Udo R. wrote 11.9.05: [snip] The reason to sand an airfoil shape, that
has shown to be

sensitive to being polished, could be as follows.



The laminar flow on a polished surface, at the transition point, turns
into a large transition bubble due to an unfavourable pressure gradient.

This bubble is large enough to cause a noticeable drag increase.

By sanding one maintains most of the designed laminar flow over that
region but the transition is forced sooner and it has enough energy to
keep the bubble small. Hence less laminar flow but overall reduced drag.

[snip]

Sorry to be ignorant, but I don't understand the technicalities of this.
What is the " . . . unfavourable pressure gradient . ." ? One in the
wrong direction, or too large, or what?

And in what sense does a transition have energy? Particularly "enough
energy to keep the bubble small" ? If it had energy, the idiot layman's
thinking is that more means bigger.

Hoping for education, not flames or sarcasm.

Chris N.

=======================




__________________________________________________ _________
To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.com