Daniel Butler asked:
Speed fast, can make raindrops shattered windshield.
Junius (via xkcd) Answer:
Call out ~
Rain, more tender little things. Even the most driving rain, raindrops in the air all add up all the air than light (which is one of several reasons for God you can not swim in the rain in). Even if you put the pedal to the floor into a single raindrop strength also hurt less than the windshield shred.
Therefore, under normal conditions, rain is resolved to not think of going to harm the windshield, but they certainly can be a threat to supersonic aircraft.
We look at the process of high-speed movement of the raindrops hit the glass:
When the water droplets in contact with the glass surface, a Unit Sasser drops back to pass back to itself.
Under normal circumstances, Sasser to the propagation velocity of sound in water - presumably propagation speed of 1300 meters per second, four times faster than air. However, due to the high-speed crash, this time the shock wave propagation velocity of sound in water is higher than the theoretical speed.
Drops due to their own motion, and the surface of the glass barrier is squeezed to squeeze along the edges of four broken splash. These stirring spill has reached supersonic speed than the initial velocity drops faster, faster than the transfer rate at this time of Sasser.
There is a paper, which did an experiment, let water droplets at a rate of 500 meters per second (Mach 1.5) hit the surface of the measured speed of the water droplets splashing broken up 6000 meters per second --19 Mach. (Note 1: This really is a substance to accelerate good way to six kilometers per second I wonder if anyone ever tried to do this to create a spacecraft propulsion.)
The impact force from the shock wave can be dramatically shattered glass. Where the greatest force is located in the edge of the contact surface raindrops, but there is only a very short time.
Surprisingly, there are a lot of experiments to study the problem, we may need a lot of high-speed flight research encountered in all kinds of weather conditions.
Since the vertical pressure acting on the surface that is hit, broken glass splash drops as would cause harm if the glass surface with tiny bubbles and cracks, these pieces will splash of water droplets to expand these scars.
Although the high-speed impact, the water drops will not produce that kind of injury bullet holes, but high density supersonic raindrops attack, the glass surface will be a little bit of erosion, fragmentation into small blizzard. (Such damage can also be found on the turbine blades), and thus, the windshield so the final play of the egg.
Fortunately, you can not bring the car to the ground than Mach 1, the conventional heavy rain also can not hurt your windshield. However, if you are in the strong convective thunderstorm days driving ......
Windshield crack will be very beautiful, but there are even better. Compared to drive to find a storm, I prefer the car parked, then stared at the lights on the dashboard in a daze, those strange things are more blurred than Guangguai broken glass pattern.
...... Hard "precipitation" as the paper put your windshield.
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