138 WAVE IMPACT ON 



to, or discharged from, the pipe. In the impact experiments 

 the coil was filled through this valve up to the point ' A, 9 care 

 being taken to displace all air. A jet of water from a 1 J-in hose 

 was then suddenly deflected into the open end of the horizonta 

 pipe ' <7,' an indicator diagram being taken simultaneously at 

 the lower end of the coil. 



TANK _~i v/ 



/r 

 A 



E 



Cl 



5) 



FIG. 2 



The length of the horizontal pipe ' C ' was varied in these 

 experiments from 5 inches to 70 inches. In some of the 

 experiments with a view of ensuring that the phenomena 

 should be due to air compression alone, the interior of this pipe 

 was bored out to a smooth parallel surface and the jet was 

 directed on to a light easily fitting piston placed immediately 

 inside its open end. In other experiments, flow was allowed 

 to take place through the valve towards the open end of the 

 coil so as to keep the latter full of water, and impact took 

 place on to the end of this moving column of water, thus 

 simulating the state of affairs which exists during wave 

 impact on a joint which is discharging water from a cavity 

 under pressure. In other of the experiments the horizontal 

 pipe was removed and the jet played vertically downwards 



