R/(R-R..) vs VV (a linear funetion), which is determined by 
compar! son with a calibrated pitot in different laminar 
velocities. 
The probe shown in Figure 3 has been used for both corre- 
lation and intensity measurements. The upper hot wire is fixed 
to the faired brass strut; the lower, is adjustable in the vertical 
plane by the micrometer screw as illustrated. Wire separation can 
be adjusted to a maximum of 3 inches *® 0.001 inch. The hot-wire 
tungsten elements are soft-soldered across two steel sewing needles 
which in turn are soldered to fine brass tubes connected to the lead 
wires, Since it is not possible to solder tungsten directly, the 
wire was first copper plated electrolytically except for the 0.20 
inch measuring section. 
TURBULENCE MEASUREMENTS IN THE MODEL CIRCULATING WATER CHANNEL 
Measurement of turbulence behind two geometrically : 
similar grids were conducted in the 1/22-scale model of the circu- 
lating water channel at the TMB. The experimental arrangement is 
illustrated in Figure 4. The hot wire probe was mounted in the 
channel at distances of 15, 20, and 25 mesh lengths downstream from 
erids of 4- and 3/4-inch mesh size. At each position, both corre- 
lation and intensity measurements of the created turbulence were 
obtained. The speed of the channel for all tests was approximately 
1.8 feet per‘second. 
The results of the experiment are illustrated in Figures 
5 through 8. In each instance it has been assumed that the turbu- 
lence was isotropic, and that the channel without the grid was 
nearly laminar. Actually, it is believed from preliminary measure- 
ments that a turbulence intensity of about 1% characterized the 
grid-free channel. , 
In Figure 6, correlations are compared with similar mea- 
surements made by Hall in a wind tunnel (5). Lack of close agree- 
ment between the two may be accounted for by the differences of the 
two media, differences in the initial turbulence of the stream, and 
insufficient correction of TMB results. Since these experiments 
are preliminary neither time constant compensation nor wire-length 
(1) corrections have been applied to the data. 
In spite of their preliminary nature, the TMB data con- 
firm qualitatively the law previously mentioned regarding the 
variation of scale with distance from the grid. Figures 6 and 7 
illustrate this in the increasing area under the correlation curves 
for the greater distances from the grid. 
The decay law of intensity, and its independence of 
Reynolds number are illustrated in Figure 8. Comparison of the 
Ae 
