James;
Mike Georgallis was the person at UBC who was in charge of the project. His
phone number is/was 604 822-3665. He would be the best person to provide the
answers to your questions.
A few thoughts;
The UBC rotors were very large and very slow turning. My impression was that
the two disks should be smaller and identical. Normally a smaller disk will
require more power. However, the slow speed of the these blades meant that
they were not operating in a vertical flow field.
In addition, these blades would have flex in the flapping direction. The
flex recovery, as the blades pass through the downwash/downdraft of the
blades of the other rotor, should maintain a fairly consistent angle of
attack throughout the rotation.
Constant taper and ideal twist should also help.
Dave
"james cho" wrote in message
...
Here's a pic of their blades layout:
http://batman.mech.ubc.ca/~hph/thunderbirddesign.gif
(note the blade rotation arrows)
What I'm wondering about the blades:
- Why the odd taper? I'm guessing the taper alleviates tip losses,
but why does it begin at the ~.6 span mark? I'd expect taper across the
entire blade for the best inflow results, but then again I'm a non-expert.
- Why no twist? Does the taper alone sufficiently linearize the
inflow?
I'd be grateful for any thoughts on these questions, and I know that
probably no one in this newsgroup has an exact answer. I'm just a student
studying helicopter aerodynamics and am interested in the UBC HPH design.
Here are some of their CFD visualizations if it helps anyone analyze:
http://batman.mech.ubc.ca/~hph/projects/cfd.html
And here's some info on another HPH design, with blades that are more
conventional (to my knowledge at least):
http://www.calpoly.edu/~wpatters/davi.jpg
Hope someone here knows more about this than I do,
jc