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 Jump Theory

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 =1 at critical flow
𝐹𝑟= 𝑉 𝑔𝑦
V = velocity, g = gravitational constant, y = depth
A hydraulic jump occurs because of Fr changes:
Fr1 >1 and 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 𝑦 1 𝑦 0 = 1+8 𝐹𝑟 2 −1 2
𝑦 1 𝑦 0 = 𝐹𝑟 2 −1 2
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.