Ultrasonic-electromagnetic composite field black hole structure and application system

Abstract

This invention discloses an ultrasonic-electromagnetic composite field black hole structure and its application system, relating to the field of multiphysics metamaterials. The composite field black hole structure includes several ultrasonic blocking components arranged circumferentially and having a gear-shaped profile in their overall cross-section. A compensation solid block is disposed within one of the ultrasonic pathways, the profile of which is determined by a second-order Bezier curve. Each ultrasonic blocking component and the compensation solid block has at least one hole distributed along the axial direction inside. The gap between two adjacent ultrasonic blocking components constitutes an ultrasonic pathway. This invention proposes and realizes a composite field black hole metamaterial capable of simultaneously converging ultrasonic and electromagnetic waves, providing a novel core functional device for multiphysics collaborative applications. Using the composite field black hole of this invention can increase the acoustic pressure modulus value of the central region by an average of 2-3 times, and improve the microwave absorption efficiency from less than 50% to over 90%, greatly improving energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of multiphysics metamaterials technology, and more specifically to the field of ultrasonic-electromagnetic composite field black hole structure and application system technology. Background Technology

[0002] Multiphysics metamaterials are artificially constructed composite materials at the subwavelength scale, enabling unnatural manipulation of multiple physical fields such as sound, electricity, magnetism, and heat. In recent years, metamaterials that simultaneously manipulate electromagnetic and acoustic waves have become a research hotspot, leading to the emergence of important functional devices such as dual-field shielding, dual-field absorption, dual-field focusing, dual-field beam splitting, and even tri-field stealth. These devices demonstrate enormous potential in integrated and multifunctional modern industrial applications.

[0003] The combined application of microwaves and ultrasound is particularly prominent in the fields of food processing, environmental protection, and chemical engineering. Microwaves utilize time-harmonic electromagnetic fields to induce the rotational vibration of polar molecules, generating internal energy and achieving rapid volumetric heating; while ultrasound generates cavitation effects through mechanical vibration, promoting liquid flow and mass transfer. The synergistic effect of the two can significantly improve processing efficiency and uniformity.

[0004] Figure 1 (a) is a schematic diagram of the dual-field concentration of a composite field black hole, which can concentrate plane electromagnetic waves and plane ultrasonic waves in the central region. Its design process can be composed of acoustic part design and electromagnetic part design.

[0005] First, we consider the acoustic design of a composite field black hole. A sound concentrator function was achieved by constructing a three-dimensional perforated spherical metamaterial. A similar approach can be used to fabricate a sound concentrator in a two-dimensional case.

[0006] First, consider a two-dimensional cylindrical anisotropic metamaterial. The dispersion relation in cylindrical coordinates can be approximated as: ; in Represents the equivalent radial density. Represents the equivalent tangential density. Represents the equivalent radial wave vector. This represents the equivalent tangential wave vector. It represents the equivalent elastic modulus. This represents the ultrasonic angular frequency. If the metamaterial can satisfy the extreme anisotropic density condition (i.e., Then, the isofrequency curve of the metamaterial can be approximated as a frequency curve in the radius vector. An ellipse with a flattened orientation, such as... Figure 1 As shown in (b), regardless of the direction of the incident sound wave, the direction of the refracted sound wave in the metamaterial is approximately parallel to the direction of the incident sound wave. This means that sound waves incident from all angles can be concentrated in the central region. To achieve this extremely anisotropic density metamaterial, a cylindrical sound concentrator made of radially parallel solid material and air can be constructed in a size much smaller than the length of a ultrasonic wave, such as... Figure 1 As shown in (c), the equivalent radial density of this composite material is formed by the parallel connection of the two materials, while the tangential density is formed by the series connection of the two materials. Therefore, the formula for the equivalent acoustic medium can be expressed as: ; ; ; in, , These represent the densities of air and solid materials, respectively. , These represent the bulk modulus of air and solid materials, respectively. This represents the volumetric filling ratio of a solid material, which can also be understood as the angular filling ratio in a two-dimensional context. Since the rigid walls of a solid material effectively suppress the propagation of sound waves, its equivalent density relative to air can be approximated as infinite (i.e.,...). Therefore, we can conclude that: ; ; From the above formula, it can be seen that for any volume fill ratio All of these can make The conditions are met, thus ensuring that sound waves are directed to the central region. However, it should be noted that, according to the acoustic characteristic impedance formula... , An excessively large radial impedance may cause excessive reflection, resulting in poor sound concentration.

[0007] However, the above studies were conducted in the audible low-frequency range of 1000-1600Hz. For ultrasonic frequencies above 20kHz, the sound concentration effect in the central region is not good because the path lengths covered by different radial "ultrasonic pathways" will exhibit significant differences. Figure 2 As shown in (a), some “pathways” interfere with each other in a constructive way, while others interfere with each other in a destructive way, resulting in an unsatisfactory sound concentration effect.

