v = 20 DEG 
NO SCREEN 
PROPELLER 4661 4710 
AR 0.67 0.63 
} 45 90 135 180 225 270 315 360 
WAKE POSITION ANGLE, Oy, (deg) 
vy =0DEG 
WITH SCREEN 
PROPELLER 
) 45 90 135 180 225 270 315 360 
WAKE POSITION ANGLE, @y (deg) 
Fig. 3 — (Continued) 
Figure 3 shows that the variation 
of the longitudinal velocity component 
ratio Vx/V behind the wake screen is 
approximately a step function, as was 
expected. However, the high velocity 
region covers a smaller portion of the 
propeller disk than the low velocity 
region, whereas it was anticipated that 
the two velocity regions would each 
cover essentially half of the disk. 
This suggests that there is some cross 
flow between the propeller and the 
screen. This non-symmetry of the wake 
profile causes no problem regarding the 
objectives of the present investigation 
since it remains the same for all 
experimental conditions. 
Experimental Conditions and Procedures 
The propeller was located 
approximately 16 in (0.41 m) downstream 
of the screen for all conditions for 
which the screen was used. A 4.0 ft by 
2.0 ft by 0.375 in (1.22 m by 0.61 m by 
9.5 mm) plate was positioned parallel to 
the flow above the propeller for all 
experimental conditions. For Propeller 
4402 at 10 degrees inclination, the 
plate clearance from the tip of the 
propeller was varied from 1.0 in (0.025 
m) to 20 in (0.51 m). For all other 
conditions the plate clearance was 
approximately 20 in (0.51 m). With this 
clearance, the plate was 2 in (0.051 m) 
below the water surface. The plate at 
this location was used to minimize any 
possible effects of the free surface on 
the propeller performance. 
The experimental conditions are as 
follows: 
ave No Wake Screen, w = 10 deg, 
Propellers 4661, 4710, and 4402. 
Qi No Wake Screen, = 20 deg, 
Propellers 4661, and 4710. 
3% Wake Screen, » = 0 deg, 
Propellers 4661 and 4710. 
4. No Wake Screen, wW = 30 deg, 
Propeller 4661. 
For each condition, the carriage 
speed was held constant and propeller 
rotation speed, n, was varied to obtain 
the desired range of advance 
coefficient, J. For each condition, the 
carriage speed for the blade loading 
Measurements was the same as the 
carriage speed for the corresponding 
wake survey. 
The first three conditions 
represent the more important types of 
experiments performed. The wake surveys 
were conducted at these conditions. The 
fourth condition was run to obtain 
limited data at a very large value 
of ~ so that the variation of loads 
with ~ could be better defined. Due to 
limited time, however, only the Fy and 
My components were measured on Pro- 
peller 4661, and no measurements were 
made on Propeller 4710. In addition, no 
wake survey was conducted at this 
condition due to limitations of the wake 
Survey apparatus. 
For each of these conditions, 
experiments were conducted over a range 
of advance coefficient J. For each 
