# Wind in a rotating space settlement?

by Agrasin
Tags: fluid, rotating, settlement, space, space settlement, swag, toroid, wind
 P: 39 Imagine a cylindrical space settlement. It spins about an axis to create pseudo gravity for residents, who will think that radially outward is "downward". The shape of this settlement is a toroid with a rectangular cross section. Air is pumped in to make a habitable environment. Then, thrusters start spinning the settlement until 1g of pseudo gravity is attained. The space settlement is huge, so it spins at 1 rpm. What is the behavior of the air in this situation? In general, what is the behavior of a fluid in a slowly spinning toroid? My guess is that it behaves opposite of a stream. The air near the walls of the toroid is dragged along, but the air in the middle is slower. Therefore, the residents wouldn't feel a breeze unless they climbed a ladder to be right in between the toroid's walls. What's the behavior after a long time, and why? Does the viscosity of air play a role? Thanks.
 Mentor P: 10,519 Initially you get some wind, but the whole air inside would follow the 1rpm quickly (relative to realistic timescales needed to set the cylinder in motion). This is the equilibrium, unless you introduce some artificial wind source. r=900m
 P: 1,231 After a long time there would be no breeze.
P: 849

## Wind in a rotating space settlement?

After a long time everything should spin along at the same 1 RPM rate. Any initial relative motion of the air has been damped by friction forces.
 P: 39 Thanks everyone. That was the first thing I wanted to know. Could you kindly give my next question some thought? What would be the best artificial "breeze" source for such a settlement? Purely for the enjoyment of residents, just to make it feel more Earth-like. I've thought of giant fans like the ones used in wind tunnels, but that would be too much of a burden for such a petty cause. Is there any simple way to create a breeze through the toroidal settlement? Thanks again.
 P: 849 Why not use the traditional method - Sun's heat?
 Mentor P: 10,519 Non-uniform irradiation would be an interesting approach. Alternatively, use some sort of ventilation system, e. g. pump air from one side of the cylinder to the other side. I guess some air circulation would be good for the environment anyway.
 P: 790 You would have Coriolis effects, so you might get a little bit of cyclone wind.
 Mentor P: 10,519 To get Coriolis forces, you first need radial motion.
P: 3,409
 Quote by mfb To get Coriolis forces, you first need radial motion.
Or tangential motion.
 Mentor P: 10,519 Right - but then you have wind already :p.

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