EAH 225- HYDRAULICS (OPEN CHANNEL)

In a uniform open channel flow,

• the total energy remains constant along the channel

• the total energy line either rises or falls along the channel depending on the state of the flow

• the specific energy decreases along the channel

• the line representing the total energy is parallel to the bed of the channel

The term alternate depths

in open channel flow is used to designate the depths

• At the beginning and end of a hydraulic jump

• Having same kinetic energy for a given discharge

• Having same specific energy for a given discharge

• At the beginning and end of a gradually varied flow profile

For a given discharge, the critical flow depth in an open channel depends on

• channel geometry only

• channel geometry and bed slope

• channel geometry, bed slope and roughness

• channel geometry, bed slope, roughness and Reynolds number

A submerged weir is one in which the water level on the downstream of the weir is

• Is above the crest level

• Just at the crest level

• Below the crest level

• At the same elevation as the upstream water surface

The flow in a horizontal, frictionless rectangular open channel is supercritical. A smooth hump is built on the channel floor. As the height of hump is increased, choked condition is attained. With further increase in the height of the hump, the water surface will

• rise at a section upstream of the hump

• drop at a section upstream of the hump

• rise at the hump

• drop at the hump

A trapezoidal channel is 10.0 m wide at the base and has a side slope of 4 horizontal to 3 vertical. The bed slope is 0.002. The channel is lined with smooth concrete (Manning’s n = 0.012). The hydraulic radius (in m) for a depth of flow of 3.0 m is

• 20

• 3.5

• 3

• 2.1

A rectangular open channel needs to be designed to carry a flow of 2.0 m³/s under uniform flow conditions. The Manning’s roughness coefficient is 0.018. The channel should be such that the flow depth is equal to half the width, and the Froude number is equal to 0.5.

The bed slope of the channel to be provided is

• 0.0012

• 0.0021

• 0.0025

• 0.0052

The sequent depth ratio of a hydraulic jump in a rectangular channel is 16.48.

The Froude number at the beginning of the jump is

• 5.0

• 4.0

• 8.0

• 12.0

The Froude number at the end of a hydraulic jump in a rectangular channel is 0.25. The sequent depth ratio of this jump is

• 2.5

• 5.2

• 8.9

• 9.8

The velocity and depth of flow in a 3.0 m wide rectangular channel are 2.0 m/s and 2.5 m, respectively. If the channel has its width enlarged to 3.5 m at a section, the discharge past that section is

• 10.0 m³/s

• 20.0 m³/s

• 15.0 m³/s

• 17.5 m³/s