Browsing by Author "Bor, Asli"

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Citation - WoS: 5
Citation - Scopus: 7
Application of Three-Dimensional Cfd Model To Determination of the Capacity of Existing Tyrolean Intake
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Bor Türkben, Aslı; Szabo-Meszaros, M.; Vereide, K.; Lia, L.; Bor, Asli
CFD models of intakes in high-head hydropower systems are rare due to the lack of geometric data and cost of modeling. This study tests two different types of software to see how modeling can be performed in a cost-effective way with scarce input data and still have sufficient accuracy. The volume of fluid (VoF) model simulations are conducted using both ANSYS Fluent and OpenFOAM. The geometry is modelled from Google Earth satellite images, drone scanning data, and design drawings from the construction period and supported by field observations for extra quality control. From the model, both capacity parameters and flow pattern are calculated. For capacity, the (Formula presented.) factor is calculated and compared with the literature. The simulations are conducted for a Tyrolean weir with rectangular bars (flat steel) in the rack. Simulated flow patterns through the rack with ANSYS Fluent and OpenFOAM are compared. OpenFOAM simulations yielded 15% to 20% higher water levels compared to the VOF model applied in Ansys Fluent. Also, when the flow rate was high, the water capture capacity calculated with ANSYS Fluent was 10% higher than that obtained with OpenFOAM. However, considering the total simulation times, modeling with OpenFOAM offered approximately 11% faster results. © 2024 by the authors.
Comparison of Levenberg-Marquardt and Bayesian Regularization Learning Algorithms for Daily Runoff Forecasting
(2025) Bor, Asli; Okan, Merve
In this study, Multilayer Perceptron (MLP) with Levenberg-Marquardt and Bayesian Regularization algorithms machine learning methods are compared for modeling of the rainfall-runoff process. For this purpose, daily flows were forecast using 5844 discharge data monitored between 1999 and 2015 of D21A001 Kırkgöze gauging station on the Karasu River operated by DSI. 6 scenarios were developed during the studies. Our findings indicate that the estimated capability of the Bayesian Regularization algorithm were close to with Levenberg-Marquardt algorithm for training and testing, respectively. This study shows that different network structures and data representing land features can improve prediction for longer lead times. We consider that the ANN model accurately depicted the Karasu flows, and that our study will serve as a guide for more research on flooding and water storage.
Citation - WoS: 3
Citation - Scopus: 4
Experimental and Numerical Investigation of Local Scour Around Square Bridge Pier
(Taylors Univ Sdn Bhd, 2022) Bor Türkben, Aslı; Güney, Mehmet Şükrü; Bor, Asli
This study examines, local scour around square pier under unsteady flow conditions, caused by five different hydrographs. The experiments were conducted in the rectangular flume of 18.6 m length, 0.80 m width and 0.75 m depth, with uniform sediment bed material D-50 = 1.68 mm. Five experiment series were conducted with a plexiglass square pier b = 8.5 cm. The unsteady flow was generated by means of triangular hydrographs. The temporal variations of the equilibrium scour depths in front of the pier and the scour hole dimensions were recorded by two different cameras. The equilibrium scour depths at lateral sides and downstream of the pier were also measured. The hydrograph peak flow rates were found to be much more effective compared to hydrograph durations. The numerical solution was realized by using the software ANSYS FLUENT with RNG k-epsilon turbulence model. The numerical and experimental values were compared and interpreted, and acceptable accordance was observed between them. The calculated lengths and widths of the scour hole were found close to the measured ones. A comparison of the final elevations (t = 15 min.) for experimental and numerical results revealed that; the values of RMSE, MAE errors, and the determination coefficient R-2 were 0.53 cm, 0.48 cm, and 0.94 respectively. The R-2 values are 0.98 and 0.95 for the measured and calculated scour hole length (L) and width (W), respectively.
