Experimental and numerical investigation of open channel flow characteristics of Newtonian and non-Newtonian fluids

This thesis explores the effects of different obstacles on Newtonian and non-Newtonian fluid flow dynamics within an open channel. The experiment involved placing obstacles, rectangular shapes, rectangular arches, cubes, cylindrical, and rectangular shapes in an open channel (4 m long, 0.3 m high, and 0.2 m wide). Flow rates ranging from 0.0035 m3/s to 0.0045 m3/s were tested across slopes of 0, 1.0156 ve 1.406 The numerical approach complemented the experiments to ensure accurate determination of the input parameters and boundary conditions. This thesis is organized into 5 Chapters, with each of the chapters describing a sequence of study as described as follows. Chapter 1 introduces the thesis, providing a brief overview of open channel flow and a comprehensive review of the relevant literature. Chapter 2 gives information about the experimental setup and numerical model. Chapter 3 presents the results of Newtonian fluid (water), by comparing the experimental and numerical results of velocity, water depth and Froude numbers. Chapter 4 presents the experimental and numerical analysis of the non-Newtonian fluids. Chapter 5 concludes the results. The results of the thesis reveal several important conclusions. For example, increasing channel slopes and flow rates amplifies the effects of obstacles on velocity profiles due to increased flow separation and density around the obstacles. Near obstacles, steeper velocity gradients indicate acceleration and deceleration of flow patterns, leading to local turbulence and eddies. The presence of space between obstacles enhances shear stress along the channel bottom and walls, affecting sediment transport and erosion processes. At 0 slope, fluid velocity remains high over obstacles. With slopes greater than 0, gravity's control over obstacle effects, especially at high flow rates, results in lower velocities after the obstacle, and sometimes lower than velocities before the obstacle. Cubic obstacle arrangements produce large velocity changes and higher fluid velocities prior the obstacles, reducing the effect of boundary layers at the channel bottom. Velocity changes in the sidewalls are affected by flow rates and obstacle arrangements due to vortex density and pressure gradients. Velocities near the wall decrease with slopes greater than 0 due to increased gravitational force. Non-Newtonian fluids show lower velocity and depth anisotropy compared to water, which is due to higher shear stress and smoother velocity changes. Obstacles induce acceleration of the flow, resulting in higher central region velocities and lower velocities near the edges of the obstructions. Depth variations in non-Newtonian fluids are less pronounced and tend to decrease. Its depth is more sensitive to high flow rates and shows a steeper decrease with increasing gradient compared to water. This comprehensive analysis provides valuable insights into the complex dynamics of fluid flow in open channels, with major implications for engineering and environmental applications.