Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Supersonic Wake Turbulence  
User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Posted (8 years 9 months 3 weeks 5 days 15 hours ago) and read 5504 times:

Hey folks, did a quick search, and didn't find anything.

What is the nature of wake turbulence for aircraft flying supersonic? I donno if it's ever happened, given the tiny number of concordes, but what kind of bump might a concorde experience as it crossed the wake of another?

Not that it could happen, but let's say a subsonic jet found itself behind concorde, or passing through its contrial. Would the effects of wake turbulence be worse?

Ok, since that's a silly scenario, what kind of wake turbulence would some other supersonic plane, a fighter maybe, experience while either crossing through, or riding behind concorde's wake? Is it different from similar size/wieght subsonic aircraft?


Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
30 replies: All unread, showing first 25:
 
User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 1, posted (8 years 9 months 3 weeks 5 days 13 hours ago) and read 5483 times:

If you could wait 12 hours, I could give you an explaination. It would be 'in principle', meaning, the real life senario may/will be different. And I'll include pictures, not photos, mind you.  Smile


The meaning of life is curiosity; we were put on this planet to explore opportunities.
User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 2, posted (8 years 9 months 3 weeks 5 days 13 hours ago) and read 5473 times:

Excellent. I'll check back in 12 hours


Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineEGTESkyGod From United Kingdom, joined Jun 2005, 1712 posts, RR: 12
Reply 3, posted (8 years 9 months 3 weeks 5 days 9 hours ago) and read 5423 times:
Support Airliners.net - become a First Class Member!

Quoting Speedracer1407 (Reply 2):
Excellent. I'll check back in 12 hours

Me too..... Interesting question.


View Large View Medium
Click here for bigger photo!

Photo © Javier Guerrero - AirTeamImages



This photo was taken by an Iberia A340 Pilot at FL380, so Concorde here is doing Mach 2 at FL500 or above. The contrail is the same... not sure about the wake though.

Try looking at this too... it may help with something, although it won't answer your question completely.

Supersonic Contrail Pictures (by EGTESkyGod Dec 2 2005 in Civil Aviation)#ID2467382



I came, I saw, I Concorde! RIP Michael Jackson
User currently offlineMir From United States of America, joined Jan 2004, 21881 posts, RR: 55
Reply 4, posted (8 years 9 months 3 weeks 5 days 8 hours ago) and read 5385 times:

I'd be interested in knowing what happens when another aircraft flies through the path of the sonic boom.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineGDB From United Kingdom, joined May 2001, 13254 posts, RR: 77
Reply 5, posted (8 years 9 months 3 weeks 5 days 7 hours ago) and read 5372 times:

What other aircraft would be anywhere near Concordes altitude, never mind any other kind of separation distance, when in supercruise?

Sometimes in the distance, pax might see another BA or AF one going the other way, the crews often mentioned this over the PA.


User currently offlineJush From Germany, joined Apr 2005, 1636 posts, RR: 3
Reply 6, posted (8 years 9 months 3 weeks 5 days 7 hours ago) and read 5369 times:

Quoting GDB (Reply 5):
What other aircraft would be anywhere near Concordes altitude, never mind any other kind of separation distance, when in supercruise?

Sometimes in the distance, pax might see another BA or AF one going the other way, the crews often mentioned this over the PA.

It's just hypothetical and a very interesting question indeed.
I can't wait to hear Lephron's explanations and drawings cause he knows alot when it comes to Concorde and supersonic cruise.

Might have something to do with the fact that he flew the bloody gorgeous thing.

Regds
jush



There is one problem with airbus. Though their products are engineering marvels they lack passion, completely.
User currently offlineEGTESkyGod From United Kingdom, joined Jun 2005, 1712 posts, RR: 12
Reply 7, posted (8 years 9 months 3 weeks 5 days 7 hours ago) and read 5358 times:
Support Airliners.net - become a First Class Member!

Quoting Jush (Reply 6):
I can't wait to hear Lephron's explanations and drawings cause he knows alot when it comes to Concorde and supersonic cruise.

While Lephron knows a lot, I think GDB might know a helluva lot more when it comes to Concorde. Also, Lephron said

Quoting Lehpron (Reply 1):
It would be 'in principle', meaning, the real life senario may/will be different

so make of that what you will.

Lephron, not doubting you by an means, though OK?

Quoting GDB (Reply 5):
What other aircraft would be anywhere near Concordes altitude, never mind any other kind of separation distance, when in supercruise?

