Mathematical Modelling of Solid-Liquid Flow in Open Channel

Abstract

This thesis investigates the complex multiphase flow of mixture of liquid and granular solids in open channels using advanced numerical modelling techniques within Ansys Fluent. By employing a Eulerian-Eulerian approach, the study provides a detailed exploration of flow behaviours across various conditions, focusing on unimodal and bimodal distributions of particle sizes. The simulation work evaluates the dynamics of solids transport under different flow scenarios, highlighting the effects of particle size variation and the interaction between solid particles and the carrying fluid. The simulations demonstrate a clear stratification process, especially in bimodal particle distributions. Coarser particles predominantly settle closer to the channel bed, whereas finer particles are more suspended within the flow. This stratification is more pronounced under certain flow conditions and adjusts with changes in particle size distribution, flow velocity, and channel slope. Increased discharge generally results in higher flow velocities and greater flow depths. This condition also affects stratification by promoting more vigorous mixing of particles and reducing the distinct layers of particle sizes. Higher discharges lead to increased turbulence within the flow, which can disrupt the settling of particles and lead to a more homogeneous mixture throughout the flow depth. The findings from this research contribute significantly to environmental engineering by offering enhanced predictive capabilities for particle transport in water bodies. Such insights are crucial for effective sediment management, erosion control, and the maintenance of hydraulic infrastructure. Furthermore, the validated models extend their utility to the optimization of channel design, supporting sustainable water resource management practices.

This thesis investigates the complex multiphase flow of mixture of liquid and granular solids in open channels using advanced numerical modelling techniques within Ansys Fluent. By employing a Eulerian-Eulerian approach, the study provides a detailed exploration of flow behaviours across various conditions, focusing on unimodal and bimodal distributions of particle sizes. The simulation work evaluates the dynamics of solids transport under different flow scenarios, highlighting the effects of particle size variation and the interaction between solid particles and the carrying fluid. The simulations demonstrate a clear stratification process, especially in bimodal particle distributions. Coarser particles predominantly settle closer to the channel bed, whereas finer particles are more suspended within the flow. This stratification is more pronounced under certain flow conditions and adjusts with changes in particle size distribution, flow velocity, and channel slope. Increased discharge generally results in higher flow velocities and greater flow depths. This condition also affects stratification by promoting more vigorous mixing of particles and reducing the distinct layers of particle sizes. Higher discharges lead to increased turbulence within the flow, which can disrupt the settling of particles and lead to a more homogeneous mixture throughout the flow depth. The findings from this research contribute significantly to environmental engineering by offering enhanced predictive capabilities for particle transport in water bodies. Such insights are crucial for effective sediment management, erosion control, and the maintenance of hydraulic infrastructure. Furthermore, the validated models extend their utility to the optimization of channel design, supporting sustainable water resource management practices.