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Unformatted text preview: RICHARSON-KOLMOGOROV-ONSAGER, CASCADE /spectral
RICHARSON transfer - ill defined.
TAYLOR, Vorticity amplification is a result of the kinematics of turbulence :
vortex lines are on average stretched rather than compressed because two particles
on average move apart from each other – RRWR . Is enhanced dissipation due to
predominant vortex stretching?
BATCHELOR, For the very smallest eddies the motion is entirely laminar.
_____________________________________ *Unlike other, e.g. involving cascade. Representation versus process.
*Passive objects, low-D systems ONE MORE ‘SIMPLE’
EXAMPLE The energy dissipation in turbulent flows remains finite at whatever Reynolds
number, i.e. inertial and dissipative the effects/terms are of the same order
# Similarly the enstrophy and strain production are are of the same order as their
viscous destruction/‘disspiation’ and even are approximately balanced.
# Turbulence is not a slightly viscous/dissipative phenomenon!
Turbulence Hence there is problem with statements like (you are welcome to discuss this in more detail) • Reynolds number represents the ratio of inertial to viscous
• For large Re the viscous interactions turn out to be quite weak.
• At large Re flow perturbations produced at scale L experience
a viscous dissipation that is small compared with nonlinear
effects. Nonlinearity then induces motions at smaller and
smaller scales until viscous dissipation terminates the process
at a scale much smaller than L, leading to a wide (so-called
inertial) interval of scales where viscosity is negligible and non
linearity plays a dominant role. The problem with misconceptions starts with the question
What is turbulence? and the attempts to give a definition of what
turbulence is? Are such attempts conceptually correct?
In a mathematical theory the definition of the main object of the
theory precedes the results; In physics, especially in new fields,
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- Spring '11
- The Land