Water- Jet Propulsion for High-Speed Surface Ships 



Asa result of this : 



- presetting of the figures mentionned in (ii) here above 

 takes account directly of the required thrust ; 



- the propeller thrust can be derived from the thrust measur- 

 ed on the "internal flow" model as described in paragraph 

 VI of our paper. 



As already mentionned the "complete flow approach" was a 

 simplified one which appeared to be applicable due to the reduced 

 contraction between the nozzle outlet and the jet diameter. (Diameter 

 ratio .95). 



According to this the downstream separating flow tube was 

 assumed to be the same as the "free-jet" flow surface. As indicated 

 in the paper, the slight discrepancy might be corrected through a li- 

 mited nozzle diameter adaptation if required. It must be noted here 

 that the "complete flow" test on the prototype did not give any evidence 

 of such effect, and no correction had to be applied. 



The determination of the "upstream separating surface was 

 made through the "potential flow approach" described in paragraph 

 V. 2. a and illustrated in Figure 1 1 attached to this annex. 



To conclude we would like to insist on the fact that the ac- 

 cordance between the "expected performances" (for instance thrust 

 versus r. p. m. etc) and the measured performances of the prototype 

 is quite satisfactory in the whole range of parameters. This, as well 

 as the relative simplicity of the approach, is, may be, the best justi- 

 fication for the way we followed. 



The tests in Toulouse have been continued through an im- 

 provement of the trailing edge of the nozzle (which was formerly un- 

 duly thick) the efficiency has been raised by more than 1%, the net 

 efficiency is then now a little more than 66, 5% . 



33 



