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Old 07-27-2019, 04:17 PM   #2 (permalink)
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box cavity

Originally Posted by hat_man View Post
Hello again,

I'm still trying to learn about aero concepts, if even in general terms for now.

Can anyone give me a quick tutorial on the idea of a box cavity on the rear of a vehicle and how and why it works? Nothing in depth mind you. Just a simple explanation.

And as usual, thank you all.
As viewed from the rear,the perimeter of the box would be inset from that of the body 'slice' onto which it's attached.
When viewed from the side,the trailing edge of the box would fall where an imaginary 'template' line would intersect that point in space.
Rather than a gentle curving surface,you'd just a rearward-facing step.
The flow would separate from the body as the downslope hit 22-23 degrees from horizontal,but re-attach right at the end of the step,capturing a vortex of circulating air.
Flow just outside the cavity would skim across this pool of captured,swirling air,and undergo decelerative pressure gain,such that when it did separate from the trailing edge of the cavity,it would be at a higher pressure than before,and behind a smaller wake,effectively increasing the base pressure,while reducing pressure drag.Not as good as a boat tail,but way out ahead of nothing!
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