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Basic pressure term in FM

  1. Sep 15, 2010 #1
    if we consider fluid flow, then bernoulis equation says that pressure must reduce when velocity is high.What is the direction of pressure when fluid is in flow?
    When fluid is stationary then pressure varies in vertical direction. It acts in downward direction on account of gravity. Means it is (h*density*gravitational acceleration).
    While the fluid is in flow none of the height,density,acceleration due to gravity changes the how the pressure reduces at high velocities?? (like in throat of venturimeter).
    If we consider solid bricks slipping on ground (one on another) with no friction between them and with ground,then pressure is weight per unit area, if velocity is high then weight per unit area does not change.
  2. jcsd
  3. Sep 15, 2010 #2


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    Pressure has no direction. It acts equally in all directions. In other words, it is always normal to whatever surface the fluid is touching.

    These factors can still affect the pressure if, in the course of the flow, the fluid is changing heights. Still, for small height changes, the pressure change will be miniscule compared to that created by the fluid's motion.

    I am not sure what exactly you are trying to get at here. A fluid and a solid are entirely different materials and do not follow all of the same patterns, obviously.
  4. Sep 15, 2010 #3
    Pressure is in all directions!

    With fluid flow you have to consider two types of pressure, static AND dynamic.
    The important thing to note is the dynamic pressure of a fluid is relative to its velocity. the equation is:

    static pressure + dynamic pressure = constant.
    p + 1/2 (density x velocity^2) = constant.

    if velocities increase, so will the dynamic pressure and because of the constant, the static pressure will DROP.
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