Abstract
The contents of the present thesis has its basis in problems related to process metallurgy. The field is closely related to chemical engineering as they both involve complex fluid mechanical multiphase problems. In process metallurgy multiphase flow situations arise when, for example, a liquid bath is stirred by injection of an inert gas. Injection of solid particles into a melt by a carrier gas is another typical situation. In some other situations raw materials are transported pneumatically which may lead to problems with erosion or fouling. Hence, depositon of solid particles from a turbulent gas stream in high temperature systems becomes another important field. The turbulent particle deposition process in liquids is relevant to clogging of nozzles and particle removal from melts. Another typical multiphase situation is fluid-particle flow in a classifier ( cyclone, centrifuge, etc.) which applies to gas cleaning and powder classification for production of fine ceramic materials. Common for all these processes is complex interactions between the different phases which involve full coupling of momentum, mass and enthalpy. The turbulent processes are further coupled to the existing dispersed phases through the momentum coupling. In the present thesis we want to focus on the dispersed flows and the turbulent transport processes in such systems. In the main body of the thesis a general discussion on the turbulent modelling of disperse multiphase flow systems is ;presented. Here we focus on the theoretical description, emphasising the fundamental aspects of transport phenomena. The aim is to present new ideas and formulations which can stimulate further development of the field. For example, is it shown that virtual mass, transversal lift forces and Basset's history forces contribute to both momentum and turbulence coupling between the continous and the dispersed phase. In the Appendix a new formulation for turbulent transport is presented which shows that the assum