School of Mechanical Engineering Seminar
Monday, December 23, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206
Paradigmatic issues in turbulence problem/phenomenon*
Prof. Arkady Tsinober
School of Mechanical Engineering, Tel Aviv University
General and Introductory notes
The general/primary premises and the reasons/causes of this talk are the absence of theory based on first principles and inadequate tools to handle both the problem and the phenomenon of turbulence, Kolmogorov, von Neumann, for references on the issue see [1, ch 9], [2, ch 11]. Among the consequences is that turbulence research is loaded with misconceptions and ill defined concepts, outdated “paradigms”, multitude of problematic analogies and alike - quite a bit of what is called “understanding” in turbulence, etc. There is still a massive belief in most of these traveling from one publication to another and exhibited in a pretty articulate fashion in crowded meetings.
Examples of most popular outdated "paradigms" - in brief
• Turbulence is an essentially inviscid, inertial phenomenon and is uninfluenced by the precise nature of the viscous mechanism;
Cascade, locality versus nonlocality, inertial range and scale invariance, utility (and futility) of decompositions.
• Vorticity amplification is a result of the kinematics of turbulence, i.e. vortex lines are on average stretched rather than compressed, because two particles on average move apart from each other.
Explicit example(s) - in more detail
• Rather than "essentially inviscid" turbulence is an essentially strongly dissipative (lots of dissipation) and rotational (plenty of vorticity) phenomenon; the "guilty" processes for these properties. Are these processes well understood as massively claimed?
Concluding remarks on the present state of matters as long-lasting and continuing paradigmatic crisis...
References [1] A. Tsinober 2009 An informal Conceptual Introduction to Turbulence, Springer Verlag. [2] A. Tsinober, 2013/4 The Essence of Turbulence as a Physical Phenomenon with Emphasis on Issues of paradigmatic nature, Springer Verlag.
