Modeling of river flow and flow dynamics near junctions
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü, Türkiye
Tezin Onay Tarihi: 2023
Tezin Dili: İngilizce
Öğrenci: TUTKU EZGİ YÖNTER
Danışman: Ali Ercan
Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu
Özet:
In river networks, confluences are critical components where their hydrological, geomorphological, and ecological properties substantially impact the downstream characteristics of a river. Particular attention should be paid to the flow behavior in these regions since they are associated with significant changes in flow dynamics, sediment transport, and bed morphology. The primary purpose of this study is to investigate river confluences a) using the 1D hydraulic model, HEC-RAS, to understand large-scale model behavior, and b) using the 3D CFD model, Flow-3D, to understand the flow behavior in detail near the confluence area.
In the HEC-RAS model, a sensitivity analysis was performed on the Ohio-Mississippi confluence, and hypothetical cases were generated and investigated by perturbing model parameters. A case study was also modeled at a nearly 9 km river reach with observed inputs to compare the model's capability in simulating a real case scenario with simple information.
In the 3D CFD model, Flow-3D, after performing a mesh independence analysis, the performance of 𝑘−𝜀, 𝑘−𝜔, and 𝑅𝑁𝐺 turbulence models were investigated with a 90° confluence channel geometry. After defining the most appropriate turbulence model and mesh size, the flow behavior at different confluence angles, 90°, 60°, and 30°, is investigated in the equilibrium flow state. Then, the effects of flow ratio on flow dynamics are investigated when the confluence angle is 90°. Specific attention was given to variables including turbulent kinetic energy, surface velocity, depth-averaged velocity, and Froude number in plan view flow analyses; and velocity magnitude, secondary velocity, and turbulent kinetic energy in cross-section flow analyses. Consistent with the literature, it is found that the width and length of the recirculation zone decrease as the confluence angle decreases. Additionally, the magnitudes of the secondary velocities become more significant as the confluence angle increases from 30° to 90°. Furthermore, it is observed that the flow ratio affects the features of the recirculation zone and influences the flow dynamics downstream of the confluence.