What causes rotational motion and condensation on the wings of sprint cars?

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Discussion Overview

The discussion revolves around the phenomenon of condensation and vortices observed on the wings of sprint cars, particularly during colder weather and on larger tracks. Participants explore the causes of these condensation patterns and their relationship to rotational motion and pressure changes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes the appearance of condensation vortices behind the tips of sprint car wings and questions their cause, suggesting a possible connection to vortices.
  • Another participant compares the phenomenon to contrails formed by airplanes, implying a similarity in the condensation process.
  • A different viewpoint suggests that the condensation is more akin to a block of low pressure rather than a traditional trail, indicating a complex interaction with the airflow.
  • One participant posits that the drop in pressure leads to a drop in temperature, which in turn causes condensation, while also noting that contrails from aircraft are typically formed by exhaust rather than pressure changes.
  • Discussion includes a hypothesis about the rotational motion of the clouds, with a participant suggesting that the rotation is outward at the top and inward at the bottom, and questioning whether the condensation forms on the underside of the wing.
  • Another participant confirms the presence of rotation, describing the left side's counter-clockwise rotation and the right side's clockwise rotation, and notes that the condensation appears where the air moves fastest under the wing.

Areas of Agreement / Disagreement

Participants express varying views on the causes of the condensation, with some agreeing on the role of pressure changes while others emphasize different aspects such as temperature drops or the nature of the vortices. The discussion remains unresolved regarding the precise mechanisms at play.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the relationship between pressure, temperature, and condensation, as well as the definitions of terms like contrail and vortex. The complexity of the airflow around sprint car wings is acknowledged but not fully explored.

c_huchel
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I used to race with a club called NSRA (www.nsraracing.com) that runs winged sprint cars on asphalt tracks. Every once in a while, especially on the larger tracks and in colder weather, you'd see little condensation vortices (plural vortex) behind the tips of the wings. Even less often one could see a "pocket" of condensation just below the trailing edge of the wing. It kind of looks like a cloud, in a way. What causes that? Is it related to the vortices? I'd like to get pictures, but it happens so abruptly, and usually at night (not camera friendly, when the air is around 40-50 degrees farenheit).
 
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is it kind of like when an airplane is flying?
[?]
 
Its probably a contrail exactly like one created by a plane.
 
I suppose it's a contrail, but it's not exactly a trail. I guess it's more like a block of low pressure (sounds like a weather system). I'll see if I can find pictures of the contrails and post them to my site.
 
Yes, it is caused by the drop in pressure, but I've recently been doing a little research which would seem to indicate that this is only the indirect cause. According to everything I've read, air kept at a constant temperature and volume will hold the same amount of water vapor regardless of pressure. So I think this must mean that the drop in pressure causes a drop in temperature, and the drop in temperature is what causes the condensation.

Although con trails from aircraft can be formed this way, it is rather rare. Usually, when you see a contrail behind an airplane, the cloud is being caused more by the water clinging to the exhaust than by the change in pressure. But if you've evr seen an airshow, you can see that the wings do indeed form little "clouds", which appear to cling to the wing's surface.

Since you spoke of vortices, I'm assuming you've actually seen rotational motion to some of these clouds. Would I be correct in my supposition that this rotation is outward at the top, inward at the bottom? And does the cloud from the "block of low pressure" form on the underside of the car's wing?
 
Originally posted by LURCH
Since you spoke of vortices, I'm assuming you've actually seen rotational motion to some of these clouds. Would I be correct in my supposition that this rotation is outward at the top, inward at the bottom? And does the cloud from the "block of low pressure" form on the underside of the car's wing? [/B]
There is a rotation. If I remember correctly, viewed from the rear, the left side rotates counter-clockwise, and the right rotates cloclwise. The cloud forms on the underside of the wing, where it seems the air is moving the fastest. The angle of attack on the wing of a sprint car is relatively high compared to an airplane wing. I have seen the condensation on the trailing edge of an airplane as it was taking off. The best view of it from an airliner is right behind the wing. You also get to watch the flaps, spoilers and airbrakes work, which is a marvel of physics if you ask me.