What is the CdA of the fairing section vs. the CdA of the duct?? The math ought
to be simple at that point.. I would suspect that the fairing is an order of
magnitude better than the duct.
Dave
john robinson wrote:
>
>
> Concerning the fairing ( or car body), most of the ones I have
> seen, seem to be solid to the air, in other words they don't allow the air
> to enter the >inside< of the fairing/body, only direct the air around on
> the outside. Now I know that there is an energy penalty from having air to
> flow through a "dirty" enclosure, but would the bike/car benefit from
> having a slightly smaller frontal area due to the air passing through the
> bike/car rather than around it? could this internal air help to partially
> fill the vacuum bubble behind the vehicle thereby reducing drag? would the
> reduction of drag be greater than the drag from the ducting? should the
> internal airflows be more "directed" by enclosing them with ducting and
> thereby cleaning up the internal airflows or is there enough benefit from a
> reduction of frontal area that there is no need for the ducting?
> I realize that cars are going to have more of a problem with doing
> an internal duct, due to the length, but motorcycles being shorter might be
> helped.....I'm thinking of the P-51 radiator that made thrust from the
> added heat from the radiator and the shape of the ducting. this might be of
> some use to me with an aircooled bike.....
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