Experimental Study of Evolution of Breach Resulting From Piping at Upper Part of Earth-Fill Dam
(Turkish Chamber Civil Engineers, 2025) Guney, Mehmet Sukru; Tayfur, Gokmen; Bor, Asli; Okan, Merve; Dumlu, Emre; Aklık, Pelin
Piping and overtopping are the most important causes of earth-fill dam failure. Such dams may erode under seepage, causing a reduction in the structural strength. The aim of this study was to investigate the temporal evolution of the breach and flow rate from the breach resulting from the piping in earth-fill dams. The experiments were carried out at Hydraulics Laboratory of Civil Engineering Department of İzmir University of Economics. The dam was constructed by using a mixture consisting of 85 % sand and 15 % fine (low plasticity clay). In the first scenario a circular tunnel with a diameter of 2 cm was created along the centreline at 6 cm below the dam crest whereas in the second one it was located at the upper edge. Six cameras at different locations recorded the evolution of the progress of the breach formation. The pump flow rate was measured by magnetic flow meter, and the continuity equation was used to calculate the flow rate values from the breach. The time-varied values of the total breach areas were determined using the Gauss Area formula. The image processing method was also applied in the determination of the breach areas. The time-dependent changes of water depth in the channel were also recorded. The obtained experimental findings are presented and commented, together with the universal dimensionless curves. The failure of the dams occurred mainly because of the head cut erosion developed from downstream to upstream. When breaching started, the orifice flow was converted to open channel flow where breach bottom behaved like a broad crested weir. In the second scenario, the rigid lateral side considerably influenced the flow rate and the development of the breach. The peak flow rate corresponding to the first scenario was found approximately 2.3 times greater than that of the second one. The maximum values of all the breach parameters were reached earlier in the case of the seepage along the centerline. The ratios between the values corresponding to the first and the second scenarios were found as 3.25 and 1.75 for maximum breach areas at downstream and at upstream sides, respectively. These ratios were 2.44 and 1.37 for the average breach widths at downstream and upstream sides, respectively. A very good agreement was found between the area values obtained from Gauss area method and image processing technique, in both scenarios. This fact demonstrated that either of these two approaches can be used to determine the time-dependent breach areas. These experimental findings provide the opportunities for the calibration and validation of the numerical models used in the relevant numerical investigations. This study also offers guidance for the strategies concerning emergency action plans related to the failure of homogeneous earth-fill dams when the piping starts at upper part of the homogeneous earth-fill dams.
Citation - WoS: 2
Citation - Scopus: 3
Experimental Study of the Evolution of the Breach and the Discharge Through the Breach Resulting From Piping Due To Seepage at the Earth-Fill Dam Top
(International Association for Hydro-Environment Engineering and Research, 2022) Güney, Mehmet Şükrü; Okan, Merve; Dumlu, E.; Bor Türkben, Aslı; Aklık, Pelin; Tayfur, G.; Bor, Asli
Internal erosion, also known as piping, is one of the most important causes of earth-fill dam breaks. Many researchers dealing with numerical analyses in this area make some simplified assumptions about the shape of the breach and the discharge of water flowing through the breach. This study was conducted in the scope of the project supported financially by the Scientific and Technological Research Council of Turkey and it consists of experimental study which aims to provide data needed to perform numerical analyses with more realistic approaches. A dam with a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m was built in a flume 1 m wide, 0.81 m high and 6.14 m long. Before the construction of the dam, some common soil mechanics tests were carried out. The dam was constructed by using a mixture consisting of 85 % sand and 15 % clay. A circular tunnel with a diameter of 2 cm was created along the centerline at 6 cm below the dam crest. In the closed system, water was pumped from the lower reservoir to the upper channel. Six cameras located at different locations recorded the evolution of the dam failure. Gauss Area formula was applied to determine the time-varied of the breach areas at upstream and downstream sides. The discharge of water through the breach and average flow velocity were determined by using the continuity equation. The changes in water depth in the channel were also recorded. © 2022 IAHR.
