Termiğin kopma anının gözünüzde canlandırabilmeniz için...

[SilverCloud]

http://www.youtube.com/watch?v=AxRT60-kw78

[mustafa çelik]

Muharrem hocam söze gerek yok, 1 saatte anlatılabilecek termik oluşumu ve kopma bilgisi için güzel bir video. Hocam birde o anda bir sis bombası olsa temriğin kopması, şiddeti, dairesel hareketi, yukarı çıktıkça etkisini kaybetmesi fevkalade görülebilir sanırım.

[poseidon81]

Çok güzel bir video. Teşekkürler.

[sarsinan]

uzun zamandır en yararlı başlık!

[Human capital]

Benim sahifem Degisik Perspektifler,e bakanlar bu filmi 4. martta izlediler.

http://www.ypforum.com/viewtopic.php?t=6948&start=90

[ucarimanda]

Süper,

Özellikle alçak irtifada termiğin toplandığı bölgede, termik dönerken, termiğin kendi etrafında dönüşünü hissedebiliyoruz (yani hisseden dönüşünü ona göre ayarlıyor). Yani aynı termiği bazen sağdan dönmek ile soldan dönmek arasında fark olabiliyor.

Bir tarafa dönerken kanadı daha sakin, yavaş ve iyi tırmanır hissederken diğer tarafa dönünce, dalışlı ve salınımlı dönüş, tutunamama hissi olabiliyor.

[ilbayram]

Dans eder gibi...

[ÇağlaR]

10 numara bi video olmuş forumda... insanların birbiri ile atışması değil bunun gibi videoları bilgileri paylaşması gerekiyor... Teşekkürler

[selmanduysak]

temel,orta,üst düzey tüm uçucular için ayrı bir tad var görüntüde.hem görsel açıdan hem de hem hayalini kurarak uçtuğumuz termik için mükemmel bir eşleştirme olmuş.bu tür yayınları bizlere aktaran akdaşlara teşekkürler.

[yppilot35]

çok hoş eline sağlık.

[muzzy145]

Bu video dan yola cikarak termiklerin donup donmedigini ogrenmek isteyenlere rmhpa forumdan bi arkadasimin aciklamasi.

Gosh,
at least once a year, this subject comes back:
rotating thermals.

I would not say anything and let it go, but i am too scientifically oriented to let it go. After all, I wrote a few peer-reviewed papers on the subject, and got one of my high level degrees in just that, the other is in aerospace engineering, so I think I can throw a couple of cents into it.

There is quite a bit of difference between a dust devil (even without dust, or snow) and the classic vision of thermals.

Both, by the way, live on scales that are not affected by Coriolis, so forget about even thinking about which way you want to rotate/turn.

While it is perhaps 'poetic' to think about thermals as rotating columns, thermals behave much differently, are generally turbulent (that means Reynolds numbers are high enough that flow is really not laminar, not that you would necessarily experience strong turbulence), and do not have a clear rotation. In fact, I proved some 6 years back, that, if anything, you may see a toroidal circulation at the top (think of a smoke ring). If the toroid gets tilted (due to various types of phenomena, such as Kutta-Joukowsky lift/torque (the curve ball effect)), you may give rise to even a counter-rotating pair of vortices towards the top of the thermal.

No scientific proof has ever been found that thermals contain rotation. I personally flew for about 140 hours, penetrating thermals from 200 ft to 26,000 ft MSL, and from a few 10s fps to >5,000fpm, aboard a fully instrumented aircraft, that, among various things, is capable of very accurately measuring wind speed and directions. We also used Doppler radar signals, and I got pseudo-3D visualizations of thermals as sampled by remote sensing. I also sampled rotors, and those flow fields (vector fields) are the real thing, not speculations.

Unfortunately we need to visualize stuff to try and get better pilots, I agree, but sometimes the oversimplification (such as Pagen's pages at times) is really misleading.

Dust devils operate on a mechanics that is yet different from both regular thermals and tornadoes. There are various hypotheses and tons of scientific papers on the subject. One that I like, is one of the older theories.

