Delta P
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2019 / 07 / 20

Delta P is the difference in pressure between two masses. When the difference is large enough, it can have some rather disturbing effects.

Pressure differential is extremely important in diving. Carbonated water does not appear to have any bubbles when sealed because the pressure increases within the container until the carbon dioxide gas is unable to overcome the pressure and be released. But when the container is opened, the air pressure at the top drops significantly and the carbon dioxide is able to once again be released from the water. This is basically what happens when a person returns from a deep dive or becomes exposed to the vacuum of space. The higher pressure enables more gas to be dissolved into their blood. Rising too fast or being suddenly exposed to vacuum causes the gasses to bubble out in the blood, resulting in decompression illness which can be fatal. This is why divers must ascend very slowly or use a decompression chamber where they can slowly return to atmospheric pressure in a comfortable environment over the course of hours or even up to a day.

A greusome example of Delta P is the 1983 Byford Dolphin incident. Byford Dolphin is a drilling platform off the coast of Norway. The incident occured when four divers returned from a deep dive. Their pressurized diving bell was attached to a similarly pressurized decompression chamber. The four men entered the decompression chamber. As they went to seal the chamber from the diving bell, one of two outside tenders prematurely detached the diving bell. This caused the air to rush out of the small opening, instantly killing the tender who caused the accident. The sudden large change in pressure instantly killed the three inside from pressure effects while the fourth diver, who was securing the seal, was pulled through a small opening, causing all of his internal organs to be forced out onto the boat, flying up to 10m (30ft) in all directions.

While these are examples of sudden drops in pressure, a sudden rise in pressure is just as fatal. A major lethal force in explosions is the shockwave, which is a sudden increase in pressure caused by the force of the explosion. This pressure crushes air cavities in the body, causing damage to the ears, lungs, and gastrointestinal system.
Mythbusters - Dumpster Diving, 2009
Releasing the air pressure on an old-fashioned diving suit containing a modified pig carcass produces a grim look at the dangers early divers were faced with.
The classic imploding barrel science experiment. The barrel is heated, capped, then cooled to create a high pressure differential, causing catastrophic failure.
unknown source
A safety test showing the effects of a failed window in an aircraft. In April of 2018, a commercial 737 jet had a window failure when an engine exploded, throwing shrapnel into the window. The higher cabin pressure rushed out pulling a passenger along with it up to her waist. The woman died but the plane landed safely.
The Backyard Scientist, 2015
A demonstration of the effects of pressure from an explosion in water. While the heat and shrapnel of an explosion is diminished in water, the pressure wave is much more intense due to water being thicker and less compressible.
unknown source
A crab getting sucked into a pipe with a much lower pressure than the surrounding water.