410 HYDRAULICS AND ITS APPLICATIONS 



in the direction of the jet with a velocity of 80 feet per second, determine 

 the efficiency of the arrangement. 



(6) Two free jets of sectional area 2 square inches and 1 square inch, 

 and of velocities 20 f.s. and 30 f.s., are inclined to each other at an angle 

 of 60, and combine to form a single stream. Determine the direction 

 and velocity of this stream and the loss of energy at impact. 



Eesultant stream makes an angle of 31 58' with 



direction of first stream. 

 Answer. y e i oc i ty = 2106 feet per second. 



Loss of head = 80'3 feet Ibs. per second. 



(6) A jet propelled vessel has a wetted surface area of 800 square feet, 

 and a coefficient of resistance of "004. If the area of the nozzle openings 

 is 3'0 square feet, determine the maximum theoretical efficiency of the 

 jet considered as a propeller. Also, assuming the pump efficiency to be 

 50 per cent, and the mechanical efficiency of the engines to be 85 per cent., 

 determine the efficiency of propulsion. 



A (Efficiency = '836. 



(Total efficiency = '355. 



(7) If the boat of the preceding example is travelling at 12 miles per 

 hour, determine the necessary jet velocity and the discharge per second, 

 for maximum efficiency. 



Ans er ' Velocity =24*56 feet per second. 

 (Discharge = 2'05 tons per second. 



(8) Water flows at 20 feet per second through a 6" pipe forming a 

 right-angled bend. Find the magnitude of the resultant force tending 

 to move the pipe. 



Answer. 215 Ibs. 



(9) A jet delivering 3 cubic feet of water per second at 100 feet per 

 second impinges tangentially on one of a series of vanes moving at 50 feet 

 per second in a direction inclined at 20 to that of the jet. If the vanes 

 deflect the jet backwards so that its final direction of motion is the same 

 as that of the vane, and if the final relative velocity of jet and vane is 

 *8 times the initial relative velocity, determine the pressure on the vane 

 in its direction of motion. 



Answer. 515 Ibs. 



(10) In the Greyhound, length 160 feet ; breadth 88| feet ; draught 13J 

 feet ; displacement, 1,160 tons ; the wetted area is 7,540 square feet. The 