Citation - WoS: 3
Citation - Scopus: 3
Investigation of Improved Energy Dissipation in Stepped Spillways Applying Bubble Image Velocimetry
(MDPI, 2024) Mikalsen, Lars Marius; Thorsen, Kasper Haugaard; Bor, Asli; Lia, Leif
This study investigates skimming flow regimes, two-phase air-water flow conditions, and simple measures to improve energy dissipation in stepped spillways. Experiments were conducted using two different scale physical models, 1:50 and 1:17, within separate rectangular flumes to define scale effects. Flow patterns were analyzed using the Bubble Image Velocimetry (BIV) technique, which tracks air bubbles. The introduction of splitters resulted in a 7% increase in relative energy dissipation. Additionally, the length of inception was reduced to Li/ks = 10, thereby decreasing the potential for subsequent cavitation. Beyond the BIV experiments, two experiments were conducted on the large-scale model using Acoustic Doppler Velocimetry (ADV), with and without splitters, to examine the impact of splitters on the velocity profile above the crest. In the experiment with splitters, the vertical velocity vector (v) contributed to turbulence by changing direction, thereby reducing average velocities both in front of and behind the ogee crest. This led to a reduction in energy on the downstream side of the spillway. Although the small-scale model appears unsuitable for studying two-phase flow, the change in relative energy dissipation from the baseline to the splitter configuration was practically identical for both scale models, thereby supporting the findings of the large-scale model.
Citation - Scopus: 1
Morphological Analysis of Buyuk Menderes River Over the Years Using Satellite Imagery
(Iahr-int Assoc Hydro-environment Engineering Research, 2023) Bor, Asli; Hazar, Oguz; Elci, Sebnem
Both bank erosion and sediment deposition on the inner margins are important watershed management problems for streams. Bank erosion not only causes the loss of agricultural lands, but also leads to the narrowing of the cross sections of the streams with the accumulation of sediment in the interior, resulting in floods, damage to the cultivated areas, reduction in dam reservoir lifespan and thus, serious damage to a country's economy. In this study, the morphological analysis of the B. Menderes River, which is one of the most important rivers of Turkey and a residential and intensive agriculture region, for the thirty-year period between 1990-2020 is made via utilization of QGIS for the analysis of Landsat satellite images. This study is thought to be a preliminary study to quantify the morphological changes in B.Menderes River and is expected to be a basis for linking these changes to the changes in the hydrological regime in the basin. During this analysis, the shoreline of the main river, approximately 570 km long, was divided into 10 segments and the sinuosity index values, which are fold parameters, were calculated for each segment. According to the study, it is found that the curvature of the meanders of the B. Menderes River varies between 1.5 and 2.5 in most places.
Citation - WoS: 9
Citation - Scopus: 13
Numerical Analysis of Three Vertical Axis Turbine Designs for Improved Water Energy Efficiency
(MDPI, 2024) Karakaya, Derya; Bor Türkben, Aslı; Elçi, Sebnem; Bor, Asli
A hydrokinetic turbine with a vertical axis is specifically designed to harvest the kinetic energy from moving water. In this study, three vertical axis water turbines, namely Gorlov, Darrieus, and Savonius turbines, were compared for their efficiency via numerical modeling for steady-state conditions via the ANSYS 2022 R2 Fluent model. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) was implemented with an SST k-omega turbulence model. The dynamic mesh technique, which allows modeling according to changes in angular velocity at each time step, was used to simulate flow around the turbines for six different velocities (from 0.5 to 3 m/s). The efficiency of the turbines was compared and the results were analyzed. The pressure, velocity, and turbulence kinetic energy distributions around the rotor were measured at different rotational angles and results indicated a wider operating range for the Darrieus and Gorlov turbines compared to the Savonius turbine. The highest power coefficient of 0.293 was achieved in the model featuring a Darrieus turbine, corresponding to a TSR value of 1.34, compared to 0.208 for the Gorlov and 0.257 for the Savonius turbine, at TSR values of 1.3 and 1.06, respectively. Numerical modeling results pointed to a significantly higher self-starting capacity for the Savonius turbine compared to the others.
