DRAGON: Ten link normalne funguje. Zkus ho jeste jednou. Autor se tvari, ze prave fyzika je jeho vec. Niz kopiruju to, co jsem puvodne vkladal, ale i se vzoreckem. Na vlozeni celeho toho prispevku je to moc dlouhy .
The increase in pressure can be calculated.
The increase will be equal to the one half the density times the velocity squared, or
ΔP = (1000 x V2)/2
with
ΔP = increase in pressure in pascals
1000 = density of fresh water, in kg/m3, use 1030 kg/m3 if seawater,
v = velocity in m/s
(To convert pascals to atm multiply by .00001)
Doing the math, you can see that in order to raise the pressure by 1 atm the watch must be traveling at 14.25 m/s. That's about 51 km/h or 32 mph.
If you can get your arms to move that fast under water, please see your local Olympic committee, you are a due for some swimming medals this summer in London.
If you are at normal scuba diving depths (50 to 60 meters) you will have to be moving faster than a nuclear submarine to exceed the depth rating of a 100 meter rated watch. (Note: most of your military submarines do not operate deeper than 300 meters.....)
But, that’s not all. Dynamic pressure only reaches its maximum at the stagnation point, which will be the point where the flow lines run into a 90 degree face. Let’s look at Figure 1, below, here we have a sphere in a fluid flow, a) shows the flow lines, and b) show the pressure distribution. You can see the maximum pressure occurs only on the front face and drops off as you move around the body, and when you get to the top the pressure is actually below ambient.
So, we can see that the flow around a watch traveling through the water will see the “increased pressure” only on the leading surface. If the leading surface is not a gasket/case mating surface, then there is no increase in pressure on gasket.