were quite distorted and non-ideal in character, as shown {n Figure 2.2.
All of these
gage stations were located near the edge of the water, except for the measurement on
Shot 6 which was preceded by some 600 feet of blast travel over an island surface; the
latter record showed only a slightly rounded wave form with a peak dynamic pressure
in good agreement with that value computed from the measured overpressure. For those
dynaric pressures measured near the edge of the water, it was assumed that the blast
wave picked up water droplets which contributed to the disturbed appearance of the wave
form and that water is not an ideal surface.
The primary objective in taking dymamic-pressure measurements was 2 study of the
pressure-time records to check the theoretical relation between dynamic pressure and
TABLE 2.3 COMPARISON OF MEASURED AND CALCULATED VALUES
OF DYNAMIC PRESSURE
—"
,
Type of Gage
pat
pat
pai
6
S/R* Pitot static
im
168.0
138.0
0.83
6
S/R® Pitot statlo
32.8
19.6
23.5
1.20
4
é
B/R®° Pitot static
Diff pree q
Drag q
4.3
23.2
23.3
11.7
10.7
11.7
138.0t
1.00
1.21
6
6
8/R* Pitot static
Pitot statio
22.4
10.2
10.4
1.00
4
@
6
8/R* Pitot statio
S8/R* Pitot static
3/R°* Pitot statio
20.0
19.0
16.8
8.17
78
6.08
9.20
8.8
8.6
1.138
1.37
0.92
4
Of pres q
14.46
4.3
7.0t
1.83
4
Drag q
148
43
7St
1.74
3
3
3/R* Pitot static
U/R* Pitot static
1.31
046
1.1
0.77
0.84
1.67
5
3
3
S/R* Pitot static
S/R* Pitot static
Caloaetns
10.7
21.0
8.8
7.62
443
3.20
3.28
0.34
0.25
sonmred
Ratio of
Measured q
to Calculated q
Sho:
L3.3t
8.5
0.47
0.60
1.24
0.96
1.38
2.00
“S/R refers to salf~recording mechanica) gages of Project 1.2b (BRL). Al) other
gages are electronic gages employed by Project 1.3 (BC).
t Maximum value of q which fs indicated here ocourred at a later time than maximum value of Ap.
overpressure.
From a somewhat-limited quantity of data, it was found that the relation
did not hold where the path of the blast wave approaching the gage station was over a
water surface. Table 2.2 shows a comparison of measured and calculated values of dynamic pressure.
2.3.8 Dynamic Pressure ag a Damage Parameter. Jeeps were used as representative
models to investigate further the role of dynamic pressure as the damage parameter to
consider for drag-sensitive targets. Participation was planned for two shots, one of
which was cancelled; actual participation was accomplished on Shots 3 and 6. The low
yield of Shot 3 gave low dynamic pressures and consequent light damageto vehicles.
Satisfactory damage—-light to severe -—was attained on Shct 6.
The limited data obtained were not conclusive enough to permit an evaluation of dynamic pressure as a damage parameter to be applied to the jeep as a drag-~-sensitive
target. The response of such a target depends on the loading, which is a function of both
dynamic pressure and duration. The results obtained did not allow a separation of the
effect of the one damage parameter from that of the other.
Furthermore, it was not possible to determine specific levels of dynamic pressure
for different degrees of damage. Consequently, it was difficult to justify the cube-roct
25