Fluid mechanics is the study of how fluids move and the forces that develop as a result. Fluids include liquids and gases and fluid flow can be either laminar or turbulent. This book presents a level set based methodology that will avoid problems in potential flow models with moving boundaries. A review of the state-of-the-art population balance modelling techniques that have been adopted to describe the nature of dispersed phase in multiphase problems is presented as well. Recent works that are aimed at putting forward the main ideas behind a new theoretical approach to turbulent wall-bounded flows are examined, including a state-of-the-art review on single-phase incompressible fluid flow.