1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Increasing car efficiency by rerouting airflow?

  1. Jan 28, 2017 #1
    This is only a semi- serious thread, since I suspect there's a simple back-of-a-napkin calculation that shows this to be infeasible.

    The idea is the following: a lot of a car's efficiency gets lost in the form of air drag, I.e. forcing the air to go around the car.
    Could one upscale a supercharger, I.e. a compressor, to consume all the incident airflow hitting the front of the car, compress it, route it through the car, and in the back expel it again?
    Intuitively this should reduce air drag, since a much smaller section of the car is now "visible" to the air.
    However, the compression and the associated own air drag might thwart the energy balance, making it negative overall. But, is that necessarily so?
     
  2. jcsd
  3. Jan 28, 2017 #2

    berkeman

    User Avatar

    Staff: Mentor

    For your back-of-the-napkin calculation, figure out how many horsepower it would require to do that air pumping, and compare that to the power wasted in the excess air resistance... :smile:

    EDIT -- Wait, you can write on both sides of a napkin, but only on one side of a used envelope... o0)
     
  4. Jan 29, 2017 #3

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    Yes - the pump would have to be free of turbulence.
     
  5. Feb 11, 2017 #4
    Sounds like you're essentially talking about a jet engine designed to generate just enough thrust to cancel out it's own drag, rendering the latter effectively zero.
     
  6. Feb 12, 2017 #5

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    . . . . . which would cost a fortune to buy and to run, of course.
    The aerodynamic design of modern fast cars does exactly what the title of the thread suggests.
    On a parallel topic, I have read that the skins of dolphins has small ridges and valleys all over it and is 'deliberately' flexible, which is thought to improve its hydrodynamic efficiency. I wasn't aware of an equivalent in air (but who knows what birds' feathers do for efficiency?) but I found this rather lightweight link which mentions the subject. There are dozens of other links about dolphin swimming efficiency being higher than you'd expect.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Increasing car efficiency by rerouting airflow?
Loading...