The Fastback bloc

[freebeard]

Creating a fastback Toyota MR2 | Chip Foose Draws a Car - Ep. 12

[aerohead]

Originally Posted by JulianEdgar

More personal belittlement.

Note the change in Aerohead's proposition - now Hucho isn't talking about the Taycan, he is talking generically about spoilers.

Hey, all one and the same, isn't it?

A good example of Aerohead misquoting a source.

I invite you to argue your point scientifically. Your comments don't move the ball down the field at all. Focus on building not destroying.
Everything I posted is germane either to spoilers, or your behavior as experienced personally.

[aerohead]

Originally Posted by JulianEdgar

No I am sorry, flow attachment caused by downwash is still flow attachment.

In fact, that was said to me by no less authority than the head of Jaguar aerodynamics.

But hell, what would he know - he should have consulted Aerohead!

Your brand of attachment comes at the expense of tremendous vortex drag.
And who died, leaving your friend in charge of aerodynamics at Jaguar. What have they ever accomplished?
Why don't we skip you as the impotent intermediary and just bring him onto the site where he can speak in the first person. He could begin his philanthropy earlier than later. He owes it to the survivors of those who died to provide the fuel p....d away by all the Jaguar owners who couldn't control their hedonism.

[kach22i]

Originally Posted by freebeard

Creating a fastback Toyota MR2 | Chip Foose Draws a Car - Ep. 12

He could have saved some time and just shown a photo of a BMW M1

[kach22i]

Originally Posted by aerohead

Your brand of attachment comes at the expense of tremendous vortex drag.

I agree, but have yet to see vortex formation in any of the wind tunnel and smoke images posted.

Is the smoke just too weak and dispersed by the time it gets to the end?

Outside of large trucks on dirt roads or aircraft landing photos, I do not recall seeing vortex formation on automobiles.

Have seen a few tufts flicking about in videos.

[aerohead]

Originally Posted by kach22i

I'm assuming downwash and or upwash is not equal to attached flow because of what the surrounding air is doing.

That is to say: if the downwash attachment is being caused by a giant drag causing vortex, then you do NOT have clean pressure or evidence of attached flow.

Yes or no on the assumption and description above.

Pressure attachment Vs Flow attachment.

Is there an article on this?

........................part II of post.

In general the objections I have about template use is the it's shadow obscuring adjacent subjects.

Sure we take time to discuss air curtains, air tabs, diffusers and testing methods, but that shadow hovers overhead.

We need not destroy or perforate the template in order to shine light on other topics.

However, sometimes we have to shove it off to the side so we can look around and see what the real world is doing. And they are doing some cool things with air management that were never dreamed of in the 1930's because they didn't have the tools the industry has today.

Us novice type folks and Ecomodders do not have these industry tools.

Hucho shared the research of Ahmed et al., with respect to vortex-induced drag as a function of aft-body downslope. Results are extremely conditional, contextual.
An example is Figure 4.10, on page 114 of the 2nd-Edition.
1) A simple prismatic model is modified.
2) Drag coefficient of a Cd 0.272 square-back is the baseline.
3) The last 28.8 % of the body length is the single area of investigation.
4) By conversion to a fastback, the drag drops to a minimum of Cd 0.23, @ 15-degrees down slope, immediately rises, reaching a peak drag of Cd 0.33 at 30-degrees, then falls again to Cd 0.2738 @ 40-degrees, the end of the investigation.
5) For this particular length of slope, as compared to total body length, 15-degrees is the 'sweet-spot.'
6) By going beyond 15-degrees, attached, longitudinal vortices form, responsible for up to Delta- Cd 0.10 of drag. ( this is what the Porsche 912/911 faced )
7) Buchheim et al. investigated a range of slope-length-to-body-length variability, generating a 'template' table from which a minimum drag could be selected for any slope size.
8) No such table is provided for 'curved' roof vehicles. Except the effective fineness ratio table. But don't go looking at that or you'll catch hell.

[aerohead]

Originally Posted by kach22i

I agree, but have yet to see vortex formation in any of the wind tunnel and smoke images posted.

Is the smoke just too weak and dispersed by the time it gets to the end?

Outside of large trucks on dirt roads or aircraft landing photos, I do not recall seeing vortex formation on automobiles.

Have seen a few tufts flicking about in videos.

I believe that some of the YouTube videos shot at A2 allow for vortex visualization.
Driving down leaf-strewn roads in the Fall are a great opportunity to observe vorticity.
Air Tab inventor Wheeler photographed long, vortical yarn streamers coming off the sides of the roof of his Honda Accord if I remember correctly, in a Popular Science article in my photo albums somewhere.
Modern curved-roof designs have really mitigated this phenomena.We've come a long way since the mid-70s. And then there's the Porsche Cayman.

[kach22i]

Thank you for the information Aerohead/Phil, I will be looking into some of this.

I have seen the results of air flow and possibly vortex formation in the snow and snow fall on my vehicles.

[freebeard]

Snerodynamics?

Originally Posted by kach22i

I agree, but have yet to see vortex formation in any of the wind tunnel and smoke images posted.

Someone has replaced the real kach22i.

ecomodder.com: Random Wind Tunnel and Smoke Pictures Thread

Remember tubercles?

The most fruitful techniques seem to be schlieren photography and hydrogen bubbles in a water tunnel. ecomodder.com: Automotive Aerodynamics (video series)
_________________

Media Burn

https://www.youtube.com/watch?v=FXY6ocvaZyE

[JulianEdgar]

Originally Posted by kach22i

I agree, but have yet to see vortex formation in any of the wind tunnel and smoke images posted.

Is the smoke just too weak and dispersed by the time it gets to the end?

Outside of large trucks on dirt roads or aircraft landing photos, I do not recall seeing vortex formation on automobiles.

Have seen a few tufts flicking about in videos.

While it would be nice to be able to see the vortices, you can directly measure their drag and lift outcomes by simply measuring panel pressures. After all, all drag and lift forces just come from air pressures acting on panels.