Friedlander Waveform
Definition
The idealised time-pressure history at a point in air following a blast: instantaneous rise to peak overpressure at shock arrival, exponential decay through the positive phase, then underpressure below ambient in the negative phase.
- Field
- Blast dynamics
- Shape
- Instant rise, exponential decay, negative phase
- Positive phase
- Overpressure above ambient
- Negative phase
- Underpressure below ambient
Common questions
Why does the Friedlander waveform show a negative phase after the positive overpressure decays?+
As the blast wave expands, the compressed air behind the shock front rushes outward faster than it can be replenished, creating a momentary partial vacuum relative to ambient pressure before conditions equalise, which produces the characteristic dip below atmospheric pressure.
How is the Friedlander waveform used in forensic explosion investigation?+
Investigators compare measured or estimated peak overpressure and decay time against the idealised waveform to back-calculate charge weight and standoff distance, and deviations from the idealised shape can indicate reflected shocks, confined venting, or a non-ideal (deflagrative) rather than detonative event.
Related terms
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- Chapman-Jouguet (CJ) Condition
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- Deflagration-to-Detonation Transition (DDT)
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- DMDNB Taggant
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- Dynamic Pressure
- The pressure component due to mass flow of gas behind the shock front, proportional to gas velocity squared; the blast wind that...
- 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...