Quote:
Originally Posted by NeilBlanchard
I'd say that the first one is lower drag, and here's why: the shape of the front accelerates the air out and around the high point on the roof, and this creates a localized high pressure, which then help the air "spring" back and it helps maintain attached flow. So, it adds to the atmospheric pressure and this improves the air flow a bit.
If the rear of the shape is most important, then the front is next most important -- it matters less, but it matters. At the very least the second one has more surface drag.
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A Fluid Dynamics professor would say that the forebody takes air at rest,and high static pressure,and accelerates it to its highest velocity pressure and lowest static pressure.Then the aft-body provides a gentle deceleration ramp in which the kinetic energy of the velocity pressure can be converted to the original ambient atmospheric pressure of the original air at rest.
The air always wants to be at a peaceful equilibrium and uniform pressure.
Streamlining allows to car to transit through a given volume of air,gently displacing it,then allowing it to gather itself back together as if you were never there.
Walter Lay's research proved that a perfect boat tail is useless if the nose isn't good enough,so the nose is not unimportant.But no amount of perfect nose can lead to low drag if the tail is wrong.
Reading last night about the EZ-HOOK 295 mph motorcycle streamliner of Cd 0.103,the Cal Tech guys reiterated that a round front is all that's necessary.The Devil's at the back.