This video came about after I sent a request to several top car aerodynamicists (ones I'd came into contact with through working on my book) about the relationship between pressures measured on the side of the car, and the base (ie wake) pressure.
My measurements show that pressures at the rear edges of cars don't always match wake pressures (although the match seems pretty good on squareback shapes). So what actually
is the connection between (say) side pressures and base pressures? If we understand that more clearly, we (as amateurs) can then develop approaches to reduce base pressure and so drag.
Dr Adrian Gaylard (Jaguar Land Rover) came back with an intriguing response that I'd never thought of before. He referenced Hoerner's classic book on aero drag, linked to a more modern paper and put that all in the context of his own understandings.
This video looks at that particular theory - I may later do others on what the other aerodynamicists told me.
My gut feeling is that this theory helps explain
some aspects of base pressure - as all the aerodynamicists told me, there is a lot going on, and so one theory is unlikely to explain everything!
It does, however, make sense in the context of the measurements I have made in the last month on cars as diverse as a Skoda Roomster squareback, W212 Mercedes notchback, Gen I Honda Insight fastback and Tesla Model 3 fastback.