Hydraulics and Irrigation Engineering

Advance Open Channel HydraulicsDr. Shahid AliDr. Shahid Ali

PhD Hydraulic & Water Resource Engineering (Fluid Dynamics) Technical University Delft, the NetherlandsMSc (Nuclear Engineering), PIEAS Nilore Islamabad , PakistanMSc (Hydraulic & Irrigation Engineering), UET Taxila, PakistanBSc ( Civil Engineering), UET Taxila, Pakistan Course OutlinesINTRODUCTIONIntroduction, Basic definitionsFlow Classification, Normal flow, Velocity Distribution in open channelsPressure Distribution (Hydrostatic and Non hydrostatic),Froude number & Reynolds numberBASIC PRINCIPLES

Reynolds transport theoremConservation of Mass, Momentum and Energy

UNIFORM FLOW Flow in rectangular and Non-rectangular channelsCritical flow, Specific energy, Flow resistance Computation of uniform flow, Normal depth in compound channel, Channel designGRADUALLY-VARIED FLOWThe gradually-varied-flow equation, Finding the friction slopeProfile classification, Qualitative examples of open-channel-flow behaviorNumerical solution of the GVF equation RAPIDLY-VARIED FLOWHydraulic jump and energy dissipationSpecific energy, Critical-flow devices, Rapidly varied flow computationVisualization of hydraulic jump, Characteristic of flow over weirsFlow over spillway, ogee weir, Flow around piersFlow in converging and diverging channel section, Forces on objectsUNSTEADY FLOWDefinitions, Height and celerity of surge wavesDerivation St. Venant equations Shallow water waveKinematic wave theory, Diffusion wave theoryHydraulic flood routing, Floodway and channel improvement Introduction to Computational Hydraulics

softwaresRIC-NaysSSIIMHEC-RAS

Recommended Textbooks

Chaudhry, M. H., 2008, Open-Channel Flow, 2nd EditionChanson, H., 2004, Hydraulics of Open Channel Flow: An Introduction, 2nd EditionAkan, A., O., 2006, Open Channel Hydraulics, 1st EditionChow, V.,T., 1959, Open Channel Hydraulics, 1st EditionChadwick, A.J., Morfett, J.C., and Borthwick, M., 2013, Hydraulics in Civil and Environmental Engineering, 5th EditionHamill, L., 2011, Understanding Hydraulics, 3rd EditionOpen Channel Flow

Typical Open Channel Shapes

Classification Of Flow Type

Basic PrinciplesMass Balance (Continuity Equation)

Momentum Balance (Force Balance)

Energy Balance

Physical ProcessesDiffusion

Convection/Advection

Distributed Flow routing in channelsDistributed RoutingSt. Venant equationsContinuity equation

Momentum Equation

46Assumptions for St. Venant EquationsFlow is one-dimensionalHydrostatic pressure prevails and vertical accelerations are negligibleStreamline curvature is small. Bottom slope of the channel is small.Mannings equation is used to describe resistance effectsThe fluid is incompressible47Continuity Equation

Q = inflow to the control volumeq = lateral inflow Elevation ViewPlan ViewRate of change of flow with distanceOutflow from the C.V.Change in massReynolds transport theorem 48Continuity Equation

Conservation formNon-conservation form (velocity is dependent variable)49Momentum EquationFrom Newtons 2nd Law: Net force = time rate of change of momentum

Sum of forces on the C.V.Momentum stored within the C.VMomentum flow across the C. S.50Forces acting on the C.V.Fg = Gravity force due to weight of water in the C.V.Ff = friction force due to shear stress along the bottom and sides of the C.V.Fe = contraction/expansion force due to abrupt changes in the channel cross-sectionFw = wind shear force due to frictional resistance of wind at the water surfaceFp = unbalanced pressure forces due to hydrostatic forces on the left and right hand side of the C.V. and pressure force exerted by banks

Elevation ViewPlan View51Momentum Equation

Sum of forces on the C.V.Momentum stored within the C.VMomentum flow across the C. S.

52Momentum Equation

Local acceleration termConvective acceleration termPressure force termGravity force termFriction force termKinematic WaveDiffusion WaveDynamic Wave53Momentum Equation

Steady, uniform flowSteady, non-uniform flowUnsteady, non-uniform flow54

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