Turbulent length scale

MissCFD · February 22, 2017, 19:33

Can somebody confirm me that the turbulent length scale that we need to input as a inlet condition (with the turbulent intensity) corresponds well to integral scale

which is the size of the largest eddies and which is also to be found in this formula:

$\eta/l=Re^{-3/4}$ where $\eta$ is the Kolmogorov scale.

The reason I ask is that there is a lot of notation for turbulent length scale:

,

,

, etc.

Thank you for your help !

piu58 · February 23, 2017, 02:12

is the length of the large eddies. It should not be larger than

(the size of the problem) of course.

can be guessed.

For pipe flows:

is the hydraulic diameter, which is identical the diameter for round pipes. For rectangular ones:

$d = 2 \frac{ab}{a+b}$

For flow around / past bodies:

is the size of the problem, for cylinders and spheres the diameter, for other bodies the diameter of the flow directed area.

February 22, 2017, 19:33	Turbulent length scale	#1
MissCFD Senior Member Join Date: Aug 2014 Posts: 160 Rep Power: 12	Can somebody confirm me that the turbulent length scale that we need to input as a inlet condition (with the turbulent intensity) corresponds well to integral scale which is the size of the largest eddies and which is also to be found in this formula: $\eta/l=Re^{-3/4}$ where $\eta$ is the Kolmogorov scale. The reason I ask is that there is a lot of notation for turbulent length scale: , , , , etc. Thank you for your help !

February 23, 2017, 02:12		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	is the length of the large eddies. It should not be larger than (the size of the problem) of course. can be guessed. For pipe flows: is the hydraulic diameter, which is identical the diameter for round pipes. For rectangular ones: $d = 2 \frac{ab}{a+b}$ For flow around / past bodies: is the size of the problem, for cylinders and spheres the diameter, for other bodies the diameter of the flow directed area. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Calculation for Turbulent Length Scale	aqib	CFX	4	December 14, 2010 06:24
Turbulent Length Scale	aqib	FLUENT	0	December 11, 2010 02:53
turbulent length scale	Cathy	FLUENT	1	July 9, 2003 08:13
Von Karman Integral Length Scale	Txingurri	Main CFD Forum	0	May 2, 2002 13:05
Length scale was zero	chris	Siemens	2	September 10, 2001 10:12