Resistance in Fluid Systems

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Resistance in Fluid Systems

• Mr. Andracke
• Principles of Technology

2
Daily Objectives

• Each student will be able accurately complete the
  following
• Understand and define the types of drag and its
  applications
• Define laminar and turbulent flow
• Explain viscosity and how it is measured

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Drag

• What is Drag??

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Drag

• Drag is defined as the force found when a solid
  object moves through a fluid, also there is a
  force that opposes the motion.
• Example When an airplane moves through air.
• What is another example of drag?

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Understanding Drag

• Thrust Drag
• Drag is an aerodynamic force that resists the
  motion of an object moving through a fluid.

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Laminar Flow

• Laminar or streamlined flow is a slow, smooth
  flow over a surface, in which the paths of
  individual particles do not cross. These
  particle follow theoretical layers of fluid.
• Laminar Flow creates frictional drag
• What is an example of Laminar Flow on an object?

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Turbulent Flow

• Turbulent flow is an irregular flow that is
  disrupted causing fluid to move in different
  directions.
• Turbulence causes a wake behind a moving object.
• Turbulent flow creates pressure drag
• What is an example of Turbulent Flow on an
  object?

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Frictional Drag

• Frictional Drag is produced by the friction
  between successive or laminated layers of fluid,
  with increasing speed away from the surface.
• When does Frictional Drag take place?

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Pressure Drag

• The pressure difference found in turbulent flow
  causes a force to act on the object in the
  direction opposite its relative velocity.
• When does Pressure Drag take place?

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Understanding Drag

• Both Frictional and Pressure Drag increase as the
  speed of an object increases.
• When turbulence is created, pressure drag
  increases more rapidly than friction drag.

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Viscosity

• What is Viscosity??

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Viscosity

• Friction between two solid surfaces causes a
  resistance to movement between the surfaces.
• Viscosity is the property of a fluid that
  describes its internal friction.

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Viscosity

• What are some items that might have a higher
  viscosity? A lower viscosity?

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Viscosity

• Different fluids resist motion differently, and
  therefore have different viscosities.
• Gum and Molten Lava have high viscosities
• Air and Water have a much lower viscosity

15
Review Questions

• What is one type of drag and give an example?
• What is the main difference between laminar and
  turbulent flow?
• Explain viscosity and give an example.