bad cd value for renault twingo 3 = why ?

[hugo1]

I did not find the cd value for renault twingo 3
but the almost similar smart C453 (for4) has cd 0.35

the twingo 3 roof follows the template (20%) !
the twingo 3 has boattailing (± 5°)

why only 0.34 (estimation) ?


the-blueprints.com/blueprints/cars/renault/68342/view/renault_twingo_iii_(2014)/]The-Blueprints.com]The-Blueprints.com - Blueprints > Cars > Renault > Renault Twingo III (2014)[/url] - Blueprints > Cars > Renault > Renault Twingo III (2014)

gallerily.com/smart+forfour+dimensions?image=60267238]Smart Forfour Dimensions images

carissime.com/renault_twingo_3_ft.htm]Renault[/url] Twingo 3 2014 : Fiche Technique dimensions

[ChazInMT]

I think it's cause the air has to rise quickly to get out of the way and then there is really nothing behind it to allow the air to gradually return to it's resting state.

This car is sort of a good thing to look at to remind us that the air does not "Blow over the car" the car is moving Through the air.

Picture a semi truck size volume of air just sitting there 40 feet in front of you on a calm day, then you ram a car through it at 70 mph. How much that air in that "box" in front of you gets moved around is what determines how efficient the shape you have is. You can imagine if the VW XL1 drove through it, the air would move very little and there would be hardly any turbulence left over after it passes. Drive a 1975 Chevy truck (with its requisite 4" lift kit) through it and the air will scramble about like mad, and long after the truck is gone, the air will still be swirling about. The energy required to move the air is what determines our Cd, the more it moves, the more energy it takes to move it, that energy comes from your engine.

This Twingo looks like it will swirl some air despite it's best efforts to follow the curve.

[Cd]

Excellent reply Chaz.


.34 versus .35 is not that great a difference.
Something as trivial as the curve of a door handle can alter the Cd that much.

The higher the Cd, the more opportunities there are for fixing the problems.

[hugo1]

A

[hugo1]

B

[hugo1]

C

[hugo1]

D

[hugo1]

https://dumpyourphoto.com/photo/7rNei0epVK

[hugo1]

Originally Posted by ChazInMT

I think it's cause the air has to rise quickly to get out of the way and then there is really nothing behind it to allow the air to gradually return to it's resting state.

This car is sort of a good thing to look at to remind us that the air does not "Blow over the car" the car is moving Through the air.

Picture a semi truck size volume of air just sitting there 40 feet in front of you on a calm day, then you ram a car through it at 70 mph. How much that air in that "box" in front of you gets moved around is what determines how efficient the shape you have is. You can imagine if the VW XL1 drove through it, the air would move very little and there would be hardly any turbulence left over after it passes. Drive a 1975 Chevy truck (with its requisite 4" lift kit) through it and the air will scramble about like mad, and long after the truck is gone, the air will still be swirling about. The energy required to move the air is what determines our Cd, the more it moves, the more energy it takes to move it, that energy comes from your engine.

This Twingo looks like it will swirl some air despite it's best efforts to follow the curve.

twingo 3 is not very low or narrow !
only consider the shape

https://dumpyourphoto.com/photo/7rNei0epVK


note : I don't have or want this car

[ChazInMT]

Hugo 1 wanted to post his I think.