It's not unusual to meet rain in the wild. For field sports enthusiasts, an impact suit with good waterproof function is a must-have. The waterproof function of impact clothing is closely related to its waterproof index.

Let's take a brief look at this index first. Their unit is millimeter water column pressure. The usual explanation is that when a 10000mm high water column is pressed on the fabric and the water seeping from the fabric does not exceed 3 drops within 24 hours, then we think the waterproof index of this garment is 10000mm.

Therefore, there are the following questions: what is the difference between 3000mm, 6000mm waterproof pressure and 10000mm waterproof pressure? What kind of impact clothing should I buy? Obviously, the higher the waterproof index, the stronger the waterproof function, and of course the higher the price. The key to choosing the impact clothing under what target depends on your own practical needs, and the right one is the best. If it is only used for inter-city tours and daily field clothes, the waterproof index is 3000mm to 5000mm. If it is a quasi-professional field hiking, camping or crossing activity, the impact clothing with a waterproof target of 6000mm to 8000mm is enough to cope with it. However, if you need to go to an environment with relatively difficult natural conditions for professional mountain climbing, exploration and other field activities, it is best to choose impact clothing with a waterproof index of more than 10000mm.

We often hear that the rainproof of this impact garment reaches the 6000, and the rainproof index of that impact garment is 10000. The 6000 and 10000 here, they're in millimeters of water pressure. The usual explanation is that when a 10000mm high water column is pressed on the fabric and the water seeping from the fabric does not exceed 3 drops within 24 hours, then we think the waterproof index of this garment is 10000mm. So someone asked, what is the difference between 6000mm waterproof pressure and 10000mm waterproof pressure? What kind of target impact clothes should I buy? Wait for similar questions. Well, let's start from the beginning.

The closing speed of raindrops

If there is no air (resistance), the clouds on the day will fall after turning into rain. After passing through the accelerated movement all the way, the speed when reaching the ground will reach 300 m/s, which is equivalent to half the speed of a bullet. There will be no living creatures on land. Thank God, due to the existence of air resistance, when raindrops form and begin to fall, they move faster (the acceleration degree gradually decreases) through a short time. When the air resistance of raindrops is equal to their own gravity, OK, at this time, raindrops begin to enter the stage of uniform falling until they reach the ground. In physics, this uniform speed is called the ending speed of the object.

the size of raindrops

It has been concluded that under normal circumstances, the diameter of raindrops is between 0.5mm and 6mm, and in rare cases, the diameter of raindrops will reach 8mm or even 10mm (observed in the Hawaiian Islands).

Scientists have found that if the water particles are smaller than 0.5mm, the effect of the atmospheric updraft is enough to keep water particles of this size in the air. And the size of the raindrops, generally will not exceed 6mm. Due to the existence of air resistance, large raindrops tend to break down into many small raindrops with a sudden decrease in volume during the falling process. In addition, these large raindrops continue to bump against each other as they fall, which also promotes their collapse. Scientists have found that under laboratory conditions, large raindrops usually begin to disintegrate when they reach a diameter of about 5mm. In the clouds, when the diameter of large raindrops reaches 5mm, they usually break up due to mutual collision. This is why raindrops with a diameter of 5mm or even larger are rarely seen on the ground, because raindrops cannot avoid the fate of bumping into each other with many others of their kind.

Raindrop size and finishing speed

The closing speed of raindrops has a strong correlation with the size of raindrops. Generally speaking, the ending speed of drizzle (diameter 0.5mm) is 2 m/s, while the maximum ending speed of raindrops (maximum diameter of raindrops is about 5.5mm) is 8~9 m/s.

Closeout speed and water column height

With the closing speed, the final kinetic energy of raindrops can be known. The kinetic energy and potential energy conversion formula of junior high school physics is enough to solve the relationship between the closing speed and the height of the water column. That is: 0.5MV 2 = MgH, substituted into the ending speed, we can get: when the raindrop ending speed is 8 m/s, H = 3.2 m; When the raindrop ending speed is 9 m/s, H = 4.05 m; When the raindrop ending speed is 2 m/s, H = 0.2 m;

Conclusion

Then integrate some factors (infiltration, increase the thickness to extend the service life of waterproof membrane, etc.), if it is only used for inter-city tours and daily field wear, the impact clothing of 6000mm waterproof target is enough to cope with it. However, if the demand goes to a more difficult environment, it is best to choose the impact clothing with a waterproof index of more than 10000mm.

Article from: Sanshun clothing customhttp://www.samsunclothing.com/