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-   -   Hovering flight and Reynolds no. (https://www.cfd-online.com/Forums/main/14979-hovering-flight-reynolds-no.html)

 Zonexo March 25, 2008 12:06

Hovering flight and Reynolds no.

Hi,

I've used my NS solver to solve flow past moving airfoils. The Reynolds no. (Re) is obtained by calculating flow past the airfoil. So now if I want to simulate a hovering flight, what changes must I make? How do I calculate the Re since velocity is now zero?

I have searched the net and there's a paper (An improved method for calculating ﬂow past ﬂapping and hovering airfoils) which uses Re = k*a*c /v where k=reduced frequency, a=horizontal oscillation amplitude of airfoil, c=chord, v=viscosity. Is there any other definition?

Also, in hovering, lift is balanced by the weight and thrust is zero. So in my calculation, if the lift is not equal to the weight or if there's thrust, does it mean that this Re definition or my results will be invalid, cos the inbalance will result in the body moving?

thank you!

 Anton Lyaskin March 28, 2008 06:26

Re: Hovering flight and Reynolds no.

From dimensional considerations, there should be just frequency, not reduced frequency. Reduced frequency is dimensionless (it's inverted Stroukhal number), so k*a will give you meters instead of meters per second.

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