The overpressure magnitude is characterized as the static pressure after the hammer shock, normalized by the steady-state pressure before the hammer shock.
Peak magnitude of the engine-face waveform was set to an overpressure ratio of 1.
The peak overpressure ratio is normalized by the ratio at the engine face.
Normalized peak overpressure ratio could be correlated with inlet diffusion area ratio (AR); this correlation is illustrated in the figure shown on this page.
This inlet, shown in the figure on page 112, matched the actual F-16 NSI in length and area distribution, both of which are believed to be the critical design parameters when considering overpressure strength.
The inlet/splitter geometry was run steady-state at the peak overpressure flight condition for the F-16 NSI with an F100-PW-200 engine (Mach 1.
Both types of exit boundary conditions produce the same peak overpressure strength, because the duct is long enough to develop a normal shock capable of yielding the same strength at the throat as a normal shock generated at the engine face.
A comparison between the 3-D CFD results to the existing F-16 characteristic overpressure ratio distribution shows that the peak inlet overpressure distribution is a collation of peak magnitudes of the hammer-shock waveform along the NSI duct, while the peak overpressure ratio is calculated at every station and normalized by the engine-face overpressure ratio.
The incident overpressure of explosion shock front and the duration of pressure increase depends on two parameter: the distance between the centre of explosion and subjected structure R and the equivalent mass of explosives Q.
The uncertainties in mathematical model of overpressure and time dependence and the uncertainties in the deterministic mechanical models used for the assessment of strains and strain rates of concrete and reinforcing steel require stochastic modelling of the enhancement factor for the evaluation of dynamic material properties.