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Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot



 
 
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  #1  
Old November 8th 13, 03:56 PM posted to rec.aviation.soaring
JohnDeRosa
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

Interesting video/animation on Dynamic Soaring produced by the IEEE (Institute of Electrical and Electronics Engineers http://www.ieee.org).

http://www.youtube.com/watch?v=uMX2wCJga8g
  #2  
Old November 10th 13, 05:55 AM posted to rec.aviation.soaring
son_of_flubber
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

The bird loses energy from drag. How does it regain the lost energy to maintain equilibrium?

My guess is that bird gains energy from the upward impetus of the "rotor" produced by the wind shear (not shown in graphics).
  #3  
Old November 10th 13, 03:53 PM posted to rec.aviation.soaring
Evan Ludeman[_4_]
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

On Saturday, November 9, 2013 11:55:11 PM UTC-5, son_of_flubber wrote:
The bird loses energy from drag. How does it regain the lost energy to maintain equilibrium?



My guess is that bird gains energy from the upward impetus of the "rotor" produced by the wind shear (not shown in graphics).


Nope.

This may help.

http://www.youtube.com/watch?v=SVN-oF6tPLc

T8
  #4  
Old November 10th 13, 04:07 PM posted to rec.aviation.soaring
[email protected]
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

An eternally fantasized about possibility... But now, except for a few famous efforts in very strong wind shear (As I recall, Ingo Renner reportedly did it with a 40 mph wind shear or something like that) can we do this in real gliders?

I tried for a bit in condor, but it doesn't look like its wind shear model is accurate enough. (I was trying to dip in to the lee of a ridge like the RC modelers do, but it looks like condor is set up with the same wind and sink behind the ridge, not the wind shadow or rotor).

These nice videos suggest that somebody somewhere has done the quantitative calculation -- including all losses, how much wind shear (mph/ 1000', or kph / 1000 m) does it take to dynamically soar a modern sailplane? Can we do it with current vnes? The duckhawk is designed with much higher vne and g loadings which make dynamic soaring more efficient. How much shear does it need?

John Cochrane
  #5  
Old November 10th 13, 05:22 PM posted to rec.aviation.soaring
jjbird
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

On Sunday, November 10, 2013 10:07:19 AM UTC-5, wrote:
An eternally fantasized about possibility... But now, except for a few famous efforts in very strong wind shear (As I recall, Ingo Renner reportedly did it with a 40 mph wind shear or something like that) can we do this in real gliders?



I tried for a bit in condor, but it doesn't look like its wind shear model is accurate enough. (I was trying to dip in to the lee of a ridge like the RC modelers do, but it looks like condor is set up with the same wind and sink behind the ridge, not the wind shadow or rotor).



These nice videos suggest that somebody somewhere has done the quantitative calculation -- including all losses, how much wind shear (mph/ 1000', or kph / 1000 m) does it take to dynamically soar a modern sailplane? Can we do it with current vnes? The duckhawk is designed with much higher vne and g loadings which make dynamic soaring more efficient. How much shear does it need?



John Cochrane


It's been done for a number of situations. For those with an AIAA paper subscription "Optimization of Dynamic Soaring at Ridges" is a nice, concise example by the same folks who made the video.

The cliffnotes version is that for something like a 15m glider, it would take about 6 knots of wind and the peak airspeed would be around 90 knots. This does assume a very sharp shear model though (among other simplifications), to my knowledge no one has actually gone out and made a high resolution map of what the separated region behind a ridge looks like.
  #6  
Old November 10th 13, 06:19 PM posted to rec.aviation.soaring
Evan Ludeman[_4_]
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

On Sunday, November 10, 2013 10:07:19 AM UTC-5, wrote:
An eternally fantasized about possibility... But now, except for a few famous efforts in very strong wind shear (As I recall, Ingo Renner reportedly did it with a 40 mph wind shear or something like that) can we do this in real gliders?



I tried for a bit in condor, but it doesn't look like its wind shear model is accurate enough. (I was trying to dip in to the lee of a ridge like the RC modelers do, but it looks like condor is set up with the same wind and sink behind the ridge, not the wind shadow or rotor).



These nice videos suggest that somebody somewhere has done the quantitative calculation -- including all losses, how much wind shear (mph/ 1000', or kph / 1000 m) does it take to dynamically soar a modern sailplane? Can we do it with current vnes? The duckhawk is designed with much higher vne and g loadings which make dynamic soaring more efficient. How much shear does it need?



John Cochrane


Gary Osoba, please pick up the white courtesy phone...

Back to Greg Cole's Barnaby lecture, which I highly recommend.

http://www.youtube.com/watch?v=Ln9fuR8uwIc

Dynamic soaring discussion starts 28 minutes in.

Discussion of some flying that Gary Osoba did in the JS-1 starts about 37 minutes in. I would really like to understand more about this particular flight ("dynamic soaring on the edge of a cloud street").

