Comments on: 221. Turbulence: Kolmogorov law derived in one line

By: Keith McNaughton

Keith McNaughton — Wed, 14 Oct 2009 01:08:10 +0000

A corollary of the derivation of the Kolmogorov spectrum by a purely dimensional argument is that any well-dimensioned model will give the same result, so an ability to predict the Kolmogorov spectrum is no test of the correctness of a model. The log law for the velocity profile is similarly “insensitive to derivation”.

Another feature of the dimensional derivation is that it works in terms of the transfer of turbulence energy, without gains or losses, from production scale to dissipation scale. Not all turbulence energy need be in the form of turbulence kinetic energy. For example, in high-Rayleigh-number flows there can be so much energy in the pressure fluctuations that the -5/3 law becomes very approximate.

By: Top 10 open problems in Physics « Grandmastermind’s World?

Top 10 open problems in Physics « Grandmastermind’s World? — Sat, 18 Apr 2009 06:26:51 +0000

[...] I wrote about it many times, it is worth writing another time. We don’t know how to analytically treat developed turbulence. We are mumbling something about 2-dimensional scalar turbulence, weak turbulence, but ultimately we don’t even know whether a general solution of Navier-Stokes equation exists, whether it is smooth or finite time singularities are getting developed in the fluid velocity flow (note that Clay Mathematics Institute currently offers 1 million USD for the solution of this problem). [...]

By: 312. Turbulence. Stochastic approach 2

312. Turbulence. Stochastic approach 2 — Wed, 18 Mar 2009 18:06:54 +0000

[...] beautiful results of stochastic approach is Kolmogorov scaling. Earlier, I have already discussed Kolmogorov’s turbulence on the blog in details, let me ramble about it today a little bit [...]

By: Dmitry

Dmitry — Tue, 17 Feb 2009 19:33:20 +0000

Hi Alex

My impression is that Kolmogorov scaling is good first approximation into the problem. There are corrections to scaling that come from many other effects such as intermittency (please see my further posts on the problem – for example, this one as well as discussion in comments), but there is no question that Kolmogorov scaling is there.

Cheers,
Dmitry.

By: Alex

Alex — Tue, 17 Feb 2009 19:05:33 +0000

I wish it is so simple. More and more evidence is out there that the picture is not as straightforward as drawn here – viscosity turns to be important at any Reynolds number and it affects the flow from smallest through the inertial (intermediate) to upper scales, etc.
Yet, the combination of physicists, especially with a non-equilibrium tools and experimentalists (engineers) with simple measurement tools could be necessary in order to tackle this >> 1Mn problem.

By: 266. First two weeks of February on NEQNET

266. First two weeks of February on NEQNET — Mon, 16 Feb 2009 19:14:08 +0000

[...] 1.1. Turbulence: Kolmogorov law derived in one line [...]

By: Dmitry

Dmitry — Sun, 08 Feb 2009 20:36:01 +0000

Dear Habib,

it means Kolmogorov’s power law scaling of the correlation functions of the energy density in the flow as well as the velocity of the flow.

Cheers,
Dmitry.

By: habib

habib — Sat, 07 Feb 2009 23:28:20 +0000

Hi,

what does similarity exactly mean in turbulent flow?

habib

By: 226. Top ten open problems in physics

226. Top ten open problems in physics — Tue, 03 Feb 2009 15:24:10 +0000

By: Dmitry

Dmitry — Mon, 02 Feb 2009 20:34:12 +0000

Do you remember the mysterious figure of 3 in Feynman’s discussions of turbulence?

I actually don’t, where was it – in Feynman’s lectures of physics?

By: Lubos Motl

Lubos Motl — Mon, 02 Feb 2009 20:16:19 +0000

Do you remember the mysterious figure of 3 in Feynman’s discussions of turbulence? Is that the same thing that appears in your exponents? If so, that’s cool!