[0008] In summary, existing technologies for ultrasonic and electromagnetic waves generally suffer from low energy utilization and uneven field strength distribution in application scenarios. To concentrate diffuse field energy into a target region, the concept of "black hole" metamaterials has been proposed. Current black hole research primarily focuses on single physical fields, such as acoustic black holes based on slow-wave effects, electromagnetic black holes based on transformation optics, or electromagnetic black holes based on graded refractive indices. Although independent black hole designs for elastic waves, Lamb waves, and microwaves exist, a "composite field black hole" technology that can simultaneously and efficiently converge planar ultrasonic and microwave fields into the same spatial region remains a gap in current technology. In particular, applying the principle of low-frequency acoustic concentrators to higher frequency (e.g., above 20kHz) ultrasonic bands results in a sharp deterioration in the converging effect due to multi-path acoustic wave interference, a technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0009] The purpose of this invention is to solve the technical problems of low energy utilization and difficulty in high-frequency sound focusing in composite fields. This invention provides an ultrasonic-electromagnetic composite field black hole structure and application system.

[0010] To achieve the above objectives, the present invention specifically adopts the following technical solution: One aspect of the present invention provides an ultrasonic-electromagnetic composite field black hole structure, comprising a plurality of ultrasonic blocking components arranged circumferentially and having a gear-shaped profile in their overall cross-section, wherein each ultrasonic blocking component has at least one hole distributed in the axial direction; the gap between two adjacent ultrasonic blocking components forms an ultrasonic path. The circumferential width and distribution of the ultrasonic pathways are configured such that, for an incident ultrasonic plane wave, the sound waves propagating in each of the ultrasonic pathways satisfy the constructive interference condition when they reach the central region of the structure, thereby achieving ultrasonic convergence. Furthermore, by adjusting the shape and distribution of the holes on each of the ultrasonic blocking components, the equivalent relative permittivity of the ultrasonic blocking components in the radial direction is made to have a specific gradient distribution, which is configured to guide and converge the incident electromagnetic waves to the central region of the structure. A compensating solid block is provided within one of the ultrasonic pathways. The outline of the compensating solid block is determined by a second-order Bezier curve to provide the required material volume for the design of the equivalent dielectric constant of the electromagnetic part without introducing acoustic reflection.

[0011] In one embodiment, the ultrasound pathway retains only phase satisfaction. An acoustic wave path ∈ (0, 0.5λ), where λ is the wavelength of the ultrasound in the background medium; the ultrasound blocking component is used to block the acoustic wave path with a phase of 0.5λ to λ.

[0012] In one embodiment, the overall width of each of the ultrasonic blocking components gradually decreases radially; each of the ultrasonic blocking components includes a first ultrasonic blocking unit arranged radially and located inside and a second ultrasonic blocking unit located outside, the dielectric constant of the first ultrasonic blocking unit being less than the dielectric constant of the second ultrasonic blocking unit, the first ultrasonic blocking unit and the second ultrasonic blocking unit forming a dielectric constant gradient required for electromagnetic wave convergence.

[0013] In one embodiment, the first ultrasonic blocking unit and the second ultrasonic blocking unit are fixedly connected, wherein the first ultrasonic blocking unit is a polyphenylene sulfide plastic with a low dielectric constant, and the second ultrasonic blocking unit is an alumina ceramic with a high dielectric constant. Both the first ultrasonic blocking unit and the second ultrasonic blocking unit have at least one hole along the axial direction.

[0014] In one embodiment, the first ultrasonic blocking unit and the second ultrasonic blocking unit punch holes of a specific shape along the axial direction; According to the equivalent medium theory of electromagnetics, the axial equivalent permittivity, within a scale much smaller than the wavelength, can be considered as a parallel combination of a solid material and air. Therefore, the axial equivalent relative permittivity... It is calculated using the following formula: ; ; in, Let be the equivalent relative permittivity along the axial direction at any point in the composite field black hole. The relative permittivity of the ultrasonic blocking component. It is the relative permittivity of air. To represent the volume percentage of the ultrasonic damping component, draw a radius [value] on the radial direction of the ultrasonic damping component. Given a circle, find the total length of the circle on the solid. The ratio of the circle's circumference to the circumference of the circle is called the ratio of the circumference of the circle to the circumference of the circle. .

[0015] In one embodiment, the ultrasonic blocking member exhibits frequency selectivity in the convergence of ultrasound, and the operating frequency of the sound pressure enhancement in the central region of all the ultrasonic blocking members is determined by the radial length difference of the ultrasonic path, preferably, the operating frequency is 20 kHz.

[0016] In one embodiment, a rotating base is also included, on which the ultrasonic blocking component and the compensating solid block are disposed. The direction of ultrasonic convergence is adjusted by actively rotating the rotating base to achieve quasi-omnidirectionality.

