Quote:
Originally Posted by brucepick
Thanks aerohead!
Is this similar to the Mythbusters pickup truck with the tailgate up, where a vortex is set up in the bed and the airflow skips over it almost as if there were a cover over the bed?
Assuming the spoiler's back edge is positioned at the template line, restoration of laminar flow would be brief at best. Would occur only at the spoiler edge. Is there value to that restoration? Would it somehow tend to restore the airflow to the ideal path and result in a smaller cross section of wake?
And - if the spoiler is positioned lower or a bit further forward so that it doesn't reach the template line, would it still "catch" the air flow and give a smaller wake? Or would it just be a mess of turbulence due to not being on the template?
Green lines show how mirror would see spoiler's edge. I drew two lines, not knowing precisely where the mirror is.
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brucepick,it does function exactly like the raised tailgate.
If the trailing edge is close to the template the spoiler captures the low-pressure vortex and isolates that low pressure in front of it,preventing it from communicating that pressure to the wake behind which would otherwise lower the base pressure,increasing the delta-P across the car,increasing drag.
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When the outer flow does separate at the trailing edge of the spoiler, it has decelerated to a lower velocity/higher pressure ( that evil Daniel Bournoulli ) leaving the base pressure of the wake higher,the delta-P lower,an concomitant lower drag.
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If you tilt the spoiler up at 30-degrees from the back of the trunklid( boot),it will hit the 'Template' sooner,and it can be 'shorter'.
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If you were to also extend the C-pillars back along the 'Template' line as I did with the CRX,you can tailor the vortex even finer with this buttress,and in so doing,foster even better side flow towards the rear by,eliminating a potential breeding ground for longitudinal attached-vortices on each side.
You'll have a bit of new blind-spot,but you can compensate for that with your mirrors.
Anyone with a 1st-gen Insight would be familiar with this.
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If you can't reconcile yourself to the 'Template' try to set 22-degrees as your maximum local tangent angle.Air cannot follow an angle steeper than this,and typically,you need to have close to a body height worth of length in progressive curvature before you can get to 22-degrees.