Quote:
Originally Posted by aerohead
*On line 1) I prefaced my comments with respect to context.
* Whether a 'fastback' is a 'pseudo-Jaray', or 'Kamm-back' is the context.
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A) on a 'pseudo-Jaray' body, a rear spoiler would have to address lift-due-to-separation, as well as 'direct lift' if that was desirable.
B) on a 'Kamm-back' fastback, no lift-due-to-separation would exist.
C) adding a spoiler to a Kamm-back would cause the streamlines to re-converge, the flow to accelerate up to a higher velocity, lower pressure, increasing the size of the wake, lowering base pressure, raising overall drag.
The 'active' spoiler attempts to navigate the dilemma. They don't obstruct rearwards vision when 'parked', can limit the hit to rear visibility at low speeds, ( Tesla Model-X original, 3-position wing ), then go for downforce at high speed, where one needs to pay close attention to what's ahead of the car.
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OK, you're back to stuff from the 1930s about shapes and imagined airflow patterns.
As someone else pointed out, it makes it very hard for you to succeed in your understanding when you refuse to read the current best descriptions of how things like rear spoilers work. Refer to
Aerodynamics of Road Vehicles, 5th edition. There is a lot there that differs from the 1987 edition.
(Or just do some tuft and pressure testing on some fastback cars.)