Hadler and He eke r 



Propeller 3820 



Fig. 20 - C^ - 77q - J diagram of propeller 3820 partially submerged 



and comes largely from the exit side of the propeller. In this flow regime, as 

 the advance coefficients were reduced toward the transition regime, there 

 seemed to be a cavity starting from the leading edge on the suction face as the 

 blade entered the water surface which became slightly larger as the advance 

 coefficient was reduced. In this regime there did not appear to be any change 

 of water-level flow into the propeller, except at the very lowest test speed of 

 5.18 ft/sec, where there appeared to be an actual lowering of the water surface — 

 suggesting that there may have been a wave effect. 



At transition there was a very marked change in the flow pattern. The spray 

 became much more intense and extended considerably higher into the air. The 

 intensification seemed to be most marked on the entry side of the propeller. It 

 was noted on most tests that in the region of transition there was strong forced 

 vibration of the propeller and propeller shaft. 



1470 



