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  • 1Fluid Mechanics Lecture 5

    Fluid mechanics(wb1225)

    Lecture 5:energy equation

  • 2Fluid Mechanics Lecture 5

    Snapping shrimp

    [1]

  • 3Fluid Mechanics Lecture 5

    The energy equation

  • 4Fluid Mechanics Lecture 5

    The energy equation (contd)

    small

  • 5Fluid Mechanics Lecture 5

    One-dimensional stationary energy flux equation

    enthalpy:

  • 6Fluid Mechanics Lecture 5

    Bernoullis equation

    Daniel Bernoulli(1700-1782)

    conservation of energy for stationaryflow in a stream tube: stationary flow no mechanical work no viscous frictionand: incompressible fluid motion along streamline no heat transfer

  • 7Fluid Mechanics Lecture 5

    Example 3.21

    [2]

  • 8Fluid Mechanics Lecture 5

    Validity of Bernoulli equation

    [2]

  • 9Fluid Mechanics Lecture 5

    Cavitation

    sonoluminescence

    [2]

  • 10Fluid Mechanics Lecture 5

    Example 3.23

    A constriction in a pipe will cause the velocity to rise and the pressure to fall atsection 2 in the throat. The pressure difference is a measure of the flow rate through the pipe.

    The smoothly necked-down system shown is called a venturi tube.

    Find an expression for the mass flux in the tube as a function of the pressurechange

    [2]

  • 11Fluid Mechanics Lecture 5

  • 12Fluid Mechanics Lecture 5

    Wind turbine

    [3]

  • 13Fluid Mechanics Lecture 5

    Wind turbine

    V

    V

    V

    f VCA A

    P Q RO

  • 14Fluid Mechanics Lecture 5

  • 15Fluid Mechanics Lecture 5

    Wind turbineV

    V

    V

    f VCA A

    P Q RO

    Power:

    See Sect. 11-6 in White

  • 16Fluid Mechanics Lecture 5

    Summary Chapter 3: 3.6, 3.7

    Examples: 3.20, 3.21, 3.23, 3.24

    Problems: (see BlackBoard)

    Study guideline:

    practice practice practice

  • 17Fluid Mechanics Lecture 5

    Source

    1. Snapping shrimp, http://youtu.be/ONQlTMUYCW42. Frank M. White, Fluid Mechanics, McGraw-Hill Series in Mechanical Engineering3. Wind turbines of Horns Rev wind farm, Denmark, photo courtesy of Vattenfall