The fluid dynamics and transport of sprays comprise an exciting field of broad importance. There are many interesting applications of spray theory related to energy and power, propulsion, heat exchange, and materials processing. Spray phenomena also have natural occurrences. Spray and droplet behaviors have a strong impact on vital economic and military issues. Examples include the diesel engine and gas-turbine engine for automotive, power-generation, and aerospace applications. Manufacturing technologies including droplet-based net form processing, coating, and painting are important applications. Applications involving medication, pesticides and insecticides, and other consumer uses add to the impressive list of important industries that use spray and droplet technologies. These industries involve annual production certainly measured in tens of billions of dollars and possibly higher. Many applications are still under development. The potentials for improved performance, improved market shares, reduced costs, and new products and applications are immense. Continuing effort is needed to optimize the designs of spray and droplet applications and to develop strategies and technologies for active control of sprays in order to achieve the huge potential.

In the first edition of this book and in this second edition, I have attempted to provide some scientific foundation for movement toward the goals of optimal design and effective application of active controls. The book, however, does not focus on design and controls. Rather, I discuss the fluid mechanics and transport phenomena that govern the behavior of sprays and droplets in the many important applications.