monotonically with advance coefficient over the range evaluated. As the 
advance coefficient based on thrust effective wake, Jp=Jy -wy) increases 
from 0.63 (at V=2.65 knots) to its design value of 1.14 (at V=6.52 knots), 
= decreases from 0.76R to 0.71R whereas i increases from 0.66R to 
mE Vy 
0.74R. This variation in he is the reason that (@ /E y< 
oh H,MAX “H,SP 
OL /M ) as discussed in the preceeding paragraph. 
Yu,MAX H,SP 
For all loading components, the variation with blade angular posi- 
tion tended to be dominated by the first harmonic for all conditions 
throughout the simulated acceleration maneuver. For all conditions at 
which there was significant variation in loading with blade angular posi- 
tion, the maximum and minimum values for all components except ES and Mm 
occurred for the blade spindle axis near 9=135 or 315 degrees (blade tip 
near §=115 or 195 degrees). This suggests that the variation in loading 
with blade angular position is produced primarily by the circumferential 
variation of the tangential velocity in the propeller plane (see Figure 
10). The angular variation of each loading component retained basically 
the same shape independent of speed and advance coefficient. 
There was a dramatic reduction in the circumferential variation of 
all measured loading components with decreasing speed V and decreasing 
rotational speed n. Previous data have shown that for a given propeller 
in a given flow field, the circumferential variation in the hydrodynamic 
loading varies approximately as the product of ship speed V and rotational 
speed n; see Wersidisma. = Figure 26 presents results in a form which 
allows evaluation of how closely the measured unsteady loading varies with 
nV. The ordinate is the first harmonic of the components of hydrodynamic 
blade loading except Fo ,» which is very small, and the abscissa is nV. 
H 
The data shown in Figure 26 indicate that the first harmonic of each of 
the presented hydrodynamic loading components is approximately proportion- 
al to nV. 
= isseeiidieme R., "Tendencies of Marine Propeller Shaft Excitation," 
International Shipbuilding Progress, Vol. 19, No. 218, pp 328-332 (Octo- 
ber 1972). 
40 
