Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Aerodynamics of a racecar undertray

  1. Apr 15, 2004 #1
    This is a question about aerodynamics & lift/downforce created by a change in the undertray design of an IRL car..

    The IRL racing series announced yesterday a number of changes to car design in order to keep cars from lifting off the ground, as they were for some unknown reason especially prone to do last year. One of the new changes is to the undertray of the car which was essentially 'flat' last year:

    Not sure that means too much to anyone, but basically the bottom of the car will be a *very-flat "V"* as you look at it from nose to tail.

    Now imagine a car skidding sideways.
    The diagram below is extremely crude & exaggerated(it is a curve in real life):

    \______ _______/
    _______V__________ <--flat ground
    ==> direction of air underneath car

    My (non-physics-background)-thinking is that air encountered by the forward side of the undertray will get squeezed or "scooped" underneath and as it gets trapped towards the centreline the lowest(narrowest) point.
    I would think this would create LIFT, the exact opposite of the desired affect.

    Someone I was discussing this with mentioned aircraft wings & the Bernoulli prinicple, but an open-wheel racecar is not 'wing' shape when looking at it from the side!

    Can someone explain how the airflow under a sideways-sliding car with a 'V' bottom would act?
    Last edited: Apr 15, 2004
  2. jcsd
  3. Apr 15, 2004 #2


    User Avatar
    Science Advisor

    If the air is 'squeezed' so that more air is forced through a given space its velocity would increase. An increase in velocity would result in a drop in pressure.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook