pressure vessel explosion

Hi All,

I am structural engineer who do not know very well fluid mechanics. I have got two following problems:

  1. I am looking for simple formula which can aproximately determine very fast flow from a tank. Tank is filled by air with some positive pressure outflowing to ambient neighbourhood. I would like to estimate time of flow and make a graph of inside pressure versus time.
  2. I would like to estimate pressure distribution versus time and distance from simple explosive charge in air. (i.e. round 100g of TNT) Do you know any solutions (even aproximate) for such problems? Maybe you can suggest me any good books or other souruces (like web based) when I can find any clue?

Best regards, Marian

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This is a standard time dependant gas dynamics problem. Solved for instance in Gas Dynamics by John.

---------- Ed Ruf Lifetime AMA# 344007 (

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Reply to
Ed Ruf

How simple do you want to go?

Simpler means further from reality, as always.

1) How about this : P = Pamb + Pmax * exp( -kt)

P is instantaneous pressure as fn of time Pmax is starting pressure (gage) k is a scaling const t is time in seconds Pamb is atmospheric ambient pressure.

2) model a supersonic transient pressure wave whose decreasing pulse height times its increasing toroidal volume is constant (to represent conserved energy)

I hope you realise I just made these up off the top.

Surely you can do better with diligence?

Brian Whatcott Altus OK

Reply to
Brian Whatcott

I believe your first question has been answered.

As for your second question, there is a chart that shows the decrease in the pressure of a spherical shock wave as it propagates away from the central point where it was initiated by a sudden energy release.

My recollection is that the x-axis of this chart is the distance from the explosion divided by the cube root of the energy released by the explosion, expressed as an equivalent number of pounds of TNT. The y-axis is the shock overpressure.

Many charts of this type have been published in cold-war-era publications on nuclear weapon effects (including the infamous nuclear weapon effects slide rule), but these might not cover your range of interest.

This url is much too long, but try:

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You might try searching for keywords such as spherical shock, blast effects, Hopkinson-Cranz, airblast.

Olin Perry Norton

Reply to
Olin Perry Norton

The blast wave charts you want can be found in:

Structures to Resist the Effects of Accidental Explosions, NOV 1990, TM-5-1300


A Manual for the Prediction of Blast and Fragment Loadings on Structures, Baker, Wilfred E.; Kulesz, James J.; Westine, Peter S.; Cox, Phineas A.; Wilbeck, James S. AUG 1981, DOE/TIC-11268

Both of these reports are available on-line through

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Reply to
Olin Perry Norton

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