[0017] Another aspect of the present invention provides an application system for an ultrasonic-electromagnetic composite field black hole structure, including the ultrasonic-electromagnetic composite field black hole structure described above. It also includes the WR430 waveguide and load; One end of the WR430 waveguide is a closed end, and the other end is an open end for feeding electromagnetic waves or planar ultrasonic waves in TE10 mode. The ultrasonic-electromagnetic composite field black hole structure is disposed at the closed end of the WR430 waveguide; The load is located in the central region of the ultrasonic-electromagnetic composite field black hole structure to absorb the converged ultrasonic and electromagnetic energy.

[0018] In one embodiment, the load is an absorbing material with a specific complex permittivity, and the load is water or an ethanol solution of different concentrations.

[0019] In one embodiment, the system is used for microwave-ultrasound synergistic food processing, chemical reaction promotion, or biomass treatment.

[0020] Working Principle: This invention discloses an ultrasonic-electromagnetic composite field black hole structure. Its core structure consists of several ultrasonic blocking components arranged circumferentially and having a gear-shaped cross-section. Each ultrasonic blocking component is perforated along its axial direction. This structure integrates two major innovations: acoustics and electromagnetics. Acoustic section: "Interference obstruction method" high-frequency sound concentrator.

[0021] This solution overcomes the limitation of traditional acoustic concentrators, which are only suitable for low frequencies (<1600Hz). By analyzing the phase difference of high-frequency ultrasound propagation in the radial path, this solution innovatively proposes an "interference blocking method." Specifically, only the acoustic wave paths with a phase difference within the range of 0 to half a wavelength (i.e., the "ultrasonic paths") are retained, while ultrasonic blocking components block the paths within the remaining half wavelength range. By precisely calculating and designing the start and end angles of each "path," it is ensured that the acoustic waves of all retained paths achieve constructive rather than destructive interference in the central region, thereby achieving efficient acoustic focusing in the ultrasonic frequency band of 20kHz and above. Furthermore, to optimize the subsequent electromagnetic design, compensating solid blocks determined by Bezier curves are added to some "paths," and the exponential acoustic horn theory is used to verify that they do not introduce significant reflections, ensuring that the acoustic focusing effect is not affected.

[0022] Electromagnetism section: "Drilled parallel" graded refractive index electromagnetic concentrator.

[0023] Without altering the external contour of the aforementioned acoustic structure, this scheme involves axially perforating the ultrasonic blocking component. By adjusting the aperture and density at different radial positions, the volume ratio of the ultrasonic blocking component to air at those positions continuously varies. Based on the parallel equivalent medium theory, this structure can precisely control the equivalent relative permittivity along the axial direction (electromagnetic wave polarization direction), resulting in an approximately inverse-square gradient distribution along the radial direction. This distribution characteristic is crucial for achieving efficient, broadband, and robust electromagnetic wave convergence (effective for loads with different dielectric constants). By selecting substrates with different dielectric constants (such as low-dielectric polyphenylene sulfide and high-dielectric alumina ceramic) and combining this with perforation, the desired gradient dielectric distribution can be flexibly and precisely constructed.

[0024] The beneficial effects of this invention are as follows: 1. Synergistic Heating: The material to be processed (such as liquid food or chemical reaction mixture) is placed in the central loading region of the composite field black hole. Simultaneously, the magnetron and ultrasonic transducer are activated. Microwave energy is efficiently guided into the material's interior by the black hole structure for heating; ultrasonic energy is focused into the material region by the black hole structure, inducing strong cavitation effects and mechanical disturbances.

[0025] 2. Process optimization: For processes that require ultrasonic action in a specific direction (such as processing non-uniform mixtures), the azimuth angle of the black hole can be adjusted in real time by a rotary servo motor connected below the black hole in the composite field, so that the ultrasonic focusing direction is aligned with the direction required by the process.

[0026] 3. Performance Comparison: The heating efficiency of this system is expected to be more than 50% higher than that of traditional black hole-free systems. Furthermore, due to the highly localized energy, thermal effects from waveguide walls and other unwanted areas are effectively avoided, enabling precise and efficient processing. This device has extremely high application value in fields such as transesterification of biodiesel, ultrasonic-microwave synergistic extraction of plant active ingredients, and rapid pasteurization of liquid foods.

[0027] 4. Filling a technological gap: For the first time, a composite field black hole metamaterial that can simultaneously converge ultrasonic and electromagnetic waves was proposed and realized, providing a brand-new core functional device for multi-physics field collaborative applications.

[0028] 5. Significantly improves energy efficiency: Compared with the control group without black holes, the composite field black hole of this invention can increase the sound pressure modulus value of the central region by an average of 2-3 times, and increase the microwave absorption efficiency from less than 50% to more than 90%, which greatly improves energy utilization efficiency.

