The speed of the object moving is directly proportional to the size of the air pressure wave, that is, the faster the object moves, the greater the air pressure wave it produces. First observe some phenomena in daily life: a car sped by on the road, and the leaves scattered on the road were sucked into the bottom of the car in an instant; When the wind blows the advertising banner hanging on the outer wall of the high-rise building, the banner is close to the wall... In fact, these phenomena occur because the air will form a wave in the transmission.
Whether it is a high-speed car or a gust of wind, they will accelerate the air velocity in the adjacent space, reduce the pressure, and produce a pressure difference with the air in the distant space, thus forming an air pressure wave. Under the action of this air pressure wave, objects such as leaves and advertising banners move rapidly. So what happens to a high-speed train running at a high speed of more than 200 km / h once the window is opened?
Obviously, the high-speed train will produce a huge air pressure wave when it runs. Once it enters the car, it will make the items on the table a mess. The dust outside the vehicle will make the air inside the vehicle turbid, and the noise outside the vehicle, especially the huge noise when the train enters and exits the tunnel and the two vehicles meet, will also take advantage of it. What's more, the passengers simply can't stand this air pressure difference. At least, it will make the passenger's eardrum feel oppressive, at least it will make the passenger feel dizzy and nausea, and even cause the eardrum to rupture in serious cases. In fact, on high-speed rail trains, not only the windows should be fixed and closed, but also the doors and car connections should be closed as much as possible, so as to ensure a comfortable riding environment for passengers.
The special technical requirements of high-speed train body for sealing performance are called air tightness in aerodynamics. Whether there is air tightness is also the main standard to distinguish high-speed train from ordinary train. You can find many special measures to pay attention to air tightness on the high-speed train body. For example, the whole window is inlaid and fixed on the vehicle body, and the joint is sealed with rubber sealing strip. For another example, the aluminum alloy shell of the carriage adopts continuous welding process, and the connection between the two carriages adopts rubber windshield to eliminate air leakage at the joint. For another example, the door adopts a technology called electric sliding plug door, which makes the door closely fit and smooth with the appearance of the car body after being closed. In addition, sealing devices are also installed at the connections between various pipelines used for air conditioning and water supply and the outside world.
Whether fixed windows that cannot be opened or air tight devices that are usually not noticeable, they are the first-class "Heroes" in creating a quiet, peaceful and comfortable environment for high-speed trains.