Chapter_4 - CHAPTER4 INTERNALLIQUIDFLOWIN PIPESANDCONDUITS...

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CHAPTER 4 INTERNAL LIQUID FLOW IN  PIPES AND CONDUITS
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Objectives Student should be able to: i. identify the characteristics of laminar flow and  turbulent flow ii. employ Poiseulle and Darcy equation in basic  problems iii. recall Bernoulli’s equation
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Objectives i. employ Bernoulli’s equation in flow  measurement ii. identify major losses iii. identify minor losses
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Flow Classification Reynolds's Experiment
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Flow Classification Laminar Flow - Flow structure is characterized by smooth motion  in lamina or layer. There is no macroscopic  mixing of adjacent fluid layer. - E.g. : A thin filament of dye injected into a  laminar flow appears as a single line. There is no  dispersion of dye throughout the flow, except the  slow dispersion due to molecular motion.
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Flow Classification Laminar flow  - Re < 2000  - 'low' velocity  - Dye does not mix with water  - Fluid particles move in straight lines  - Simple mathematical analysis possible  - Rare in practice in water systems. 
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Flow Classification Laminar (Viscous) Filament of dye
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Flow Classification Transition Filament of dye
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Flow Classification Turbulent Flow - Flow structure is characterized by random, three- dimensional motion of fluid particles  superimposed on the mean motion. - E.g.: If a dye filament injected into a turbulent  flow, it disperses quickly throughout the flow  field; the line of dye breaks up into myriad  entangled threads of dye. 
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Flow Classification Turbulent Filament of dye
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Flow Classification Turbulent flow  - Re > 4000  - 'high' velocity  - Dye mixes rapidly and completely  - Particle paths completely irregular  - Average motion is in the direction of the flow  - Cannot be seen by the naked eye  
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Flow Classification - Changes/fluctuations are very difficult to detect.  Must use laser.  - Mathematical analysis very difficult - so  experimental measures are used  - Most common type of flow. 
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Reynolds Number - Used to determine whether a flow is laminar or  turbulent.  - Reynolds Number is dimensionless. - Re < 2000: Laminar Flow - Re between 2000 to 4000 : Transitional Flow - Re > 4000 : Turbulent Flow
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Reynolds Number Where: ρ = density, kgm -3 u = average velocity , ms -1 d = diameter of the pipe, m μ = fluid viscosity,     kgm -1 s -1 μ ρ ud = Re
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Reynolds Number Example:
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Chapter_4 - CHAPTER4 INTERNALLIQUIDFLOWIN PIPESANDCONDUITS...

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