Instrument Measurement Principles

Instrument Measurement PrinciplesPHYS6008

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Flow Measurement

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Learning ObjectivesWhen this section is completed the learner will be able to:Explain What is a fluid?Describe fluid flowDifferentiate between different types of fluid flowCalculate Reynolds Number

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What is a fluid?

A fluid is a substance that can flow liquids or gases

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Types of FlowLaminar Turbulent

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Types of FlowFlow is steadyParticles follow streamlinesAll particles flowing past a point in the flow will have same velocityLaminar

PipestreamlinesFLOW PATTERNVELOCITY PROFILEVelocity profile is parabolic due to the frictional forces between the layers of fluid and between the fluid and the pipe wall.

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Types of FlowTurbulentFlow is disorderlyAt any position in the flow the velocity is time dependent and eddies occur.

FLOW PATTERN

VELOCITY PROFILEpipeThe velocity profile is more uniform.The velocity is 0 ms-1 at the pipe boundaries.

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Reynolds NumberWhat are the units for each parameter?

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SymbolUnitsfluid densitykg m-3vaverage velocity ms-2dpipe diametermfluid viscosityNsm-2

What is the unit of the Reynolds number?

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If Re > 3000Turbulent Flow

If Re = 0 to 2000Laminar Flow

For 2000 < Re < 3000Transition region

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Example 1Oil of density 800 kgm-3 flows with a velocity of 3.0 ms-1 at 20 0C in a pipe of diameter 300 mm. The viscosity of the oil at 20 0C is 0.110 Nsm-2.

Determine whether the flow is laminar or turbulent?

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If Re > 3000Turbulent Flow

If Re = 0 to 2000Laminar Flow

For 2000 < Re < 3000Transition region

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