The term alternate depth is used in open channel flow to denote the depths 

Explanation:

• In open channel flow, alternate depths refer to two different flow depths that correspond to the same specific energy for a given discharge.

• For a rectangular channel and constant discharge, two different depths — one subcritical (deep and slow) and one supercritical (shallow and fast) — can have the same specific energy. These are called alternate depths.

• Alternate depths are two different flow depths that exist for the same specific energy at a given discharge in a channel.

• They occur in a channel when the flow shifts between supercritical and subcritical regimes, but total specific energy remains the same.

• Example:

  • For a given discharge, a shallow and fast flow (supercritical) and a deep and slow flow (subcritical) can have the same specific energy.

  • These two depths are known as alternate depths.

 Additional Information

• A hydraulic jump is a sudden transition from supercritical flow (fast and shallow) to subcritical flow (slow and deep) in an open channel. This occurs to conserve energy and momentum when flow velocity decreases rapidly due to downstream conditions.

• It typically forms when high-velocity water is discharged into a channel with a mild slope, causing the water to rise abruptly and form turbulent eddies. The upstream depth is low, while the downstream depth increases sharply after the jump.

• Hydraulic jumps are characterized by intense turbulence, surface rollers, and energy loss in the form of heat, noise, and air entrainment. Despite these losses, the momentum across the jump is conserved.

• The location and formation of a hydraulic jump are influenced by the Froude number before the jump. A Froude number greater than 1 indicates supercritical flow, which is a necessary condition for a jump to occur.