GENERAL PRINCIPLES OF HYDRAULICS 455 
the velocity of approach, for values of the head between 10 feet and 
14. The following results were obtained during an experiment to determine 
the quantity of water which would be discharged t — a small circular orifice 
in the side of a tank. The diameter of the orifice, which had sharp edges, was 
Number of experiment . 
: , : : . ‘ 1 2 3 4 
| Duration of experiment ; : - minutes | 15 15 | 15 15 
e . lbs. | 57 660 | 733 827 
| Head of water above centre of orifice . _ inches | 15 20 | 25 | 827 
| Number of experiment . 
> ; ; ‘ ‘ 5 6 7 8 
Duration of experiment wy a hntw nlebesi 88 15 | 10 10 
Actual discharge . . . Ibs. | 915 | 1011 | 737 788 
g Head of water above centre of orifice f inches | 4°01 50 | 60 70 
Plot on squared paper a curve to show the relation between the discharge 
in lbs. per minute and the head of water above the centre of the orifice. From 
_ your curve determine the discharge in gallons per hour when the head of water 
_ was 54 inches. 
Plot also on squared paper a curve to show the relation between the discharge 
in tbs. per minute and the square root of the head of water above the centre 
of the orifice. From your curve, what would you consider the relation to be 
between the quantity of flow and head? 
Determine for each of the experiments in the above table the “ coefficient of 
discharge” for this orifice, and plot a curve to show the relation between 
* coefficient of discharge” and head of water. [B.E.] 
15. Water flows through a sharp-edged circular orifice 0°3 inch in diameter 
in the side of a tank, The head of water above the centre of the orifice is 4 feet. 
The jet poe through a ring whose internal diameter is slightly larger than 
that of the jet, and the centre of this ring is found to be 48 inches horizontally 
and 13°1 inches vertically from the centre of the vena contracta. In 5 minutes the 
weight of water discharged is 90°2 lbs. Calculate the coefficients of discharge, 
_ velocity, and contraction for this orifice. 
16. If the miner’s inch is defined as the flow through an orifice 1 inch square, 
in a vertical plane, under the head of 6} inches measured to the centre of the 
orifice, and if the flow is found to be 14 cubic feet per minute, what is the 
coefficient of discharge ? 
17. A tank 10 feet square and 10 feet deep has a circular orifice 4 inches 
diameter in the bottom, which may be regarded as a thin plate. Water is 
admitted to the tank until it is full, and is then shut off. In how many seconds 
will the tank be empty ? [Inst.C.E.] 
; 18. A rec ular chamber 120 feet square contains 15 feet depth of water, 
_ which is allowed to flow out through a vertical rectangular orifice 2 feet by 1 
foot, the top of which is level with the floor of the reservoir and tail-water. 
Calculate the time it will take to empty. [Inst.C.E.] 
19. Two chambers with vertical sides, each £0 square feet in area, are 
connected by means of a rectangular sluice, 3 feet by 2 feet, near the bottom. 
One chamber contains water to a depth of 25 feet, and the other a depth of 
10 feet. If the sluice is opened, find how long it will be before the water is 
at the same level in the two chambers. {Inst.C.E.] 
20. Find the answer to the preceding exercise when the chamber in which 
the depth of the water is 10 feet has an area of 80 square feet instead of 50 
Square feet, the other particulars being the same. 
21. A hemispherical cistern is 20 feet in diameter, and it is full of water. 
How many minutes will it take to lower the depth of the water 5 feet, if the 
water escapes through a 3-inch diameter sharp-edged hole in the bottom of 
the cistern? The coefficient of discharge for the hole is 0-60. [U.L.] 
22. A cylindrical tank 2 feet in diameter and 6 feet high is full of water. 
On opening an orifice 1 inch in diameter in the bottom of the tank it is found 
