The Beijing Winter Olympics thus realized the freedom of snow

Source: Science and Technology Daily

80%―90%

Snow sports on the climate and venue requirements are very strict, in order to ensure the smooth progress of snow projects, 80% -90% of the winter Olympics with snow with artificial snow, through our "self-reliance" to achieve the winter Olympics snow freedom.

The 2022 Beijing Winter Olympics are in full swing, and in the seven major events of the Winter Olympics, skiing will produce 55 gold medals, accounting for half of the total number of gold medals at the Beijing Winter Olympics. Athletes slide down snowy slopes, or snake through, or jump and spin in the air to complete a variety of difficult actions, such a scene makes the audience's blood boil.

Winter Olympics use snow not to "rely on the sky to eat"

"In fact, most of the world's ski resorts at present use a combination of natural and artificial snow." Zhang Haiyang, associate professor of Beijing Institute of Technology, introduced it in an interview with a reporter from Science and Technology Daily.

It is understood that the Winter Olympics held in Vancouver, Sochi and Pyeongchang have all used artificial snow in large quantities. Especially at the 2018 Winter Olympics in PyeongChang, artificial snow accounted for 90% of the total snow used.

Why does so much artificial snow be used in the Winter Olympics?

Zhang Haiyang pointed out that the physical characteristics of new snowfall produced under natural conditions, snow that re-condenses after melting, and snow accumulated for a long time are different, which affects its properties. The International Ski Federation (hereinafter referred to as the International Snow Federation) has set corresponding technical indicators for the competition slopes of different events to ensure the fairness and safety of the competition, and the stability of snow is very important for the ski slopes.

Artificial snowmaking is more controllable than natural snow, which has more variable physical properties. Artificial snow is squeezed, leveled and filled with water, making it easier to make a race-ready piste.

For example, Zhang Haiyang said that the U-shaped trough field of Chongli Wanlong Ski Resort, according to the requirements of the Winter Olympic Games, its snow trough length should reach 150 to 170 meters, the width should reach 19 to 22 meters, the depth should reach 6.7 meters, and the slope should reach 17 to 18 degrees. To create such a site, not only does it take a lot of snow, but also to control the humidity of the snow in order to accurately slope. "The site staff will detect the moisture content of the snow, and only by controlling the water content within the appropriate range can the U-shaped trough site maintain this shape and not deform at a certain temperature." Zhang Haiyang said.

In addition, the Winter Olympics will consume a lot of snow in a short period of time, and it is obviously unreliable to rely on God alone to "appreciate rice and eat".

At the 1980 Winter Olympics in Lake Placid, artificial snow first appeared on the winter Olympic site because of the low amount of snow in Lake Placid in the winter of that year.

According to the FIA document "Design Requirements for Freestyle Skiing and Snowboard Skiing Venues for the 2022 Winter Olympics", the snow track needs to guarantee about 71,500 cubic meters of snow, and when this figure is added to the melting coefficient, it will reach 107,200 cubic meters. Even smaller, large-jump tracks need to maintain at least 11,000 cubic meters of snow.

Zhang Haiyang said that such a large amount of snow consumption, relying on transportation alone, the cost is too high. If it snows naturally, it needs to be snowed continuously for dozens of days. And the ski area needs to be molded and maintained every day, and it also needs a lot of reserve snow, so be sure to help with artificial snow.

There are two main requirements for artificial snow materials

"It takes a lot of time to create so much artificial snow, so in order to ensure the use of snow for the event, many Winter Olympic ski resorts have been artificially snowmaking since the end of November 2021, and the snowmaking time will last until January 2022." Zhang Haiyang said that an important tool for artificial snowmaking is the snow machine, which can imitate the process of natural snowfall and turn water into snow, but it is different from the natural snow process.

Zhang Haiyang introduced that in the natural state, the water vapor in the sky must have two conditions for becoming snow: one is to have a certain degree of water vapor saturation (that is, cold clouds below 0 degrees Celsius), and the other is that there must be condensation nuclei. When small droplets of water in cold clouds encounter dust particles in the air, ice crystals form at this time; ice crystals gradually increase, and when their weight reaches a certain level, they can overcome the buoyancy of the air and fall from the sky and become snowflakes.

Artificial snowmaking is to break the water mist below 5 degrees Celsius into small particles through a snowmaker, and then quickly condense and crystallize these particles, and then the snow is sprayed out by the wind turbine to expand the snowmaking area.

"Water is an indispensable raw material for artificial snowmaking." Zhang Haiyang said that in principle, well water, river water, pure water, reclaimed water, rainwater, and snowmelt water can all be used as artificial snow water, but before these waters become snowmaking raw materials, they must adjust the "body temperature", that is, to control the temperature between 0 and 5 degrees Celsius, the water temperature is too high to make snow, and the water temperature is too low to make snow. At the same time, the water should not be too dirty, although the snow machine has a filtration device, but if the water is too dirty, it will not only clog the filter, but also may clog the nozzle.

Each ski resort of this Winter Olympic Games will have fixed snow machines and mobile snow machines. A fixed snowmaker only needs a pumping pipe to make snow on a large scale. "But for the competition venues with high molding requirements and the need to repair snow, it is necessary to 'dispatch' mobile snow machines." Zhang Haiyang said.

