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Hydraulic Jump Phenomena

Explore the fascinating phenomena of hydraulic jumps, from theory to practical applications, with examples from nature and industry. Learn about different types of jumps and their crucial role in dissipating energy and reducing damage to structures.

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Hydraulic Jump Phenomena

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  1. Water Can Jump!!!!Hydraulic Jump Phenomena Bader Anshasi Matthew Costello Alejandra Europa Casanueva Robert Zeller

  2. Introduction • Due to excess kinetic energy (Fr>1) • Results in "jump" to a higher fluid height • Increase in Potential Energy • Seen both in nature and industry • Rapids, waterfalls • Dams, spillways • Primary function is to dissipate energy • Increased Turbulence • Reduce erosion • Reduce damage to structures

  3. Examples

  4. Hydraulic JumpTheory

  5. Jump Requirements • Occurs during “Rapidly Varied Flow” • When flow depth changes rapidly in the direction of flow within a short length • Flow changes from supercritical to subcritical condition

  6. Froude’s Number • “Rapidly Varied Flow” can be characterized by the Froude’s Number • Fr =1at critical flow • V = velocity, g = gravitational constant, y = depth • A hydraulic jump occurs because of Fr changes: • Fr1 >1and Fr2 <1

  7. Phenomena • Flow depth increases abruptly with the formation of eddy currents • Kinetic energy is converted to potential energy • Results in a change of height • When eddies downstream of the jump break up, the fluid entraps air • The fluid loses energy after a jump • Leading to many practical applications

  8. Types of Hydraulic Jumps

  9. No hydraulic Jump • Fr<1 • Theoretically this would be a negative hydraulic jump, i.e. the fluid depth will decrease • Only physically possible if some external force accelerates the fluid at that point

  10. Undular Jump • For (1 < Fr1<1.7) • Characterized by: • Slight undulation • Two conjugate depths are close • Transition is not abrupt – slightly ruffled water surface

  11. Weak Jump • For (1.7<Fr1<2.5) • Characterized by: • Eddies and rollers are formed on the surface • Energy loss is small • The ratio of final depth to initial depth is between 2.0 and 3.1

  12. Oscillating Jump • For (2.5 <Fr1<4.5) • Characterized by: • Jet oscillates from top to bottom – generating surface waves that persist beyond the end of the jump • Ratio final depth to initial depth is between 3.1 to 5.0 • To prevent destructive effects this type of jump should be avoided

  13. Stable Jump • For (4.5<Fr1<9) • Characterized by: • Position of jump fixed regardless of downstream conditions • Good dissipation of energy (favored type of jump) • Considerable rise in downstream water level • Ratio of final to initial depth is between 5.9 and 12.0

  14. Strong or Rough Jump • For (Fr1 > 9) • Characterized by: • Ratio of final to initial depth is over 12 and may exceed 20 • Ability of jump to dissipate energy is massive • Jump becomes increasingly rough • Fr1 should not be allowed to exceed 12

  15. Hydraulic Jump Applications

  16. Practical applications • Engineers design hydraulic jumps to reduce damage to structures and the streambed • Proper design can result in a 60-70% energy dissipation • Minimizes erosion and scouring due to high velocities • Dams, weirs and other hydraulic structures

  17. Other Practical Applications • Recover pressure head and to raise water levels downstream of a canal • Maintain a high water level for irrigation or other water-distribution purposes • Mix chemicals in water purification • Aerate water for city water supplies • Remove air pockets from water to prevent air locking in supply lines

  18. Recreational Applications • Traveling down rivers/rapids • Kayaking and canoeing: playboat/surf hydraulic jumps

  19. Conclusion • An ideal design for energy dissipation would result in a “Stable Jump” • Characterized by a 4.5<Fr1<9 • Position of jump is fixed • Provides the most effective energy dissipation • Protects the structures and streambed by reducing velocity • Energy dissipation ranges from 45-70%

  20. Demonstration • Representing a hydraulic jump in your sink: Shallow fluid • A smooth flow pattern forms where the water hits • Further away, a sudden hydraulic jump occurs • Specific characteristics of this jump: • Water flows radially and it continues to grow shallower • It slows down due to friction (decrease in Froude number) up to the point where the jump occurs • From supercritical to subcritical flow • Diameter of the jump decreases as water depth increases.

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