Taylor microscale

anishtain4 · November 17, 2012, 06:19

has anyone calculated taylor microscale in openfoam?
Appreciate it if you share the code.

anishtain4 · November 20, 2012, 06:33

any one has any Idea?

chegdan · November 20, 2012, 12:16

People might be more likely to help if you provide a little more information e.g. equations; sources; what you have tried already; what type of simulation your are performing. I'm interested in the topic if you can provide more details.

anishtain4 · December 7, 2012, 05:28

thanks for the interest chegdan,
Taylor microscale is the main length scale measured in turbulent homogeneous box to determine Reynolds number since there is no physical length scale. here is a more descriptive of what it naturally is:
http://en.wikipedia.org/wiki/Taylor_microscale
but a formula to calculate it is presented in "turbulent flow" by Pope in page 199.
Can you tell me how to put that formula in Opefoam?

chegdan · December 10, 2012, 14:50

Looking at Pope, around the page that you suggested, I find that the longitudinal Taylor microscale $\lambda_f(t)$ can be related to the transverse Taylor microscale $\lambda_g(t)$ via

$\lambda_f(t) = \sqrt{2}\lambda_g(t)$

where

$\lambda_g = \frac{k^{\frac{3}{2}}}{\epsilon}\sqrt{\frac{10\epsilon\nu}{k^2}}$

However, this formulation seems simplistic compared to the definition by pope using the longitudinal (

) and transverse (

) autocorrelation functions. If you are looking for those, then I will have to think about this some more.

If you are satisfied with the second equation formulation, then I would suggest you look into the post-processing utilities as to how variables are read in at each time and used to calculate what you want e.g. Co utility. Give it a try and post back if you run into problems.

November 17, 2012, 06:19	Taylor microscale	#1
anishtain4 Senior Member Mahdi Hosseinali Join Date: Apr 2009 Location: NB, Canada Posts: 273 Rep Power: 18	has anyone calculated taylor microscale in openfoam? Appreciate it if you share the code.

November 20, 2012, 12:16		#3
chegdan Senior Member Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 621 Rep Power: 0	People might be more likely to help if you provide a little more information e.g. equations; sources; what you have tried already; what type of simulation your are performing. I'm interested in the topic if you can provide more details. Last edited by chegdan; November 21, 2012 at 07:54. Reason: edit: this sounds better

December 10, 2012, 14:50		#5
chegdan Senior Member Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 621 Rep Power: 0	Looking at Pope, around the page that you suggested, I find that the longitudinal Taylor microscale $\lambda_f(t)$ can be related to the transverse Taylor microscale $\lambda_g(t)$ via $\lambda_f(t) = \sqrt{2}\lambda_g(t)$ where $\lambda_g = \frac{k^{\frac{3}{2}}}{\epsilon}\sqrt{\frac{10\epsilon\nu}{k^2}}$ However, this formulation seems simplistic compared to the definition by pope using the longitudinal () and transverse () autocorrelation functions. If you are looking for those, then I will have to think about this some more. If you are satisfied with the second equation formulation, then I would suggest you look into the post-processing utilities as to how variables are read in at each time and used to calculate what you want e.g. Co utility. Give it a try and post back if you run into problems. anishtain4 likes this.

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November 20, 2012, 06:33		#2
anishtain4 Senior Member Mahdi Hosseinali Join Date: Apr 2009 Location: NB, Canada Posts: 273 Rep Power: 18	any one has any Idea?

December 7, 2012, 05:28		#4
anishtain4 Senior Member Mahdi Hosseinali Join Date: Apr 2009 Location: NB, Canada Posts: 273 Rep Power: 18	thanks for the interest chegdan, Taylor microscale is the main length scale measured in turbulent homogeneous box to determine Reynolds number since there is no physical length scale. here is a more descriptive of what it naturally is: http://en.wikipedia.org/wiki/Taylor_microscale but a formula to calculate it is presented in "turbulent flow" by Pope in page 199. Can you tell me how to put that formula in Opefoam?