Horizontal vorticity (imagine a tornado like structure, or a rolling cigar) runs along the plain field due to vertical airspeed shear. A thermal kicks the vorticity up, and kinks the cigar, and while doing so it stretches it upward. It can be easily proved from vorticity budget that stretching is equivalent to increasing the vorticity, in the vertical (this time). More or less analogous to the skater extending her/his arm upward and spinning faster. That is your dust devil. Now, the interesting thing is that the thermal core is not initially co-located with the vertical cigar (pardon the analogy), and in fact you may have 2 cigars (counter-rotating) on both sides of the thermal. For other complex reasons, once and if the colocation occurs, one side can persist, while the other branch of the initial vorticity dies out, or decays (vorticity diffuses until opposite sign vorticity is encountered that kills the original one). The winning branch (cigar) is your "dust devil" type of phenomena.

That video is spellbinding.

With RC planes we often change directions on the fly or circle in opposite
directions (with our combat wings, specifically to try to hit each other) and
I can say that we almost never can see any significant
rotation of any big thermals around Zion, certainly not of the scale that
this one was. This video is of a proper dust devil, just without the dust.

We had a whole series of dust devils roll through the upper launch area
at Williams one year at our big combat event, and they were flyable but
still sometimes tossed our planes around like leaves.

ian

Ian is absolutely right in his observations. While you may encounter some rotation in a pure thermal, chances are it is due to some other mechanical shear type of phenomena, or perhaps even the observed tilt of the initially upright toroid which can take the appearance of vertical vorticity (i.e., like the one in a tornado).

The u-tube video comments degenerated into absurdities when the commenter was suggesting heat stored under the plastic that, puff!, got released into the "thermal".... let us leave it at that, I hope we all know how heat transfer works, time scales and all....

Beautiful video! Thank you Rick.

Makes me think about whether it matters which direction we turn when we enter a thermal. Clockwise or counter clockwise? This one happened to be turning clockwise. How do you know which way it is turning? Ground speed?

i think at no wind conditions ground speed would increase once you get close to the core. But it wouldn't show us the thermal turn direction. When there is wind, the drift would make it tough to see small changes in speed. I don't think that we can determine the thermal direction as long as we keep turning same direction. Once we change the turn direction in a thermal, a nice eye constantly kept on ground speed can probably tell the thermal direction. If we turn opposite of thermal direction we would probably experience better climbing performance. Gosh i am confused I can't even express myself

Also whoever tries to figure out the thermal direction in no wind by switching turn directions should have the sensitive hands of a swiss watchmaker to keep the wing at same angle. loopy you have the necessary genes. Do it

Finally, Muzzi refers to stronger winds near the core. If the core is the center, nope, it is like the eye of the hurricane, no significant wind acceleration there. There are various models of vortex induced velocity, but usually the peak is kind of in the middle between the geometrical center and what one could consider the outer edge of the vortex based on some criteria of wind speed.

If anyone is interested I can provide some papers on the subject, or just radar 2D and 3D vector field views.

Have a nice thermal day, oh yes, and a mild 'dusty' day as well!

Rick

Ceviri demeyin daha bir kac kere okuyup anladiktan sonra belki birseyler yazabilirim

[teamstratus]

Merhabalar termikler böyle gözle görünür olsaydı ne güzel olurdu diye düsündüm güzel bi resim paylaşmak istedim ,ara bul hayal et hisset ve dön sevgiler

[tuncay]

Yıllar yıllar önce biz de termiklerin görülebilir olmasını ya da termikleri gösteren gözlük yapılabilir mi diye düşünmüştük. Eğer görülebilseydi çok korkunç olacağını ve pilotların uçmayı bırakabileceğini düşündük ve gözlük projesinden vazgeçtik

[teamstratus]

Süpermiş gözlük projesi dogrusu ama korkunc'ta olabilir hakkaten ,bu arada seyrettigim bi videoda bi cihaz kullanıyolarda hazır konu acıldı belki bilen vardır deltakanatla ucan bi pilotun videosu trapeze monte etmiş bu cihazı ,aslında video linkide ekleyecektim ama bulamıyorum sevgilerimle

[biscen]

(Kuş veya domuz tam hatırlamıyorum) bol paranoyalı grip günlerinde havaalanlarından bir uygulama tv'ye yansımıştı; buna benzer termal kameralara daha sıcak kanlı:) takılanları ayırıp, hasta olarak kontrol altına alıyorlardı.

Modası geçtiği için olabilir belki bu yıl grip haberi duymadım, o kameralar kesin boşa çıkmıştır:)