Peri Hartman via EV wrote:
Won't it also make a large difference overall, depending on the tow
vehicle? If the trailer fits in the trailing vacuum, I would think
there would be less resistance than if it were punching a new hole. I
suspect this could have a larger difference than the frontal area and Cd.
But of course! To find the difference, you would do the roll-down test
with just the tow vehicle, and then with the tow vehicle + trailer. Then
you could calculate the difference in drag coefficients.
Aerodynamics is complicated, and does not lend itself to intuitive
guesses (unless you are an aerodynamics expert). In special cases, a
trailer can even *reduce* the aerodynamic drag of a vehicle! For
example, a teardrop trailer can "fill in" the hole behind a truck or van
with a squared-off back. But you still consume more energy due to the
trailer's weight and rolling resistance.
Lee Hart
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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