# What is physics behind of explosion under Atmospheric pressure?

An explosion is a rapid increase in volume and release of energy in an extreme manner. A blast wave in fluid dynamics is the pressure and flow resulting from the deposition of a large amount of energy in a small very localised volume. The equation for a Friedlander waveform describes the pressure of the blast wave as a function of time:

$$P(t)=P_oe^{-\frac {t}{t^*}}(1-\frac {t}{t^*})$$ where P$_o$ is the peak pressure and t$^*$ is the time at which the pressure first crosses the horizontal axis (before the negative phase).

My Question: Why does the pressure temporarily drop below ambient after the wave passes?

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Ehh... what exactly do you need to know? –  Deer Hunter Jul 16 '13 at 4:51
Are you asking why the pressure temporarily drops below ambient after the initial blast wave passes? –  Michael Brown Jul 16 '13 at 5:33
Yes thats what i want to know –  Neo Jul 16 '13 at 6:09