Crash Course in Fluid Mechanics

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Crash Course in Fluid Mechanics

• By Aisha Jorge

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Compressible and incompressible Flow

• Compressibility is dependant on density (density
  mass per unit volume)
• Compressible density changes appreciably
  (typically by a few percent) within the domain of
  interest.
• Incompressible density is constant everywhere.
  All fluids behave incompressibly (to within 5)

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Viscous and inviscid flow

• Viscosity is the magnitude of fluid shear
  stresses to the fluid strain rate, or more
  simply.
• Viscous Flow shear stresses have a significant
  effect on fluid flow
• Inviscid Flow shear stress do not have a
  significant effect on fluid flow
• perfect flow means inviscid A perfect fluid is
  defined as a fluid with zero viscosity

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Laminar and Turbulent Flow

• Flow is Laminar or Turbulent based on Reynolds
  number (Re).
• where r density, u mean velocity, d
  diameter and m viscosity
• Re internal forces divided by viscous forces

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Laminar and Turbulent Flow

• Laminar flow
• Re lt 2000
• 'low' velocity
• Fluid particles move in straight lines
• Simple mathematical analysis possible
• Turbulent flow
• Re gt 4000
• 'high' velocity
• Particle paths completely irregular
• Average motion is in the direction of the flow
• Mathematical analysis very difficult - so
  experimental measures are used
• Most common type of flow.

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Laminar and Turbulent Flow