Laminar to turbulent flow transition

[Anashim]

Is it true that the laminar to turbulent flow transition has been finally solved? From what I've read, it seems to be well described by the Directed Percolation Model. I can hardly believe it since I haven't seen the news in the press (from my point of view, it's a long standing unsolved issue in Theoretical Physics).

https://www.nature.com/collections/rxsztdqblr/

 

[Anashim]

Apparently, turbulence is a something that a Physicist cannot be bothered with. Landau and Feynman would not agree if they were alive!

https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics

https://en.wikipedia.org/wiki/Landau-Hopf_theory_of_turbulence

http://www.feynmanlectures.caltech.edu/II_41.html

https://en.wikipedia.org/wiki/Millennium_Prize_Problems

 

[boneh3ad]

As someone who works in the field of laminar-turbulent transition (albeit in boundary layers, not confined flows like the Poiseuille and Couette flows contained here), I've not heard of any of this and it was from two years ago. In other words, it must not have been broadly impactful enough to make its way into use in any engineering sense, nor has it found its way into use (or even mention) in the broader fluid dynamics community. That said, I haven't read through all of this yet (and I've downloaded the papers, so I do intend to do so).

From what I can tell, none of this is claiming that transition and turbulence have been "solved". Rather, it seems to indicate that the transition process itself (i.e. the growth and propagation of turbulent spots) can be described using this directed percolation idea from statistical mechanics (a topic with which I am admittedly not very familiar). It doesn't seem to do much to address how the flow arrives at the point where the spots form, nor the actual process by which a flow otherwise dominated by stable and unstable waves transitions to one dominated by the energy cascade that is the hallmark of turbulence.

In other words, this seems to be a potentially interesting piece of a puzzle, but it certainly doesn't form the whole picture.

 

[Anashim]

The title of the last two letters, namely,

'A universal transition to turbulence in channel flow'

'Directed percolation phase transition to sustained turbulence in Couette flow'

seem to indicate that the Directed Percolation Model contains all the relevant statistical information concerning the space-temporal transition to turbulence in the two analyzed flows.

If this is not an explanation of turbulence onset, then all the second order phase transition universality classes models are not physical descriptions of those phenomena either. In my opinion, they are physical explanations since you can caculate all critical exponents using either the Renormalization Group method (an approximate method) or solving the Conformal Field Theories that they define.