Free Surface Effects in Hull Propeller Interactton 
IV. CONCLUDING REMARKS 
It has been demonstrated by practical application to a speci- 
fic example that our conceptual scheme for determining the potential, 
viscous and wave components of wake and thrust deduction is indeed 
workable. It has required the concerted application of miscellaneous 
analytical, computational and experimental techniques, The varying 
degrees of success achieved with the individual techniques have been 
discussed in detail in the appropriate sections and need not be repeat- 
ed here. Several results were obtained by more than one method, for 
instance by independent calculation and measurement, and in most 
cases there was fair agreement, at least there were no striking con- 
tradictions except perhaps in the calculated and measured wavemaking 
resistance at low Froude numbers, which came as no surprise. 
It would be rash to try to derive general conclusions concern- 
ing the quantitative role of wavemaking at the free surface in the phe- 
nomenon of hull propeller interaction on the basis of one single exam- 
ple. However, two salient results do seem to have a broader signifi- 
cance. First, it was found that contrary to common belief the wave 
component can be dominant in the wake and quite significant in the: 
thrust deduction at Froude numbers around F, = 0.3. Second, there 
seemed to be an appreciable viscous component in the thrust deduc- 
tion at practically all Froude numbers. Moreover, the undulating va- 
riation of this component with Froude number points to a complicated 
interaction of viscous boundary layer, hull wave pattern and propeller 
suction near the stern, 
These two effects are of direct relevance to the hydrodyna- 
mic design of fast ships and also to the methods of extrapolating pro- 
pulsive performance from model to full-scale. 
It is recommended that further studies of this nature be under- 
taken to resolve the remaining issues and to collect systematic design 
data on the effect of wavemaking on the propulsive performance of 
ships. 
V. ACKNOWLEDGMENTS 
We want to sincerely thank the following individuals and orga- 
nisations for their valuable contributions to this project : 
Mr. J.L. Beveridge and Dr. W.B. Morgan of the Naval Ship 
Research and Development Center for crucial consultations in the 
planning stage of this work, 
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