Panel Discussion 



Fig. 3b - Curves of incipient cavitation phe- 

 nomena o£ screw of the B 5-75 series 



Propulsion tests with ship models in a towing tank are carried out under 

 atmospheric pressure (thus, a relatively high pressure). The consequence is 

 that during a propulsion test in a towing tank no cavitation occurs as it does in 

 reality. The arrangement as indicated in Fig. 4 forms the first part of a re- 

 search on the consequences of neglecting of cavitation during propulsion tests 

 in a towing tank. The effect of cavitation on propeller- hull interaction and on 

 propeller -induced dynamic transverse forces will form the most important 

 research items of ship propulsion in the coming years. It might be that the 

 results of this research will prove that the results of a propulsion test in a 

 conventional towing tank are inadequate both for quantitative predictions and 

 qualitative selections. 



In Fig. 6. an example has been given of an extension of the "open-water" 

 screw diagrams of the Wageningen B- series. This extension refers to the so- 

 called "four -quadrant" measurements. The thrust coefficient C^ and the 

 torque coefficient Cq are given for the following conditions: 



1579 



