WATER RESOURCES MANAGEMENT

SUPER CRITICAL FLOW IN HUMPRASHID ALI (2012-BT-CIVIL-09) |

WATER RESOURCES MANAGEMENT

HumpIt is a structure or obstruction that is constructed across a river or stream to raise the level of water on upstream side so that it can be diverted to canals to meet the irrigation requirements. Super-critical flow.It is the flow for which Fraud’s number is greater than one.

Effect of hump on depth of flow and specific energyIf Q and S are constant and If the flow is super-critical flow, then the depth of flow over the hump will increase. the flow coming is sub-critical flow then the water level will be decreased due to the decrease in specific energy. Critical hump height: Min. hump height which can cause the critical depth or critical flow over the hump and is denoted by yc

Effect of hump height over flow conditions: If the u/s of the hump is super-critical flow, then the depth of flow increase.

When depth of flow is forced to change from a supercritical depth to a subcritical depthOr Froude number decreases from greater than 1.0 to less than 1.0. Jump does not occur from subcritical to supercritical flow – only vice versa.

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WATER RESOURCES MANAGEMENT

Specific Energy conditions in the Hydraulic jumpLoss of energyTheoretical depth after jump – alternate depthActual depth after jump – sequent depthLength of jump – varies – but about 7 times the subcritical depth.Practical applications of hydraulic jumps:Dissipation of energy of water flowing over dams and weirs – to prevent possible erosion and scouring due to high velocities.Raising water levels in canals to enhance irrigation practices and reduce pumping headsReducing uplift pressure under the foundations of hydraulic structuresCreating special flow conditions to meet certain special needs at control sections – gaging stations, flow measurement, flow regulation

Different Cases.Case A:

Conditions:

1. E2>Ec2. y1<yc

in other words a sub critical flow remain sub critical and a super critical flow remain super critical remain super critical.

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WATER RESOURCES MANAGEMENT

Case B:Conditions:

1. E2=Ec2. y1=yc

Case C:Conditions: it means the hump hight is to large and it chockes the flow,

1. E2<Ec2. y1>yc

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