in the machine operation, and may be eliminated by, for example, always 
starting the machine with the generating blade in the same position, In 
addition, baffles have been attached to the wavé-generating bulkheads and 
are being studied for effectiveness in reducing parasitic crossS-—waves. 
Consideration is now being given to the possibility that some of the ef- 
fect may result from slightly changed reflection patterns caused by slight 
changes in the beach face due tothe incident wave action. In the meantime, 
accurate determination of the incident wave conditions for the littoral 
tests, or rather, interpretation of the wave records obtained during these 
tests, remains a problem. In general, incident wave values are obtained 
from a 1 to 2 scale model of the generating system in a narrow wave flume, 
in which reflection-caused resonance phenomena are not a problem. 
Two of the tests conducted this past fiscal year were used as the 
vehicle for radioactive and luminescent tracer studies. The primary pur- 
pose of these tests was to develop procedural techniques, although limited 
research objectives were also explored. In both tests, glass grains con- 
taining an irradiated element, having the same specific gravity and size 
distribution as the beach sand, were injected onto the beach. Following 
injection, waves were generated at an angle to the beach, moving material 
alongshore, The first test involved a wave of constant height and period, 
and the second a wave of varying characteristics. The beach and bottom 
were periodically sampled to allow counts of luminescent and radioactive 
grains, and a radiological survey was made with a scintillation counter. 
The tracer used in the first test was sodium 24 (with a half-life of 15 
hours), and the tracer in the second test was lanthanum 40 (with a half- 
life of 40 hours). The techniques used and the data collected inthe first 
test are presented in a report, "Laboratory Applications of Radioisotopic 
Tracers to Follow Beach Sediments", by N. E. Taney in the Proceedings of 
the 8th Conference on Coastal Engineering, Council on Wave Research, 
Engineering Foundation (1963). Particle velocity in the second test was 
as great as 15 feet per minute. Maximum depth of burial of tracer part- 
icles, determined from a relatively small number of cores, was 0.1 foot. 
Analysis of the data gathered from the fluorescent samples is still under- 
way with particular attention now being applied to determination of size 
of sample and number of samples required in such tests to give statistical 
validity to the resulting grain count contours. 
(e) Measurement of Suspended Material in Laboratory Wave Tanks. 
Additional suspended samples were obtained under wave action using a 
pump-type sampler in a wave flume testing crushed coal rather than sand. 
It is hoped that these measurements may aid in defining scale relations by 
comparison with prototype measurements. An eductor type sampler was tested 
in conjunction with other tests in the large tank, and found satisfactory. 
It provides certain advantages and convenience of use over the previously 
used centrifugal pump-type sampler. 
(f) Equilibrium Profile, Beach Deformation, and Model Scale Effect 
Studies. 
Testing was continued in a small tank using low specific gravity 
crushed coal to study the effect of scale on movable bed models under 
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