Cd and blunt front ends

[Duffman]

Gen2 Camaros VEE in the front and there is a good rake in the grill too, like I said before you are being harsh on the stock design, it's not a van or a 1/2 ton.

[Cd]

Originally Posted by Frank Lee

I'm surprised they achieved that low of a Cd with those small radii at the front/sides transitions. Evidently they are smooth enough for good flow along the sides, though.

Yup. This is what throws me off.

Of note :
The Ford Prodigy seemed to have a blunt front end, but in this image, you can see the true shape of the front end which has a good radii :

[Cd]

I hope I'm not coming off as a smart ( dumb) ass.
I'm just really confused, since this goes against everything that I ever thought I knew about aerodynamics.

[ebacherville]

the camareo isnt flat if you look its a slight v and also a slight lean back in the fron then the grill leans back even more..

However by looking at my nose and bug splat etc.. even the slightest angle deflects air quite a bit.. the nose on my crx is a half circle and and once the angle got more than a few degrees bug splats lessened quite significantly.. I'm sure there is some "air cushion effect" but I cant see a square being better than a rounded or angled surface.

However on the comareo look at the anglke from the tip of the spoiler and the top of the roof.. pretty good to keep the air moving over the car smoothly.. would have been better if it was filled.. but none the less decent.

as bajoos and other have proven keeping air attached at the rear provides the biggest gains.. but improving frontal aerodynamics has some play also.

[Duffman]

Originally Posted by ebacherville

as bajoos and other have proven keeping air attached at the rear provides the biggest gains.. but improving frontal aerodynamics has some play also.

That goes with what I know about vehicle aero as well. GM & Ford have both built some decent fastback models since the 60s. Take it from a guy that has a 75 Camaro, much rear seat and trunk space are sacrificed to do this. Probably why they are not doing them like that today.

[Cd]

Originally Posted by Frank Lee

So a blunt leading edge is OK so long as the flow doesn't go turbulent as it transitions to flow along the sides.

But what of the higher pressure that results from all of that air smacking into itself ? Does this indeed induce turbulence , or am I just misunderstanding ?

I guess what I am asking is if AndrewJs' Civic would have the same .Cd if he made a more rounded front end like the AeroCRX project here on this site.

Andrews' front end is barn door flat, but has a good curve along the edges like the Prodigy picture I posted above, so my guess would be that there would be no change .... but my gut feeling is that if he had a pointed nose on the car it would create less drag.

I'm just confused.

[NoCO2]

Originally Posted by TheDon

I need to do the coast down test on my brick and let you know what the .cd is...

What is the "coast down" test you are referring to? I would like to see what my .Cd is as well.

[ttoyoda]

But what of the higher pressure that results from all of that air smacking into itself ?

If you can keep that air attached onto the back end of the car or shape you recover all those pressure losses. If the flow detaches you lose them.

[apgrok1]

In my opinion, a blunt front end is a Chevy pick up truck 1973-87. Anybody know the Cd of that?

[Cd]

Originally Posted by ttoyoda

If you can keep that air attached onto the back end of the car or shape you recover all those pressure losses. If the flow detaches you lose them.

I have read about this sort of thing - reattaching flow and such.

So as an extreme example, when you have a tailgater 'drafting' behind your ultra slick car, he is actually ruining you aerodynamics by following too closely ?
You are pulling him in your wake, and if it is a large SUV then he just ruined your aero big time.

( In this case, it you might end up getting better MPG by driving 85 MPH and not having a string of SUVs in you wake ... right ? )

So if I drive a Hummer and had an Aptera tailgaiting me, then the .Cd on the Dummer would go down as well since the flow would reattach onto the Aptera ??