Why is the tape so noisy?Because this is about a rocket launch

The following article comes from WeChat public account: Global Science, author Global Science

Picture source: pixabay

Speaking of supersonic shock waves, we may subconsciously think of nuclear explosions, jet fighters, rocket launch, etc. The process of these energy burst instantly, no matter how they look, they are far from the champagne. But it is interesting that according to "Champagne Studies" research, the opening of champagne is very similar to a mini rocket launch, both of which will produce supersonic shock waves.

Written article | No week

Audit | Erqi

After a fierce shaking, we stared at the champagne bottle, looking forward to the bottle plugged in the next second. With a "bang", the liquor and foam burst out, and cheers broke out in the crowd -this is a common scene in celebration. But this is not the correct way to open champagne, but it is quite dangerous, and people are injured every year.

Let's come back again, don't shake champagne, and remove the wire covering the cork. Press the bottle with one hand and rotate the bottle slowly in one hand. The bottle plug will naturally slowly push out by the air pressure in the bottle, and then the "啵" pops out, and then the bottle mouth appears a faint white mist.

Perhaps the white mist is concerned. In an article in "Science Advances" in 2019, physicists are transformed into "champagne scholars", and they have taken a high -speed camera to shoot the champagne bottle opening the bottle. moment. They were surprised to find that after the plug popped, the high -pressure airflow in the bottle would form a supersonic shock wave.

The supersonic shock wave, essentially when the object performs the supersonic movement, will disturb the surrounding medium (such as air), thereby constantly forming compressed air current in front of the object. These compressed air flow carry huge energy, which will impact around the form of supersonic air waves.

The upper right corner of the picture is shooting time: from 583 microseconds to 1000 microseconds. The high -speed camera is captured, and the Mach (the position referred to as the arrow) is gradually away from the position A closer to the bottle mouth, and gradually distances away from the bottle mouth to the location of the figure, until Figure F completely dissipates. (Image source: Original Thesis)

Mach

The air flow is often colorless, which means that we cannot see the shock wave directly. So why can you catch the supersonic shock wave of the champagne bottle with a camera? In fact, instead of seeing the supersonic shock wave, we are better to observe the phenomenon that can only be formed by supersonic air flow.

When you carefully observe the photos of these champagne bounds, you will find that a white line is gradually away from the bottle mouth until it dissipates. And if you look at it from the front of the bottle mouth, you will find that this line is actually a ring -this is the Mach Disk.

A string of bright aura-Mach Ring at the rear of the F-20 fighter in my country. (Picture source: Xinhuanet)

If you pay attention to the take -off of the supersonic aircraft or the rocket launch, you may notice that their tails always have a string of bright aura, which is also the Mach ring. Both the rocket and the plane need to spray supersonic airflow to get a strong thrust. The sprayed supersonic airflow pressure is high, so when it is sprayed into the atmosphere from the nozzle, it will directly swell; but the airflow pressure after expansion will be lower than the atmospheric pressure, so it will be compressed again. In this way, the supersonic airflow will circulate between the expansion and compression. This process will form expansion waves and compression waves. The two are superimposed during the transmission process, forming a ring one by one, that is, the Mach ring.

It is not difficult to see the necessary conditions of the Mach Ring phenomenon: first, the supersonic airflow; the other is that the air flow pressure and environmental pressure are different. The former meets the conditions of the shock wave; while the latter can change the airflow and cause different waves.

The Mach Ring of the Champagne bottle is the same as the Mach of the Rockets, but the two have a significant difference: the temperature of the supersonic airflow. The moment when the champagne plugs pops up, the airflow in the bottle is quickly overflowing, causing the air pressure and temperature of the bottle to fall sharply. The carbon dioxide and water vapor mixture will condense into ice crystals, forming a gray -white mist. Because of this, the Mach of the Champagne bottle will appear in the white mist. The temperature of the rocket spraying airflow is too high, which will ignite a small amount of fuel mixed in it, making the Mach ring particularly dazzling in it.

The moment when the bottle plug pops up

However, although the airflow of the champagne bottle can exceed the speed of sound and generate the Mach ring, the specific process and physical mechanism have not yet been clarified. This year, in an article published in the magazine of "Physics of Fluids", scientists further revealed that the shock wave formation, evolution, and ultimately revealed by computer simulation in the 1,000 microsecond (1000 microsecond) popped up in champagne bottle plugs. The process of dissipation.

The champagne is rich in carbon dioxide. The air pressure in the bottle is about 6 times the atmospheric pressure. The compressed carbon dioxide gas in the bottle will continue to exert the outward thrust to the cork and want to push it out. In the case of stability, the static friction between the cork and the bottle wall will balance the outward thrust. However, once you start to twist the cork, the static friction will quickly transform into dynamic friction, and no longer can compete with the air pressure. The plug was like a rocket at this time, and it was ready to go.

