Preface

Vortical flows are flows with vortices as their skeleton structures. Vortices are seen everywhere in our universe and on the earth: from spiral galaxies, atmospheric and oceanic circulations to hurricanes and typhoons, tornadoes to bath stub vortices; from volcanoes’ erupted smoke rings and mushroom clouds of nuclear explosions to vortex rings ejected from the mouth of dolphin and smoker, or formed in a heart downstream of the mitral valve that separates the left atrium and left ventricle; from tip vortices of aircraft, rotor blade, and turbo fan to complicated ring-like structures in the wake of birds, insects and fishes; from well organized laminar vortices to coherent turbulent structures. This book provides a systematic introduction to the physical theory of vortical flows at graduate level. It grew from our monograph Vorticity and Vortex Dynamics (Springer 2006), but has been thoroughly rewritten. Some advanced topics in the monograph have been removed, and more basic topics have been added. Recent advances since 2006 in the field of fundamental interest are included. Nevertheless, two basic characteristics of the monograph are inherited and further enhanced, which make both the monograph and the present book differ from other existing books on the subject: (1) We consider the theory of vortical flows as a branch of fluid dynamics focusing on shearing process in fluid motion, measured by vorticity. A vortex is defined as a fluid body with high vorticity concentration. The evolution of vorticity field is governed by vorticity dynamics. Coexisting with this process is the compression–expansion process (compressing process for short) measured by dilatation, pressure, or other thermodynamic variables, of which the main structure is shock waves where entropy process is naturally involved. The three fundamental processes in fluid motion are coupled with each other both inside the flow field and at solid boundary. We believe that only on the basis of this broad background can the physics of vortical flows be fully understood. (2) We study vortical flows according to their natural evolution stages, from being generated to dissipated. As preparation, the first three chapters of the book provide background knowledge for entering vortical flows. Due to the coupling of shearing process with other processes, this knowledge appears wider and more