Any which way the wind blows (physics brainteaser)

[spork]

One last warning, as already noted these are really only my own thoughts about roughly what might happen as steady sideways wind mixes with a thermal and I haven't really researched this at all. Therefore, treat what I say with caution!

Well Clive, I'd say you did a pretty good job of describing the nature of thermals. I would add a couple of notes... Thermals are a bit like waves - they come in a million varieties. Some are big fat slow smooth lift, and some are very tight turbulent and rock 'n roll all the way. Some are tall columns that reach from the ground to the clouds and some are just a big bubble (if you follow someone into one of these, but enter below them, you find you've missed it). Some are well organized, and some have multiple cores (which sometimes coalesce into a single, or at least fewer) cores. This is just the tip of the iceberg when it comes to thermals. On top of this you can have many other types of lift (such as shear, convergence, ridge lift, wave...).

One other point on thermals... when the air rises it's normally considered to expand adiabatically (in other words it doesn't lose it's heat, but it does get cooler due to the expansion). The rate of cooling due to adiabatic expansion, is greater than the lapse rate (the rate the atmosphere gets colder with altitude). This ends up defining the height to which the thermal will rise. So we don't normally think of the thermal as mixing much with the outside air, but as it cools due to adiabatic expansion, it eventually ends up at the same temp as the rest of the atmosphere - this is "cloud-base".

Fortunately, I feel no shame in asking questions about things that might seem silly to those know a field well.

Definitely no shame in asking - and if someone tells you they know most everything there is to know about thermals, they're lying. We're still learning more everyday - and a lot of what was believed seems to be changing.

The wacky idea I had involved entering the thermal and rotating the wings to be perpendicular to the ground. That would create a profile to "catch" the most wind if you had a thermal moving east to west and you entered it from the north or south.

What you're describing can be used to extract energy from wind sheers or strong wind gradients. Thermals are basically a rising airmass that just happens to drift with the wind. There are however a number of situations that create horizontal wind sheers, and there are birds that use this energy to travel great distances without ever flapping their wings.

As a general rule, many kinds of birds are pretty darn good at exploiting thermals, ridge lift, sheer, convergence... But for some reason ducks seem to be too dumb to use lift even when it's hard to miss. I have no idea why.

 

[I Ratant]

Ducks have high wing loadings. Itty bitty wings, fat fuselages.
Were it necessary for a duck to soar, nature would have provided the physical configuration.
What they have works well in the duck world.
Ravens they aren't!
Or pelicans.
Watching a flock of pelicans with their choreographed manuvering is one of natures freebies.
Ducks have mastered formation flight, sharing the load on the lead bird by shifting the lead along the string, like geese.
Many smallish sea birds like puffins are known to be brickish except when pumping their wings furiously.

 

[spork]

Ducks have high wing loadings. Itty bitty wings, fat fuselages.
Were it necessary for a duck to soar, nature would have provided the physical configuration.

True, but if nature simply provided them with a few more brain cells I wouldn't see ducks flying up the coast behind the ridge while the seaguls and hawks stay in the lift in front of the ridge.

 

[I Ratant]

Ducks don't chose their flight ways.
They're ducks, there's no Johnathan Livingstone Canard to persuade them to modify the only life patterns they follow.
For sheer animal tenacity when there must be easier ways to do it, the Arctic Tern's yearly migrations from the Arctic to the Antarctic and back again certainly indicate nothing more than an inborn "habit".
Some of these birds don't land for years at a time!
(I suspect some may cheat and spend some time floating on the ocean.)
Breeding grounds in red, over-winter grounds in blue.

 

[Tumbleweed]

Well at least I learned there are a lot if things to consider when piloting a powerless aircraft. Who knows maybe I'll take lessons someday. My Dory guide Amy, who rowed me through Class 10 Lava Falls in the G,C., teaches ultralight flying in the off season. Her husband flew through slot canyons in the IMAX film, Hidden Secrets of the Grand Canyon. Utterly breathtaking.

 

[spork]

Ducks don't chose their flight ways.

I can't get inside a duck's mind (nor can much else it seems). But many times I've been hang gliding at the coast and wathched ducks fly all the way up the coast 100 yards downwind of the ridge (out of the lift) while the hawks and seagulls are boating effortlessly in the ridge lift 100 yards away.

Well at least I learned there are a lot if things to consider when piloting a powerless aircraft. Who knows maybe I'll take lessons someday. My Dory guide Amy, who rowed me through Class 10 Lava Falls in the G,C., teaches ultralight flying in the off season. Her husband flew through slot canyons in the IMAX film, Hidden Secrets of the Grand Canyon. Utterly breathtaking.

Unpowered flight of all kinds can be a lot of fun. I've been into hang gliding and sailplanes for years. Just took up paragliding last year. I recommend any way you can get into the air.

Ultralights can be a lot of fun too, but in some ways they're on the opposite end of the spectrum. With a few exceptions, they tend to have extremely poor glide performance (which is OK - it's just a different aerial pasttime).

Some friends recently put an engine on their ultralight sailplane, and we've been taking it to the central valley. I tried to loop it yesterday - but failed.