Kinetic energy dissipationUp to General comments
Kinetic energy dissipationPosted by Bimlesh Kumar at February 09. 2008
How to measure kinetic rate dissipation through turbulence data obtained by Vectorino plus? If you have any literature please give me
Re: Kinetic energy dissipationPosted by Atle Lohrmann at February 11. 2008
a) Check out ExploreV. You can access (I think) the Help section without buying the software license.
b) check one of the previous threads --- http://www.nortek-as.com/forum/current-profilers-and-current-meters/579860345
or http://www.nortek-as.com/forum/velocimeters/30180970#498521376 --- a general search of the forum should be quite helpful.
Best regards, Atle Lohrmann
Re: Kinetic energy dissipationPosted by Bimlesh Kumar at February 11. 2008
I have also purchased ExploreV software. If i am going to 5/3 figure and click on extract dissipation rate, each and every point it is giving some value. So i am confused which one is teh real one, or i am infact bot understanding teh concept properly. So please suggest me
Re: Kinetic energy dissipationPosted by Atle Lohrmann at February 12. 2008
Have you checked the help section in the program? - Atle Lohrmann
Re: Kinetic energy dissipationPosted by Bimlesh Kumar at February 14. 2008
Explore V help gives brief description about it. There is no section detailing how it calculates and where to calculate. In fact help is not clear
Re: Kinetic energy dissipationPosted by Atle Lohrmann at February 15. 2008
Dear Bimlesh Kumar
The calculation of the dissipation rate in ExploreV is, as far as I know, based on the Taylor hypthesis of frozen turbulence and that you can use the mean flow to scale between frequency and wave number space. I would recommend getting a book on turbulence so you can better understand how the dissipation rate is related to the spectrum that is displayed in ExploreV.
Nortek is just an instrumentation company -- we are not really specialists in fluid mechanics.
Best regards, Atle Lohrmann
Re: Kinetic energy dissipationPosted by Subhendu Maity at January 03. 2011
Re: Kinetic energy dissipationPosted by P.J. Rusello at January 03. 2011
Can you clarify your question? I'm not sure what you mean by "order of dissipation rate" in your question. If you're just looking for units, it should be [L]^2/[T]^3 (length squared per time cubed).
Re: Kinetic energy dissipationPosted by Subhendu Maity at January 04. 2011
Re: Kinetic energy dissipationPosted by P.J. Rusello at January 04. 2011
Based on your plot, I would say it's in cm^2/s^3. Expected values are typically 10^-7 to 10^-9 m^2/s^3 for many flows, so your value is a little high but I don't know what type of flow this data was taken in.
Re: Kinetic energy dissipationPosted by Subhendu Maity at January 06. 2011
Re: Kinetic energy dissipationPosted by P.J. Rusello at January 06. 2011
The presence of the grid so close to the measurement location could account for the higher dissipation rate you are measuring. I suggest doing some estimates based on simple scaling arguments for the flow (check for instance Tennekes and Lumley's A First Course in Turbulence ) since you seem to be measuring decaying grid turbulence in your experiment. This should let you know if your measurements can be believed or if there is a potential bias you are measuring. Otherwise, the Vectrino appears to be performing well based on the spectra you provided. The two peaks in the green line are probably due to the probe stem vibrating in the flow.