Snow for different competitions has "private customization"

"The snow quality requirements are different for each snow project, even if it is different parts of the same site, the snow quality requirements are not the same." For example, Zhang Haiyang said, such as alpine skiing competitions, because it is a racing event, its track needs to be individually suppressed, and the snow density laid on the track is very large, which is called "ice-like snow". "icy snow" is 5 to 13 times denser than natural snow, and its surface has a thin layer of hard ice shell, which is snow and ice-

"This type of snow has a high water content, high density, and its surface layer is equivalent to a layer of ice, which can reduce the friction between the track and the skis, improve the comfort of athletes, and help improve the performance of athletes." Zhang Haiyang said that in the deceleration zone and the end zone, in order to protect the athletes from injury, it is necessary to slow down. Therefore, the snow in this area needs to reduce the moisture content to maintain the fluffy state of the snow, thereby increasing the friction between the track and the skis.

Slide down from a high platform more than 100 meters above the ground, dive, accelerate, jump from the end of the jump platform to the air, and draw a beautiful parabola in a "V" shape... In the field of this Winter Olympic Games, the highly ornamental ski jumping project was brilliantly staged at the Zhangjiakou National Ski Jumping Center. "The competition is good, but it is not easy to make snow on the slopes used for ski jumping competitions." Zhang Haiyang said that the artificial snow laid on the ramp is from the bottom to the top, the grassroots, the middle layer, and the surface layer, and the density of each layer of snow is different. The snow quality humidity at the base level should be large, so that the snow layer and the slope can be firmly "frozen". Considering that athletes should do some actions at high altitude, the slopes should not be too hard when landing, so the humidity of the surface snow should be low, so that a certain degree of looseness can still be guaranteed after flat pressure, and the safety of athletes' sliding can be ensured to the greatest extent.

At the Winter Olympics, at the end of the day, the night staff will maintain the ski slopes. "Because after each race, the hardness of the slopes will be reduced, and the surface of the slopes will become choppy and bumpy, which will affect the next day's race." Zhang Haiyang introduced that the maintenance of the pistes should be supplemented with snow on the one hand, and on the other hand, the snow was pressed by snow grooming vehicles to meet the hardness standards of the race slopes.

Chinese the technology of snowmaking

In March 1950, American Wayne Pierce built the world's first snow machine with a paint spray compressor, nozzles and some hoses used to water flowers and trees.

Since then, artificial snow technology has continued to evolve, which has made it possible to use artificial snow on a large scale at the Winter Olympics. However, due to the late start of mainland research on artificial snow, domestic track snow technology is almost blank, and foreign countries have imposed technical blockades on China in this regard, making it impossible for China to obtain the parameter standards for track snow. Before 2016, China would not even be able to build a qualified "ice-like snow" track.

In order to provide a good event experience for athletes around the world, mainland scientists have carried out concentrated attacks. In 2017, under the leadership of Qin Dahe, academician of the Chinese Academy of Sciences and honorary director of the State Key Laboratory of Cryosphere Science of the Chinese Academy of Sciences, the research team of key technologies for snow protection for the Beijing Winter Olympics was formally formed, vowing to create Chinese its own "ice-like snow".

After a large number of observations and experiments, the team obtained the territorial parameters of the "ice-like snow" manufactured in the Yanqing and Zhangjiakou race areas of Beijing, clarified the snow quality requirements of high-quality snow tracks from the mechanism, and successfully produced qualified "ice-like snow" that adapted to the characteristics of continental monsoon climate.

In the end, the production technology of the "ice-like snow" track with different climatic conditions was overcome, and Chinese created the "ice-like snow" track by himself. In addition, China's snowmaking to snow removal technology has all reached the international event standards, realizing the freedom of snow use; professional monitoring equipment for "ice-like snow" tracks such as ice and snow hardness measuring instruments and ice and snow particle size measuring instruments has also been localized, which has greatly reduced the cost of running the race.

Better tools make good work. Snow grooming vehicle is a large equipment necessary for the construction and maintenance of race slopes, with the first large-scale snow grooming vehicle independently developed and produced by the mainland - SG400 snow grooming vehicle off the production line, the mainland has achieved a breakthrough from 0 to 1 in the field of high-power high-end snow grooming vehicle products.

In order to cope with extremely cold weather, the SG400 snow grooming vehicle is designed to work in a working environment of minus 40 degrees Celsius, a large number of low-temperature resistant materials are used in the design, and the modified snow plough has a tooth shape that is easier to break the snow layer, which meets the actual needs of the mainland snow field.

At the same time, under the premise of meeting the strength requirements of the main structure, the R & D personnel have carried out a lightweight design of the frame and core components of the snow grooming vehicle, and the frame weight is only equivalent to 1/3 to 1/5 of the frame weight of the general engineering vehicle, making it particularly suitable for running under extremely soft working conditions of the snow track. Together with the winch system, the snow groomer can climb alpine ski slopes with a gradient of 45 degrees.

In addition, the intelligent control system of the snow groomer allows multiple controllers of the whole vehicle to methodically process feedback signals from sensors, motion control handles, and electronic pedals, so that it has a sensitive "nervous system". (Chen Xi)