Flow in Open Channel

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QUESTION

1. Verify the forc forcee of the stream stream on either either side side of the jump jump is the same and and that the specific energy cure predicts a !oss e"ua! to

∆ H / dc

.

 F before = F after #. Su Sugg gges estt app! app!ic icat atio ion n $her $heree the the !oss !oss of ener energy gy in hydr hydrau au!i !icc jump jump $ou! $ou!d d %e desira%!e. &o$ is the energy dissipated'

The hydraulic jump flow process can be illustrated by use of the specific energy concept. Equation energy dissipated can be written in the term of the total head loss: 2

(

2

V  V  ∆ H = d a + a − d b + b 2g 2g

Wher Wheree

da

is the depth depth of flow flow before before hydrau hydraulic lic jump (m),

elocity before jump (m!s),

db

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)

V b

V a

  is the mean

 is the mean elocity after hydraulic jump (m) and

 is the depth of flow after hydraulic jump (m).

(IS)USSION " hydraulic jump can be iewed as discontinuous waes of all frequencies

(waelengths), which are generated and propagate from a point near the jump. The waes propagate both upstream and downstream. #ince a large fraction of the waes fall in a waelength range where they are shallow water graity waes that moe at the same speed for a gien depth, they moe upstream at the same rate.

$oweer as the water shallows upstream, their speed drops quic%ly, limiting the rate at which they can propagate upstream. #horter waelengths, which propagate more slowly than the speed of the wae in the deeper downstream water, are swept away downstre downstream. am. " fairly wide range range of waelen waelength gthss and freque frequenci ncies es are still still

 present, so &ourier would suggest that a relatiely abrupt wae front can be formed and this is indeed obsered in practice. 'ne of the most important engineering applications of the hydraulic jump is to dissipate energy in channels, dam spillways, and similar structures so that the ecess %inetic energy does not damage these structures. The energy dissipation or loss across a hydraulic jump is a function of the magnitude of the jump. The larger the jump as epressed in the fraction of final height to initial height, the greater the head loss. #ome of the errors occurred during measurements by ta%ing erroneous reading of  depths and in operation of sluice gates.

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)ON)+USION The conclusion from this eperiment, we can inestigate the characteristic a

standing wae (the hydraulic jump) produced when water beneath an undershot weir  and obsere the flow patterns obtained. &rom the eperiment, we can get the force at weir opening. n the water channel, water following rapidly changes to slower tranquil flow a hydraulic jump or standing wae is produced. This phenomenon can be seen where water shooting under a sluice gate mies with deeper water downstream. t occurs when a depth less than critical changes to a depth which are greater than critical and must be accompanied by loss of energy.