Airflow around a vertical cylinder (such as a cigar)

In summary, airflow around a vertical cylinder, like a cigar, involves the flow of air interacting with the object's surface, creating patterns of pressure and turbulence. As air approaches the cylinder, it accelerates, resulting in a low-pressure zone at the sides and a high-pressure zone at the front. This interaction leads to the formation of vortices, which can influence the overall drag on the object. Understanding this airflow is crucial in applications such as aerodynamics and fluid dynamics, affecting design and performance in various fields.
  • #1
DaveC426913
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TL;DR Summary
Which side of a cigar in the wind will burn faster?
Writing from Cuba.

This is canoeing:
1713197313523.png

There are multiple causes for it but the one I'm interested in is when it is caused by directional air flow (AKA wind).

If a breeze is blowing across my stogie from the same direction for an extended duration, one side will burn down much more than the other. I would have thought it would be the side facing the wind but I can never be sure. I try to experiment but I mess it up every time.

I suspect the opposite is true: the windward gets its heat stolen and carried to the leeward side, where it burns faster.

Does anyone know of any relevant physics that codifies this phenomenon?
 
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  • #2
DaveC426913 said:
I suspect the opposite is true: the windward gets its heat stolen and carried to the leeward side, where it burns faster
I doubt it. The extra oxygen should make the upwind side burn faster. Try it with a hair dryer blowing on one side; that should solve the issue.
 
  • #3
DaveC426913 said:
I suspect the opposite is true: the windward gets its heat stolen and carried to the leeward side, where it burns faster.
I think that explains it.

Bush fires in strong winds ignite vehicles and structures from the down-wind side. On the upwind side, flame is blown up and off the structure by the wind. An eddy forms downwind, where embers circulate until they are caught low down, starting a fire maybe 10 minutes after the fire front passed.

With a cigar, I expect hot combustion products will gather in the lee. That will dry and heat the surface, initiating earlier combustion of the outer wrapping in the eddy.
 
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  • #4
@DaveC426913 how about you try my suggested experiment and let us know how it works out.
 
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  • #5
phinds said:
@DaveC426913 how about you try my suggested experiment and let us know how it works out.
Perhaps when I get home. Seems a less than ideal way to enjoy a cigar, but...
 
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  • #6
DaveC426913 said:
TL;DR Summary: Which side of a cigar in the wind will burn faster?

Does anyone know of any relevant physics that codifies this phenomenon?
Which side burns faster - top or bottom - in still air?
With no sideways wind, the natural convection will transport heat to the top, and the bottom will receive fresh new air. No swirls or eddies to be seen swirling about the cigar from this non-turbulent flow.
So does the top burn faster, or the bottom?

So what wind speed are you looking at - slight breeze, unpleasant breeze, blowing off hats breeze, hurricane force?

If you notice the cigar burning faster on one side, is it attributable to the wind, or in addition to some other cause?
Such as sucking on it with one side facing up to heat the end.
and then holding the cigar with the side that was previously up now facing another direction to let the end smoulder.
 
  • #7
I think you would turn the cigar as you smoked it, so the wind effects would tend to average out.

The other explanations confound the wind analysis.

One reason given for canoeing, is that a poorly rolled cigar, has varying thickness or grade of outer leaf, that burn at different rates. Buy a better quality, a more expensive cigar. Another reason given is poor storage, where one side of the cigar has higher moisture than the other. Store the cigars so that moisture, throughout the cigar, can equilibrate. Packaging is important.
 
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  • #8
256bits said:
Which side burns faster - top or bottom - in still air?
It should burn evenly under that small an effect.

256bits said:
With no sideways wind, the natural convection will transport heat to the top, and the bottom will receive fresh new air. No swirls or eddies to be seen swirling about the cigar from this non-turbulent flow.
So does the top burn faster, or the bottom?
I think you've got a point. I suspect top burns very slightly faster.
256bits said:
So what wind speed are you looking at - slight breeze, unpleasant breeze, blowing off hats breeze, hurricane force?
Unpleasant breeze, by your rating system.
256bits said:
If you notice the cigar burning faster on one side, is it attributable to the wind, or in addition to some other cause?
Other factors being equal, I know it burns unevenly in a strong breeze.

What I always forget is which way I had it when it did that, and thus which way to to turn it so it will even out.

And that is the answer I seek.
 
  • #9
DaveC426913 said:
And that is the answer I seek.
SO ... quite guessing and do my suggested experiment !
 
  • #10
And speaking of airflow around vertical cylinders I was facinated to learn that these spiral wings on smokestacks are NOT stairs.

Know what they're for?

1713281007156.png
 
  • #11
phinds said:
SO ... quite guessing and do my suggested experiment !
I will eventually, but I'm also interested in the theory of it.
 
  • #12
DaveC426913 said:
Know what they're for?
Yes.
And did you know they are twisted the opposite way in the Southern Hemisphere.
 
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  • #13
DaveC426913 said:
... Know what they're for?
Copied from:
https://seas.harvard.edu/news/2021/...g-winds-and-flowing-water-look-marine-sponges

“Today’s approaches for reducing vortex shedding don’t actually prevent it from happening,” .... “Rather, they simply shift the shedding to a more downstream location. In contrast, the sponge’s ridge design completely stops vortex shedding across a wide range of flow regimes.”

Please, also see:
https://en.wikipedia.org/wiki/Kármán_vortex_street#Solutions

 
  • #14
Baluncore said:
Yes.
And did you know they are twisted the opposite way in the Southern Hemisphere.
You jest!
 
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FAQ: Airflow around a vertical cylinder (such as a cigar)

What is the basic principle of airflow around a vertical cylinder?

The airflow around a vertical cylinder is primarily governed by fluid dynamics principles, particularly the behavior of laminar and turbulent flow. As air approaches the cylinder, it experiences a change in velocity and pressure due to the obstruction created by the cylinder. The flow can separate from the surface of the cylinder, leading to the formation of vortices, which are crucial in determining the drag and lift forces acting on the cylinder.

How does the diameter of the cylinder affect airflow?

The diameter of the cylinder significantly influences the flow characteristics. A larger diameter increases the surface area for airflow interaction, which can enhance the drag force experienced by the cylinder. Additionally, the Reynolds number, which characterizes the flow regime, is affected by the diameter; higher diameters can lead to a transition from laminar to turbulent flow, altering the flow pattern and pressure distribution around the cylinder.

What are the common flow patterns observed around a vertical cylinder?

The common flow patterns around a vertical cylinder include laminar flow, where the fluid moves in smooth layers, and turbulent flow, characterized by chaotic and irregular motion. In the case of laminar flow, the fluid adheres closely to the surface of the cylinder, while in turbulent flow, the fluid separates from the surface, creating wake regions behind the cylinder. The transition between these flow regimes is influenced by the Reynolds number.

What factors influence the drag force on a vertical cylinder?

The drag force on a vertical cylinder is influenced by several factors, including the flow velocity, fluid density, viscosity, and the cylinder's diameter. The shape of the cylinder and surface roughness also play a role. The drag coefficient, which quantifies the drag force relative to the dynamic pressure of the fluid, varies with the Reynolds number and the flow regime, affecting the overall drag experienced by the cylinder.

How can airflow around a vertical cylinder be modeled or simulated?

Airflow around a vertical cylinder can be modeled using computational fluid dynamics (CFD) simulations, which solve the Navier-Stokes equations governing fluid motion. These simulations allow researchers to visualize flow patterns, pressure distributions, and forces acting on the cylinder under various conditions. Experimental methods, such as wind tunnel testing, can also be employed to validate the simulation results and gain insights into the aerodynamic behavior of the cylinder.

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