Ike Measurement of the six components 
of blade loading under various 
idealized conditions including: 
a. In inclined flow without an 
upstream hull. 
b. In a once-per-revolution 
variation of longitudinal flow 
produced by an upstream 
wire-grid screen. 
Cre Over a range of propeller 
advance coefficients. 
d. Over a range of clearances 
between the propeller tip and 
a flat plate above the 
propeller. 
2. Measurement of the field point 
velocities induced by a propeller 
operating in inclined flow. 
Bie Measurement of the pressure 
distribution on the surfaces of the 
blades of two propellers operating 
in inclined flow. 
This paper presents the results of 
the blade loading experiments under 
idealized conditions, and correlation 
with available theories including one 
which considers the influence of 
slipstream for operation in inclined 
flow. These results supercede the 
preliminary results presented in 
Reference 10. More details of these 
results will be presented in future 
DTNSRDC Reports. The field point 
velocity measurements were reported in 
Reference 11. The results of the blade 
surface pressure measurements will be 
presented in a future DTNSRDC Report. 
EXPERIMENTAL TECHNIQUES 
The experiments were conducted on 
DTNSRDC Carriage 2. The propellers were 
mounted at the front of the downstream 
drive system containing the dynamometer 
and the drive motor. This system was 
the same as that used in the experi- 
ments described in detail in References 
2 and 3 except that the downstream body 
was modified so that it could be 
operated fully submerged. The 
modifications included a waterproof 
housing for the drive motor, waterproof 
electrical cables and connectors, 
removal of the upper apron which had 
extended the sides of the boat, and the 
addition of a non-waterproof top to the 
boat. 
The sensing elements were flexures 
to which bonded semi-conductor 
strain-gage bridges were attached. 
Three flexures were necessary tO measure 
all six components of forces and 
Moments. Flexure 1 measured Fy and 
My, Flexure 2 measured Fy and My, 
and Flexure 3 measured Fz and Moi 
see Figure 1. The flexures were mounted 
\ 
inside a propeller hub specifically 
designed for these experiments. Only 
one flexure could be mounted at a time 
because of space limitations, and this 
necessitated three duplicate runs for 
each condition. The flexure calibration 
procedure was identical to that 
described in References 2 and 3. 
Wake Screen and Wake Survey 
A 16-inch (0.405 m) diameter wake 
screen designed to produce a dominant 
first harmonic of the circumferential 
variation of the axial velocity, was 
used in the experiments. This screen 
consisted of simply a base screen with 
one overlay screen and no support 
members in the region through which flow 
is drawn into the propeller disk. 
Wakes were measured for three 
different flow regimes: 
Ls Shaft inclination = 10 deg with 
no wake screen, 
De y 20 deg with no wake screen, 
3a w 0 deg with the wake screen. 
Figure 3 shows the velocity 
component ratios at the radial position 
near r=0.7R at which the various wake 
surveys were conducted. The 
circumferential variations of the 
velocity component ratios in the axial, 
tangential, and radial directions 
contained primarily first harmonic 
components. 
¥ = 10 DEG 
NO SCREEN 
PROPELLER 4661 4710 | 4402 
oR 0.67 | 0.63} 0.60 
2 0 
> 
02 =| 
0 45 90 135 180 225 270 315 360 
WAKE POSITION ANGLE, dy (deg) 
Fig. 3 — Distribution of Wakes in 
Propeller Disks 
