Physics:Overpressure
Overpressure (or blast overpressure) is the pressure caused by a shock wave over and above normal atmospheric pressure. The shock wave may be caused by sonic boom or by explosion, and the resulting overpressure receives particular attention when measuring the effects of nuclear weapons or thermobaric bombs.
Effects
According to an article in the journal Toxicological Sciences,
Blast overpressure (BOP), also known as high energy impulse noise, is a damaging outcome of explosive detonations and firing of weapons. Exposure to BOP shock waves alone results in injury predominantly to the hollow organ systems such as auditory, respiratory, and gastrointestinal systems.[1]
An EOD suit worn by bomb disposal experts can protect against the effects of BOP.[2][3]
| Overpressure | Effects |
|---|---|
| 1 pound per square inch (6.9 kPa; 0.069 bar) |
|
| 2 pounds per square inch (14 kPa; 0.14 bar) |
|
| 3 pounds per square inch (21 kPa; 0.21 bar) |
|
| 5 pounds per square inch (34 kPa; 0.34 bar) |
|
| 10 pounds per square inch (69 kPa; 0.69 bar) |
|
| 20 pounds per square inch (140 kPa; 1.4 bar) |
|
Calculation for an enclosed space
Overpressure in an enclosed space is determined using "Weibull's formula":[4][5]
[math]\displaystyle{ \Delta p = 22.5 \left( {m \over V} \right)^{0.72} \text{bars} }[/math]
where:
- 22.5 is a constant based on experimentation
- [math]\displaystyle{ m\, }[/math] = (kilograms) net explosive mass calculated using all explosive materials and their relative effectiveness
- [math]\displaystyle{ V\, }[/math] = (cubic meters) volume of given area (primarily used to determine volume within an enclosed space)
See also
References
- ↑ "Pulmonary Biochemical and Histological Alterations after Repeated Low-Level Blast Overpressure Exposures", Nabil M. Elsayed, and Nikolai V. Gorbunov, Toxicological Sciences, 2007 95(1):289-296 , online version 2006, http://toxsci.oxfordjournals.org/cgi/content/abstract/95/1/289
- ↑ Pavlus, John (March 4, 2010). "Real-life Hurt Locker: how bomb-proof suits work". http://dvice.com/archives/2010/03/hurt-locker-sui.php.
- ↑ "1) Effects of blast pressure on the human body". https://www.cdc.gov/niosh/docket/archive/pdfs/niosh-125/125-explosionsandrefugechambers.pdf.
- ↑ Weibull, Hans R. W. (1968). "Pressures Recorded in Partially Closed Chambers at Explosion of TNT Charges". Annals of the New York Academy of Sciences 152 (1): 357–361. doi:10.1111/j.1749-6632.1968.tb11987.x. Bibcode: 1968NYASA.152..357W.
- ↑ , Frank T. & Cristobal Bonifaz"Laboratory barricade" US patent 4474052, issued October 2, 1984
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