Fluid mechanics is a complicated and extremely challenging field of study. It is central to several matters that are significant not only technologically, but also sociologically. This book emphasizes on a cross-section of procedures in fluid mechanics, each of which explains new ideas and relates to one or more matters of high interest during the early 21st century. The challenges constitute multi-phase flows, compressibility, non-linear dynamics, flow instability, transforming solid-fluid boundaries and fluids with solid-like characteristics. The procedures relate difficulties like weather and climate forecast, health care, efficiency of fuel, wind/wave energy harvesting, air quality, erosion, lessening landslides and noise.