Liquid metal quantization orbit and metal droplet chasing effect triggered by navigation wave field

[ Instrument R & D of Instrument Network ] Recently, the joint research group of the Institute of Physical and Chemical Technology of the Chinese Academy of Sciences and Tsinghua University used "The Pair of Liquid Metal Drops Chased by Quantization in the Orbit of the Composite Navigation Wave Field" in the Physical Review Fluids In this paper, the quantized orbital phenomenon and the chasing effect of metal droplets in a liquid metal oscillation liquid pool triggered by navigation waves are reported. Commenting on this work, Professor John WM Bush from the Massachusetts Institute of Technology said: "The authors have opened a whole new window for the study of fluid navigation waves by introducing liquid metals."

In classical fluid mechanics, a droplet placed on a vibrating liquid surface in the vertical direction will be guided by a local wave formed by its impact on the liquid surface to produce a directional horizontal motion. The droplet movement guided by the surface wave in the fluid navigation wave system is strikingly similar to the movement of quantum particles depicted by the navigation wave theory in quantum mechanics. It has been confirmed that the suspended droplets in the fluid navigation wave system can simulate a series of mysterious behaviors in the quantum field, such as tunneling, interference, and diffraction. The understanding of the wave-particle duality at this macro level has led to the attention of the scientific community in the study of fluid navigation waves in recent years. In addition to quantum systems, particle movements accompanied by fluctuations are common in physical systems. However, these behaviors usually occur at extreme scales or require special conditions to achieve them. This has brought great tremendous direct observation and control in the corresponding systems. difficult. For the macroscopic fluid navigation wave system, its driving parameters and system structure can be flexibly changed, which provides an easy way to study the wave-particle duality and the motion guided by the wave field in other physical systems.

Prior to this, some studies have examined the dynamic behavior of single droplets or multiple droplets in conventional fluid navigation wave systems, and explored their similarity to quantum systems. However, the previous research on the dynamic behavior of droplets is usually limited to the interaction between a single particle and the navigation wave, that is, the droplet motion is only guided by the local navigation wave generated by its impact on the liquid surface. This single navigation wave situation limits the driving conditions of the droplet movement to a very narrow interval. In order to break through the structure of the traditional fluid navigation wave system, there are also studies to change the movement of liquid droplets by adjusting the structure of the liquid pool, such as using a liquid tank with a stepped height, or controlling the container to rotate. However, these methods artificially increase the complexity of the system structure. Therefore, in order to further expand the theory and research scope of fluid navigation waves, while looking for a new droplet motion mode, it should avoid increasing the complexity of the system and control.

In this published research work on the liquid metal navigation wave system, the authors pioneered the introduction of a new liquid metal liquid pool-drop system with high surface tension, using the global navigation wave generated by the metal liquid pool boundary oscillation Construct a composite navigation wavefield with the local navigation wave of the droplet itself (Figure 1). The study found that when two metal droplets of different sizes meet on the liquid pool, they will self-lock to form a pair of droplets that rotate around the center of the liquid pool. Moreover, different self-locking distances can be achieved between the droplet pairs, and the movement trajectory of the droplet pairs is locked in the surface wave orbits of concentric rings of different radii formed on the surface of the liquid pool. More interestingly, the self-locking distance and the radius of the orbit between these pairs of droplets chased by rotation represent a series of quantized discrete values. By adjusting the set of variables such as the self-locking distance of the droplet pair and the orbit radius, a variety of droplet pair motion patterns can be achieved (Figures 1 and 2).

Through further research, it was also observed that the coordinated rotation chasing motion of the droplet pair is directional: either large droplets can chase smaller droplets, or in turn, small droplets can chase large droplets, and the direction of chasing Depends on the self-locking distance between two droplets. If two droplets are adjacent to each other (short-range self-locking), large droplets chase the movement of small droplets behind; conversely, if droplets are far from each other (long-range self-locking), large droplets take the lead, small liquid After the drop, the chase is reversed. However, no matter for the droplet pair of short-range self-locking or long-range self-locking, the center of its rotational movement is the center point of the liquid pool, not the center point along the line connecting the two droplets. (Silicon oil for example) The phenomenon of droplet rotation observed in the navigation wave system. It should also be pointed out that the chasing direction of the liquid metal droplet pair is completely determined by the self-locking distance of the two droplets, and is not affected by other factors (Figure 3). The droplets found in the past can be adjusted by changing the acceleration by chasing the movement direction. The unique behavior of these liquid metal droplet pairs means that the liquid metal system hides new modes of action.

The study designed a series of experiments to explore the principles behind the orbital chase effect of liquid metal droplet pairs. By using high-speed imaging, digital image tracking, particle imaging velocimetry and other methods, the authors revealed the hydrodynamic characteristics of the vibrating liquid metal liquid pool (Figure 4 and Figure 5) and bouncing droplets (Figure 6). By comparing the vertical movement of a single droplet in a different pair of chasing droplets, it is found that there is always a certain phase difference in the vibration of the two droplets, and the phase of the large droplets hitting the liquid surface always lags behind the small droplets. . It is the existence of this phase difference that when the droplet hits the liquid surface, it will be affected by the local navigation wave of another droplet that is self-locking, and a horizontal driving force is generated, which leads to the horizontal chasing behavior of the droplet. Occurred (Figure 7). At the same time, the common motion of the droplet pair will be limited by the global surface wave of the liquid pool, so that it is constrained in different circular orbits. The existence of this global navigation wave is the fundamental reason that distinguishes the current system from other systems. The orbital rotation chase effect of the liquid metal droplet pair is that the droplet is simultaneously affected by the local navigation wave and the global navigation wave field of the liquid pool. Caused by the guidance of a complex wave field.

The exploration of the liquid metal navigation wave system has enriched the research scope and knowledge of fluid mechanics instability, on the other hand, it has greatly expanded the meaning of wave-particle duality in fluid dynamics. The orbital chasing motion of the pair of liquid metal droplets found in this work is strikingly similar to the motion pattern of the pair of nanoparticles in the optical system. At the same time, the theory and methods of the composite navigation wave field proposed in this study are also expected to be extended to other physical systems of different types and scales, such as the transmission of electron pairs in the microcosm to planetary motions in the universe.

The above research was supported by the National Natural Science Key Fund, the Dean Fund of the Chinese Academy of Sciences and cutting-edge projects.