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Old   October 23, 2001, 05:35
Default help in seeing separation
Andrew Parker
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Dear all

My question is related to CFD, but at the moment I am trying to get some experimental results before I use CFD to try to recreate them. I am trying to use flow visualisation techniques to find the point of separation on the airfoil (that's what I am modelling). In particular I would like some information on the composition of the oil mixture that can be placed on the airfoil. It would be of great help if anybody knows of the 'recipe'of how to make this mixture up, so that I can put it on the airfoil. In particular it would be good if any references given are not the net-and hence free.


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Old   October 23, 2001, 10:07
Default Re: help in seeing separation
Axel Rohde
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A simpler way of determining the point of flow separation would be to attach so-called "tufts" (say 1cm long nylon or garment thread) on the surface, and see which way they are pointed.
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Old   October 23, 2001, 10:20
Default Re: help in seeing separation
Axel Rohde
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The same thing can be done numerically, i.e. in CFD. Again, let me refer you to page 106 of my 'frequently cited' dissertation...

For the case of the non-rotating disc, you can clearly see the line of separation on the top aft portion of the disc where the tufts reverse direction.
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Old   October 25, 2001, 16:19
Default Re: help in seeing separation
Paul Taniguchi
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An alternative to using an oil coating to determine separation is a liquid crystal coating. Reda & Wilder wrote an article on the web discussing this:

Regards, Paul
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