3. Determining free-field overpressures

3.1 Preamble

Assessing the effects of a gas explosion on the environment or on a structure mainly involves characterizing the overpressure field caused by the propagation of the overpressure wave from the source of the explosion.

The airborne overpressure wave propagating from the explosion site is called the incidental or free-field overpressure. This is the explosion overpressure without interference from any obstacles that may modify the flow characteristics, and in particular induce local amplification phenomena.

The overpressure wave can be broken down into two terms, the effects of which can be significantly different at obstacles:

• a "static" overpressure or "blast" in the sense of...