# Shock Front Velocity

Not Reviewed
Equation / Last modified by cataustria on 2015/07/05 20:02
"Shock Front Velocity" =
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cataustria.Shock Front Velocity
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174226c0-1148-11e5-a3bb-bc764e2038f2

The Shock Front Velocity Calculates the velocity using the speed of sound, peak on-side pressure and ambient pressure.  This is part of the Rankine-Hugoniot equations.

Note: speed of sound in dry air (343.2 m/s) as the default.  Condition outside of dry air (e.g. underwater) will warrant another value.

## Ambient Pressure

The ambient pressure on an object is the pressure of the surrounding medium, such as a gas or liquid, which comes into contact with the object.

### Atmosphere

Within the atmosphere, the ambient pressure decreases with height above ground and by measuring ambient atmospheric pressure, a pilot may determine height (see pitot-static system). Near the ground, a change of ambient pressure of 1 millibar is taken to represent a change of height of 9 metres (30 ft).

### Underwater

The ambient pressure in water with a free surface is a combination of the hydrostatic pressure due to the weight of the water column and the atmospheric pressure on the free surface. This increases approximately linearly with depth. Since water is much denser than air, much greater changes in ambient pressure can be experienced under water. Each 10 metres (33 ft) of depth adds another bar to the ambient pressure.

Ambient pressure diving is underwater diving exposed to the water pressure at depth, rather than in a pressure-excluding Atmospheric diving suit suit or submersible.

### Ambient Pressure Examples

• Top of Mount Everest  - 0.333 atm
• Pressurized passenger aircraft cabin altitude 8,000 ft (2,400 m) -  0.76 atm
• Sea level atmospheric pressure  - 1 atm
• 10m depth in seawater  - 2 atm
• 20m depth in seawater  - 3 atm
• Recreational diving depth limit (40m) - 5 atm
• Common technical diving depth limit (100m) - 11 atm
• Deepest point in the Earth's oceans - 1100 atm

### Resource:

• "Formulae for Ammunition Management." International Ammunition Technical Guideline. 1st ed. New York: UN, 2013. 2-3. UN SaferGuard. United Nations Office for Disarmament Affairs (UNODA), 20 May 2013. Web. 12 June 2015. <http://www.un.org/disarmament/convarms/Ammunition>.
• Wikipedia: en.wikipedia.org/wiki/Ambient_pressure