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Richarson kolmogorov onsager cascade spectral

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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 : TAYLOR 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. BATCHELOR, _____________________________________ _____________________________________ *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 forces. • 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 The 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, it i...
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