جمیل بهرامی

There have been more studies on the numerical modeling of spillways in the last few years due to the quick development of numerical simulation technology. In contrast, the case of gates particularly vertical plane gates was not as well studied in the literature, which focused primarily on uncontrolled spillways. Hence, this thesis addresses this gap by exploring the simulation of flow characteristics over a controlled Ogee-type spillway surface. The main objective of the research is to simulate and assessing flow characteristics over a controlled Ogee-type spillway for two models. The investigation and analysis focused on how altering each of the three parameters (flow rate, height of the gate opening, and width of the spillways) influenced: the water level changes along the spillway, the pressure distribution across the spillway surface, comprehending the variations in water velocity along the spillway, and the variations in shear stress across the spillway surface. Numerical simulations are conducted in the study using the FLOW-3D program. To simulate the turbulent flow, the software uses both the Two-Equation (k−ε) model and the Large Eddy Simulation (LES) model to numerical modeling for two distinct model into four different scenarios to compute the pressure, velocity, and shear stress at seven sensors along the controlled Ogee-type spillways. The results are compared with observed data from the literature as experimental and another numerical simulation result of the turbulence model (𝑘−𝜀) obtained. A good agreement was achieved between the numerical results from both equations and the experimental data except for sensors 5, 6, and 7, for the first case, and sensor 6, and 7 for the second case due to varying the three parameters for every simulation. Furthermore, the results in both equations matched more closely with the numerical output of the uncontrolled (k−ε) model from FLOW-3D compared to the experimental data. The results showed that the pressure distribution typically decreases with increases the flow rate. Conversely, it tends to increase as height of the gate opening or width of the spillway increases. Also decreasing just height of the gate opening, it causes to decreasing the pressure distribution in the first region the negative region and increasing from all remain sensors. The first region shows that as discharges increase, the negative pressure decreases and vice versa. Furthermore, the first model analysis identified two regions of negative pressure throughout the domain: one situated at the Ogee curve and the other located at the end of the sloping straight line, after the Ogee curve. In this study, the performance of numerical models in predicting pressure distribution was evaluated using surrogate models that considered three parameters and applied the Pareto optimization method. MATLAB codes were used to solve the equations. The surrogate model results showed good agreement with the numerical results from FLOW-3D, achieving a coefficient of determination (R²) of 1 for both the exact and predicted pressure distribution data at each sensor, as well as for Latin Hypercube cases 1 and 2 for both equations. This indicates that surrogate modeling is an effective tool for predicting responses in controlled Ogee-type spillways and is useful for optimizing the three variables to determine the optimal pressure. The result in both scenarios, the (LES) equation model consistently yields optimal pressures that are closer to zero or even positive, which is beneficial for reducing the risk of cavitation. Additionally, these pressures are closer to atmospheric pressure, further lowering the probability of cavitation. The main goal of assessing and optimizing pressure distribution for a controlled Ogee spillway is to boost its structural integrity, hydraulic performance, and safety. This brings numerous advantages, including better operational efficiency, enhanced safety, lower maintenance costs, and a longer lifespan for the spillway structure. The numerical results for velocity and shear stress data using the (k−ε) turbulence model equation show good agreement when comparing a controlled Ogee-type spillway to an uncontrolled Ogee spillway using the (k−ε) turbulence model equation. This study shows that FLOW-3D modeling can efficiently assess controlled Ogee-type spillways' hydraulic performance.