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Basic turbulence concepts, vortex stretching energy cascade concepts help

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Old   August 4, 2013, 05:34
Default Basic turbulence concepts, vortex stretching energy cascade concepts help
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Muhammad Irti
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Hi guys. i am a newbie in studying turbulence in cfd. I am really having hard time getting basic concepts of turbulence like, how and why vortices are formed, vortex stretching concept, energy cascade, stability theory etc. I am unable to fully understand first few pages of malaseekra's book chapter 3.
So any help regarding clearing the mentioned topics above would be greatly appreciated. Thanks in advance
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Old   August 4, 2013, 05:59
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Here are two videos I found on youtube that show nicely how vortex stretching creates a range of scales. Maybe this helps you!

http://www.youtube.com/watch?v=59LL_IRs1MQ

http://www.youtube.com/watch?v=JaABLY6E8HE

It shows the stretching. turning and reconnection mechanisms quite nicely.
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Old   August 4, 2013, 06:14
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@cfdnewbie

seems like these two videos are way too complex to be understood by me. No commentary no nothing, no understanding of what is flow direction,( just seem like some colors are randomly mixing in a bucket of paint) so kindly suggest some better notes
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Old   August 4, 2013, 06:53
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Quote:
Originally Posted by irtiza View Post
@cfdnewbie

No commentary no nothing, no understanding of what is flow direction,( just seem like some colors are randomly mixing in a bucket of paint)
What you are seeing is the interavction of two perpendicular vortices in a periodic box, and how they create a turbulent cascade. This is the basic mechanism that produces a range of scales, and thus, turbulence.
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Old   August 4, 2013, 07:29
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thanks, but i am well below that level to even understand that..
Can you recommend me a book
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Old   August 4, 2013, 13:17
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Quote:
Originally Posted by irtiza View Post
thanks, but i am well below that level to even understand that..
Can you recommend me a book
I reccomend the book of Pope, as well as the book http://www.amazon.it/Introduction-Tu.../dp/0521775388
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Old   August 4, 2013, 13:53
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I reccomend the book of Pope, as well as the book http://www.amazon.it/Introduction-Tu.../dp/0521775388

Two great books, it doesnt get much better than Pope, but I would start with the second one - very easy to read, the kind of book you can into the bathtub and still learn a lot!
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Old   August 4, 2013, 16:37
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Thank you Fmdenaro and cfdnewbie, i will definitely go through the books as both are available in library and will inform you if i face any problem. thank you soooooo much
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