ABSTRACT 
Periodic single-blade loads were 
Measured on model propellers in inclined 
flow and in a single-cycle circumferen- 
tially non-uniform longitudinal velocity 
field. The experimental results were 
correlated with predictions by the 
following methods: 
Ike A quasi-steady procedure developed 
by McCarthy at David W. Taylor 
Naval Ship Research and Development 
Center (DTNSRDC), 
Be An unsteady lifting surface theory 
developed by Tsakonas and his 
colleagues at Davidson Laboratory, 
336 An unsteady lifting surface theory 
developed by Kerwin and Lee at MIT, 
4. A refinement by Kerwin to the 
method of Kerwin and Lee to con- 
sider the inclination of the pro- 
peller slipstream. 
In inclined flow, all four of the 
calculation methods evaluated consis- 
tently underpredicted the experimental 
values of the periodic single-blade 
loads. The method of Kerwin, which 
considers the inclination of the slip- 
stream relative to the propeller axis, 
produced the best correlation with ex- 
perimental values. These correlations 
show that the inclination of the pro- 
peller slipstream relative to the pro- 
peller axis significantly influence the 
periodic single-blade loads. The impor- 
tance of this inclination increases with 
increasing timeaverage loading. 
In longitudinal flow, all of the 
calculation procedures predicted period- 
ic singleblade axial force at design 
advance coefficient to within 20 percent 
of the experimental values, but agree- 
ment waS not as good at off-design ad- 
vance coefficients. The method of 
Kerwin and Lee produced the best overall 
correlation with experimental results 
considering both amplitude and phase of 
the periodic single-blade axial force 
over a range of advance coefficients. 
NOMENCLATURE 
R 
Ar Expanded area, Z| cdr 
Th 
Ao Propeller disk area, 
mD2/4 
c Blade section chord length 
Fx,y,2 
V 
VA 
Vr (©, 8y) 
Ve (Ll, Ow) 
Vx (rl, Ow) 
VvM 
Propeller diameter 
Force components on blade 
in x,y,z directions 
Advance coefficient, 
J=Va/nD 
Torque coefficient, 
Q/ (on2p9) 
Thrust coefficient, 
T/ (pn2p4) 
Moment components about 
x,y,z axes loading on one 
blade 
Propeller revolutions per 
unit time 
Propeller blade section 
pitch 
Time-average propeller 
torque arising from 
loading on all blades, 
-2My 
Radius of propeller 
Radial coordinate from 
propeller axis 
Time-average thrust of 
propeller, positive 
forward, ZF x 
Model speed 
Propeller speed of advance 
Radial component of wake 
velocity, positive towards 
hub 
Tangential component of 
wake velocity, positive 
clockwise looking 
upstream for left-hand 
propeller, positive 
counter-clockwise looking 
upstream for right-hand 
propeller 
Longitudinal component of 
wake velocity, positive 
forward 
Volume mean longitudinal 
velocity through propeller 
disk determined from wake 
survey 
