Stilling basin

Types of Stilling Basins

1. Types  of Hydraulic Jump For hydraulic jump to occur, upstream flow  must   be   supercritical  ( F    >  1) Type of jump  depends  on value  of F1

2. Types of Hydraulic Jump

3. Hydraulic  jumps used downstream of gates  & other structures  to dissipate  energy   & avoid damage   downstream Best  for design: “Steady Jump” 4.5 <  F <  9.0 Avoid  “Oscillating Jump”   2.5 <  F <   4.5

4. Stilling  Basins Use  stilling basin to initiate jump Allows dissipation of  energy  within a structure that  will minimize  damage Baffle blocks used to make jump  position more  stable

5. Stilling  Basins: Design Considerations Length  of  jump Governs length of stilling basin Approximately   6  y2 for    4.5 <  F1 < 13 Surface profile of jump – Governs height of sidewalls of – Dictates pressure on floor of basin – Depends on y 1 and F 1 Control  of jump ( 1) Chute  Blocks (2 ) Baffle  Blocks (3 ) End Sill Components  used to initiate jump, stabilize  jump ,  &  make basin as short as possible

6. Control of jump by baffle piers

7. Control of jump by baffle piers

8. Stilling Basin Design General stilling basin designs from USBR–Types I II III and IV based on   F 1 Type I: 1.7 <  F 1 <  2.5 Weak  jump No  special structures  needed 4 . 5 < F < 9 for best design Type  II or III stilling  basin Type II 4.5 < F 1

9. TYPE III 4.5 < F 1 Use for incoming velocity V1 < 60 ft/s

10. Use for incoming velocity  V1 > 60 ft/s Dentated sill, no baffle blocks TYPE II 4.5 < F 1

11. Type  IV 2.5 < F 1 < 4.5 Oscillating  Jump,  unstable No baffle blocks because of wave action