Looking at streamlining, I came across the following:
' Aerodynamic Testing and Development of Sunswift eVe ', Simon Ambrose & Graham Doig, 53rd AIAA Aerospace Science Meeting, Proceedings: Kissimmee, Florida, January 5-8, 2015
Sunswift is a World Solar Challenge competitor, Cd 0.16, and Af 0.7875 m-squared.
There are some CFD images. The side elevation indicates fully-attached flow down the roofline profile.
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' Aerodynamics Concept Study of Electric Vehicles, Drag Reduction and Range Increase, Master's Thesis in Automotive Engineering, Umat Aktas, Kristian Abdallah, for National Electric Vehicle Sweden, Chalmers University of Technology, 2017.
As with the Porsche Macan vs Mitsubishi Mirage, Cd 0.37 vs Cd 0.27, ' the largest drag reduction are the diffuser and roof/ trunk spoiler extension concepts.'
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' Aerodynamics Development for a New EV Hatchback Considering Crosswind Sensitivity,' SAE Paper 2018-01-0715, Yusuke et al., Nissan Motor Co., Ltd., April 3, 2018.
For EVs, they attribute 59% of total drag to aerodynamics, at 100-km/h.
In Figure 4, page-4, they give a CFD image of ' lowest Cd streamlined shape.'
It's familiar. Fully-attached flow until truncation, then a very small wake.
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From: INSIDE EVs,
GAC ENO. 146
' Most Aerodynamic EV in The World Being Tested,' May, 27, 2020. GAC R & D Center, China.
They report Cd 0.146.
In plan-view, the car is very much a 1938 'Lange car.'
A very 'low' active splitter.
Seating for six.
Tire width looks reasonably like a 'real' tire.
They include smoke-flow imaging footage from wind tunnel testing.
This car has been reported already here at EcoModder.
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These gentle, continuous curved rooflines tend to show up on the lowest drag vehicles. They provide the pressure recovery which 'IS' the drag reduction.
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From: Modifying the AERODYNAMICS of Your Road Car, by Julian Edgar :
* ' flow separation...explains the low recorded pressures' page 79
* ' You can see that the proposed wing location matches what you'd expect from the smoke testing.' page-83
* ' rear lift... reflects the airflow generating low pressures over the rear half of the car...' page-173
* ' attached flow from nose to tail ' ( Figure 2.45, page-48, [ he's inadvertently describing the 'template', as the Volkswagen XL1 is the 'template' shape ])
* ' world's slipperiest road car', page-48, referring to the 'template' Volkswagen XL1, Cd 0.186. [ It's slippery for Volkswagen, but for no one else, and don't you dare bring it up, because it's 'magical ' and only works at Wolfsburg, Germany ]
* ' it is best if the spoiler is placed in an area of attached flow ', page- 194, ( which suggests that some spoilers are placed in separated flow ( and comparison of some production vehicles with rear spoilers to the 'template' indicate this very thing.)
* ' Another way in which a rear spoiler on a sedan can reduce lift and drag is to simply promote flow reattachment.' page-195 ( but we better be talking about pre-1990 automobiles, as no notchback sedan produced after that date is capable of separated flow, according to the author )[ this rule violated by Audi's 2010 A7 Sportback ( obviously 2010 is 'before' 1990 )]