Evan Ludeman / T8



  #7  
Old November 11th 13, 02:42 PM posted to rec.aviation.soaring
Bob Cook[_2_]
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

Another weird example of dynamic soaring:

A friend of mine used to fly control line model airplanes, "back in the
day".

One day, he just happened to be flying in an up and down flight path. A
day with strong wind. The tank ran dry and the engine stopped. He figured
he would land the model, but for some reason, continued another circle with
the same flight path....low, almost to the ground on one side, while very
high on the other.

To his surprise, the model did not loose speed, and was able to climb to
the same height. He continued circling, and the plane continued on the
same flight path, same speed, without engine!!!

It was pure luck that his up and down circle was in perfect alignment with
the wind direction so as to take full advantage of the wind gradient near
the ground.

I later read in magazines about other control line pilots who experienced
the same phenomenon. There were a series of control line modes which were
designed to specifically take advantage of the "dynamic soaring"...I don't
think those guys called it that.

These models had no engines...they were build very light and extremely
strong. You did have to use a "whipping" action of the control lines to
initially get the plane flying, but once up to speed, and the up and down
flight path established, the models would continue at high speed, and were
fully maneuverable...just like a powered model!!

Cookie









  #8  
Old November 13th 13, 06:47 AM posted to rec.aviation.soaring
Matt Herron Jr.
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

In theory, it should be possible to dynamically soar straight into the wind.. What is important is the rate of change of the wind shear as well as the delta in wind velocity.

Here is the scenario:
by some misfortune you find yourself 300 ft over unlandable Nevada scrub in a flat valley, 2 miles directly downwind of the only airport. Your airspeed is 40 knots at 300ft agl, and your flight computer is showing a 20 kt headwind. screwed? probably, but wait...

You get this crazy idea, and dive for the ground. You know you need about 100 knots of airspeed to climb 300 ft and push over at 40 knots again. As you dive rapidly to get out of the headwind, you pick up speed and skim along the brush in ground effect. now your flight computer says you have a 5 knot headwind, so your wind shear is 15 knots. But your airspeed is already below 100 knots so you can't get back to 300 ft without stalling! Really screwed!, Ah, but wait.

You have a free 15 knots of airspeed waiting for you at 300 ft as you climb through the wind shear. So you wait until your speed drops to 90 knots (for maneuvering losses) before pulling up firmly, but not radically, and climbing climbing climbing back to 300 ft at 40 knots airspeed. No radical "U" turns at high Gs needed

True, your groundspeed has slowed due to the new headwind, but you have been moving forward the whole time at a speed greater than the max windspeed. You definitely made forward progress and now you are back at 300 AGL, and 40 knots, so you can repeat as needed, all the way to the airport!

But where did the energy come from to get you back up there? It might help to think of the opposite scenario that we are all familiar with, landing into a headwind. You are on a perfect final approach, nose down at 65 knots because of the 15 knot headwind. As you descend through the wind shear your airspeed drops, robbing you of energy you had just a few minutes ago at 300 ft. you no longer have the airspeed to pull up or extend your glide.

Or another way of thinking about it: lets say the wind shear kept increasing up to 200 knots headwind at 2000 ft. You pull up and as your airspeed starts to drop from converting kinetic energy to potential energy, it is replenished by the ever increasing wind shear. You can keep on climbing indefinitely, as long as THE RATE OF INCREASE IN HEADWIND DUE TO WIND SHEAR IS GREATER THAN OR EQUAL TO THE RATE OF DECREASE IN AIRSPEED DUE TO CLIMBING. So the rate of change in wind speed in the shear is important in this example.

Magic.

Let me know how it works out as I don't have the guts to try this maneuver myself...

Matt
  #9  
Old November 13th 13, 07:08 PM posted to rec.aviation.soaring
Soartech
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

On Wednesday, November 13, 2013 12:47:02 AM UTC-5, Matt Herron Jr. wrote:
In theory, it should be possible to dynamically soar straight into the wind.


Magic.


Matt


This is quite an incredible theory! It should be possible to test this in a big field with any RC sailplane, no? Based on Cookies observation of the old control line planes (an RC sailplane has much less drag) so it would work even better. The RC guys who practice dynamic soaring currently use a U turn to pick up speed going downwind. But they use the energy to go faster (record currently over 400 MPH), not so much to climb. We would want to climb.
  #10  
Old November 13th 13, 07:28 PM posted to rec.aviation.soaring
JS
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Default Dynamic Soaring Animation IEEE - ASH25 w/ Albatross Pilot

Perhaps read this before attempting it.

"Have Bladder"
http://www.dtic.mil/dtic/tr/fulltext/u2/a461327.pdf

An L23 Blanik dynamic soaring experiment over Rogers Dry Lake, Edwards AFB about 6 years ago.
One important factor. Unlike Matt's scenario, everywhere was landable.
A flight computer was programmed for the occasion using software developed for dynamic soaring. Current wind gradient was displayed in-cockpit. It was found that you must fly the maneuvers with great precision.

Over lunch, one of the participants casually observed:
"It doesn't scale up well."
Jim
 




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