Stromingsleer_college5 [Compatibility Mode]
Transcript of Stromingsleer_college5 [Compatibility Mode]
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1Fluid Mechanics – Lecture 5
Fluid mechanics(wb1225)
Lecture 5:energy equation
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2Fluid Mechanics – Lecture 5
Snapping shrimp
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3Fluid Mechanics – Lecture 5
The energy equation
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4Fluid Mechanics – Lecture 5
The energy equation (cont’d)
small
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5Fluid Mechanics – Lecture 5
One-dimensional stationary energy flux equation
enthalpy:
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6Fluid Mechanics – Lecture 5
Bernoulli’s 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
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7Fluid Mechanics – Lecture 5
Example 3.21
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8Fluid Mechanics – Lecture 5
Validity of Bernoulli equation
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9Fluid Mechanics – Lecture 5
Cavitation
sonoluminescence
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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
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11Fluid Mechanics – Lecture 5
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12Fluid Mechanics – Lecture 5
Wind turbine
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13Fluid Mechanics – Lecture 5
Wind turbine
V
V
V
f VCA A
P Q RO
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14Fluid Mechanics – Lecture 5
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15Fluid Mechanics – Lecture 5
Wind turbineV
V
V
f VCA A
P Q RO
Power:
See Sect. 11-6 in White
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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 …
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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