T o d d P a t t i s t wrote:

Eric Greenwell wrote:


I'm going to retract these comments about the thermal position relative
to the glider.


I was going to comment on your earlier post, but saw that
you made this second one and decided to read it first. After
reading it, I'm still not sure whether we agree or disagree,
but unless you tell me otherwise, I'm going to assume we
agree that even with a constant wind speed, no shear with
altitude and instantaneous acceleration of the thermal mass
to equal wind speed, the glider can still drop out of the
bottom of a thermal that starts from a fixed ground
location.

Yes, I do agree.

As to thermals like the dust devil you describe, I can only
dream about thermals strong enough to produce dust devils.

You have to have the dust, too! Come out West sometime.

I'm beginning to think that "many" thermals might act like the dust
devil I described, even ones from a fixed ground point. These thermals,
above a certain altitude, would be vertical in the air mass. Perhaps, as
the bent over portion stretches, it eventually breaks and starts a new
thermal closer to the origin point. The upper portion would drift off
with the wind and eventually dissipate, since it's no longer connected
to it's feed source.

Pilots would interpret this breaking and restarting as "bubbles" or the
thermal source dying, even though the fixed origin may be pumping out a
continuous thermal for hours.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA