CE 230-Engineering Fluid Mechanics

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CE 230-Engineering Fluid Mechanics

• Lecture 4and5
• Fluid properties (2)

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Examine velocity distribution in pipe
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Viscosity

• Consider two plates separated be a thin film of
  fluid. The lower plate is fixed and the upper is
  moving with a constant velocity.
• Investigate what is happening in the fluid in
  terms of flow or stresses.

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Viscosity

• No slip boundary condition
• Relation between shear stress and velocity
  gradient
• Classification of fluids

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Mechanisms of fluid resistance to shear stress

• Particle cohesion
• Transfer of molecular momentum
• Influence of temperature on viscosity

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Units of viscosity

• Dynamic viscosity
• absolute viscosity
• viscosity
• Kinematic viscosity

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• Influence of temperature on viscosity

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Classification of fluids according to relation of
shear to strain rate
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Problems on viscosity

• Board sliding on an inclined surface separated by
  a thin film of oil
• Is there a shear stress in the film?
• lets calculate the terminal velocity

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Problem 34
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Problem 39

• Calculate the weight of piston given
• Terminal velocity
• µ
• Spacing between piston and cylinder
• Piston dimensions

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Problem 2.39
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Problem 2.41