172 



HYDRAULICS AND ITS APPLICATIONS 



EXAMPLES. 



(1) A lock, 1,000 square feet area, is filled through a submerged orifice 

 3 feet long by 2 feet deep. The depth of water above the centre of this is 

 initially 19 feet on the outside and 7 feet on the inside. Assuming a 

 coefficient of discharge of '61, determine the time occupied in filling the 

 lock if the outside level remains constant. 



Answer. 236 seconds. 



(2) Assuming the level on the lower side of the above lock to remain 

 constant, determine the time of emptying the lock, the sluice being the 

 same size as on the entry side. 



Answer. 236 seconds. 



(3) Using Francis' formula, determine the discharge over a rectangular 

 notch 36 inches long, and with heads of 3, 6, and 12 inches. 



(a) With no side contractions 



(b) one 



(c) two 



Answer. 



(4) A submerged weir, 10 feet long, has a depth of water on the up- 

 stream side of 17 inches, on the down-stream side of 9 inches. The 

 velocity of approach = 1'96 feet per second. Assuming the head equiva- 



v 2 

 lent to this velocity of approach to be given by h = 1*4 ^ , determine the 



* 9 



discharge in cubic feet per minute. Assume c = -592. 

 Answer. 3,090 cubic feet per minute. 



(5) Show that in a triangular right-angled notch, discharging from a 

 tank of sectional area A square feet, the time of lowering the surface level 

 from HI feet to H* feet above the vertex of the notch is given by 



