The dream team is perfect! Divers' secrets to suppress splashes →

The 19th Asian Games is in full swing in Hangzhou, Zhejiang. Now that the schedule is halfway through, the Chinese team has swept all ten gold medals in the diving events, once again achieving "perfection". Pang Ke only remembers that they entered the water without much splash, and their legs were stretched very straight, and they turned several times in the air, and then dived into the water with a whoosh. Without further ado, let's take a look at the wonderful moments of diving!

Why do some people make such a big splash when they enter the water, while others make such a small splash? Let’s explain it from a scientific perspective!

In diving competitions, when watching slow-motion replays, you will find that when athletes enter the water, it is their palms that make contact with the water surface , not their fingertips as commonly believed.

Why was this method of water entry chosen? As the saying goes, practice makes perfect. The development and maturity of the "water splash" technology was also discovered and improved through continuous exploration.

At the beginning, athletes' entry into the water mostly uses the technique of making their limbs into a sharp shape. If the hands enter the water first, they should put their hands together and stretch their arms, forming a wedge shape with a sharp front and a large back. If the feet enter the water first, the feet should be stretched straight and the toes should be inserted into the water first. Although this can effectively reduce the impact force on the human body when entering the water, the effect of "suppressing the splash" is not obvious.

Later, some people occasionally failed to straighten their toes properly, and the water splash was small when they entered the water with their feet hooked (this is what the saying "no coincidence, no success" means), so everyone began to try the technique of hooking their feet to enter the water with flat feet, and tried to use both hands to make fists when entering the water, which gradually evolved into today's "water splash" technique of pushing the arms and turning the palms when entering the water first, or overlapping the two hands to form a flat face into the water. You see, it is true that "practice is the only way to test truth"!

Although this set of movements originated from a small "misunderstanding", the scientific basis behind it has been proven by expert research. Experts used computers to simulate the "splash" movement and conducted a comprehensive analysis in the "Biomechanical Research on Diving's "Splash" Technique".

First, simplify water into an ideal fluid, and simplify the human body with both hands combined into a sharp shape to enter the water into a wedge-shaped body. The sharp angle is determined by the oblique rise angle of the wedge (that is, the angle between the hypotenuse of the wedge and the horizontal line). The larger the oblique rise angle, the sharper the water-impacting solid. When the oblique rise angle is reduced to 0°, the wedge becomes a square body, which is the water-impacting action with both hands turned over into a plane, which is currently commonly used in diving.

Based on relevant mechanical principles, experts derived and established a set of differential equations of motion for the collision process of a wedge-shaped solid and an ideal fluid, and used a computer to repeatedly simulate the liquid surface height during the collision of a wedge-shaped body with water at different angles. The results show that the magnitude of the impact force and the attenuation of the solid velocity during the collision are inversely proportional to the oblique rise angle of the wedge, while the splash height of the liquid surface is directly proportional to its angle.

In other words, the smaller the oblique rise angle, the smaller the height of the splashing water, and the more successful the "water splashing" is. This proves the superiority of the flat palm water-impacting technique (oblique rise angle of 0°).

So does it mean that you just need to raise your shoulders, turn your palms and enter the water flat?

Can it definitely suppress the splash?

Experts have conducted research and analysis on the characteristic that "when water is under pressure, it moves in the direction where the pressure is the smallest, that is, the direction where it is easiest to escape"↓↓↓

When a wedge-shaped body hits the water surface with its sharp end downward, the water closest to the inclined surface of the wedge-shaped body is squeezed by the pressure perpendicular to the inclined surface and moves in that direction. At this time, the water at the intersection of the inclined surface and the liquid surface can only move in the direction of the inclined surface upward, where there is no counter-pressure from other water. Since the water above has already escaped in this direction, this direction becomes the easiest direction for the water below to escape, so it continues to move in this direction, thus forming a huge splash. In other words, the faster the falling speed, the greater the impact force, and the larger the splash.

When the oblique rise angle of the wedge-shaped body is reduced to 0°, that is, when the square body (top shoulder and flipped palm) hits the water surface, the water moves downward under the extrusion force perpendicular to the horizontal plane. At this time, the water has no obvious direction to escape easily, but spreads around. Due to the counter-extrusion pressure of other water around it, part of the water will move upward along the straight wall, but the square body moving downward at high speed will bring the water close to it downward together. When the movement speed is greater than the speed of the water moving upward along the wall due to compression, no obvious splashes will appear.

Then, as long as you make sure your palms are perpendicular to the water surface when you fall,

Can it suppress the splashes?

Don't jump to conclusions.

First of all, the premise of "vertical entry into the water" is too idealistic.

In real life, when a high-speed flipping cube hits the water, the direction of the speed is not vertically downward, but the direction of the various movement speeds during the falling process is combined, and the direction of the combined speed usually points to the side and downward. If it still hits the water with a flat surface, once it hits the water surface, the cube will move in a certain angle direction, producing a wedge effect, and the water will escape along the side to form a splash. At this time, the athlete must autonomously rotate the wrist according to the different flipping directions, keeping the palm plane facing the direction of the combined speed to obtain the best square effect.

Therefore, athletes must not only raise their shoulders and turn their palms so that their hands hit the water surface in a certain shape to lower the height of the splash, but they must also use certain "water kneading" techniques to keep the surface formed by the palms perpendicular to the direction of movement speed. Only by taking these two approaches can they more effectively control the splash and reduce it to a minimum.

In addition to watching the splashes, the referees will also give an overall score based on the run-up (i.e., running board, treadmill), take-off, mid-air and entry into the water. Therefore, when watching "diving", we must also make a comprehensive analysis!

at last,

Fat Ke wants to leave a small question for everyone↓

See the gif above?

What is its professional name in competition?

Welcome everyone to leave a message in the comment area to discuss~

Review expert: Guo Liang, Director of the Institute of Mechanics, Chinese Academy of Sciences

Videos and pictures are from the Internet

Source: China Science and Technology Museum