# Why Temperatures Drop Inside a Vortex:

Discussion in 'General Science & Technology' started by paddoboy, Jan 17, 2017.

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Researchers reveal why temperatures drop inside a vortex
January 17, 2017

Credit: Concordia University
With winter upon us in full force, outdoor temperatures are plummeting. But inside an intense tornado, it's always chilly—no matter the time of year. A new study from Concordia proves why that's the case.

In an article forthcoming in the Journal of Aircraftof the American Institute of Aeronautics and Astronautics, mechanical engineering professor Georgios Vatistas looks into the case of a violent tornado that touched down in 1955 in Scottsbluff, Nebraska.

During the storm, three broadcasters from the mobile unit of a local radio station were reporting live on the scene and had to take shelter in the basement of a stone building. There, as the tornado's funnel passed overhead, they reported strange climatic changes. The temperature dropped from a mid-summer average, down to chilly, until the broadcasters were actually cold. They also found it difficult to breathe.

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http://arc.aiaa.org/doi/10.2514/1.C034106

Thermal Properties of Compressible Line Vortices

A simple mathematical model to simulate the temperature, pressure, and density distributions in intense turbulent compressible line vortices is reported. Based on the previous n=2" member of the n family of vortices, a wider-range model that includes the rudimentary combined features of turbulence and compressibility is built. In antithesis to the previous laminar theoretical approaches, where the converging flow cooled down monotonically with decreasing radius, it is now discovered that, far from the axis of rotation, the gas is first heated up, reaching a static temperature maximum that is higher than the ambient value; then, it chills down to a subambient minimum at the vortex center. The cause of this effect is recognized to be the outcome of competition between two fundamental mechanisms: gas heating because of mechanical dissipation, and cooling due to mainly fluid parcel’s dilation. Thus, the present investigation identifies the cause of the Ranque–Hilsch-like thermal effect observed in unconfined compressible vortices. In comparison to laminar vortices, the center of a turbulent gaseous vortex is found to be cooler, thinner, and under lower-pressure conditions. All thermodynamic properties are shown to be functions of the vortex Mach number and level of turbulence.

5. ### exchemistValued Senior Member

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Pope discovered to be Catholic? I thought we'd all known for ages that there is a severe pressure drop inside tornadoes - stories of houses "bursting" etc. And if you get a pressure drop you expect adiabatic cooling, presumably.

The clever bit seems to me to be the modelling, rather than the conclusion. But I may be missing something.

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7. ### Q-reeusValued Senior Member

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Journalistic license at it yet again imo. Change the title to e.g. "Researchers reveal why temperatures drop inside a vortex more than previously expected.", and less readers might get to be sucked in.

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You would probably be really surprised how many people would not have been aware of it.

And a definite yes to the modelling.

9. ### exchemistValued Senior Member

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I suppose the point with a tornado is that it is dynamic, i.e. there is a constant flow of new air in and out, so new supplies of air are continually expanding adiabatically, thereby maintaining the cooling effect.

10. ### Boris2Valued Senior Member

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11. ### exchemistValued Senior Member

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How ingenious! I had never come across such a thing. Thermodynamically, another form of heat pump, with no moving parts!

Walter L. Wagner and Boris2 like this.