Understanding separated and attached flows
 

From what I see people write, I think that there may be some confusion here as to the significance of attached and separated flows (eg it doesn't seem often stated that attached flow can cause drag, and attached flow can cause thrust).

Modern car shapes basically have attached flow (on the upper surfaces at least) from nose to tail, so understanding the forces it develops is a great help to understanding current car aero.

https://www.youtube.com/watch?v=OKAn4uMjxnc

Thanks for posting this. Watching the video reminded me of the Dave Heinrich diagram of the New Beetle I first saw in an old AutoSpeed article and the tuft test photos in your book on page 65. It shows attached flow all the way down the back hatch and a terrible drag coefficient of 0.39 for the New Beetle.