FREE - SURFACE EFFECTS IN HULL PROPELLER 
INTERACTION 
Horst Nowacki 
Untverstty of Michtgan 
Ann Arbor, Mtchtgan, U.S.A. 
Som D. Sharma 
Hamburg Shtp Model Bastn 
Hamburg, Germany 
ABS TRACT 
The quantitative role of wavemaking at the free sur- 
face in the phenomenon of hull propeller interaction 
is investigated by means ofa general scheme devised 
to determine the potential, viscous and wave compo - 
nents of wake and thrust deduction. It requires the 
concerted application of various analytical tools such 
as the lifting line theory of propellers, the method 
of singularities for representing the hull and propel- 
ler by source distributions and the linearized free- 
surface theory of wavemaking, as well as model ex- 
periment techniques suchas the conventional Froude 
analysis of propulsion factors, nominal wake mea- 
surements and wave profilemeasurements. The pro- 
cedure is actually applied to the specific case ofa 
thin mathematical hull form driven by a four-bladed 
propeller of simple geometry. It is found that the 
wave component is dominant inthe wakeand quite si- 
gnificant in the thrust deduction at Froude numbers 
around 0.3. Surprisingly, there seems to be an ap- 
preciable viscous component in the thrust deduction 
at practically all Froude numbers. 
1845 