[0029] 6. Solving the problem of high-frequency sound convergence: The original "interference obstruction method" fundamentally solves the problem of high-frequency ultrasound convergence failure caused by interference in multi-channel structures, and successfully raises the working frequency of the sound concentrator from the kilohertz level to the ultrasonic frequency band above 20 kilohertz.

[0030] 7. Simplified structure and materials: Only common polyphenylene sulfide plastics and alumina ceramics are needed. Complex dual-field control functions can be achieved through a simple drilling process. It is low in cost and easy to process and integrate.

[0031] Excellent performance and robustness: The electromagnetic focusing function exhibits excellent robustness to changes in the dielectric constant of the load (e.g., from 10 to 80, and different concentrations of ethanol solution); the acoustic focusing function can be quasi-omnidirectionally controlled by rotating the base.

[0032] 8. Broad application prospects: It can be directly applied to existing microwave-ultrasound co-processing equipment to significantly improve the efficiency and uniformity of food processing (such as sterilization, extraction, drying), biodiesel preparation, wastewater treatment and other processes. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a dual-field composite black hole, in which... Figure 1 (a) Schematic diagram of the convergence of two fields in a composite field black hole; Figure 1 (b) Isofrequency curves of extremely anisotropic acoustic metamaterials; Figure 1 (c) Toothed extreme anisotropic acoustic materials.

[0035] Figure 2 This is a schematic diagram of a composite field black hole dual field, as described in this application. Figure 2 (a) is a schematic diagram of the "interference obstruction method". Figure 2 (b) is the acoustic black hole after using the "interference jamming method". Figure 2 (c) is the acoustic black hole after adding the compensation block. Figure 2 (d) is the composite field black hole after incorporating electromagnetic design. Figure 2 (e) is a three-dimensional model of the ultrasound-microwave combined system.

[0036] Figure 3 This is a diagram of the acoustic condensation results of a composite field black hole. Among them, Figure 3 (a)- Figure 3 (c) A planar ultrasonic field is fed into one end of a WR430 waveguide, and the other end is open. The ratio distribution of the real part of the sound pressure to the incident sound pressure is as follows: Figure 3 (a) is a diagram showing the acoustic condensation results of a composite field black hole. Figure 3(b) is a diagram showing the acoustic condensation results of the composite field black hole of the homogenized acoustic black hole. Figure 3 (c) is a diagram of the acoustic condensation results of a composite field black hole without a black hole. Figure 3 (d)- Figure 3 (f) A planar ultrasonic field is fed into one end of a WR430 waveguide, and the other end is closed. The distribution of the ratio of the acoustic pressure mode to the incident acoustic pressure is as follows: Figure 3 (d) is a diagram showing the acoustic condensation results of a composite field black hole. Figure 3 (e) is a diagram showing the acoustic condensation results of the composite field black hole of the homogenized acoustic black hole. Figure 3 (f) is a diagram showing the acoustic condensation results of a composite field black hole without a black hole. Figure 3 (g) is a graph showing the frequency response characteristics of the average sound pressure and incident sound pressure in the central region near the reference frequency. Figure 3 (h) is a graph showing the relationship between the average sound pressure in the central region of the composite field black hole and the rotation angle of the composite field black hole.

[0037] Figure 4 This is a diagram showing the electromagnetic concentration results of a black hole in a composite field. Figure 4 (a)- Figure 4 (c) Simulation results of the relative magnitude distribution of electric field modulus under the same incident power: Figure 4 (a) is a diagram showing the electromagnetic concentration results of a composite field black hole. Figure 4 (b) is a diagram showing the electromagnetic concentration results of the composite field of a gradually varying electromagnetic black hole. Figure 4 (c) is a diagram showing the electromagnetic concentration of a black hole in a composite field without a black hole. Figure 4 (d) is a graph showing the relationship between S11 (power reflection efficiency in decibels) and alcohol concentration for three groups of black holes: composite field black hole (CB), graded electromagnetic black hole (GB), and no black hole (No BH). (Solid line: simulation; dashed line: experiment)

[0038] Figure 5 This is a schematic diagram of a black hole structure in an ultrasonic-electromagnetic composite field.

