Fluid Mechanics: HGL and TEL Concepts

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Questions and Answers

What is the main cause of minor energy losses in a pipe?

  • Pressure differences in the fluid
  • Friction in the pipe
  • Temperature variations of the fluid
  • Change of velocity of the fluid (correct)

Which of the following is NOT considered a case of minor loss of energy?

  • Loss of head due to sudden enlargement
  • Loss of head due to bend in the pipe
  • Loss of head due to friction (correct)
  • Loss of head at the entrance of a pipe

In which scenario can minor losses be neglected without serious error?

  • In short pipes
  • In long pipes (correct)
  • In low flow rate conditions
  • In pipes with sharp bends

What does the Total Energy Line (T.E.L.) represent?

<p>The sum of pressure head, datum head, and kinetic head (C)</p> Signup and view all the answers

Which type of loss occurs due to an obstruction in a pipe?

<p>Minor loss (A)</p> Signup and view all the answers

What does the Hydraulic Gradient Line (H.G.L) represent?

<p>The pressure head at different sections of the pipe. (D)</p> Signup and view all the answers

What causes major energy losses in pipes?

<p>Friction between the fluid and the pipe walls. (D)</p> Signup and view all the answers

What indicates a sudden drop in pressure head at the entrance section of the pipe?

<p>A well-defined hydraulic gradient line becomes unclear. (D)</p> Signup and view all the answers

What represents the total energy of the fluid at any section of the pipe?

<p>Piezometric head equation (p/w + z). (D)</p> Signup and view all the answers

What is considered a minor energy loss in a pipe system?

<p>Sudden expansion of the pipe. (A)</p> Signup and view all the answers

At which section does the hydraulic gradient line meet the liquid surface?

<p>At the exit section of the pipe. (C)</p> Signup and view all the answers

Which formula is used for calculating major energy losses in pipes?

<p>Chezy’s formula. (A)</p> Signup and view all the answers

The height of the liquid surface in a piezometer reflects which aspect of a fluid in a pipe?

<p>The pressure intensity at that section. (B)</p> Signup and view all the answers

Flashcards

Minor Energy Losses

Energy loss due to changes in fluid velocity (magnitude or direction) in a pipe.

Obstruction in pipe

A blockage reducing the fluid's flow in a pipe

Major Energy Losses

Energy loss due to friction in a pipe

Total Energy Line (TEL)

Represents sum of pressure, datum, and kinetic energy of a flowing fluid in a pipe.

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Sudden Enlargement/Contraction

Causes energy loss in pipes due to changes in fluid velocity.

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Hydraulic Gradient Line (HGL)

A line representing the pressure head at different points in a pipe carrying a fluid.

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Piezometric head

The sum of pressure head and elevation head at a point in a pipe.

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Darcy-Weisbach equation

An equation used to calculate major energy loss due to friction in a pipe.

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Sudden expansion

A rapid increase in pipe diameter that results in a minor energy loss in fluid flow.

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Sudden contraction

A rapid decrease in pipe diameter that results in a minor energy loss in a fluid flow

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Study Notes

Hydraulic Gradient Line (HGL) and Total Energy Line (TEL)

  • Hydraulic Gradient Line (HGL): A sloping line plotted from pressure head measurements along a pipe. It represents the piezometric head at each point, which is the sum of pressure head (p/w) and elevation head (Z).
  • Pressure Head: The height of liquid in a piezometer above the pipe axis, directly related to pressure intensity.
  • HGL and Pressure Line: The vertical distance between the pipe axis and the HGL is equivalent to the pressure head.
  • Piezometric Head: The vertical height of the HGL above a datum, calculated as (p/w + Z).
  • HGL and Datum: HGL position above a datum point provides the piezometric head at each section.
  • HGL Entrance and Exit: Near the pipe entrance, the HGL isn't precisely defined due to pressure drop. At the pipe exit, the HGL meets the liquid surface of the reservoir.

Energy Losses in Pipes

  • Major Energy Losses: Energy loss due to friction within the pipe. Calculated using Darcy-Weisbach or Chezy's formulas.
  • Minor Energy Losses: Energy losses due to changes in flow velocity or direction (not friction).
    • Sudden pipe expansions or contractions
    • Pipe bends
    • Fittings and obstructions

Minor Energy Losses (Head Losses)

  • Definition: Energy loss due to velocity changes, distinct from major losses caused by friction.

  • Common Minor Loss Sources:

    • Sudden enlargements / contractions
    • Pipe entrance/exit
    • Obstructions within the pipe
    • Pipe bends
    • Pipe fittings
  • Significance: Minor losses are typically smaller than major friction losses in long pipes, but can be comparable in shorter pipes.

Total Energy Line (TEL)

  • Definition: A line representing the sum of pressure head, elevation head, and kinetic head for fluid flow in a pipe.
  • Calculation: Determined as the sum of pressure head, elevation head and kinetic head from the pipe center.
  • TEL vs HGL: The TEL is always above the HGL, and their difference represents the kinetic head for the flowing fluid at any point.

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