I'm trying to develop a simple model for estimating induced power
savings for birds based on Wieselberger's (1922) work on ground effect
in fixed wings.

As I only want a basic picture of what's happening as the wing
approaches the ground, I only want an equation for a curve that'll
roughly predict z (1-sigma) for given values of h (height) and b
(wingspan), (I don't want to involve any calculus!!!).

I wanted to use the tabulated values that Wieselberger gives (below),
but they don't show z for any values above h/b = 0.25 (i.e. they don't
cover altitudes in the region of z = h/b. Does anyone out there know
of a source of a predictive equation that I could use (I'm pretty sure
its just some kind of log curve), or failing that, reliable data that
I could develop one from?
Thanks,

Marc.

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h/b 0 .025 .05 .075 .1 .125 .150 .175 .2 .25 inf
z 0(*) .22 .345 .439 .515 .630 .673 .710 .742 .770 1.
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(*) Values at zero HAGL are not covered by Wieselberger's theory.