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Homework Help: Fluid Mechanics local acceleration and convective acceleration

  1. Feb 10, 2008 #1
    1. The problem statement, all variables and given/known data
    The velocity of the water in the pipe is given by v1=.5t m/s and v2=1tm/s, where t is in seconds. Determine the local acceleration at points 1 and 2. Is the average convective acceleration between these two points negative, zero, or positive?

    2. Relevant equations

    A figure of pipe (funnel like) that is larger at the input end with v1 and smaller end with out put speed of v2.

    3. The attempt at a solution

    I don't really know how to start answering this question, I don't have the text with me (still in delivery) and don't have any notes thats on this topic.

    My try: d (v1)/dt=0.5t so a=d(v1)/dt=.5 m/s^2
    d(v2)/dt=1t so a2=d(v2)/dt=1 m/s^2
  2. jcsd
  3. Feb 11, 2008 #2

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    The local accn changes because the flow is not steady and time dependent, and the values are as you have derived.

    The convective accn is positive because a particle of fluid has to speed up due to the area at point 2 being smaller than area at point 1.

    For a steady flow, there would be convective accn only.
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