Dynamic Pressure
Definition
The pressure component due to mass flow of gas behind the shock front, proportional to gas velocity squared; the blast wind that propels fragments and exerts drag on structures and bodies.
- Relation to velocity
- Proportional to gas velocity squared
- Also known as
- Blast wind
- Distinct from
- Static overpressure (the crushing component)
- Main hazard
- Fragment propulsion and drag loading on structures/bodies
Common questions
How does dynamic pressure differ from overpressure?+
Overpressure is the static crushing force that acts equally on all surfaces, while dynamic pressure is the drag force from moving air mass, acting mainly on the side facing the blast. Both arise from the same shock front but injure and damage by different mechanisms.
Why does dynamic pressure matter for injury interpretation?+
It explains translational injuries, being thrown into objects and struck by flying debris, which are classed as tertiary and secondary blast injury respectively. Overpressure alone accounts mainly for primary blast injury to air-filled organs.
Related terms
- Brisance
- The shattering power of a detonating explosive, distinct from heave (bulk displacement). Measured by the Trauzl lead block test. High-brisance explosives (RDX,...
- Chapman-Jouguet (CJ) Condition
- The steady-state condition in a detonating explosive at which the coupled shock and reaction zone travel at the same velocity (the detonation...
- Deflagration-to-Detonation Transition (DDT)
- The acceleration of a deflagrating burn front to supersonic detonation velocity, triggered by confinement. Relevant to understanding how improvised devices using low...
- DMDNB Taggant
- Dimethyldinitrobutane, a detection marker incorporated into plastic explosives (including Semtex) under the ICAO 1991 Convention on the Marking of Plastic Explosives; allows...
- Friedlander Waveform
- The idealised time-pressure history at a point in air following a blast: instantaneous rise to peak overpressure at shock arrival, exponential decay...
- Hopkinson-Cranz Scaling
- The law relating peak overpressure and positive-phase duration to the ratio of range to cube-root-of-charge-mass (the scaled distance Z = R /...
- Mach Stem
- The reinforced shock front that forms near a reflective surface when the direct blast wave and its reflected wave merge, producing anomalously...
- Mott Formula
- An empirical relationship, derived from wartime UK research by N.F. Mott, predicting the statistical distribution of fragment masses from a metal casing...
- Peak Static Overpressure (Ps)
- The maximum pressure increase above ambient at the shock front, the primary structural damage parameter, scaling with the inverse cube root of...