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GATE, PSUs - Hydraulics, Irrigation, water resource Engg. notes - part 6

Hello there,
How have you been? Here is the 6th part of our notes for preparation of GATE and other examinations related to Civil Engineering.

  • The Hardy Cross method of hydraulic analysis of pipe networks, besides satisfying the continuity and energy principles, must also satisfy the condition that the algebraic sum of the head losses around any closed loop is zero.
  • Given that, S = Slope of channel bottom,  Se = Slope of the energy line, F= Froude number, the equation of gradually varied flow is expressed as    dy/dx = (S-Se)/(1-F^2).
  •  A fluid motion in which stream lines are concentric circles is known as a vortex flow.
  • A fluid motion is free vortex flow when the fluid particles moving in concentric circles may not rotate about their mass centre.
  • In a Sutro weir, the rate of flow for all flows above the rectangular base of width W and depth 'a' is proportional to the head above a datum a/3 above the crest.
  • In a steady laminar flow through a circular pipe, shear stress is zero at the centre, velocity is maximum at the centre and hydraulic gradient varies directly with the velocity.
  • Boundary layer thickness is the distance from the boundary where velocity is 99% of uniform velocity.
  • Displacement thickness is the distance from the boundary by which the main flow can be assumed to be shifted.
  • Turbulent boundary layer is the distance from the boundary where from the flow ceases to be laminar.
  • Laminar boundary layer is the region near the boundary where viscous stress is also present.
  • An irrigation canal has a steady discharge Q at a section where a cross - regulation(gated) is provided for control purposes. If the gate of the regulator, which is normally fully open, is suddenly lowered down to a half open position, then a rapidly varied unsteady flow results. In such a case, it would take the form of a +ve surge moving u/s and a -ve surge moving d/s. [ES 93].
  • The specific energy 'E' in a critical flow at depth Yc occurring in a triangular channel is given by 1.25*Yc.   [ES 94].
  • When no external energy is imposed, Energy line always falls in the direction of flow and Hydraulic gradient line never rises in the direction of flow.
  • Stream lines - Tracing of motion of different fluid particles
  • Streak lines - Identification of location number of fluid particle.
  • Path lines - Tracing of motion of any one fluid particle.
  • Equipotential Lines - Location of equal piezometric heads.
  • As the depth of the immersion of a vertical plane surface increases, the location of pressure comes closer to the centre of gravity of the area.

All information is learned through books and practical exercises.


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