Civil Engineering / İnşaat Mühendisliği
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Article Citation - WoS: 46Citation - Scopus: 53Distorted Physical Model To Study Sudden Partial Dam Break Flows in an Urban Area(American Society of Civil Engineers (ASCE), 2014) Güney, Mehmet Şükrü; Tayfur, Gökmen; Bombar, Gökçen; Elçi, ŞebnemA distorted physical model, based on Ürkmez Dam in Izmir, Turkey, was built to study sudden partial dam break flows. The distorted model had a horizontal scale of 1/150 and a vertical scale of 1/30, containing dam reservoir, dam body, and downstream area-from dam body to Ürkmez urban area until the sea coast. In the model, the reservoir is approximately 12 m3, the dam body has a width of 2.84 m and a height of 1.07 m, and the downstream area is nearly 200 m2. The Ürkmez Dam was chosen because Ürkmez Town is located right at its downstream area, allowing the study of dam break flows in an urban area. Furthermore, the dimensions were suitable such that it allowed the construction of a physical model (dam reservoir, dam body, and downstream area) having a horizontal scale of 1/150 in the available space of 300 m2. The features creating roughness such as buildings, bridge, and roads were also reflected in the physical model. The dam break flow was investigated for sudden partial collapse, which was simulated by a trapezoidal breach on the dam body. The water depths at downstream area were measured at eight different locations by using e+ WATER L (level) sensors. The velocities were measured at four different locations by ultrasonic velocity profiler (UVP) transducers. The propagation of the flood was recorded by a high-defnition camera. The experimental results show that the Ürkmez area can be flooded in a matter of minutes, at depths reaching up to 3 m in residential areas in 4 min. The flood wave front can reach the residential areas in 2 min and to the sea coast in 4 min. Flow velocities can reach 70.9 km/h in sparse residential areas, close to dam body. Away from the dam body in the sparse buildings part of the town, the velocities can reach 27.7 km/h. In dense residential areas of the town, the velocities are too low (2.8 km/h) but flow depths can reach 3 m. Velocity profiles show similar behavior like unsteady and nonuniform open channel flow in nonresidential areas close to the dam body. In residential areas away from the dam body, the velocity profiles are more uniform, having lower velocity values. Vertical variations of velocities show markedly different behavior during rising and recession stages. The profiles are smooth during the rising stage in sparse residential area, yet it shows fluctuating behavior during the recession stage.Article Citation - WoS: 60Citation - Scopus: 69Experimental and Numerical Investigation of Bed-Load Transport Under Unsteady Flows(American Society of Civil Engineers (ASCE), 2011) Bombar, Gökçen; Elçi, Şebnem; Tayfur, Gökmen; Güney, M. Şükrü; Bor, AslıThe dynamic behavior of bed-load sediment transport under unsteady flow conditions is experimentally and numerically investigated. A series of experiments are conducted in a rectangular flume (18 m in length, 0.80 m in width) with various triangular and trapezoidal shaped hydrographs. The flume bed of 8 cm in height consists of scraped uniform small gravel of D 50=4.8 mm. Analysis of the experimental results showed that bed-load transport rates followed the temporal variation of the triangular and trapezoidal hydrographs with a time lag on the average of 11 and 30 s, respectively. The experimental data were also qualitatively investigated employing the unsteady-flow parameter and total flow work index. The analysis results revealed that total yield increased exponentially with the total flow work. An original expression which is based on the net acceleration concept was proposed for the unsteadiness parameter. Analysis of the results then revealed that the total yield increased exponentially with the increase in the value of the proposed unsteadiness parameter. Further analysis of the experimental results revealed that total flow work has an inverse exponential variation relation with the lag time. A one-dimensional numerical model that employs the governing equations for the conservation of mass for water and sediment and the momentum was also developed to simulate the experimental results. The momentum equation was approximated by the diffusion wave approach, and the kinematic wave theory approach was employed to relate the bed sediment flux to the sediment concentration. The model successfully simulated measured sedimentographs. It predicted sediment yield, on the average, with errors of 7% and 15% of peak loads for the triangular and trapezoidal hydrograph experiments, respectively.Article Citation - WoS: 15Citation - Scopus: 18Influence of Stratification and Shoreline Erosion on Reservoir Sedimentation Patterns(American Society of Civil Engineers (ASCE), 2007) Elçi, Şebnem; Work, Paul A.; Hayter, Earl J.Sedimentation in the main pool of a deep (maximum depth: 50 m), 227 km2 hydropower reservoir was modeled using a three-dimensional numerical model of hydrodynamics and sedimentation for different wind, inflow, and outflow conditions. Short-term velocity measurements made in the reservoir were used to validate some aspects of the hydrodynamic model. The effects of thermal stratification on sedimentation patterns were investigated, since the reservoir is periodically strongly stratified. Stratification alters velocity profiles and thus affects sedimentation in the reservoir. Sedimentation of reservoirs is often modeled considering only the deposition of sediments delivered by tributaries. However, the sediments eroding from the shorelines can contribute significantly to sedimentation if the shorelines of the reservoir erode at sufficiently high rates or if sediment delivery via tributary inflow is small. Thus, shoreline erosion rates for a reservoir were quantified based on measured fetch, parameterized beach profile shape, and measured wind vectors, and the eroded sediments treated as a source within the sedimentation modeling scheme. The methodology for the prediction of shoreline erosion was calibrated and validated using digital aerial photos of the reservoir taken in different years and indicated approximately 1m/year of shoreline retreat for several locations. This study revealed likely zones of sediment deposition in a thermally stratified reservoir and presented a methodology for integration of shoreline erosion into sedimentation studies that can be used in any reservoir.