22) PropilieuRe flectinalty. 
The changing Kp with the contour movements along the center ranges 
of each tank is compared in Figure 43. The Kp in experiment 72B-06 
(Fig. 43) fluctuated considerably during the first 5 hours as the major 
profile adjustments occurred. From 5 to 150 hours the mean K, gradu- 
ally rose, with fluctuations about the rising mean; the only profile 
changes were a gradual steepening of the upper part of the offshore 
between the -0.6- and -1.7-foot contours. | 
The K, in experiment 72B-10 (Fig. 43) was higher than in experiment 
72B-06. The Kp increased during the initial profile development (0 to ~ 
10 hours) and then fluctuated about an average 0.16 from 10 to 80 hours ; 
during a period when profile changes were minimal. The K, increased 
from 0.16 to 0.24 between 90 and 100 hours and then fluctuated about an 
average 0.21; the offshore zone developed steeper slopes between stations 
12 and 15 and between stations 18 and 20. 
IV. SUMMARY OF RESULTS 
1. Wave Height Variability. 
Four probable causes of the wave height variability measured in ex- 
periments 72B-06 and 72B-10 are (a) wave reflection from the changing 
profile, (b) re-reflection from the wave generator, (c) secondary waves, 
and (d) transverse waves. These experiments were designed primarily to 
quantify the amount of variability due to reflection from the profile, 
but the data were reduced in a manner which also allowed the quantifica- 
tion of the variability due to the transverse wave. 
a. Wave Reflection From the Profile. The Kp in the fixed-bed tanks 
did not vary greatly and there was no long-term increase or decrease in 
Kp in these tanks. The slight variation is a measure of the accuracy of 
the reflection measurements in the movable-bed tanks; the range of varia- 
tion was +0.015 in experiment 72B-06 and +0.035 in experiment 72B-10. 
The Kp in the movable-hed tank of experiment 72B-06 varied from 
0.03 to 0.14. During the first 30 hours the Kp fluctuated greatly, 
but the maximum values declined. After 30 hours the Kp again increased 
with continuing fluctuations about the increasing mean. These variations 
were not caused by any apparent change in profile shape. 
The average Kp in the movable-bed tank of experiment 72B-10 varied 
0.11 to 0.24 with a similar time variation. However, the increases in 
Kp in this tank coincided with increasing steepness of the offshore 
slope between stations 10 and 15. As the height of the .top of this 
steeply sloped section increased from -1.0 to -0.8 foot, the Kp 
increased. The variation of this critical elevation across the tank 
apparently caused corresponding variations in Kp: 
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