Not that it ever happened, but in theory, Tu144 could, SR71 could and I think I'm right in saying the Eurofighter and the F14(?) could. But it never happened so I think I deserve a slap for attempting to be smart.



I came, I saw, I Concorde! RIP Michael Jackson
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 8, posted (8 years 9 months 3 weeks 5 days 7 hours ago) and read 5352 times:

Quoting GDB (Reply 5):
What other aircraft would be anywhere near Concordes altitude, never mind any other kind of separation distance, when in supercruise?

Perhaps a G-IV or a G-V (Gulfstream) near the beginning of it's (Concorde's) supercriuse...
 Big grin



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineEGTESkyGod From United Kingdom, joined Jun 2005, 1712 posts, RR: 12
Reply 9, posted (8 years 9 months 3 weeks 5 days 6 hours ago) and read 5345 times:
Support Airliners.net - become a First Class Member!

Quoting KELPkid (Reply 8):
Perhaps a G-IV or a G-V (Gulfstream) near the beginning of it's (Concorde's) supercriuse...

Wouldn't be supersonic wake turbulence, though would it.



I came, I saw, I Concorde! RIP Michael Jackson
User currently offlineDavid L From United Kingdom, joined May 1999, 9546 posts, RR: 42
Reply 10, posted (8 years 9 months 3 weeks 5 days 6 hours ago) and read 5345 times:

Quoting EGTESkyGod (Reply 7):
Not that it ever happened, but in theory, Tu144 could, SR71 could and I think I'm right in saying the Eurofighter and the F14(?) could. But it never happened so I think I deserve a slap for attempting to be smart.

So I'm not the only one who has one-man arguments!  biggrin 


User currently offlineVc10 From United Kingdom, joined Nov 2001, 1412 posts, RR: 15
Reply 11, posted (8 years 9 months 3 weeks 5 days 6 hours ago) and read 5337 times:

In the early commercial years of Concorde's operation the crews of Concorde were asked to keep a visual lookout for aircraft below them and to broadcast Concorde's presence so as to warn the subsonic aircraft that it's instruments might be disturbed by Concorde's sonic boom. After the first few years , as no one seemed to be too bothered the practice died out

The nearest, two Concordes would get to each other whilst both being supersonic was probably if a BA Concorde was doing a round the bay charter and going roughly north to south, whilst an AF one would be coming home from New York going west to east . This sometimes resulted in a lot of work for the French ATC as the light charter aircraft would be climbing quite rapidly even above 50000ft whilst the French would be looking for descent from approx 58000 ft and with both aircraft having little room to manoeuvre due to boom clearance he/she had to predict where they would cross and at what height. They were normally very good at it and I think the liked the challenge to, although it did become somewhat nail biting on times

All good fun and kept the brain cells active

little vc10


User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 12, posted (8 years 9 months 3 weeks 5 days 6 hours ago) and read 5337 times:

Quoting EGTESkyGod (Reply 9):
Wouldn't be supersonic wake turbulence, though would it.

IIRC, Concorde requests a block altitude on it's transatlantic crossing from FL450 to FL600, because when she begins supercruise, it's at FL450, but when it ends on the other side of the pond, due to fuel burn, she's at FL600. So, yes, in theory, the supersonic wake would begin at FL450, which is attainable by a Gulfstream...



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6546 posts, RR: 54
Reply 13, posted (8 years 9 months 3 weeks 5 days 6 hours ago) and read 5327 times:

Wake turbulence is not a special issue when going supersonic.

Wake turbulence increases with increased all up weight.

Wake turbulence decreases with increased speed and increased wing span.

Consequently wake turbulence is by far most violent at takeoff and landing when speed is low.

The Concorde was a somewhat "bad guy" at takeoff/landing, but mainly because of its relatively short wing span.

During supersonic cruise it was probably in league with a Boeing 757. And probably more like a DC-10 at subsonic cruise after takeoff when still fuel heavy.

At landing the weight of the Concorde was little more than half of take off weight. That helped a lot.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineVC10 From United Kingdom, joined Nov 2001, 1412 posts, RR: 15
Reply 14, posted (8 years 9 months 3 weeks 5 days 6 hours ago) and read 5320 times:

KELPkid,
BA Concordes would actually ask for cruise /climb clearance between 50000and 60000 ft and from London to New York she would start her climb/ acceleration at 28000ft and would be above Mach 1.0 from 30000ft upwards .
Now normally the airspace immediately above 30 to 40000 ft would be clear but the old girl would often overtake subsonic aircraft only a few thousand below {but usually a little ofset} during her initial accel climb between Mach 1.0 and Mach 2.0 and this was always a thrill for the Concorde crews, like being in a racing car


User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 15, posted (8 years 9 months 3 weeks 5 days 3 hours ago) and read 5272 times:

Jush

...Might have something to do with the fact that he flew the bloody gorgeous thing...

