|
[Sponsors] |
April 25, 2021, 07:15 |
Length Scale - Wavenumber Context
|
#1 |
New Member
Fab
Join Date: Nov 2020
Posts: 25
Rep Power: 5 |
Hey People,
Im a little bit confused with the terms "Length Scale" and "Wavenumber". In the idea of richardsons energy cascade, it is called that the energy flows from the big eddies to small eddies. The smallest eddies have the kolmogorov length scale l_k. The different areas of the energy cascade are distinguished on the basis of the length scale. Is this term of "length scale" equivalent to the term of the wavenumber? I think it is, but why are some scientific articles or simulation programms refering to the wavenumber, others to the length scale? |
|
April 25, 2021, 07:30 |
|
#2 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,842
Rep Power: 73 |
Quote:
No, a wavelenght is dimensionally a lenght, the wavenumber is an integer. To understand better, consider a periodic function over a lenght L. This way, L is the maximum wavelenght in the domain. It corresponds to the wavenumber 1. Mathematically you can see that from the Fourier basis exp(i*k*x) where k=n*2*pi/L being n the wavenumber and k the spatial frequency (dimension L^-1). That means the L=2*pi/k is the wavelenght at the wavenumber =1. |
||
April 26, 2021, 05:33 |
|
#3 |
New Member
Fab
Join Date: Nov 2020
Posts: 25
Rep Power: 5 |
Allright, Thanks for the reply.
But now i wonder, is the length scale the same as 1/(spatial frequency)? Or is there no correlation? |
|
April 26, 2021, 07:10 |
|
#4 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,842
Rep Power: 73 |
||
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
to determine Integral length scale in Fluent | raunakjung | FLUENT | 3 | February 7, 2017 09:03 |
Problem with large time scale and minute length scale | mech_engg_swag | OpenFOAM | 0 | August 23, 2016 07:39 |
Difference between mixing length and turbulence length scale | MissCFD | CFX | 1 | May 7, 2015 12:58 |
Length Scale vs. Hydraulic Diameter? | Will | FLUENT | 1 | April 13, 2004 06:09 |
Characteristic Length Scale | Thomas P. Abraham | Main CFD Forum | 2 | April 20, 1999 17:16 |