Tramshatt, verkar som jag läst betydligt fler poäng fysik än vad du har. Nedan följer ett utlägg:
...We've had a heated discussion over in Breitling forum. on this very topic of dynamic vs. static pressure and I think the differences are WAY overblown. Any arm movement, water current, shower head, water jet, or dive from a diving board, etc. simply cannot not add much INCREMENTAL dynamic pressure ABOVE what a watch is already experiencing at even ONE atmosphere of static pressure, or about 10 meters depth. If a watch is TRULY a 30 meter watch, and properly assembled, then nothing you encounter while swimming or free diving (from a board) should effect it (disregarding possible shock damage). My explanation is as follows...
: Consider that pressure at sea level (or the weight of one atmosphere) is equal to about 15 lbs/square inch (i.e. a vacuum will raise a 1 square inch column of water about 33 ft. at sea level, and this column weighs about 15 lbs.). Furthermore, this weight increases linearly as we descend down into the sea., i.e. pressure 66 feet down is equal to twice that of sea level, or two atmospheres. Furthermore, consider that Bernoulli’s law tells us that total pressure at any liquid depth is equal to static pressure + dynamic pressure. Given that we already know what static pressure is at any depth, we then need only concern ourselves with dynamic pressure – How much more would we ADD, by anything we might do or encounter, above what we already expect? That is, if a watch is rated for 10 atmospheres, what might be the maximum pressure that that watch might ever encounter, due to other conditions or circumstances, at any lesser depth? What might this be, as a maximum? As a generous estimate (interpolating from various on-line sources), I would say that no person could generate a velocity of greater than 50 feet/second (or 34 mph), either INTO or UNDER water, and survive. This is approximately the terminal velocity of a free dive into a pool from 150 feet (for reference, a sky diver generates a terminal velocity of only about 170 feet/second, or about 120 mph). That is, nothing you yourself could do, and no condition you could ever survive, would generate a momentary or continuous water velocity greater than 50 feet/second. So, 50 ft/sec = 600 inches/second. Therefore, any movement into or under water at any velocity up to 600 inches/second, would load 600 cubic inches of water onto every square inch of watch surface area, or .3472 cubic feet (i.e. 600 / (12*12*12)). At 62.427 lbs./cubic foot of water, this yields a pressure of 21.67 lbs./square inch, or about 1.44 atmospheres (21.67 / 15 lbs. per atmosphere) maximum momentary dynamic pressure. Note that this is a VERY generous maximum, and I stand by my assertion that no one is likely to EVER encounter or generate an INCREMENTAL pressure greater than 1 ADDITIONAL atmosphere above what the watch wearer is already experiencing in any given condition. Again, unless the watch is improperly assembled or specified, a true 10 atmosphere watch would NEVER experience a momentary pressure greater than 10+1.44 = 11.44 atmospheres at any depth UP TO 10 atmospheres. So, for a 30 meter watch, rated to 3 atmospheres, if you are able to free dive to 33 feet (and generate one atmosphere static pressure), you have my immense respect because your are in world class condition. Add 1.44 possible dynamic pressure and you're still below the 3 atmosphere total loading capacity of the watch. RIGHT?
Så det handlar inte om att jag inte förstått. Jag tror inte på det hen skrev, helt enkelt. Det lät inte rimligt.