Hmmm....Really?  

I'm not aware that he has ever claimed that himself, so I was just wondering what prompted you to make that remark?

Regards

Bellerophon

[Edited 2006-03-08 22:34:48]

User currently offlineJush From Germany, joined Apr 2005, 1636 posts, RR: 3
Reply 16, posted (8 years 9 months 3 weeks 5 days 2 hours ago) and read 5246 times:

Quoting Bellerophon (Reply 15):
Jush

...Might have something to do with the fact that he flew the bloody gorgeous thing...

Hmmm....Really?

I'm not aware that he has ever claimed that himself, so I was just wondering what prompted you to make that remark?

Regards

Bellerophon

Sorry Bellerophon I might be wrong here. There is a strong possibility that I'm incorrect here. The reason why I said this is cause a while ago there was a thread about Concorde pressurisation and I thought he gave us all the insight information, well at least I thought it was him. Anyway, if it's not him who was the Concorde Captain then.... but I still think it was him.

Edit: I just checked his profile and now I'm quite sure that I stand corrected here and he's no captain of Concorde at all or at least was. I don't really know why I connected his name to it. Hmmm...  Confused  Confused

Regds
jush

[Edited 2006-03-08 23:37:10]


There is one problem with airbus. Though their products are engineering marvels they lack passion, completely.
User currently offlineBuyantUkhaa From Mongolia, joined May 2004, 2915 posts, RR: 3
Reply 17, posted (8 years 9 months 3 weeks 5 days 2 hours ago) and read 5227 times:

Quoting Jush (Reply 16):
Anyway, if it's not him who was the Concorde Captain then....

The Concorde Captain may be someone else.  Wink



I scratch my head, therefore I am.
User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 18, posted (8 years 9 months 3 weeks 5 days 2 hours ago) and read 5225 times:

Don't worry, it's really not important  Smile  Wink

Schoen Gute Nacht

Bellerophon


User currently offlineDavid L From United Kingdom, joined May 1999, 9546 posts, RR: 42
Reply 19, posted (8 years 9 months 3 weeks 5 days 2 hours ago) and read 5211 times:

Quoting Jush (Reply 16):



Quoting BuyantUkhaa (Reply 17):



Quoting Bellerophon (Reply 18):

Oops!  biggrin 


User currently offlineVikkyvik From United States of America, joined Jul 2003, 10352 posts, RR: 26
Reply 20, posted (8 years 9 months 3 weeks 5 days 1 hour ago) and read 5197 times:

That......was funny. Sorry Jush  Wink

Quoting Bellerophon (Reply 18):
Don't worry, it's really not important

Of course not  Smile



How can I be an admiral without my cap??!
User currently offlineVc10 From United Kingdom, joined Nov 2001, 1412 posts, RR: 15
Reply 21, posted (8 years 9 months 3 weeks 5 days ago) and read 5181 times:

I have to agree with Bellerophon here that as far as I know although Lehpron postings are both knowledgeable and informative he has never been a Concorde pilot but I do not think he has ever claimed to be. However that does not mean that his posting on the subject are not worth reading far from it indeed

little vc10


User currently offlineBa97 From Canada, joined Apr 2004, 377 posts, RR: 0
Reply 22, posted (8 years 9 months 3 weeks 4 days 22 hours ago) and read 5130 times:

Reading VC10:
"... the old girl would often overtake subsonic aircraft only a few thousand below {but usually a little ofset} during her initial accel climb between Mach 1.0 and Mach 2.0 and this was always a thrill for the Concorde crews, like being in a racing car".

Makes me wonder if anyone had the experience of seeing her zip overhead like that. I know I would be amazed and cheesed. When I fly home out of Heathrow after a crazy week and settle in thinking 7+ hours to go and (curse curse) I see something leaving me in the dust....



there is economy class, business class, first class...then Concorde..pure class
User currently offlineJush From Germany, joined Apr 2005, 1636 posts, RR: 3
Reply 23, posted (8 years 9 months 3 weeks 4 days 16 hours ago) and read 5094 times:

Quoting Vc10 (Reply 21):
However that does not mean that his posting on the subject are not worth reading far from it indeed

Certainly not. His replies remain valuable to this thread.
When does the 12 hour timeframe end?  Wink

Regds
jush



There is one problem with airbus. Though their products are engineering marvels they lack passion, completely.
User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 24, posted (8 years 9 months 3 weeks 4 days 16 hours ago) and read 5092 times:

First of all, I'd like to thank Speedracer1407 for starting this thread, it's my favorite subject and I love genuine curiosity. Second, a thank you to everyone else, I never realized that ya'll respect what I had to say, per se.

