(1) Positive Phase p-T Curves. For the positive phase of a blast

wave, it is suggested that a close approximation of the p-T curve can be

obtained by using the following relationship:

EQUATION:

Ps = Pso(1 - ts/to)e -[alpha](ts/to)

(13a)

where,

Ps

=

pressure at time ts

Pso

=

peak incident pressure

ts

=

positive phase time of interest

to

=

positive phase duration

[alpha]

=

constant that determines the form of the p-T curve

The values of [alpha] can be expressed as a function of constant, k, which,

in turn, is defined as:

EQUATION:

k = is/Psoto

(13b)

where is, Pso, and to are obtained from Figure 4-5 of NAVFAC P-397.

The numerical relationship between k and [alpha] is listed below:

k

0.70

0.60

0.50

0.40

0.30

0.20

0.10

[alpha] - 0.93

- 0.52

0

0.71

1.77

3.67

8.87

To simplify the solution, normalized plots of the positive phase p-T curve

as a function of k values are presented in Figure 7a. For pressures up to

10 psi, these curves are applicable to both incident and reflected

pressures.

(2) Negative Phase p-T Curves. The negative pressure curve can be

approximated by a cubical parabola expressed as:

_

_

_

_

_

_

EQUATION:

Ps = Pso(6.75ts/to)(1 - ts/to)2

(14a)

where,

_

_

Ps

= negative pressure at time ts

_

Pso

= peak incident negative pressure

_

ts

= negative phase time of interest

_

to

= negative phase duration

2.08-19