Topic 2.1 Flow in Closed Conduit.pptx

Topic 2.1 – Flow in Closed Circular Conduits Official (Open) 2.1 Flow in Closed Conduits (Circular) Learning Objectives Explain what is laminar, turbulent and transition flow. Relate types of flow to the Reynolds number....

Topic 2.1 – Flow in Closed Circular Conduits Official (Open) 2.1 Flow in Closed Conduits (Circular) Learning Objectives Explain what is laminar, turbulent and transition flow. Relate types of flow to the Reynolds number. Compute Reynolds number for the flow of fluids in round pipes and tubes. Introduce the terms, hydraulic radius and Reynolds number for non-circular conduits. Explain the role of friction loss in pipe flow, friction factor and Darcy’s equation. Determine friction factor in turbulent flow using Moody’s diagram. Explain various types of energy losses in pipe flow and the resistance coefficient. Page Official (Open) 2.1.1 Laminar, Turbulent and Transition Laminar Flow Flow: When velocity is low Fluid molecules move in an orderly fashion as adjacent layers There is no mixing of fluid Fluid velocity profile across pipe particles Fluid velocity profile: Fluid velocity is max. at center of pipe Fluid velocity is 0 at pipe wall Thin shells sliding over one another In circular pipes: Flow pattern is like a series of thin shells that are sliding over one another. Page Official (Open) 2.1.1 Laminar, Turbulent and TransitionFlow: Turbulent Flow When velocity is relatively high Eddie currents are formed Flow pattern : eddy currents formed and There is mixing of the fluid mixing occurs particles The fluid particles have a random motion that is transverse to the main flow direction. Turbulence causes the velocity to average out Fluid velocity profile across pipe across the cross-section of the pipe. Page Official (Open) 2.1.1 Laminar, Turbulent and Transition Flow Transition Flow: Also known as Transient flow When velocity is between laminar and turbulent flow A transition stage when the flow cannot be classified as Laminar or Turbulent flow. Page Official (Open) 2.1.2 Reynolds Number, Re Reynolds concluded through experiments that the type of fluid flow through pipes is dependent on 4 factors: Osborne Reynolds Page Official (Open) 2.1.2 Reynolds Number, Re Reynolds concluded through experiments that the type of fluid flow through pipes is dependent on 4 factors: 1) Average velocity of the fluid (v) 2) Pipe diameter (d) vd 3) Dynamic viscosity of the fluid () 4) Density of the fluid ( ) A dimensionless parameter was formed - known as the Reynolds Reynolds Number, Re : a number, Re. dimensionless parameter to determine fluid flow type Official (Open) 2.1.2 Reynolds Observation of fluid flow by Reynolds Number, Re Laminar flow exists at low Reynolds No. : 𝑅𝑒 𝜌𝑣 =𝑑 𝑣 Inertial Force 𝑑  Viscous Re 2,000 = Force 0 Max. veloci ty 0 Turbulent flow exists 0 at high Reynolds No. : Re 4,000 Avera ge velocit y 0 Page 8 Official (Open) 2.1.2 Reynolds Observation of fluid flow by Reynolds Number, Re Laminar flow exists at low Reynolds No. : 𝑅𝑒 𝜌𝑣𝑑 = Inertial Force 𝑣𝑑 Viscous Re 2,000 = Force 0  Max. veloci ty 0 Turbulent flow exists 0 at high Reynolds In practice, pipe flow is generally No. : Re  4,000 turbulent Avera ge velocit y 0 Transient flow exists when 2,000 < Re < 4,000 Florence CLC221 / CLB221 – FLUID MECHANICS & Page 9 Official (Open) 2.1.2 Reynolds Number, Re Re < 2000 Laminar Flow Re > 4000 Turbulent Flow 2000 < Re < 4000 Transient Flow Page Official (Open) 2.1.2 Reynolds Number, Exercise Re In an oil refinery, diesel oil flows through a 30 cm diameter pipe at the rate of 700 m3/h. If the kinematic Give dviscosity = 0. 3 m;of the2.4 = oilxis10 2.4 - x 10-5 m2/s, determine the nature of the n: flow. 5 m2/s Q = 700/3600 = 0.1944 m3/ s Page End of Topic 2.1 Flow in Closed Conduits (Circular) Florence CLC221 / CLB221 – FLUID MECHANICS Page