Quoting Jush (Reply 6):
Might have something to do with the fact that he flew the bloody gorgeous thing.

Nope. I did mention here once that I had a classmate that claimed to be a retired BA Concorde pilot back the mid-90's. He told me some pretty cool stuff, though I was too young to fully appreciate it.

Quoting EGTESkyGod (Reply 7):
I think GDB might know a helluva lot more when it comes to Concorde.

Well he worked with her for years, which is admirable enough; he's the first member on my RU list when I found these network forums. But he can be a stick in the mud when it comes to his pessimism regarding a next gen product...but then I'm the one with the relentless optimism, so that has got to be annoying for someone. 


Sorry for being late; I had to sleep, wake up for class and go on with my day. Anyway...maybe I should have said I be back in 22 hours...? The following took me 5 hours to type as it is from memory and half are part of my own theories on sonic boom mitigation - a subject so new that there are no books on it, I've had to teach myself via thought experiments over the past 6 years. Even 2 years ago, I postulated on ideas about killing off the sonic boom in a thread here in the techops, I think it was April 2004? Here's the link, knock yourselves out: http://www.airliners.net/discussions...ech_ops/read.main/87606/6/#ID87606

Quoting Speedracer1407 (Thread starter):
What is the nature of wake turbulence for aircraft flying supersonic?

well first it's not like subsonic wakes, per se, the definition changes (more than likely others will know it by a different term). Subsonic wakes are primarily wing induced (partially fuselage) and are strongest during low-speed like in and around airports. Imagine a sheet of cardboard, the amount of air you can disturb increases as you angle the sheet up. When the aircraft speeds up however, the 'wake intensity' drops because the wing's angle to the wind drops down. Again think of the cardboard sheet as you angle it almost flat. You have to move it faster to support the force you did before.

Now we go even faster.

Supersonic/hypersonic wakes have little to do with the induced flow; in fact they eventually get cut off. Their wakes root from a different source: ram-air. I'll get back to that later.

First: the subsonic effect of the traditional SST.

Delta wings, like those on Concorde, produce what is known as vortex lift. At this point the wing is like a giant version of an engine cowling fin. Those swirls that flow around most subsonic wing tips instead flow around and over the wing's entire leading edge as shown in photo below:
View Large View Medium
Click here for bigger photo!

Photo © Joe Pries - ATR Team



The way a wing lifts is due to the low pressure on top and high pressure underneath. The effect of that higher pressure air wanting to go around and into the lower pressure region creates those swirls.

Second: Compression

When a plane goes past the speed of sound, it must push air out of the way that cannot move faster than the speed of sound, so they form a wave, many in fact, like from a boat. At Mach 2, a plane like Concorde spends 1/10th of one second traveling its own length. In that time, what was air below freezing spikes up past the boiling point of water and the ambient air pressure multiplies by 8 in places. That is the condition of the wake just behind Concorde: hot and thick air, but it doesn't stay that way. It drops in pressure and cools rapidly but not all is recovered. Perhaps two or three lengths of Concorde behind her, the air returns to ambient, for the most part. But the shock wave is expanding away from the plane.

Third: The boom

When a boat travels it pushes all of the water underneath and to the side, I refer to this volume change as displacement, it probably has another name. For the boat, it would be the distance from the keel to the water line times the area of the boat, but this would be an initial volume as it doesn't take into account how fast it's moving. Ever stand on a street corner and a bus or large truck passes you by and feels this gust of air? I refer to that gust as a displacement; I mean if you were underwater and a large boat passed over, you will be pushed down, I guarantee it.

Well a supersonic airplane also displaces air, and those air pressure ripples travel down while still expanding, push at your eardrums; you hear a sonic boom. Luckily though, you are not hearing the entire boom, maybe about 30% or less.

