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November 5, 2013, 05:12 |
Characteristic length
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#1 |
Member
Join Date: Aug 2011
Posts: 53
Rep Power: 14 |
Hi all,
I am trying to simulate flow over an aircraft that has an external storage. I would like to estimate the drag on the external storage. What should be my characteristic length to calculate the Re and hence the near wall node spacing? and why? Can anyone help me out pl. Regards Studentdrak |
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November 5, 2013, 16:17 |
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#2 |
New Member
Jim KIT
Join Date: Aug 2012
Location: Germany
Posts: 25
Rep Power: 13 |
Hi,
please correct me, when I am wrong. you can choose any lenght for your problem as charactristic length. But If you want to know if flow is turbulent or laminar can u estimate it from flow over a flat plane Re(x) = 5 e5, where x is the distance from the leading edge of the flat plate. (you should know that cfx doesnt simulate Transition) How fine should be the meh near the wall can you estimate from y+: Simulate your case and see the y+ term in Post. Or you may estimate Cf frome a flat plane and calculate shear stress on Wand. and thus, takking to account that y+ should be smaller than 1, you can find your y (wall node spacing). However you have take to the account that RANS use wall function and you must not have y<1 you can have y to 5 or 10. Vile Grüße, |
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November 5, 2013, 17:12 |
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#3 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,716
Rep Power: 143 |
As a starting point the length scale should be the chord of the wing. But then do a sensitivity analysis on your mesh to check if your starting point was correct or not.
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