Q1: The phenomenon occuring in an open channel when a rapidly flowing stream abruptly changes to a slowly flowing stream causing a distinct rise of liquid surface, is

ANS:B - hydraulic jump

The phenomenon occurring in an open channel when a rapidly flowing stream abruptly changes to a slowly flowing stream causing a distinct rise of liquid surface is called a hydraulic jump. In a hydraulic jump, there is a sudden change in the depth and velocity of the flowing water. This occurs when supercritical flow (fast, shallow flow) transitions to subcritical flow (slow, deep flow). The kinetic energy of the rapidly flowing stream is converted into turbulence and potential energy as it encounters a higher depth of water, resulting in the rise of the liquid surface. Hydraulic jumps are commonly observed in various hydraulic engineering applications, such as spillways, dam outlets, and rivers. They play a significant role in dissipating energy and controlling water flow in open channels. Therefore, the correct phenomenon described in the scenario is a hydraulic jump.