A Three-Dimensional Solid-Liquid Two-Phase Two-Fluid Turbulence Model For Water-Sediment Movement With And Without The Effect Of Vegetation

This thesis developed a three-dimensionalκ-ε-A_p and aκ-ε-κ_p solid-liquid two-phase two-fluid turbulence models in both Cartesian coordinate system and non-orthogonal curvilinear coordinate system based on continuum theory to study the water-sediment movement.Furthermore,by taking account the drag force and additional turbulent kinetic energy due to vegetation into the relevant governing equations of above mentioned models,a three-dimensionalκ-ε-A_p solid-liquid two-phase two-fluid turbulence model with the effect of vegetation was constructed to investigate the influence of vegetation on water-sediment movement.After reviewing the progress of the three-dimensional water-sediment mathematical models,the disadvantages of one-fluid turbulence model(diffusion model)and the advantages of the solid-liquid two-phase two-fluid turbulence models were analyzed. Following Zhou lixing's and Liu dayou's works,theκ-ε-A_p andκ-ε-k_p solid-liquid two-phase two-fluid turbulence model with interphase actions in tensor form were developed.Theκ-ε-A_p andκ-ε-κ_p solid-liquid two-phase two-fluid turbulence model in Cartesian coordinate system were constructed and were solved by finite difference method. Three-dimensional characteristics of particle number density,time-averaged and fluctuation velocities of solid-liquid two phases in both horizontal and vertical rectangular pipes were computed,and the numerical results are in good agreement with measured results.Numerical results also proved the advantages ofκ-ε-κ_p solid-liquid two-phase two-fluid turbulence model overκ-ε-A_p solid-liquid two-phase turbulence model.A three-dimensionalκ-ε-κ_p solid-liquid two-phase two-fluid turbulence model in non-orthogonal curvilinear coordinate system was proposed to study water-sediment movement with complicated computational boundaries,which was solved by finite-volume method in adaptive grids.The flow structure in an S-shaped flume was used to validate the liquid-phase module,the movement of water flow and sediment in a 120°bend was used to validate the solid-phase module by computing the sediment concentration,longitudinal velocity,transverse velocity and vertical velocity,the movement of bed-load and channel bed aggradation and degradation processes in 120°and 180°bends were used to validate the bed topography deformation module.Comparisons between numerical results and experimental results show that two-fluid turbulence model describes the effect of secondary flow on the transverse sediment transport better than one-fluid turbulence model.A three-dimensionalκ-ε-A_p solid-liquid two-phase two-fluid turbulence model with the effect of vegetation on flow and sediment movement was constructed by adding the drag force or turbulent kinetic energy due to vegetation into relevant control equations. Experimental results in a flume covered with emergent and submerged vegetation validate the vertical flow structure changes due to vegetation.Experimental results in a partly vegetated straight open channel and a partly vegetated 60°channel bend validate the plan flow structure changes and three dimensional flow structure changes due to vegetation.The model also was used to investigate the vertical profiles of sediment concentration and the horizontal velocities of both liquid phase and solid phase in vegetated channels.The bed-load module and bed topography deformation module with the effect of vegetation were validated by sediment movement and channel bed aggradation and degradation processes in a straight partly center-vegetated flume and a 60°partly vegetated channel bend.