolute deviation and the correlation of mean errors between the computed and the observed data. The calibration analysis was performed by the EPANET2. The results of the pressure and the chlorine residual concentration demonstrate that the average absolute deviation between the measured and the simulated data is fairly low with a high correlation between the means, signifying that the model is fitted well to the network.
Nehir tipi bir hidrokinetik türbinin dizayn ve simülasyonu
Hydrokinetic turbines are electromechanical devices that convert kinetic energy inside the flowing water into electricity without requiring water head. There are many different designs of large scale hydrokinetic turbines for tidal applications, however little efforts have been made on small scale river turbines. In the present study a fixed speed, stall regulated, riverine hydrokinetic turbine rotor (TIGRIS-27H) has been designed and simulated. The blades were optimized by genetic algorithm. The computational fluid dynamics (CFD) simulations have been conducted using ANSYS CFX software. The simulation results of power, torque and thrust have been found to be in a very good agreement with the theoretical design parameters. TIGRIS-27H is a 3 bladed horizontal axis hydrokinetic turbine rotating at 45 rpm and generates up to 27 kW power at the rated velocity of 2.7 m/s with an average power coefficient of 0.43.
Analysis of flow field in open channels with a backward facing step
Computational examinations were performed on flow field in an open channel having a single backward facing step with a constant water depth of 1.5 m. The effects of the expansion ratio and the flow velocity on the reattachment length are investigated by employing two different expansion ratios of 1.5 and 2, and eight diverse flow velocities of 0.5, 1, 2, 3, 4, 5, 7.5 and 10 ms-1 in the computational fluid dynamic (CFD) simulations. Analyses were performed by using two equation turbulence closure models, namely, standard k-ε, RNG k-ε, realizable k-ε, Wilcox's k-ω and SST k-ω. Commercially available CFD software, ANSYS FLUENT, was used for simulations. The analyses have revealed that the reattachment length increases with increase in the expansion ratio, the flow velocity and the Reynolds number. The results acquired for both expansion rates and eight unlike flow velocities have shown insignificant differences from one turbulence closure model to the other. Keywords: Backward facing step, Reattachment length, expansion ratio, k-ε model, k- ω model, FLUENT.