Dynamic Soaring of Air masses Video

rcgldr

If the model is just circled around a horizontal plane at minimal sink speed, then altitude is gained at the quickest rate as long as the model in in the updraft. A model can continue to climb as long as it is in an updraft, but a model can only go some finite distance above the updraft shear boundary in the two mass case.

The main difference in the two air mass case for a slope site is that the model is descending in a horizontal wind during a dive, so less vertical component of aerodynamic force opposing the descent, allowing a bit more vertical speed when it reaches the shear boundary. Assume a model is flown horizontally in the updraft just below the shear boundary, it reaches some maximum speed, and is then flown upwards above the updraft, reaching some maximum altitude. The question is if the model is now flown downwards back into the updraft and then pulled upwards again, will it acheive an even higher alititude, and I'm not sure if it will. I would assume that the size of the shear boundary, speed of the updraft, and the efficiency of the model would be factors. If the slope and the induced upwash are not wide enough for the model to achieve it's maximum speed in a horiztonal glide, then the pump maneuver should allow more maximum altitude.

Trying to apply math to this problem, note that the lift is related to speed² while the duration of time spent doing a partial loop upwards in the updraft is related to some constant / speed. This means the impulse (force x time) should increase with increased velocity from the dive, resulting in more momentum change, the updraft decelerated more and the glider accelerated more.

In the case of extreme dynamic soaring like 468 mph, I think the models are achieving speeds greater than their terminal velocity would be in a straight dive.

I'm not aware of a special term for this, so I assume it's just aerobatics done in updraft.

silverdollar1

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I talked to Taras K on the phone. He said since all thermals are bumpy that some dynamic soaring takes place within any thermal with high G vectors.

He also taught me that its not possible to gain the speed and height without the extra energy from ds in my videos without going out of the thermal and re entering.

Turns out its been done for the last 35 years in full scale gliders....

A.T.

If you pull the stick back, when entering the updraft, and push it forward on exit, you are definitively doing it.

But even if you do nothing and cross the shear layers perpendicularly, the plane will "bounce" between the air-masses, and reduce their velocity difference. So there is a certain DS component.

A.T.

Here is a video of a vulture soaring above a wind turbine (and getting hit by the blade):



My question is: Is just a coincidence that it chooses the soar there? Is it because the turbine is build on a hill, the creates updrafts (slope soaring). Or is it maybe also doing some dynamic soaring, between the wake of the turbine and the free stream?

A.T.

There is a new paper, where they (apparently for the first time) tracked an albatross with GPS, and examined the energy extraction:
http://www.plosone.org/article/info%...l.pone.0041449

A.T.

Here is another one on potential UAV usage: "Dynamic Soaring in Hurricanes"
http://vader.cse.lehigh.edu/publicat...12_gre_mon.pdf

A.T.

Could it be that flying fish use that, to glide up to 200m far at low altitude?



In the second video it seems, they occasionally dip the tail into the water and accelerate by wiggling it. They glide very low, so it could be ground effect too.