Laminar and Turbulent Flow

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Laminar and Turbulent Flow

• SPH4C

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Fluid Dynamics

• Fluid dynamics is the study of the factors that
  affect fluids in motion.

Computational fluid dynamics can simulate the
flow of air around a vehicle.
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Internal Friction

• As a fluid flows, the forces of attraction
  between the molecules cause internal friction, or
  resistance to the flow.

Some fluids have more resistance than others.
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Viscosity

• The resistance of a fluid to flow is called its
  viscosity.
• Water has a low viscosity. Syrup has a higher
  viscosity.

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Temperature Dependence

• As temperature increases, the viscosity of a
  liquid generally decreases because the particles
  of the liquid have more energy and flow more
  easily.
• However, gases generally increase in viscosity as
  the particles collide more often making it more
  difficult for them to flow in one direction.

Choosing the right oil viscosity grade for your
vehicle requires consideration of the
temperatures in which your vehicle will be
operating.
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External Friction

• As fluids flow, their particles also interact
  with their surroundings and experience external
  friction.
• In a pipe the water flowing close to the sides is
  almost not moving while the water in the middle
  of the pipe can be moving quickly.

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Laminar Flow

• If the speed of a flow is slow and adjacent
  regions flow smoothly over one another, the flow
  is called laminar flow.
• This term can also be applied to air flow over a
  smooth object.

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Laminar Flow Video

• http//www.youtube.com/watch?featureplayer_embedd
  edvp08_KlTKP50

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Eddies

• Laminar flow is difficult to achieve because as
  the fluid flows past the object, the flow becomes
  irregular, resulting in whirls called eddies or
  vortices.

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Turbulent Flow

• Eddies are common in turbulent flow, a fluid flow
  with a disturbance that resists the fluids
  motion.

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Turbulent Flow

• Eddies are common in turbulent flow, a fluid flow
  with a disturbance that resists the fluids
  motion.
• Turbulent flow decreases kinetic energy as some
  of the energy is converted into thermal and sound
  energy.

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Velocity

• Turbulence increases with the velocity of the
  fluid.

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Reducing Turbulence

• One mechanism of reducing turbulence in liquids
  is introducing small amounts of liquid plastic.

Blood flow in arteries is typically turbulent.
The introduction of liquid plastic into the
bloodstream can help people who have problems
with blood flow.
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Turbulence and Design

• Engineers consider the effects of turbulence when
  designing structures.
• For example, high rise buildings can direct
  strong gusts of air down to street level.

The circular podium between the towers of Toronto
City Hall was placed there to reduce winds.
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More Practice

• Laminar and Turbulent Flow Lab Activity

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Extension

• Cornstarch and Water A Non-Newtonian Fluid