Computer simulation image. From top to bottom, each row corresponds to the first and second stages of the impact wave evolution. When the first line of 500 microseconds, the wood plug just popped up, and the airflow could only expand along the gap between the plug and the bottle mouth horizontally; when the second line 917 microsecond, the wood plug was from the bottle mouth to a certain distance, and the airflow could be sprayed directly, but A bending shock waves will be collided with bottle plugs; when the third line is 1167 microseconds, the pressure difference between the inside and outside of the bottle is reduced, and the airflow cannot support the supersonic speed. From left to right, each column displays the spatial distribution of flow velocity, air pressure and temperature. Combining row and column variables can correspond to the state of each stage and the interval distribution of different variables. (Image source: Original Thesis) According to the computer simulation, in the 1 millisecond population popped up, the changes in the supersonic airflow can be divided into three stages descriptions:

In the first stage of the cork pops (within 600 microseconds), the carbon dioxide airflow in the bottle will be quickly reached by supersonic. This process is very similar to the airflow acceleration of the rocket. The nozzle at the tail of the Rockets is a narrow funnel shape in the middle of both sides, also known as Laval Nozzle. The high -pressure airflow that is heated after ignition is continuously compressed and accelerated when the first half of the nozzle is narrowed. The narrow shape of the champagne bottleneck also has a similar effect, allowing the air to accelerate to the supersonic at the mouth of the bottle.

Just as the crowd is blocked at the narrow intersection, the speed is slow, and once the open space will be decentralized and accelerated, the airflow will enter the open space after the narrow path is compressed, and it will also be eager to expand and accelerate. Therefore, when the high -pressure airflow is echoed out of the bottle mouth and enters a relatively low -pressure external environment, it will get supersonic speed; the rocket airflow can reach the supersonic speed in the second half of the nozzle. Unlike the Rockets, the bottle plug at the champagne bottle is too slow than the airflow, which will hinder the airflow directly spray. At this stage, the supersonic airflow can only be expanded horizontally along the gap between the plug and the mouth of the bottle, forming a crown -like shock wave, and the phenomenon of Mahh is at the same time.

The second stage of the cork plug left the bottle mouth (600-1000 microseconds). As the gas in the bottle continues to emerge, it can finally be sprayed directly like a rocket air. Form a curved shock wave.

In the third stage (more than 1000 microseconds), the pressure in the bottle gradually flattened at the atmospheric pressure, and the pressure difference at the mouth of the bottle could not be maintained, and the airflow lost power. Therefore, the jet airflow will continue to slow down until the speed of sound, and the shock waves will completely dissipate.

Defined from the inspiration of life

This interesting study has associated the rocket launch with the champagne bottle, which not only promotes the progress of "champagne", but also provides a reference for a series of important applications, such as the ballistic research of rocket launch and missile launch. This study can also help the development of underwater aircraft and wind turbine engineers, so that they can better understand the process of fluid dynamics (the movement of motion of migrants under the action of force).

However, in fact, not only the champagne opening will produce supersonic shock waves. I wonder if you pay attention to the two very penetrating sounds in your life: the sound of "tearing!" When tearing the transparent tape, and the "snap!" In the park's whip exercise.

If you tear the tape vigorously, you will find that the tape is always ticked away, and it sounds like a section of "tearing" sound. When you tear the tape from the attached surface hard, the tape adhesive stretchs like a spring and stores elastic potential energy (so it cannot be torn continuously). After the bonding agent "spring" cannot withstand a larger tension break, the cumulative elastic potential energy will immediately convert into the kinetic energy of the tape split edge (the dividing line of attachment tape and the separation tape).

If you shoot this process with a high -speed camera, you will see that the edge of the tape will be moved at a speed of 650 to 900 meters per second, far suettime speed, and even exceeding the speed of the fighter. This means that every time the adhesive tape accumulates potential energy, and then stripped, a tiny supersonic shock wave will be released. So it is not difficult to understand. Of course, the superposition of mini -tone explosions will be very harsh.

When tearing the transparent tape, you can't avoid the harsh "tearing" sound (picture source: pixabay)

The loud "pop! Pap!" In the park, some people may mistakenly think that this is the sound of the whip hitting on the ground, but in fact, this is a mini supersonic shock wave that erupts in the air. When people throw their whip hard, they will pass the kinetic energy to the whip. Usually the whip handle is thicker and the quality is larger. When the kinetic energy is passed to the thin and light whip ends along the soft whip body, in order to ensure the constant momentum, the speed of the whipper will be greater than the speed of the handle, and it is easy to exceed the speed of sound speed. , To form a local supersonic shock wave.

This phenomenon is also known as the whipper effect. It is the same as that of champagne, which originated from life, but also contains complex physical mechanisms.

Now, if anyone asks: What is the common to champagne, tape and whip?

Do you know how to answer?

Cover source: pixabay

The thesis link:

https://www.science.org/doi/10.1126/sciadv.aav5528

https://aip.scitation.org/doi/abs/10.1063/5.0089774

https://journals.Aps.org/prl/abstract/10.1103/physrevlett.122.068005 Reference link:

https://www.smithsonianmag.com/smart-News/what- really-hpper-dhen-dhampagne-vo-science-180980218/

https://www.liverscience.com/champagne-bottle-Preates-shockwaves.html

https://www.decanter.com/wine-news/german-scientist- logs-champagne-cork-dEd-75173/

https://kns.cnki.net/kcms/detail/detail.aspx?dbcode=cjfd&DBNAME=cjfd9495&FILENAME=LXys505.026

This article is authorized to reprint from WeChat public account: Global Science Author: Global Science

Reprinted content only represents the author's point of view

It does not represent the high energy office of the Chinese Academy of Sciences

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Edit: Jin Yan

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