There's a fundamental disconnect in all of the above between idealized theory and reality. Idealized theory is useful for understanding physical phenomena and mechanisms. In 2nd semester physics we were given many calculation problems dealing with charged surfaces of infinite area or wires of infinite length because such idealized setups simplify the problem and isolate one or a few variables. The previous semester we dealt with many problem setups of systems with massless pulleys or balls flying through the air with no aerodynamic resistance--situations that do not exist in the real world but nevertheless are useful to build understanding. Similarly, idealized aerodynamic shapes are useful for understanding the mechanisms that give rise to drag and lift, not prescriptions for real cars. Further, in the current literature there is a great deal to be learned about idealized shapes which Hucho's book, especially the very old 2nd edition, doesn't talk about--especially lift, ground clearance and underside shape.
Quote:
Originally Posted by aerohead
* The only explanation possible is, that the PRIUS is experiencing flow separation. Just like the 2010 Audi A7 Sportback. 2020 Porsche Taycan.
|
This theory, drawn from simplified ideals, that the 2010 Prius suffers from flow detachment because it does not conform to the "template" is easily disproven with a few wool tufts and some tape:
The flow over the rear of a Prius is nicely attached. And it should be, given that the Prius underwent hundreds of hours of wind tunnel testing--more than any other Toyota at the time, according to the company--was optimized for low drag, and at the time it went on sale was the lowest-drag production car on the US market.
You can easily see the difference by fitting a spoiler at the top of the window. Now the flow is forced to separate and looks very different from the stock configuration above:
All this should make a reasonable person step back, look at the examples of real-world testing (here and in numerous other threads), and assess the theory in light of them. In this case, the theory that "flow attachment is dictated by conformity of rear body shape in profile to this particular idealized template" clearly needs some work.