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

Current theorys in fluid dynamics for jet propulsion

  1. Jul 9, 2003 #1
    anyone know any theories being used for fluid dynamics? any formulas? I aint no physicist, im just curious. Are there any developments today involving jet propulsion by going faster with only half the fuel? if that sounds right.

    any help would be appreciated
  2. jcsd
  3. Jul 10, 2003 #2


    User Avatar

    Staff: Mentor

    Pretty broad question. And there are lots of formulas. Do a google search for "gas dynamics." And the first equation to know is the various forms of Bernouli's.

    As far as efficiency, its really not that hard - you just have to make tradeoffs. An SR-71 for example has engines (turbo-ramjet hybrid) so efficient that its speed is limited only by the temperature at which the plane will melt. The efficiency increases as the speed increases. But as a result the engines are very INefficient at low speed so it takes miles of runway to take off.

    By contrast, a turbofan is highly efficient at low speed, but less efficient at high speed.
  4. Jul 10, 2003 #3


    User Avatar
    Science Advisor

    There are attempts to build Scramjet engines which are
    designed for hypersonic travel (Mach 5+). These are tubes
    that do not even slow the air that goes through but
    just add a bit of hydrogen and thus ignite the flow
    through interaction with atmospheric oxygen. Unfortunetly,
    these engines, for now, have huge problems to overcome.
    They overheat in a matter of a few minutes and even seconds and
    the egnition of the hydrogen in the thruster in such a powerfull
    and quick airstream is extremely difficult to achieve. There are
    also other ideas using other types of fuel with the general concept
    being an air-breathing rocket where the oxygen comes from
    the atmosphere as the air flows through the open thruster.

    Live long and prosper.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook