bookworm:
Thanks!
At first you've lost me on the relevance of the pencil example, but eventually I think I get it. Any amount of viscosity changes things.
The question still remains: is it absolutely necessary?
Is it a question that can be demonstrated in a realistic experiment?
Increasing the viscosity will change the lift a little, but not much, even as the viscosity increases by orders of magnitude, and the lift actually tends to decrease as viscosity increases (Reynolds Number decreases).
I'll break it down to a short sentence for thick heads like me:
Increasing viscosity descreases lift. Hm.. Do you meant, beyond certain point, or always? Or, is it that you are mentally changing size to change Reynolds, which you equate with viscosity? Something doesn't tally with the need for viscosity.
chornedsnorkack:
I appreciate your replies, but... my questions aim to find how much the two physical properties of air / fluid contribute to the lift.
Your 1st example didn't separate the two.
Your 2nd example promises to decrease viscosity [effects] by
... increasing the size of the airfoil
. Hm.. And divide the results by surface area? Any link with results?
Can we perhaps confine our discussion to one flat plate of fixed dimensions, and not introduce this dreaded Raynolds number. To place us on any graphs that you may have at your disposal, let's say that the flat plate is 10m X 1m (not terribly, but close to C-172).
PS: Merry Christmas.