Click on the audio below to let your ears "feel" the mechanics
In the freezing environment of northern winter, there is one outdoor sport that is starting to heat up, and that is skiing. Putting on a ski suit, putting on ski goggles, stepping on skis, and speeding down from a high place, the feeling of speeding is exciting. The fun of skiing is self-evident, but did you know that the slopes of the ski resorts we often go to are basically made of artificial snow? I don't know if you have ever wondered how they make snow when you see the "snow cannons" and "snow guns" spraying snow?What is the difference between the snow that is made and the snow that falls naturally?
How is natural snow formed?
Natural snow is solid precipitation that occurs when water vapor in the atmosphere is condensed, and its structure changes with temperature and humidity, so snowflakes take on a kaleidoscopic shape. Snowflakes that are exactly the same shape, size, or perfectly symmetrical cannot be formed in nature.
According to the physics knowledge learned in junior high school, we know that under certain temperature conditions, the content of water vapor in the air reaches the maximum, and the different phases of water (solid, liquid, gas) can be converted into each other. When the temperature decreases, the saturated water vapor becomes supersaturated, and it is easy for them to condense on the suspended fine dust and form ice crystals.
After that, the ice crystals continue to absorb the surrounding water vapor and become larger, and the water vapor near the ice crystals decreases. In this way, the density of water vapor near the ice crystal is lower than that of the ice crystal, resulting in a relatively high water vapor pressure gradient. Driven by gradient pressure, water vapor gradually moves from around the ice crystals to where the ice crystals are, so that stellate snowflakes gradually form.
The process of stellate snowflake formation.
To sum up,For water vapour to crystallize and form snowfall, two conditions must be met: one is saturation of water vapour and the other is that there must be condensation nuclei in the air. Water vapor saturation refers to the maximum amount of water vapor that air can contain at a certain temperatureSaturated water vapor。The temperature at which the air reaches saturation is called。When the saturated air cools to a temperature below **, the excess water vapor in the air turns into water droplets or ice crystals. Because the saturated water vapor content of the ice surface is lower than that of the water surface, the water vapor saturation required for the growth of ice crystals is lower than that of water droplets.
As for condensation nuclei,Condensation nuclei are tiny solid particles suspended in the air。The most desirable condensation nuclei are those particles that absorb the most water. For example, particles of sea salt, sulfuric acid, nitrogen, and other chemicals.
How is artificial snow formed?
fromIn principle, there is no difference between artificial snow and natural snow。Both natural and artificial snow are ice, which is crystals formed by water molecules. But,In contrast to the ever-changing nature of snowflakes, artificial snow is mostly carved out of a mold.
Artificial snow.
The common artificial snow is to mix the high-pressure water in the high-pressure water pump and the high-pressure air in the air compressor at the double inlet nozzles, and the high-pressure air will then split the water into tiny particles, which will solidify into ice crystals in the cold air, and further contact with the water vapor to allow the crystals to grow. Due to the short "growth" time, it is mostly white, opaque, and almost spherical or conical.
Why do you use artificial snow for the Winter Olympics?
The amount of natural snow is difficult to meet the requirements
Abundant snow is the most basic condition to ensure the development of the Winter Olympics, but in the early years of relying on natural snow, there was a situation where God "did not give face" and made the Winter Olympics unable to be held smoothly. With the development of science and technology, artificial snowmaking has gradually changed the situation of "relying on the sky to appreciate the face" of the Winter Olympics, and solved the embarrassment of no snow and less snow in the host city. Since the 1980 Winter Olympics in Lake Placid, USA, where artificial snow was first introduced, the Winter Olympics in Vancouver, Sochi and Pyeongchang have made extensive use of artificial snow.
Artificial snow makes the competition fairer and more just
First of all,The snow cover in artificial snow resorts is single and stable。This feature ensures that athletes from different parts of the world can enjoy stable and fair track conditions, regardless of the starting order and race time. Secondly, inIn different climates of the world, there are significant differences in snow density, moisture content and snow crystal development in snow resorts, which will affect fair play for athletes from different parts of the world. Artificial snow is completely controlled by artificial conditions, which is the same in the world, which can completely overcome the differences in the characteristics of the snow field brought about by the regional climate and environment, thereby affecting the fairness of the sport.
Artificial snow can meet the high requirements of snow for the Winter Olympics
We know that ski jumping, snowboard pursuit, etc., are all carried out in high-speed impact and high-speed pursuit, so the Winter Olympics require snow on the slopes to be resistant to high impact and high pressure. Due to its large porosity, low density and low intensity, natural snow cover cannot meet the snow needs of ski jumping, snowboard chase and other events. However, even if the snow is compacted with a snow compactor, it does not fully meet the ideal standards for skiing.
High-speed cornering impact in snowboarding.
The International Ski Federation (FIS requires that the surface of alpine skiing slopes must remain in a crystalline state similar to that of the ice surface, so that the slopes are hard and can ensure that the surface of the slopes is relatively flat under the condition of high-speed impact and turning of athletes. In addition, regardless of the number of competitors appearing, the condition of the slopes and the shape of the snow will remain stable. Snow crystal type single.
1. The artificial snow field with stable characteristics can well meet the above requirements.
References
**From the Internet, for popular science reference only
Popular science of mechanicsMechanics Science Popularization *** is a popular science public account under the Chinese Society of Mechanics, which publishes relevant popular science news and competition news, recommends the latest developments in science and technology and popular science related information, and is committed to letting the public enter science, understand mechanics, and stimulate the interest of learning Xi science and technology.
Tips
If you like this article, please share it, please indicate the source.
For cooperation and submission, please contact:[email protected]