The importance of vorticity and vortex dynamics has now been well rec- nized at both fundamental and applied levels of ?uid dynamics, as already anticipatedbyTruesdellhalfcenturyagowhenhewrotethe?rstmonograph onthesubject, The Kinematics of Vorticity(1954);andasalsoevidencedby the appearance of several books on this ?eld in 1990s. The present book is characterizedbythefollowingfeatures: 1. A basic physical guide throughout the book. The material is directed by a basic observation on the splitting and coupling of two fundamental processes in ?uid motion, i.e., shearing (unique to ?uid) and compre- ing/expanding.Thevorticityplaysakeyroleintheformer,andavortex isnothingbuta?uidbodywithhighconcentrationofvorticitycompared to its surrounding ?uid. Thus, the vorticity and vortex dynamics is - cordinglyde?nedasthetheoryofshearingprocessanditscouplingwith compressing/expandingprocess. 2. A description of the vortex evolution following its entire life.Thisbegins from the generation of vorticity to the formation of thin vortex layers andtheirrolling-upintovortices,fromthevortex-corestructure,vortex motionandinteraction,totheburstofvortexlayerandvortexintosma- scalecoherentstructureswhichleadstothetransitiontoturbulence,and ?nallytothedissipationofthesmalleststructuresintoheat. 3. Wide range of topics.Inadditiontofundamentaltheoriesrelevanttothe abovesubjects,theirmostimportantapplicationsarealsopresented.This includes vortical structures in transitional and turbulent ?ows, vortical aerodynamics, and vorticity and vortices in geophysical ?ows. The last topic was suggested to be added by Late Sir James Lighthill, who read carefullyanearlydraftoftheplannedtableofcontentsofthebookin1994 andexpressedthathelikes"allthematerial"thatweproposedthere. These basic features of the present book are a continuation and - velopment of the spirit and logical structure of a Chinese monograph by the same authors, Introduction to Vorticity and Vortex Dynamics, Higher VI Preface EducationPress,Beijing,1993,butthematerialhasbeencompletelyrewr- tenandupdated.Thebookmay?tvariousneedsof?uiddynamicsscientists, educators,engineers,aswellasappliedmathematicians.Itsselectedchapters canalsobeusedastextbookforgraduatestudentsandseniorundergraduates. Thereadershouldhaveknowledgeofundergraduate?uidmechanicsand/or aerodynamicscourses.