Twitter user
KnoelWester has found an interesting trail over Bristol, and is interested in whether I've ever seen anything similar to the 'donuts' in this formation, and an explanation of what causes this.
Anybody know the technical? I'm sure I've seen it mentioned here.
External Quote:
Look at this trail over Colston Hall in Bristol. Scram jet? Any ideas what caused this? Aroura? fb.me/2zltySwpY
http://twitpic.com/c82c0h
Vortices entrain and drag each other together under conditions of power or propinquity. They regenerate a NEW vortex, generally at right angles to their previous axes. This is described as a "sinusoidal mutual inductance instability".
This enlightens:
[video=youtube_share;XJk8ijAUCiI]http://youtu.be/XJk8ijAUCiI[/video]
More can be found under "Crow Instability - More about vortices", "Trails seen from Space" at
http://jazzroc.wordpress.com
In this case the vortices are aircraft
wake vortices, and ordinary aircraft will make "doughnuts" (out of the cylindrical tip wake vortices) in turbulent conditions or high-angle-of-attack conditions where greater energy is being put into the wake vortices. A heavily-loaded aircraft traveling slower than normal will do it, or a laden bomber with low aspect ratio wings traveling at high speed will do the same. The vortices behave this way whether they are visible or not. At high altitudes the engine trails are swept into the wake vortex and render them visible.
The wake vortices of flight 175 were plainly visible, written in flames and smoke, briefly attached to WTC 2 after the impact, stuck to the tower face, and linked to each other with subsidiary rings and braids.
The centerline of a vortex is a line of least pressure, and so will attach itself to a surface if it can, whether it's an aircraft wake vortex attached to a tower, or a tornado attached to the ground.
Jay knew this stuff before I did.
If you find the Japanese smoke ring experiment (GIANT VORTEX BOX 20M TEST) in YT's suggestions and play it, I hope you laugh as much as I did.
