Quote:
Originally Posted by freebeard
Is it fair to say that molecules, in addition to moving normal to the direction of travel, also get sucked forward and back in the direction of travel?
Renormalizing all that in my head is tough. Could you edit the post and number the illustrations for reference purposes? In fact here's a test:
  
Yes you can. Just place each IMG separated by a Return, Go Advanced and wrap the whole block with Ordered List. Voila!
Thanks for including the Notchback.  Here's mine:
You can almost make out the Reggae/Deadhead sticker on the hood. |
I've gone back in an numbered the early images,with source credits.Hope that helps.
And yes,the air can move in all directions,including sideways (transverse contamination),depending on pressures and their location on the body.
Post-1985 cars,with body camber,typically have the boundary layer held against the body by a favorable pressure gradient created by the attacking 'source' flow,right up to the position of maximum cross-section.
It's in the aft-body where we are cautioned,as here,we are in an unfavorable pressure gradient,and any 'fast' contour, would create too fast of a pressure rise, overwhelming the turbulent boundary layers ability to receive momentum energy from 'above.'