Aerodynamics Intuition Proven Wrong Again

[RedDevil]

Originally Posted by freebeard

I'd assert just the opposite. The protrusion dies out with the curve of the bottom of the windshield. The creases in the hood are in a pronounced V-shape. It's like a 'bug deflector' that cause the air close to the hood to divert to the sides. Maybe to energize the air around the rear-view mirror?

They need to come together somewhat, the pressure over the slanted hood makes the air flow go sideways anyway,even more than those lines indicate.
If they went straight over the hood they would have a large angle compared to the direction of air flow, that would cause extra friction and turbulence.
Like an aircraft wing, the optimal angle of attack is not the maximal one.
This angle just nudges the air upwards without blocking it too much.

When I first saw cars with protruding A pillars I thought they had misplaced the windscreen. It went completely against my intuition.
As more and more models employ this trick I had to accept here must be a reason for it, and I believe it to be what I've explained in this thread.

[freebeard]

I'm probably biased because I had a 1958 VW Beetle convertible. The frame stood proud of the flat glass. The wiper couldn't move snow out of it's normal range, let alone clear the whole thing.

[godscountry]

I'm sure most of you know about the effect dimples have on golf balls.Check this out Morphable surfaces could cut air resistance | MIT News Office

[freebeard]

I was reading about something similar just the other day:

Elastomeric camouflage switches texture and colour

[sqidd]

That guy should be fired for those headlights. Now I can't get a new F150.

[aerohead]

Originally Posted by calry

To paraphrase Brad Richards, Exterior Design Manager for the new Ford F-150 in this USA Today video on the new aerodynamic Ford F-150, at the 40 second mark, that they angled it much more thinking it was going to get better aerodynamics, but it did not. Instead, they gave it a harder edge which worked better.

This proves once again prove that I know less than I thought I did about aerodynamics. His discovery makes me think that those flat air dams on the front of semi tractors might not be as bad as they look.

In everyone's wanderings around and musings on aerodynamics, are there any good aerodynamics cheat sheets? Yes, I know people get Ph.D.s and spend decades of their lives studying these phenomenon, so I am possibly asking for the impossible. After all, aerodynamics, is a subfield of fluid dynamics which in turn is a subfield of fluid mechanics. That is lots of material to cover. But I have had a lot of college and graduate science and I have found short intense summaries can sometimes be a quicker way to occasional insight.

Yes, I could pick up an aerodynamics text book. Its just, just that....they are so heavy.

Bear in mind,that in the forebody,the boundary layer is in the most favorable pressure gradient,and is essentially held against the body as long as it is 'attacking' the flow field.
And as Ford aerodynamicists essentially said decades ago,"there is no magic radius",just enough softening and you've got full attachment.
This isn't so for the aft-body which is the major source of drag with road vehicles.Back there you've got to be especially careful with your contours or the whole thing goes to the worms.Control of aft-body separation is the premise for aerodynamic streamlining.

[Big time]

Originally Posted by calry

To paraphrase Brad Richards, Exterior Design Manager for the new Ford F-150 in this USA Today video on the new aerodynamic Ford F-150, at the 40 second mark, that they angled it much more thinking it was going to get better aerodynamics, but it did not. Instead, they gave it a harder edge which worked better.

This proves once again prove that I know less than I thought I did about aerodynamics. His discovery makes me think that those flat air dams on the front of semi tractors might not be as bad as they look.

In everyone's wanderings around and musings on aerodynamics, are there any good aerodynamics cheat sheets? Yes, I know people get Ph.D.s and spend decades of their lives studying these phenomenon, so I am possibly asking for the impossible. After all, aerodynamics, is a subfield of fluid dynamics which in turn is a subfield of fluid mechanics. That is lots of material to cover. But I have had a lot of college and graduate science and I have found short intense summaries can sometimes be a quicker way to occasional insight.

Yes, I could pick up an aerodynamics text book. Its just, just that....they are so heavy.

Once upon a time the car body was designed first (for aesthetic reasons) and then they began thinking how they could fit the passengers, engine, suspension, etc. inside it.

Now they (a lame committee) decide the layout and then think on how they can fit a not-so-ugly somewhat aerodynamic body over it. Yes most modern cars are ugly and boring IMO.

They should do it backwards again. First design an eye-catching aero body and let Marquis de Sade design the ergonomics!

[freebeard]

Once upon a time the car body was designed first (for aesthetic reasons) and then they began thinking how they could fit the passengers, engine, suspension, etc. inside it.

When? Certainly not before Harley Earle. The stylist was always handed a set of parameters. Cowl height, for instance is set early on.

Now they (a lame committee) decide the layout and then think on how they can fit a not-so-ugly somewhat aerodynamic body over it. Yes most modern cars are ugly and boring IMO.

Some committees as less lame than others.



This committee took an extremely aerodynamic body and stuffed a Ducati V-twin in it.

[calry]

Originally Posted by aerohead

Bear in mind,that in the forebody,the boundary layer is in the most favorable pressure gradient,and is essentially held against the body as long as it is 'attacking' the flow field.
And as Ford aerodynamicists essentially said decades ago,"there is no magic radius",just enough softening and you've got full attachment.
This isn't so for the aft-body which is the major source of drag with road vehicles.Back there you've got to be especially careful with your contours or the whole thing goes to the worms.Control of aft-body separation is the premise for aerodynamic streamlining.

Aerohead, your answer combined with your aero lessons have already improved my understanding significantly. Thank you.