If The Profile Is Good For Depasrture Angle...

[Angel And The Wolf]

High MPG transportation.

[freebeard]

It's better to convoy brick-shaped vehicles.

[Angel And The Wolf]

I don't need to pull that much weight. Interesting point, though.NASCAR teams have been doing that for a few years. (Makes for a dull race!)

[aerohead]

Originally Posted by kach22i

Thank you for finding it, that was a good thread.

Brings to mind a new question though; when a car is lowered so much and chin spoilered so much that it almost behaves like a surface blister, does the pressure wave change enough to warrant an optimized shape change?

That is to say, the lower you go, the more slope you need at the front?

index


And in the same vein of thought; the higher you go the more important it is to curve the chin inward and not have an abrupt splitter-like "cut-off" that could cause turbulence below it.

Or are these two different phenomena?

I'm not certain that I fully understand the question,but I'll throw this out.
*The bulbous nose,as on the Template is ideal.There's nothing you can do to lower the drag.All you're trying to do is provide for the approach angle and achieve attached flow.If you extend the nose further forward it won't improve flow attachment (you're already there),and the added surface friction will increase drag.With around 40mm of radius under the chin spoiler,you're golden.
*Ground clearance doesn't change the flow,other than the consideration that,you've got to have ground clearance around town so you don't tear the front and rear end off the car,or high center in the middle.
*On a perfectly smooth highway,with no road kill laying in the lane,you could drop the car 'into the weeds' and get closer to the drag minimum,or just leave the clearance alone and do full wheel fairings.
*The only pressure you're concerned with is that produced by separation.With the template,there is no separation and there's no lift.The high pressure at the nose and tail cancels any Bernoulli lift due to flow acceleration.

[aerohead]

Originally Posted by Angel And The Wolf

To the end of lowering CD

It won't lower a thing.Really! It will add drag.

[Angel And The Wolf]

It is obvious that the profile is optimized for passing through air at a certain airspeed. If the airspeed is doubled, would the profile need to be stretched horizontally in the direction of travel to prevent laminar flow separation? If the profile were applied to a taller, or lower vehicle, would it need to be stretched, or shortened to maintain attachment?

[freebeard]

Reread Permalink #6.

[aerohead]

Originally Posted by Angel And The Wolf

It is obvious that the profile is optimized for passing through air at a certain airspeed. If the airspeed is doubled, would the profile need to be stretched horizontally in the direction of travel to prevent laminar flow separation? If the profile were applied to a taller, or lower vehicle, would it need to be stretched, or shortened to maintain attachment?

The body's drag coefficient is constant between 20-mph and 250-mph.Above that,compressability effects begin to come into play as shockwave-dependent transonic flow begins to initiate.
The length of the body is a function of height and all proportions remain the same.(just as if you put it in a copy machine and enlarged or shrunk it)
You could 'stretch' the body simply by adding to the very center,and pay for the added skin friction,as limousines are done.

[Angel And The Wolf]

Thank you.

[kach22i]

Originally Posted by aerohead

*The only pressure you're concerned with is that produced by separation.With the template,there is no separation and there's no lift.

The high pressure at the nose and tail cancels any Bernoulli lift due to flow acceleration.

I have to give this some more thought.

I somehow believed there was a great deal of lift with the Aero-template.

The airfoil myth
The airfoil myth

As said, the low-pressure pocket forms because of the Bernoulli effect, which is why Bernoulli plays a role in wing lift, but not in the way it's classically explained.

A flat wing requires a steeper angle of attack to achieve the same amount of lift, and the consequence of this is increased drag.

That is the reason why the airfoil shape is optimal for flight, not because it would be mandatory for flight to happen.

I'm not sure how mainstream the blog above is, perhaps some sort of radical or heretic?

Note that helicopter rotor blades are basically flat wings in a steep angle. The mechanism by which they form lift is exactly the same.