[0039] Figure 6 This is a schematic diagram of the structure of an application system for an ultrasonic-electromagnetic composite field black hole structure. Detailed Implementation

[0040] To make the technical problems, technical solutions, and technical effects of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] Example 1 like Figure 5 As shown, this embodiment provides an ultrasonic-electromagnetic composite field black hole structure, including a number of ultrasonic blocking components arranged circumferentially and having a gear-shaped profile in their overall cross-section. Each ultrasonic blocking component has at least one hole distributed in the axial direction. The gap between two adjacent ultrasonic blocking components forms an ultrasonic path. The circumferential width and distribution of the ultrasonic pathways are configured such that, for an incident ultrasonic plane wave, the sound waves propagating in each ultrasonic pathway satisfy the constructive interference condition when they reach the central region of the structure, thereby achieving ultrasonic convergence. Furthermore, by adjusting the shape and distribution of the holes on each ultrasonic blocking component, the equivalent relative permittivity of the ultrasonic blocking component in the radial direction is made to have a specific gradient distribution, which is configured to guide and converge the incident electromagnetic waves to the central region of the structure. A compensation solid block is provided in one of the ultrasonic pathways. At least one hole is distributed inside the compensation solid block along the axial direction. The outline of the compensation solid block is determined by a second-order Bezier curve to provide the required material volume for the design of the equivalent dielectric constant of the electromagnetic part without introducing acoustic reflection.

[0043] The ultrasound pathway retains only phase satisfaction An acoustic path ∈ (0, 0.5λ), where λ is the wavelength of the ultrasound in the background medium; an ultrasound blocking component is used to block the acoustic path with a phase of 0.5λ to λ.

[0044] The overall width of each ultrasonic blocking component gradually decreases radially; each ultrasonic blocking component and the compensation solid block includes a first ultrasonic blocking unit arranged radially and located inside and a second ultrasonic blocking unit located outside. The dielectric constant of the first ultrasonic blocking unit is smaller than that of the second ultrasonic blocking unit. The first ultrasonic blocking unit and the second ultrasonic blocking unit form a dielectric constant gradient required for electromagnetic wave convergence.

[0045] The first ultrasonic blocking unit and the second ultrasonic blocking unit are fixedly connected. The first ultrasonic blocking unit is made of polyphenylene sulfide plastic with a low dielectric constant, and the second ultrasonic blocking unit is made of alumina ceramic with a high dielectric constant. The first and second ultrasonic blocking units of the ultrasonic blocking component are each provided with at least one hole along the axial direction.

[0046] The first ultrasonic blocking unit of the compensation solid block is provided with at least one hole along the axial direction.

[0047] According to the electromagnetic equivalent medium theory, the axial equivalent permittivity, within a scale much smaller than the wavelength, can be considered as a parallel combination of the ultrasonic impeding component and air. Therefore, the axial equivalent relative permittivity... It is calculated using the following formula: ; ; in, Let be the equivalent relative permittivity along the axial direction at any point in the composite field black hole. The relative permittivity of the ultrasonic blocking component. It is the relative permittivity of air. To represent the volume percentage of the ultrasonic damping component, draw a radius [value] on the radial direction of the ultrasonic damping component. Given a circle, find the total length of the circle on the solid. The ratio of the circle's circumference to the circumference of the circle is called the ratio of the circumference of the circle to the circumference of the circle. .

[0048] The ultrasonic blocking components exhibit frequency selectivity in the convergence of ultrasound. The operating frequency of the sound pressure enhancement in the central region of all ultrasonic blocking components is determined by the radial length difference of the ultrasonic path, preferably 20 kHz.

[0049] It also includes a rotating base, on which an ultrasonic blocking component and a compensating solid block are mounted. The direction of ultrasonic convergence is controlled by actively rotating the rotating base to achieve quasi-omnidirectionality.

[0050] In this embodiment, the final structure is as follows: Figure 2 (c) shows the gear-shaped acoustic black hole structure. The dark area is the ultrasonic blocking component (which can be made of polyphenylene sulfide or alumina ceramic), and the blank area is the air passage.

[0051] Example 2 This embodiment is a further optimization based on Embodiment 1, as detailed below: exist Figure 1 Based on (a), half a phase of the ultrasonic pathway is retained, while the other half of the ultrasonic pathway is blocked by an ultrasonic blocking component (solid material). For example... Figure 2 As shown, let Figure 2 (a) The radius of the outer circle is The inner diameter is The central angle is defined. That path is phase Only the phase is satisfied The ultrasound pathway, according to the path formula: ; in The wavelength of sound waves in air at 20kHz (the velocity of sound is taken as...) The reference frequency is taken ), which can be deduced in reverse The ranges are shown in Table 1 (only listed). The range of central angles is within the given range; the range of other central angles can be obtained based on symmetry.

[0052] Table 1: Starting and ending angles for different channels

[0053] Based on the above perspectives, acoustic modeling is performed to obtain... Figure 2 The model in (b) shows the dark areas as ultrasonic pathways blocked by ultrasonic obstruction components. The blank areas represent ultrasonic pathways that can be smoothly passed through by ultrasound. Considering that this scheme also requires the design of an isotropic electromagnetic black hole, and... Figure 2 (b) model in or The region is almost empty, which makes it inconvenient to design isotropic electromagnetic black holes. Therefore, a compensation block needs to be added to the first channel region of the composite field black hole, such as... Figure 2 As shown in (c). The contours of this pair of compensating solid blocks are formed by... , , The second-order Bézier curve composed of three points is determined.

