This book is a comprehensive and intensive book for graduate students in fluid dynamics as well as scientists, engineers and applied mathematicians. Offering a systematic introduction to the physical theory of vortical flows at graduate level, it considers the theory of vortical flows as a branch of fluid dynamics focusing on shearing process in fluid motion, measured by vorticity. It studies 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. The rest of the book deals with vortices and vortical flows, following their natural evolution stages. Of various vortices the primary form is layer-like vortices or shear layers, and secondary but stronger form is axial vortices mainly formed by the rolling up of shear layers. Problems are given at the end of each chapter and Appendix, some for helping understanding the basic theories, and some involving specific applications; but the emphasis of both is always on physical thinking.

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.

This book is a comprehensive and intensive book for graduate students in fluid dynamics as well as scientists, engineers and applied mathematicians. Offering a systematic introduction to the physical theory of vortical flows at graduate level, it considers the theory of vortical flows as a branch of fluid dynamics focusing on shearing process in fluid motion, measured by vorticity. It studies 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. The rest of the book deals with vortices and vortical flows, following their natural evolution stages. Of various vortices the primary form is layer-like vortices or shear layers, and secondary but stronger form is axial vortices mainly formed by the rolling up of shear layers. Problems are given at the end of each chapter and Appendix, some for helping understanding the basic theories, and some involving specific applications; but the emphasis of both is always on physical thinking.

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.