treating unresolved scale

student2 · January 28, 2011, 04:44

Hello, every one.
I have a question with filtering in LES.

Let original flow u and filtered flow <u>.
Then unresolved scale become u'=u-<u>

If I filter the unresolved scale, i.e., <u'>,
I want to know whether this value will be 0 or not?

Thank you for reading!
YE.

sbaffini · February 14, 2011, 13:34

The answer is "no", unless you use a projective filter. Try by yourself in MATLAB with a simple 1D function (sum of sines) and different filters. The spectral cut off is the only filter which gives exactly 0.

student2 · February 14, 2011, 20:51

Quote:

Originally Posted by sbaffini

The answer is "no", unless you use a projective filter. Try by yourself in MATLAB with a simple 1D function (sum of sines) and different filters. The spectral cut off is the only filter which gives exactly 0.

Thank you for your help!

January 28, 2011, 04:44	treating unresolved scale	#1
student2 New Member YE Join Date: Jan 2011 Posts: 6 Rep Power: 15	Hello, every one. I have a question with filtering in LES. Let original flow u and filtered flow <u>. Then unresolved scale become u'=u-<u> If I filter the unresolved scale, i.e., <u'>, I want to know whether this value will be 0 or not? Thank you for reading! YE.

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February 14, 2011, 13:34		#2
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,152 Blog Entries: 29 Rep Power: 39	The answer is "no", unless you use a projective filter. Try by yourself in MATLAB with a simple 1D function (sum of sines) and different filters. The spectral cut off is the only filter which gives exactly 0.