THE SHAPE OF THE BLAST WAVE: STUDIES OF THE FRIEDLANDER EQUATION

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THE SHAPE OF THE BLAST WAVE STUDIES OF THE
FRIEDLANDER EQUATION
by John M. Dewey Dewey McMillin
Associates 1741 Feltham Road, Victoria BC
Canada (www.blastanalysis.com)
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Characteristic Shape
Ps
t
t
t
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Friedlander 1946

• Friedlander suggested that the classic
• pressure time-history could be described by

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Press. vs Time 523.5m SB ANFO 2.205 kt (MINOR
UNCLE)
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Friedlander Fit
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Density vs Time
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Total (Pitot) Pressure vs Time
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Dynamic Pressure (½?u2) vs Time
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Friedlander Fails at Higher Overpressures

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Modified Friedlander Equation

• Additional coefficient a

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Properties of Friedlander Equation

• Impulse in positive phase

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Properties of Friedlander Equation

• Total Impulse

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Properties of Friedlander Equation

• Minimum Pressure

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Blast Wave Profile

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Blast Wave Profile

• Low Overpressures

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Particle Tracer Photogrammetry

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Spherical Piston Path

MISERS GOLD 2.445 KT ANFO SURFACE BURST
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Friedlander Fit to Piston Path

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Conclusions

• The time histories of the physical properties of
  centered blast waves are well described by the
  Friedlander equation at peak overpressures less
  than 1 atm.
• 2. The wave profiles of the physical properties
  are well described by the Friedlander equation at
  peak overpressures greater than 1 atm.

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Conclusions

• The trajectory of the spherical piston that
  drives a centered blast wave has the form of the
  Friedlander equation
• 4. Are there physical reasons why it should be
  expected that a point source release of energy
  would generate a spherical piston path of this
  shape?

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Properties of Friedlander Equation

• Relaxation Time t