AERODYNAMICS, book, Fredrick W. Lanchester

[aerohead]

here's a link to Lanchester's 1907 book.
He coined the term 'streamline body' and much more.
On page 27, you'll see the genesis of CYBERTRUCK's nose.
https://babel.hathitrust.org/cgi/pt?...iew=1up&seq=59

[freebeard]

I picked this thread because it had zero response and I want you to see this. I want to propose something to someone, and I seek your estimation.

A stock Arcimoto FUV weighs 1200lb and has 80HP. Koenigsegg has as new, very similar drivetrain that weighs 200lb and has 670HP www.motortrend.com/news/koenigsegg-gemera-quark-terrier-motor-specs-details/
I'm interested in a four-wheel class so add 200lb, 100 for drivetrain and 100 for a tandem bogey rear.



Assume a sub 0.20 Cd (Arcimoto front A-arm suspension), and 1400/670 power to weight ratio. For purposes of argumentation, what would the Cd be?

[aerohead]

Originally Posted by freebeard

I picked this thread because it had zero response and I want you to see this. I want to propose something to someone, and I seek your estimation.

A stock Arcimoto FUV weighs 1200lb and has 80HP. Koenigsegg has as new, very similar drivetrain that weighs 200lb and has 670HP www.motortrend.com/news/koenigsegg-gemera-quark-terrier-motor-specs-details/
I'm interested in a four-wheel class so add 200lb, 100 for drivetrain and 100 for a tandem bogey rear.



Assume a sub 0.20 Cd (Arcimoto front A-arm suspension), and 1400/670 power to weight ratio. For purposes of argumentation, what would the Cd be?

Sighard Hoerner would have us figure the CdA of each component, and add them together, along with a hook-vortice, 5% interference drag added to that total; then divide by the total frontal area. That's how Messerschmitt Aircraft Company used to do it. Hoerner worked for them.
Since the rear tandem wheels are almost completely wake-riding, they might be considered a freebie.

[freebeard]

Thank you.

One can estimate 7sq ft for the body, 1.5 sq ft for each wheel; But what is the Cd of a vertical disk edge on in ground contact?

[aerohead]

Originally Posted by freebeard

Thank you.

One can estimate 7sq ft for the body, 1.5 sq ft for each wheel; But what is the Cd of a vertical disk edge on in ground contact?

1) naked wheel Hoerner puts at Cd 0.58
2) Cd 0.49 with rear fairing
3) Cd 0.41 with front fairing
4) Cd 0.27 with total fairing
5) Cd 0.66 on a strut
6) Cd 0.19 half-enclosed
7) Cd 0.10 half-exposed but with rear fairing
8) A 1980 Indycar/ Formula-One car without wheels = Cd 0.25.
9) Cd 0.54 with wheels. really-wide wheels!

[freebeard]

Thanx. I'll go with 5) on a strut, plus 5%.

It's just an estimate.

[aerohead]

According to Sighard Hoerner, it would be close to Cd 1.20 - Cd 1.19. It may depend on Reynolds number. Don't recall for sure.

[aerohead]

The perspicacious have probably already noticed from smoke-flow imaging that, streamline flow filaments begin to displace from their 'rest' position before the vehicle's nose actually 'arrives'.
They take on the trajectory of Lanchester's pointed 'head', whether or not actually 'pointed.' Figure 4, page- 10.
You're witnessing the Lanchester/Prandtl 'surface of discontinuity.' ( Figure 20, page 30 ).
Fluid ( air ) in the presence of an obstruction, demonstrates a path of least resistance around the obstruction.
And as with Lanchester's 'pointed' nose, later in his book you notice that the streamlines follow the same trajectory if the nose is simply rounded, but also if part of the leading edge is actually removed.( Figure 16, page-27 )
The identical trajectory is maintained.
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If one observes the 'lowest' streamline which passes over a vehicle, and notes the location of where this streamline first diverges from a straight path, the 'length' of this streamline, compared to a distant streamline ( at infinity ), at any position, comparatively, this difference in length establishes the average difference in velocity between the two streams, as both, by definition, reach the same position of longitudinal distance at the same time.
Distance vs Time. d/t
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One will also observe the vertical distance a specific molecule of air will displace from it's rest position, as a function of 'where' it is along the contour of the body, and the 'time' when it's there.
On a 'streamlined' body, in which zero separation occurs, this is extremely important with respect to local pressure.
As a given air molecule resumes it's 'pre-encounter' position, it's essentially regained all it's rest energy ( static pressure ), with the exception of what it lost to friction drag heating of the atmosphere, which due to the viscosity of air, is inescapable.