This is a fact: Air pressure acts normal to a surface, which is science jargon for perpendicular. On an sonic airplane, while it flies in a volume of hot-thick air, that pressure reflects away from the plane, in all directions from all surfaces including wings (both sides), fins, fuselage, engines -- everything. Imagine a series of shells shaped like Concorde expanding away from the plane, these shell waves ripple out and expand backward, upwards, and downward and all shape the same point, the nose. I guess if you took a model of Concorde and dipped it into a pool of water; you could see the 2D version of all these shells in the water ripples. The fuselage would have a circular expansion, the wings/fins would start off with flat wall expansions, the leading edge of the wings would reveal half-moon expansions, etc.

But see we the people of Earth only care about what goes down, so for planes like Concorde, her 3800 sq. ft. wing against her nearly 11,000 total surface areas, comes out to about 30%. That pressure starts out at approximately 1500psf (the weight of the plane plus the pressure after the oblique waves times the total surface area all divided by the total area) and depressurizes while it expands. But like I said, it doesn't go to ambient, by the time that wave hits your ears, and you experience 2 psf of 'boom pressure' for a plane like Concorde.

In more than 10 miles of altitude the pressure dropped by over 700 times. From my own calculations, I've fit an approximate curve for the pressure change from altitude tables as natural logarithms, for simplicity. Based on that, I have concluded that the sonic pressure boom decays on a similar curve. That if you were at FL300, you would experience approx 80 psf boom from a M2 plane flying @ FL528. But because you may be in a large airplane, you would not notice it. There isn't enough of an energy transfer in terms of momentum from a thin shockwave washing over another airplane, you wouldn't jolt. The reason windows and houses shake is because they are smaller and absorb some of the energy. Even if it were another Concorde passing by, the shockwaves go through each other; the planes will not be affected.

If the separation was within a mile...I'll theorize a subtle crosswind situation.  

NOTE: the above conclusions are assuming the observer is directly below the flight path. Deviating from this will drop the pressure more as the wave would travel farther.

NOTE: I'm not done; I haven’t even got to the good part.  I have a test on Friday and I want to spend all day tomorrow studying. I hope this will be entertaining, I hope ya'll have questions, comments, corrections if any, complaints, etc. Well, I don’t hope for complains but we cannot please everybody. OTOH, it is my life goal to create a cheap (fare-wise, not a piece of sh*t) SST. I should be back here Friday afternoon (local time here is 200am Pacific Standard in USA)

10-Q,

lehpron

[Edited 2006-03-09 10:05:37]


The meaning of life is curiosity; we were put on this planet to explore opportunities.
25 Post contains images EGTESkyGod : Yeah, 9 times out of 10, I lose though, which is frustrating. She started supersonic acceleration at FL280, so you're only 17000 feet out! Just had a
26 Jush : Although not always easy to understand for me it was a pleasure to read. Thank you and I can't wait to hear more of that. Regds jush
27 EGTESkyGod : Well what you just wrote was awesome, it's certainly given me more of an insight into the theory supersonic. Lehpron, I'd like to add you to my RU li
28 Speedracer1407 : Really interesting reading folks!! Lehpron, what an answer. I wish all questions were given the same response. I wish I had some questions or somethin
29 GDB : Great post Lephron, yes I suppose I am a pessimist, but I don't believe in dangling false hopes, hence my (and many others) anger at Sir BS Branson's
30 Post contains images Lehpron : I had realized that whatever else I planned to mention had little to do with the topic, which was one of the reasons why I hadn't been in here. The ot
Top Of Page
Forum Index

Reply To This Topic Supersonic Wake Turbulence
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
C-17 Wake Turbulence Picture posted Tue Sep 5 2006 12:06:55 by Zarniwoop
Wake Turbulence - Is There A Sop Or Qrh Procedure? posted Thu Jun 8 2006 20:23:26 by JulianUK
Wake Turbulence - How Is It Measured? posted Tue Dec 20 2005 16:20:28 by Alphafloor
Wake Turbulence Stories Needed. posted Thu Dec 8 2005 18:47:07 by Julesmusician
Does Payload Increase Wake Turbulence? posted Thu Jun 9 2005 21:46:20 by Skywatch
Wake Turbulence posted Fri Apr 1 2005 08:43:49 by Lehpron
757 W/Winglets And Wake Turbulence posted Thu Mar 10 2005 04:04:58 by KAUST
Wake Turbulence posted Wed Jan 5 2005 12:00:08 by Phil747
Wake Turbulence posted Sat Dec 25 2004 05:59:39 by AAFLT1871
The A380 And Wake Turbulence posted Fri Oct 8 2004 07:37:02 by Jason McDowell

Sponsor Message:
Printer friendly format