Unformatted text preview: and other reduced descriptions of turbulence, in
particular, as well as in construction of a kind of statistical mechanics of turbulence
generally.
It is a matter of principle and a conceptual question whether studying turbulence via
(some) decompositions is aiding understanding of its fundamental physics. More that
one hundred of experience sems to be a clear indication that it is not:
I think that the kspace decomposition does actually obscure the physics,
MOFFATT, 1990; see also LIEPMANN 1962, TENNKES 1976, and many others.
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* It is well known that theoretical physics is at present almost helpless in dealing
with the problem of strong interactions. LANDAU 1960. The situation in turbulence seems to be not
better if not worse . # If we assume as a basic starting point in every theory of
turbulence its representation in terms of spectral coefficients,
statistical or physical averages, or more generally simple
objects conditionally extracted by a weak background,
turbulence modelling could be defined reductively, as the
art of writing the equations that produce directly such
quantities. GERMANO 1999
# Perhaps the biggest fallacy about turbulence is that it can
be reliably described (statistically) by a system of
equations which is far easier to solve than the full timedependent threedimensional NavierStokes equations
BRADSHAW 1994 CONCLUDING
CONCLUDING Too little is (still) known about the properties of
Too
real turbulence. So it seems not justified to put
too much (pretty futile) efforts in it’s modeling
which mostly is mimicking it without much
understanding. Hence the necessity to follow the
advice of LEONARDO DA VINCI: Remember, when discoursing about water, to induce
first experience, then reason with the emphasis on the physical aspects based in the first place on
observations and empirical facts as distinct from
intuitive conjectures, hypotheses and ‘models’. The observational aspect is not that trivial as it
The
involves directly the skill/art/ability to ask the
right and correctly posed questions. In our view
the first priority should be given to study of
basic physical mechanisms of turbulence with the
emphasis on qualitative aspects, keeping in mind
a somewhat oldfashioned view that curiosity
drives better science than `strategies'. This
priority includes the study of turbulence itself
(per se), rather than multitudes of its models.
(per
The only exception seems to be the NavierStokes
equations. A SMALL HOME WORK:
WHAT IS WRONG WITH
THE PAPER BELOW?
THE
OR WHY THE ‘RIGHT’
OR
RESULT IS FOR THE
RESULT
WRONG REASON?
WRONG...
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 Spring '11
 Staff
 Fluid Dynamics, The Land, Marie Curie, Turbulent Flows

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