http://yetl.yabesh.ir/yetl1/handle/yetl/19000 Fri, 24 Apr 2026 13:05:37 GMT 2026-04-24T13:05:37Z http://localhost:80/yetl1/bitstream/id/184317/ http://yetl.yabesh.ir/yetl1/handle/yetl/19000 http://yetl.yabesh.ir/yetl1/handle/yetl/4309072 Flow through the Bosphorus B. Mutlu Sumer; V. S. Ozgur Kirca This paper presents the results of a numerical study on a two-layer flow system in the Bosphorus, the strait connecting the Black Sea and the Marmara Sea. The numerical model is a three-dimensional (3D) model incorporated with the large Eddy simulation model for the horizontal turbulence closure and a modified mixing-length model for the vertical turbulence closure. The model, tested and validated against field data and other numerical models, was used to study hydrodynamic processes associated with the two-layer flow system in the Bosphorus. It was found from the 3D model calculations that the length-averaged flow rates are 18.55 × 103 m3/s for the upper layer and 6.55 × 103 m3/s for the lower layer for the mean flow conditions, corresponding to the mean head difference between the Black Sea and the Marmara Sea of 33 cm, in good agreement with the field observations. It was also found that, for the mean flow conditions, a net amount of transfer of water of 2.9 × 103 m3/s from the lower layer into the upper layer occurs, and this is due to mixing between the two layers, also in good agreement with the field observations. It was further found that the present model captures the location of the density interface between the layers and its variation with the longitudinal distance quite well. Given the time variation of the head difference between the Black Sea and the Marmara Sea over a time span of a year, the time variations of the flow rates in the upper and lower layers, calculated through the present model, compared favorably well with the field data. The present model solution indicated that the flow in the lower layer essentially stops when the head difference between the Black Sea and the Marmara Sea approaches approximately 40 cm, and, by contrast, the upper layer, likewise, stops when the head difference approaches approximately 10 cm. However, the model indicated that, for truly stagnant water in the upper layer, the head difference needs to approach nil. Additionally, hydrodynamics of the water body in the Marmara Sea adjacent to the Marmara Sea end of the Bosphorus and that in the Black Sea adjacent to the Black Sea end of the Bosphorus were unveiled by the implementation of the present 3D model. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4309072 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4309071 Experimental Investigation of Overflow on the Lee Side of River Groins due to Long-Period Primary Ship-Induced Waves Using Particle Image Velocimetry Analysis Ahmad AlYousif; Tobias van Batenburg; Sargol Memar; G. Melling; B. Hofland The passage of ships in confined waterways creates a stern wave that can overflow bank protection structures such as groins. This overflow, due to the long-period primary ship-induced waves, can be high in velocity, especially at the lee-side slope of groins, potentially causing significant damage to the structure. This study derives an equation to express overflow velocities, intended as a design tool for groins exposed to these types of waves. A detailed experimental investigation was performed on four physical models of groins with different slopes and stone sizes in the armor layer under the influence of different hydraulic heads. Particle image velocimetry (PIV) was used to measure the flow velocities at the crest and lee sides of the structure. All PIV measurements were performed thrice under free-flow conditions with no initial water level at the lee side of the structure. The depth- and time-averaged flow velocities (Uavg) were extracted from four positions along the lee-side slope and accelerated from 0.7 to 2.2 m/s. A dimensionless equation of the overflow velocities was obtained as a function of the hydraulic head (h), slope (θ), freeboard (Rc), and nominal rock diameter (dn50). Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4309071 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4309069 Investigation of Wave Power Conversion Efficiency and Hydrodynamic Characteristics of a Floating Twin-Hybrid Wave-Energy Device in Random Waves Nourah Almashan; Subramaniam Neelamani; Benhur Joseph Raju; Dana Al-Houti The potential advantages of wave-energy converters can be extended beyond their capability to produce clean and safe energy, including wave attenuation using hybrid devices. This study presents an experimental investigation of the power production and wave attenuation capabilities of a floating twin-raft hybrid device. Model tests were performed using different random waves and damping values for a simulated power take-off (PTO) system. The coefficients of wave transmission (Kt), reflection (Kr), dissipation (Kl), and mechanical power conversion efficiencies for the seaside raft (η1) and rear side raft (η2) were estimated. It was observed that varying the peak wave period considerably affects the hydrodynamic characteristics, whereas wave height has a lesser influence. The PTO simulation is an area of uncertainty in wave-energy converters. Moreover, the study of the influence of PTO damping on device performance is new. Varying the PTO damping marginally influenced the Kt, Kr, and Kl, whereas the power conversion efficiencies of both seaside and rear-side rafts varied significantly. η1 and η2 were maximized at low-input wave height conditions. As the wave height increased, η1 and η2 decreased. This occurred due to the significant wave-energy dissipation. Liberal (Kt < 0.5 and η1 or η2 > 0.2) and stringent (Kt < 0.2 and η1 or η2 > 0.4) hydrodynamic performance conditions were used to discuss the effective range of available wave frequencies under different PTO damping conditions. This would help identify the areas where this type of device can be applied. This study validated the concept of a floating twin-body hybrid wave-energy converter. This study belongs to the concept development stage of wave-energy conversion technologies, and the conclusions can help further develop and improve this concept. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4309069 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4309068 Measurement of Changes in Beach Sand Soil Stiffness due to Fluctuating Tides Jonathan F. Hubler; Thomas Mayer; Nina Stark; Elise Hummel; Jiaye Zhang; Tian-Jian Hsu Understanding the penetration resistance and geotechnical properties of beach sands is important for erosion modeling and performance-based design; however, data for beach sand penetration resistance with depth is sparse, and particularly temporal and spatial investigations are lacking. This study presents the results of a series of instrumented dynamic cone penetrometer (DCP) tests that were performed in the intertidal zone of the Atlantic-side sandy beach in Duck, North Carolina, over a tidal cycle. Spatial (cross-shore) and temporal (tidal) changes in soil stiffness in the upper 2 m of the beach surface were investigated. In total, 13 DCP soundings that measured the sediment resistance at two cross-shore locations were approximately 3 m apart. The soundings were performed every 30 min, which alternated between the two locations and started with the ebb tide, followed by the low tide and flood tide. The results showed changes in the soil penetration resistance that were related to the tidal cycle. Location A, which was closer to the dune, had overall lower penetration resistance values compared with Location B, which was closer to the water. Near low tide, the differences between the penetration resistance diminished, and differences between the penetration resistance values increased during the ebb and flood tides. Therefore, the observed changes in penetration resistance could be related to groundwater dynamics that follow the tidal water elevations. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4309068 2025-01-01T00:00:00Z