The Essence of Turbulence as a Physical Phenomenon : With Emphasis on Issues of Paradigmatic Nature This book critically reexamines what turbulence really is from a fundamental point of view and based on observations from nature laboratories and direct numerical simulations. It includes critical assessments and a comparative analysis of the key developments their evolution and failures along with key misconceptions and outdated paradigms. The main emphasis is on conceptual and problematic aspects physical phenomena observations misconceptions and unresolved issues rather than on conventional formalistic aspects models etc. Apart from the obvious fundamental importance of turbulent flows this emphasis stems from the basic premise that without corresponding progress in fundamental aspects there is little chance for progress in applications such as drag reduction mixing control and modeling of turbulence. More generally there is also a desperate need to grasp the physical fundamentals of the technological processes in which turbulence plays a central role