Big Whorls have little Whorls!!
Locked
 
|
I missed the initial posting re Vortices! Can someone kindly repeat the question. I spent 50 years dealing professionally with vorticity and its curious consequences.
Peter Lissaman, Da Vinci Ventures ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Big Whorls have little Whorls!!
|
|
Peter, You missed it because the original video-links did not find their way into my messages, for some reason. I have been fascinated by thunderstorms all my life, and particularly by the big ones. So, after every tornado outbreak, I go on the web and watch tornado videos and wonder at how such a thing could ever be produced. Even tho I failed to post the material last night, still we had an extended discussion at FRIAM today of the origination of tornadoes. Nobody at the table knew much about the subject, but that didn’t keep us from trying. Two theories were offered, one the tipped up roll theory and the other the descending collar theory. Both theories start with a complex laminated atmosphere which one often finds east of the Rockies, in which hot dry air over runs cooler most air. The tipped-up roll theory stresses the shear between the two layers as the eastward moving dry layer encounters the westward moving moist one. Rolls form between the two layers and these can get tipped on end by convection and form the seed for a tornado. The descending collar theory focuses on the tremendous instability of the layered atmosphere as the days heating moistens and heats the cooler most air at the surface. At some point in the diurnal cycle, the relatively cooler moister air at the surface becomes lighter than overrunning relatively warmer air and starts to poke holes through it. At this point the surface air starts rushing through the “hole” toward the stratosphere, which is why you see these plumes of cirrus blowoff at the tropopause down wind of the these mesoscale convective complexes. Coreolis force imparts a twist to this violently rising column of air and selection focuses most of the upward movement in one area of the storm, so essentially the entire lower atmosphere drains up through this hole. So, this gives you a high altitude mesoscale rotation which forms the “collar”. It imparts rotation to the slightly smaller collar below it, which rotates faster because of conservation of momentum, that imparts rotation to the slightly smaller collar below IT, etc. As long is there is not too much sheer within the moist air at the surface, the rotation can propagate to the ground and form a tornado. (As you can see from my descriptive enthusiasm, I am a proponent of the latter theory.) We also needed you for a discussion concerning the dynamics of lift in airplane wings. Again, two theories were offered: the differential velocity over curved top of the wing diminishing the pressure on the top of the wing or the viscosity of the air pulling the wing up. The conclusion of the discussion was that both effects occurred but that the viscosity of the air was the more important. I hope I have that right. It was asserted that the latter theory must be correct because otherwise planes could not fly upside down. I couldn’t quite follow that line of argument since it seemed to involve a mixing of the two previous arguments with an assumption that the upside down aircraft would maintain its position in the sky by having a slight upward angle of attack. ANYWAY: Here’s an example of the tornado videos. I assume it’s not a fake. The really good examples I found last night seem to have been taken down. I will look again later tonight. If you search “tornado videos” you will get all you want. Look out for the Kansas one. I think that IS a fake. Sorry about the ads. Love Nick From: [hidden email] [mailto:[hidden email]] On Behalf Of [hidden email] I missed the initial posting re Vortices! Can someone kindly repeat the question. I spent 50 years dealing professionally with vorticity and its curious consequences. Peter Lissaman, Da Vinci Ventures ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
| Free forum by Nabble | Edit this page |