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Old 04-01-2022, 08:18 AM   #23 (permalink)
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Originally Posted by AeroMcAeroFace View Post
I can't comment on the specifics because I have never seen that vehicle, but it is always possible that the increased wake area and differing recirculation actually reduces drag.

By increasing the height of the rear spoiler it may reduce drag from the underside, increase flow under the car, reduce drag at the corners where the side meets the back.
Exactly--there's much more going on than wake area. The flow around cars is three-dimensional, complex, and not possible to predict using simple principles. This isn't me arguing this; look in any textbook. For example, RH Barnard, 2009: "There are no straightforward methods for predicting how air will flow around a given shape." It's literally on the first page of the book!

A spoiler can also reduce drag and lift by increasing pressure on the surfaces ahead of it.
UIUC Aerospace Engineering
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