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

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).

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

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

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.

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

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

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

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.

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

http://www.youtube.com/watch?v=T4OGUYlx_28

Joe Manor flying an 11' rc model on the backside of a ridge.
diving into the windshadow and climbing into the wind.
483mph recorded as the glider was flying up and into wind . .

One flight carried an accelerometer, glider was pulling in excess of
90g on the top turns.

Glider had an airspeed in excess of 500mph on the top turns too.

the theory works, not too keen on the 90g turns tho.

here's one to ponder....

http://phys.org/news194851568.html


Cookie






At 18:28 13 November 2013, JS wrote:
>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
>

On Wednesday, November 13, 2013 1:58:39 PM UTC-8, Cookie wrote:
> here's one to ponder....
>
>
>
> http://phys.org/news194851568.html
>
>
>
>
>
> Cookie
>
>
>
>
>
>
>
>
>
>
>
>
>
> At 18:28 13 November 2013, JS wrote:
>
> >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
>
> >

It sold recently on EBay.

http://www.ebay.com/itm/Blackbird-Faster-Than-The-Wind-vehicle-/281114481020?pt=LH_DefaultDomain_0&hash=item4173ba917c

Craig

On Tuesday, November 12, 2013 11:47:02 PM UTC-6, Matt Herron Jr. wrote:
> 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

Two problems, Matt. Since you dove down through this 15 knot wind shear (15 knot less wind over the ground), your indicated speed went from 40 to 85 and not 40 to 100. Remember, you lost that speed just like you would have in descent on final.

Second problem. With the ever increasing shear, and that 200 MPH wind at 2000 feet, you may be able to pull up to 40 MPH indicated at that altitude due to the increasing wind speed as you climb, but your ground speed at the top of that pull is 160 MPH in the other direction. Yeah, you may have more altitude, but you aren't going to get home any easier from there! Not without some changes in direction.

The key is proper alignment with the changes in energy in the atmoshpere in order to impart the energy to your plane. And the slower the plane, the greater the percentage of total energy you can gain for the same energy available in the atmosphere. 5 MPH change in wind speed is 56.25% increase in kinetic energy for something travelling initially at 20 MPH, but only 17.36% for something initially travelling at 60 MPH. The more manueverable the plane, the more of this energy you can extract.

Steve

On Wed, 13 Nov 2013 21:58:39 +0000, Bob Cook wrote:

> here's one to ponder....
>
> http://phys.org/news194851568.html
>
>
That's make three of these odd devices that I've heard of. That article
mentions one called the BUFC that also ran recently.

The first one was built by Andrew Bauer in 1969. It was a small, unmanned
proof of concept device that was run on a deserted supermarket car park
to win a bet. I think it used a mechanical drive (belt? chain?) to
connect the wheels to the propeller while Rick Cavallero's machine used
an electric drive: generator driven by the wheel and electric motor to
spin the prop.

Andy Bauer was well known in free flight model flying circles, but not
for that: his son Ken told us the story when we heard about Rick
Cavallero's machine. There is a video, copied from an 8mm film, of Andy's
one here:

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


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Friday, November 8, 2013 6:56:23 AM UTC-8, JohnDeRosa wrote:
> 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

True, but I have still extracted energy from the shear; 2000 ft of potential energy, and 160 kts of kinetic energy. If I am trying to go into the wind, that may (or may not) be a problem, but if I am trying to go somewhere else, its a win-win.

>Two problems, Matt. Since you dove down through this 15 knot wind shear (15 knot less wind over the >ground), your indicated speed went from 40 to 85 and not 40 to 100. Remember, you lost that speed >just like you would have in descent on final.

I think it depends on how you descend. I agree you can't take the same glideslope both up and down, but if you dive aggressively as I suggested, then you are using you kinetic energy mostly in the light headwind close to the ground. I suspect the energy gain may be related to the area between the two curves. There are lots of gains and losses going on, but it should be possible to run the numbers on this and see if it works out.

1) steep dive through shear
2) level in ground effect w 5 kt headwind
3) moderate pull up to altitude through shear

Matt

On Wednesday, November 13, 2013 12:28:33 PM UTC-6, JS wrote:
> 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.
>

This was really interesting and sobering. Even in a very strong windshear, and a computer-optimized flight path, they came nowhere close to achieving dynamic soaring. I

'm still a little puzzled though. RC models do it, though pulling more Gs than we can. Albatrosses do it though, and they sure are not pulling 10+gs. Albatrosses have about the glide ratio of a blanik too. Maybe by going right down to 1 foot off the water, or in the lee of a wave, they get a greater shear? Exactly what does not scale up?

An interesting line of the article:

Sonic Detection and Ranging (SODAR) equipment was used to monitor thermal activity

??? I want that!

John Cochrane