Faculty of Engineering and Information Technologies, School of Civil Engineering
Abstract
This thesis is concerned with particle transport in a reservoir model subject to periodic thermal forcing at the water surface. A commercial Computational Fluid Dynamics (CFD) code coupled with a Discrete Phase Model (DPM) is adopted to examine particle motions under various conditions. The following investigations have been carried out: Firstly, a previously reported concurrent Particle Image Thermometry and Particle Image Velocimetry (PIT/PIV) experiment has been numerically reproduced. Both qualitative and quantitative agreements are achieved between the present numerical simulation and the experiment. It is found in the parametric study that the Grashof number plays an important role in determining the onset time for the instability, the time duration of the unstable phase, and the time lag of the flow response to the switch of the thermal forcing. Secondly, the numerical model is adopted to investigate particle dispersion in the reservoir in a pseudo real-life scenario in which nutrient particles are injected from the sidearm of the reservoir. Both of the qualitative and quantitative studies have confirmed that natural convection has an indispensable role to play in terms of the pollutant transport in reservoirs. A case study based on an event of algal bloom with potentially severe effects on the water quality in Lake Burragorang in Sydney has been discussed. Finally, the numerical model has been extended to include particle collision and augmentation, and a preliminary study has been carried out to examine the effect of particle collision on the transport of particles in the water body. The results obtained with the inclusion of a particle collision model are compared with those obtained using a non-colliding particle model. It is revealed that, whilst the particle collision model may have a significant effect on the particle size distribution, depending on the initial particle concentration, its impact on the particle mass distribution is insignificant