Uncertainty Assessment of the Impacts of Climate Change on Streamflow in the İznik Lake Watershed, Türkiye
(MDPI, 2026) Tezel, Anil Caliskan; Akpinar, Adem; Bor, Asli; Elci, Sebnem
Study region: This study focused on the Iznik Lake Watershed in northwestern T & uuml;rkiye. Study focus: Climate change is increasingly affecting water resources worldwide, raising concerns about future hydrological sustainability. This study investigates the impacts of climate change on river streamflow in the Iznik Lake Watershed, a critical freshwater resource in northwestern T & uuml;rkiye. To capture possible future conditions, downscaled climate projections were integrated with the SWAT+ hydrological model. Recognizing the inherent uncertainties in climate models and model parameterization, the analysis examined the relative influence of climate realizations, emission scenarios, and hydrological parameters on streamflow outputs. By quantifying both the magnitude of climate-induced changes and the contribution of different sources of uncertainty, the study provides insights that can guide decision-makers in future management planning and be useful for forthcoming modeling efforts. New hydrological insights for the region: Projections indicate wetter winters and springs but drier summers, with an overall warming trend in the study area. Based on simulations driven by four representative grid points, the results at the Karadere station, which represents the main inflow of the watershed, indicate modest changes in mean annual streamflow, ranging from -7% to +56% in the near future and from +19% to +54% in the far future. Maximum flows (Qmax) exhibit notable increases, ranging from +0.9% to +47% in the near future and from +21% to +63% in the far future, indicating a tendency toward higher peak discharges under future climate conditions. Low-flow conditions, especially in summer, exhibit the greatest relative variability due to near-zero baseline discharges. Relative change analysis revealed considerable differences in Karadere and Findicak sub-catchments, reflecting heterogeneous hydrological responses even within the same basin. Uncertainty analysis, conducted using both an ANOVA-based approach and Bayesian Model Averaging (BMA), highlighted the dominant influence of climate projections and potential evapotranspiration calculation methods, while land use change contributed negligibly to overall uncertainty.
Citation - WoS: 1
Citation - Scopus: 1
Water Quality Evaluation Using Various Water Quality Indices: a Case Study for B. Menderes River, Turkey
(International Association for Hydro-Environment Engineering and Research, 2022) Bor Türkben, Aslı; Elgi, Ș.; Bor, Asli
Water quality is an important factor for public health and aquatic life, and it has become an increasingly important problem due to the growth ofthe population, urban expansion, and development. Forthis reason, the evaluation of surface water quality is an important issue for countries. Water quality indexing is widely used to present complex water quality data in a more comprehensible form and provides decision-makers and non-technical managers ofwater resources with concise information about water quality status. In this study, the water quality is determined based on the water quality monitoring data obtained from the Kocarli Bridge gauging station in the B. Menderes Riverforthe 9 years period between 2006 and 2014. The main pollutants in this region, with parameters exceeding border limit values PH were found to be Sulphate (S04), Nitrate (N03), Ammonia (NH4), Nitrite (N02), Phosphate (P04), Electrical Conductivity (EC), Total Dissolved Solids (TDS) Calcium (CA), Magnesium (MG), Sodium (Na), Potassium (K) and Bacteriological Parameters (E-coli, F-Strp, and Total Coli). In addition, five different WQI performances are compared so that the data can be easily interpreted. The methods used were the weighted arithmetic index (WAI-WQI) Environmental Water Quality Index (CCME-WQI) Canadian Council of Canada (CCME-WQI), Universal Water Quality Index (UWQI), Oregon Water Quality Index (0WQI), and Aquatic Toxicity Index (ATI). The applicability of different methodologies is discussed, and significant inconsistencies were observed between the classification results. © 2022 IAHR.