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Consider an outdoors scenario, with good weather and no sensible air currents at the floor level. How turbulent or laminar is the air surrounding this environment?

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    $\begingroup$ Turbulent state is defined for a flow, not a fluid. So you have to define what the air flow you want to consider? Flow around you as you walk? Flow around a candle or an incense stick? Cannot answer the question satisfactorily without more details. $\endgroup$ – FrenchKheldar Aug 28 '14 at 18:44
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Use an incense stick to test. You will find that the only turbulence is from the heated air (smoke) rising from the stick, or from moving the stick around. If you can cool the smoke to room temperature without heating the area of interest, you are likely to get layers unless the room or outdoor area has no temperature gradient with height.

Where is gets interesting is a calm day at ground level and being able to see two layers of clouds moving in different directions. What the heck is going on where the layers meet?

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Assuming absolutely no wind there will still be areas of turbulence, things will still be transferring heat to the air causing it to move, it doesn't take much motion for air to become turbulent because of its low viscosity. Viscosity will dampen any instability, so low viscosity means its easy for instability and turbulence to occur

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If you would just calculate the Reynold number to Troposphere, say, 10 000 m thick. Kinematik viscosity of air is, say, 1.2 x10^-5

so you found that with Re 4000 you would have just need to have a 0.0000048 m/s velocity In praxis, though, this is not the case, but it's a stratified fluid system;

https://www.youtube.com/watch?v=9hmjcIfy8wE&list=PL0EC6527BE871ABA3&index=22

You can often see a stratified layer on a cumulus cloud base, Which might be just 600 m above ground. This doesn't change too much; for Re 4000, you still need only .00008 m/s. So i'ts obvious that the air is Turbulent near the ground most of the time. But it's as obvious that it's not so Turbulent up there, or how you can explain that the cumulus clouds are not completely mixed away immediatly?

In Finnland, at night there is also a notable phenomenon on calm lakes. You hear even the smallest sounds far away. To me it's a sign of a laminar air. Just found this example video about the issue; https://www.youtube.com/watch?v=6oatyxA3n0g

To conclude; It's Turbulent most of the time near the surface. It's mostly (Jet streams etc. exluded) laminar on the upper layers, and sometimes it's Laminar even near surface.

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