[0054] The addition of a compensating solid block in the first channel region will inevitably cause a change in the overall acoustic impedance of the metamaterial. Since the first channel region with the added compensating solid block can be considered a gradually changing cross-section acoustic duct, and the cross-sectional area of ​​this acoustic duct varies with the radius... Since the impedance distribution is approximately exponential, the theory of exponential sound horns can be used to prove that this impedance change will not cause strong reflections in the sound field. First, the meandering coefficient is calculated. Then calculate the cutoff frequency of the sound horn. Therefore, the change in the cross-section of the first channel will not significantly enhance the reflection of the sound field.

[0055] Design of the electromagnetic component for a composite field black hole. Without altering the external contour of the ultrasonic blocking component, only internal perforations are made to incorporate the electromagnetic design without changing its acoustic properties. The design couples the electromagnetic field black hole design to the existing acoustic design. The team's research is based on the dielectric equivalence theory, constructing a medium with continuously varying dielectrics. When the dielectric constant at a point in the medium is inversely proportional to the square of the distance from that point to the origin, it can efficiently concentrate 2.45 GHz electromagnetic waves to the central load region, regardless of how the real part of the load's dielectric constant changes from 10 to 80. Theoretically, the dielectric distribution along the radius of the electromagnetic black hole should be as shown in equation (1-1). Since a WR430 waveguide is used to feed TE10 mode electromagnetic waves as excitation, the electric vector direction remains parallel to the z-axis throughout the electromagnetic wave transmission process. Therefore, only the z-component of the dielectric constant tensor needs to satisfy equation (1-1). ; Therefore, the acoustic black hole material is first divided into two types of materials along the radius r (such as...). Figure 2 As shown in (d), the light blue portion is made of polyphenylene sulfide plastic with a dielectric constant of 4, while the dark blue portion is made of alumina ceramic with a dielectric constant of 9.9. Holes of specific shapes are then punched along the z-axis in each material. The equivalent dielectric constant along the z-axis can be considered as [value missing] in a scale much smaller than the wavelength. Figure 2 (d) is formed by the parallel connection of the solid material and the air, so the equivalent z-direction dielectric can be constrained by equation (1-1).

[0056] ; in Let be the equivalent relative permittivity along the z-axis at any point in the composite field black hole. The relative permittivity of the solid material portion. It is the relative permittivity of air. This represents the volume percentage of solid materials. To obtain... The specific value can be found in Figure 2 (d) Draw a circle with a radius of Given a circle, find the total length of the circle on the solid. The ratio to the circumference of the circle is sufficient: .

[0057] Example 3 Figure 2As shown in (e), this embodiment provides an application system for an ultrasonic-electromagnetic composite field black hole structure, including an ultrasonic-electromagnetic composite field black hole structure as described in Embodiment 2; it also includes a WR430 waveguide and a load; one end of the WR430 waveguide is a closed end, and the other end is an open end for feeding electromagnetic waves or planar ultrasonic waves in TE10 mode; the ultrasonic-electromagnetic composite field black hole structure is disposed at the closed end of the WR430 waveguide; the load is disposed in the central region of the ultrasonic-electromagnetic composite field black hole structure for absorbing the converged ultrasonic and electromagnetic energy.

[0058] In this embodiment, the load is water.

[0059] Example 4 To verify the rationality of the acoustic design, this embodiment performed a two-dimensional pressure acoustic simulation on Embodiment 3 to simulate the distribution of the sound pressure solid part or sound pressure modulus, as detailed below: The left boundary is excited by a uniform linear radiation sound source with a frequency of 20kHz and an amplitude of 1Pa. The right boundary is set as the sound radiation boundary, and the upper and lower boundaries, as well as the solid material part, are all set as hard sound field boundaries. The background medium is set as air, thus obtaining... Figure 3 (a) Figure 3 (c) Figure 3 (e) shows the acoustic compaction distribution, with the three simulation results representing a composite field black hole, a homogenized acoustic black hole (where the non-uniformly distributed solid material in the composite field black hole is replaced with a uniformly distributed solid material while maintaining the total area of ​​the solid material unchanged), and a black hole-free simulation. Figure 3 The simulation results in (a) show that the sound fields of all ultrasonic pathways exhibit constructive interference near the central region, thus enhancing the sound pressure in the central region compared to... Figure 3 (c) In the group without black holes, the composite field black hole does indeed have a sound-concentrating effect. Furthermore, in comparison... Figure 3 The simulation results in (c) also show that if the "interference inhibition method" is not used, the sound fields in different paths may interfere with each other near the central region, resulting in poor sound concentration.

