Does fire create drag?

[Alex Franke]

This is for you physics/chemistry folks out there... It seems to be that fire would create drag -- you can hear it when watching poi, baton, torch performers, etc. -- but I'm not sure why it would... I mean the bottom of the flame isn't somehow connected to the top, is it?

[Bill in Buena Park]

Are you sure what your hearing isn't normal drag produced by the moving object passing through air, just louder because of the effect of turbulence on the oxidation process ("flame")?

[LCHIEN]

Are you asking if a frictionless-wheel cart being towed along has greater resistance to being pulled when there are flames coming out the top than the same cart not on fire?

The drag in such a scenario would be the wind resistance of the cart.
A cart in thermal equilibrium would have no rising current from it so the aerodynamic drag profile would be relatively smooth, limited to the air flowing over the shape of the cart.

If it was on fire with flames pouring out the top then the flames are really indications of hot plasma areas and associated air currents rising. I think these air currents would interfere with the normal airflow, so yes the flames would create drag in this case.

So the next question is what rate of material burn off would compensate for the additional airflow drag? if we lost five pounds of material per minute due to burn off that would allow the cart to speed up offsetting the drag from the flames?

[Kristofor]

I agree that there would be some additional drag compared to room temperature object. I'm not very sure that this is what changes the noise from a whistle/whoosh to a low roaring type noise though.

I think a lot of what you're hearing is the increased rate of burning... When you spin a torch around you expose it to a lot more oxygen than when convection is driving the process. If you blow on a fire or use a bellows on it I think you'll hear a similar change.

[conwaygolfer]

I am really curious - did someone beat you on the drag strip while your car caught fire? Just wondering?

Conwaygolfer

[Alex Franke]

Are you asking if a frictionless-wheel cart being towed along has greater resistance to being pulled when there are flames coming out the top than the same cart not on fire?
[snip]
If it was on fire with flames pouring out the top then the flames are really indications of hot plasma areas and associated air currents rising. I think these air currents would interfere with the normal airflow, so yes the flames would create drag in this case.

This makes sense to me. I was actually thinking of those burning poi balls that they swing around down under. The consensus among the poi swinger that I know and her poi-swinging friends is that it takes a bit more effort to swing them when they're burning.

So the next question is what rate of material burn off would compensate for the additional airflow drag? if we lost five pounds of material per minute due to burn off that would allow the cart to speed up offsetting the drag from the flames?

Um... Wow. That's a great question...

I am really curious - did someone beat you on the drag strip while your car caught fire? Just wondering?

You caught me.

Hm... what if the car is only burning on the back? Would that make you go a hair faster than if it were burning in the front?