Dissipative particle dynamics for mesoscopic particle-based thermal-fluid simulations

The primary objective of this dissertation is to develop theoretical and computational tools to simulate engineering problems in fluid mechanics and heat transfer using a mesoscopic framework Phase change phenomena are ubiquitous in day to day technological and engineering applications. They are amongst the most complex transport processes and involve the interplay of multiple time and length scales, nonequilibrium and interfacial effects. Previous work on phase change phenomena at the continuum level has focused mainly on semi-theoretical models and correlations with experiments. Studies at the atomistic level using molecular dynamics have been limited to smaller nanoscopic length and time scales. Grid-based mesoscopic methods such as lattice Boltzmann have been very useful for problems in fluid mechanics but suffer from an inadequate multiphase thermal model. Problems associated with grids and lattices can be avoided by using particle-based methods. In addition, boundary conditions can be easily applied and thermal fluctuations can be incorporated easily using particle-based methods. The focus of this work will be on the dissipative particle dynamics mesoscopic method and its use in modeling problems in the thermal-fluids area. Previous work on dissipative particle dynamics has focused primarily on an isothermal model and had inconsistencies in notation and nondimensionalization. In this work, a new and consistent notation is introduced for multicomponent systems and scaling factors for unknown parameters are determined. The dynamic properties of an ideal dissipative particle dynamics fluid are characterized by varying the integration algorithm, time step and friction factor. The energy-conserving model is studied in great depth and is shown to work very well for higher dimensional heat conduction problems for the first time. The model is further extended to investigate the Rayleigh Benard convective instability problem in a single phase fluid for the first time and can easily be used to study other problems in convection. To develop a multiphase thermal framework, a phase change model is incorporated into the energy-conserving model using the density functional theory formulation of inhomogeneous fluids and is used to study the homogeneous vapor nucleation phenomena at mesoscopic length and time scales.