[0060] If Figure 3 Setting the right boundary of the three images on the left to a hard sound field boundary yields the following result. Figure 3 (b) Figure 3 The sound pressure modulus distribution diagrams for (d) and (f). A radius of [missing information] is taken in the central region of each of them. The statistical circle was used to calculate the average acoustic pressure modulus value of the statistical circle region, and the simulation results are shown in Table 2. The simulation results show that the acoustic pressure modulus value of the composite field black hole group is significantly higher than that of the group without a black hole and the homogenized acoustic black hole. Therefore, the composite field black hole can effectively focus planar ultrasound into the central region, and the "interference obstruction method" is necessary.

[0061] Table 2. Average values ​​of acoustic pressure modulus within the circular area under terminal closure conditions, unit: Pa

[0062] To investigate the frequency response characteristics of composite field black holes, ultrasonic waves at frequencies from 19.5 kHz to 20.5 kHz were fed into a WR430 waveguide closed at one end. The average sound pressure in the central region was simulated and measured, thus obtaining... Figure 3 (a) Results. The results show that, compared to the group without a black hole, the acoustic focusing performance of the composite field black hole only shows a significant effect around 20kHz, exhibiting strong frequency selectivity. Furthermore, to verify the anisotropy of the sound field converged by the composite field black hole, we simulated and experimented with the effect of different rotation angles on the average sound pressure in the central region, such as... Figure 3 As shown in (b), the results show that the composite field black hole exhibits significant acoustic concentration characteristics only when the rotation angle is within 5°.

[0063] Example 5 like Figure 6 As shown, this embodiment simulates and verifies the electromagnetic concentration characteristics of an ultrasonic-electromagnetic composite field black hole structure in Embodiment 3.

[0064] Three groups of black holes—a composite field black hole, an electromagnetic black hole with uniformly varying dielectric constant, and one without metamaterials—were placed at the closed end of a single-ended WR430 waveguide. Absorbing loads with different real parts of the complex permittivity (the imaginary part was always 10) were inserted at the center of the black hole. The other end was fed with 2.45 GHz microwaves for single-mode transmission in the TE10 mode. Figure 4 It can be seen that the absorption effect and electric field distribution of the composite field black hole can be approximately equivalent to an electromagnetic black hole with uniform dielectric variation. Moreover, the absorption effect is significantly improved compared to the group without metamaterials. Therefore, it is proven that the composite field black hole has an electromagnetic concentration effect on loads with different dielectrics.

[0065] To verify the accuracy of the simulation results, a microwave absorption experiment was conducted using water as the load. We measured the incident and reflected power using a directional coupler, and the absorption efficiency is shown in Table 3. The experimental results agree well with the simulation results, proving the accuracy of the simulation.

[0066] Table 3: Microwave absorption efficiency under water load

[0067] Example 4 To further verify the accuracy of the electromagnetic concentration performance of the ultrasonic-electromagnetic composite field black hole structure disclosed in Example 2, this embodiment uses ethanol solutions of different concentrations as the load and sets corresponding values ​​for the load's relative permittivity. The following simulations and experiments were conducted, and the results are as follows: Figure 4 As shown.

[0068] Figure 4 (a) Figure 4 (b) Figure 4 (c) are simulation results of the relative magnitude distribution of electric field modulus under the same incident power for three cases: composite field black hole, graded electromagnetic black hole, and no black hole. Figure 4 (d) represents three groups: composite field black holes (CB), graded electromagnetic black holes (GB), and no black holes (No BH). S 11 The curve showing the relationship between power reflection efficiency (expressed in decibels) and alcohol concentration ( Figure 4 (d) In this diagram, the solid line represents the simulation results; the dashed line represents the experimental results.

[0069] Depend on Figure 4 (c) shows that the composite field black hole can significantly improve the efficiency of microwave absorption by ethanol solutions of various concentrations compared with the non-black hole, and the simulation and experimental values ​​are in good agreement.

[0070] In summary, by employing the "interference obstruction method," the frequency range of existing acoustic concentrators was successfully extended from low frequencies to 20kHz ultrasound, thus constructing an ultrasonic black hole. Utilizing the parallel dielectric equivalence theory, by creating appropriately shaped holes in the solid material portion of the ultrasonic black hole and incorporating the design of an electromagnetic black hole, a ultrasonic-electromagnetic composite field black hole was ultimately formed. A series of simulations and experiments were then conducted. By feeding planar ultrasound into the waveguide port, the acoustic concentration characteristics, frequency selectivity, and anisotropy of the ultrasonic-electromagnetic composite field black hole were confirmed. By feeding TE10 mode electromagnetic waves into the waveguide port, the robustness of the electromagnetic concentration performance of the ultrasonic-electromagnetic composite field black hole to loads with different dielectrics was confirmed. This research fills a gap in the design of ultrasonic-electromagnetic composite field black holes and has potential applications in the food processing and chemical industries.

