Day 32-Oct 21-worksheet-Diploma-Notches&weirs

In a suppressed rectangular weir, ventilation beneath the nappe is essential primarily to

• Increase crest length

• Reduce velocity of approach

• Avoid negative pressures below nappe

• none

For a triangular notch, discharge sensitivity with respect to head measurement is high because

• Q ∝ H²

• Q ∝ H^3/2

• Q ∝ H^5/2

• Q ∝ H^0.5

The main hydraulic reason for providing bevelled upstream edges in sharp-crested weirs is to

• Increase coefficient of discharge

• Promote uniform overflow

• Avoid clinging of nappe

• Reduce approach velocity

In stepped notches, increase in total discharge takes place mainly due to

• Progressive submergence of lower steps

• Successive triangular contributions

• Incremental rectangular areas at each stage

• none

In a triangular weir, a small percentage error in head measurement produces a larger percentage error in discharge compared to a rectangular weir.

• True

• False

Suppressed weirs do not require ventilation of nappe since there is no contraction.

• True

• False

Assertion (A): Ventilation holes are provided on the downstream side of a suppressed rectangular weir. Reason (R): They ensure continuous atmospheric air supply beneath the nappe to prevent vacuum formation.

• A and R are true; R is the correct explanation

• A and R are true; R is NOT the correct explanation

• A is true but R is false

• A is false but R is true

The sheet of water flowing over the crest of a weir is called (a)   .

In a trapezoidal (Cipolletti) weir, the side slopes are provided to eliminate the effect of (a)   .

The ……… of a weir is the top surface over which flow takes place.

(a)