(1) Why is the diffuser necessary to increase downforce ? I mean specifically how come a flat bottomed car with no diffuser has less downforce. In McBeath's book on aerodynamics he says the diffuser doesn't produce much downforce. He say though the pressure in the diffuser
is slightly lower than atmospheric pressure and therefore produces a little downforce, it is the effect of the diffuser on the mass flow rate under the cars flat bottom area the produces the downforce. He says it is diffuser allows the venturi airflow to rejoin with air behind the car
more efficiently. But why does this increase downforce compared to car without a diffuser ?
(2) Secondly, increase the diffuser angle (steeper slope) increase mass flow rate under the car (up to a point). Why does this change increase the mass flow rate ?
Many thanks to everybody and I apologize for any errors I made in my description if any.
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