Claims

1. An ultrasonic-electromagnetic composite field black hole structure, characterized in that, It includes several ultrasonic blocking components arranged circumferentially and having a gear-shaped profile in the overall cross-section. Each ultrasonic blocking component has at least one hole distributed in the axial direction. The gap between two adjacent ultrasonic blocking components forms an ultrasonic passage. The circumferential width and distribution of the ultrasonic pathways are configured such that, for an incident ultrasonic plane wave, the sound waves propagating in each of the ultrasonic pathways satisfy the constructive interference condition when they reach the central region of the structure, thereby achieving ultrasonic convergence. Furthermore, by adjusting the shape and distribution of the holes on each of the ultrasonic blocking components, the equivalent relative permittivity of the ultrasonic blocking components in the radial direction is made to have a specific gradient distribution, which is configured to guide and converge the incident electromagnetic waves to the central region of the structure. A compensating solid block is provided within one of the ultrasonic pathways. The outline of the compensating solid block is determined by a second-order Bezier curve to provide the required material volume for the design of the equivalent dielectric constant of the electromagnetic part without introducing acoustic reflection.

2. The ultrasonic-electromagnetic composite field black hole structure according to claim 1, characterized in that, The ultrasound pathway retains only phase satisfaction. An acoustic wave path ∈ (0, 0.5λ), where λ is the wavelength of the ultrasound in the background medium; the ultrasound blocking component is used to block the acoustic wave path with a phase of 0.5λ to λ.

3. The ultrasonic-electromagnetic composite field black hole structure according to claim 1, characterized in that, The overall width of each of the ultrasonic blocking components gradually decreases radially. Each of the ultrasonic blocking components and the compensation solid block includes a first ultrasonic blocking unit arranged radially and located inside and a second ultrasonic blocking unit located outside. The dielectric constant of the first ultrasonic blocking unit is smaller than that of the second ultrasonic blocking unit. The first ultrasonic blocking unit and the second ultrasonic blocking unit are used to construct the dielectric constant gradient required for electromagnetic wave convergence.

4. The ultrasonic-electromagnetic composite field black hole structure according to claim 3, characterized in that, The first ultrasonic blocking unit and the second ultrasonic blocking unit are fixedly connected. The first ultrasonic blocking unit is a polyphenylene sulfide plastic with a low dielectric constant, and the second ultrasonic blocking unit is an alumina ceramic with a high dielectric constant. Each of the first and second ultrasonic blocking units of the ultrasonic blocking components has at least one hole along the axial direction.

5. The ultrasonic-electromagnetic composite field black hole structure according to claim 4, characterized in that, The first ultrasonic blocking unit of the compensation solid block is provided with at least one hole along the axial direction.

6. The ultrasonic-electromagnetic composite field black hole structure according to claim 5, characterized in that, It also includes a rotating base, on which the ultrasonic blocking component and the compensating solid block are disposed. The direction of ultrasonic convergence is adjusted by actively rotating the rotating base to achieve quasi-omnidirectionality.

7. The ultrasonic-electromagnetic composite field black hole structure according to claim 6, characterized in that, According to the electromagnetic equivalent medium theory, the equivalent dielectric constant in the axial direction is considered as the parallel connection of the ultrasonic barrier member and air in the scale range much smaller than the wavelength, so the axial equivalent relative dielectric constant is calculated by the following formula: ； ； in, Let be the equivalent relative permittivity along the axial direction at any point in the composite field black hole. The relative permittivity of the ultrasonic blocking component. It is the relative permittivity of air. To represent the volume percentage of the ultrasonic damping component, draw a radius [value] on the radial direction of the ultrasonic damping component. Given a circle, find the total length of the circle on the solid. The ratio of the circle's circumference to the circumference of the circle is called the ratio of the circumference of the circle to the circumference of the circle. .

8. The ultrasonic-electromagnetic composite field black hole structure according to claim 1, characterized in that, The ultrasonic blocking components exhibit frequency selectivity in the convergence of ultrasound, and the operating frequency of the sound pressure enhancement in the central region of all the ultrasonic blocking components is determined by the radial length difference of the ultrasonic path.

9. An application system for an ultrasonic-electromagnetic composite field black hole structure, characterized in that, Includes a supersonic-electromagnetic composite field black hole structure according to any one of claims 1 to 8; It also includes the WR430 waveguide and load; One end of the WR430 waveguide is a closed end, and the other end is an open end for feeding electromagnetic waves or planar ultrasonic waves in TE10 mode. The ultrasonic-electromagnetic composite field black hole structure is disposed at the closed end of the WR430 waveguide; The load is located in the central region of the ultrasonic-electromagnetic composite field black hole structure and is used to absorb the converged ultrasonic and electromagnetic energy.

10. The application system of an ultrasonic-electromagnetic composite field black hole structure according to claim 9, characterized in that, The load is an absorbing material with a specific complex permittivity.

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