WO2021206330A1 - Metasurface having one smooth and exposed surface and method for designing same - Google Patents

Metasurface having one smooth and exposed surface and method for designing same Download PDF

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Publication number
WO2021206330A1
WO2021206330A1 PCT/KR2021/003748 KR2021003748W WO2021206330A1 WO 2021206330 A1 WO2021206330 A1 WO 2021206330A1 KR 2021003748 W KR2021003748 W KR 2021003748W WO 2021206330 A1 WO2021206330 A1 WO 2021206330A1
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Prior art keywords
metasurface
exposed
smooth surface
concave portions
smooth
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PCT/KR2021/003748
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French (fr)
Korean (ko)
Inventor
최원재
오주환
승홍민
하종문
김미소
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한국표준과학연구원
울산과학기술원
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Publication of WO2021206330A1 publication Critical patent/WO2021206330A1/en

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/002—Devices for damping, suppressing, obstructing or conducting sound in acoustic devices
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/162—Selection of materials
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/321—Physical

Definitions

  • the present invention relates to a metasurface having a smooth surface exposed and a design method thereof, and more particularly, a metasurface formed on the surface of a moving means running in a fluid medium and having a smooth surface exposed to conceal the moving means from acoustic waves. and to a design method thereof.
  • Metamaterials use periodic artificial structures to implement wave characteristics that are difficult to have in natural materials, such as zero (0) refractive index and negative refractive index.
  • acoustic metamaterials can be used to microscopically focus sound in a region smaller than a wavelength, freely change the path of travel, or improve sound wave and ultrasound imaging quality.
  • artificial structure design technology that freely adjusts the elastic modulus, density, and refractive index through periodic arrangement of structures smaller than the wavelength is essential.
  • meta-surface structures made by arranging unit structures designed based on physical principles on a two-dimensional thin film has been conducted, and a concealment technology against the detection signal of acoustic waves, that is, stealth ), the development of metasurfaces with functionalities is required.
  • An object of the present invention is to provide a metasurface that reflects an acoustic wave at an angle different from an angle of incidence and a metasurface exposed to a smooth surface, and a design method thereof.
  • the metasurface to which a smooth surface according to the present invention is exposed includes a plurality of identical unit cells arranged in one direction in the metasurface that is attached to the surface of a moving means running in a fluid medium and has a smooth surface exposed,
  • n a natural number equal to or greater than 4
  • concave portions having different depths in the one direction on one surface are formed with the same width and the same spacing, and the different depths of the n concave portions are the smoothness of the meta surface.
  • the different depths of the n concave portions allow acoustic waves incident on the normal of the smooth surface of the metasurface to be reflected at a constant angle with respect to the normal.
  • the unit cell is fabricated from one material selected from among materials similar to the acoustic impedance of the fluid medium.
  • n recesses are filled with a supplementary material made of a material selected from among materials different from the acoustic impedance of the fluid medium.
  • the one material is ABS resin.
  • the replenisher is air or aluminum.
  • the method for designing a metasurface with a smooth surface exposed is a method for designing a metasurface in which a smooth surface is exposed and attached to the surface of a moving means operated in a fluid medium, one unit of the metasurface, designing a unit cell in which n (n is a natural number equal to or greater than 4) concave portions having different depths are formed with the same width and the same spacing; processing the meta surface so that the unit cells are arranged in the one direction; and attaching the metasurface to the surface of the moving means so that the other surface of the metasurface on which the recess is formed is attached to the surface of the moving means.
  • the step of designing the unit cell includes the wavelength of the acoustic wave detecting the moving means and the reflection angle at which the acoustic wave incident to the normal of the smooth surface of the metasurface is reflected from the bottom of the n concave portions and travels. selecting the arrangement period of the unit cell, selecting the width and the spacing of the n concave portions, and being incident on a smooth surface of the metasurface and reflected from the bottom surface of each of the n concave portions and deriving different depths of the n concave portions so that the acoustic waves have equally spaced phase gradients.
  • the step of deriving the different depths of the n concave portions includes calculating a phase difference of the acoustic wave according to the depth of the concave portions.
  • the step of machining the metasurface includes selecting a material of the unit cell and a material of a supplementary material to be filled in the n recesses, and processing the n recesses.
  • the metasurface with a smooth surface exposed according to the present invention can conceal the movement means running in the fluid medium in which the metasurface is formed from the detection signal of the acoustic wave through the implementation of a phase gradient according to the change in depth of each point of the reflective surface. have.
  • the matta surface on which a smooth surface according to the present invention is exposed, the surface on which the concave portion is formed is attached to the surface of the moving means operated in a fluid medium, and the surface formed smoothly without bending is exposed to the outside, so that when moving, the fluid by the surface
  • the phenomenon of increasing the resistance does not occur, and the phenomenon of weakening of the stealth function due to foreign substances does not occur, and the management of the surface is easy.
  • the method for designing a metasurface with a smooth surface exposed according to the present invention avoids the detection of acoustic waves of a specific frequency by reflecting the acoustic waves at an angle different from the incident angle through the implementation of a phase gradient according to the change in depth of each point of the reflective surface. It can be designed to have a physical structure for
  • FIG. 1 is a perspective view of a meta surface on which a smooth surface is exposed according to an embodiment of the present invention.
  • FIG. 2 is a cross-sectional view of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
  • FIG. 3 is an enlarged view of FIG. 2A , and is a cross-sectional view of a unit cell of a metasurface having a smooth surface exposed according to an embodiment of the present invention.
  • FIG. 4 is a cross-sectional view of a state in which a metasurface having a smooth surface exposed is attached to the surface of a moving means operating in a fluid medium according to an embodiment of the present invention.
  • FIG. 5 is a simulation diagram illustrating the behavior of an incident wave and a reflected wave with respect to a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
  • FIG. 6 is a flowchart of a method for designing a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
  • FIG. 7 is a flowchart of a method of designing a unit cell of a metasurface to which a smooth surface is exposed according to an embodiment of the present invention.
  • FIG. 8 is a view for explaining the principle of designing a unit cell of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
  • FIG. 9 is a view for explaining the principle of designing a unit cell of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
  • FIG. 10 is a graph illustrating a phase difference of an acoustic reflected wave according to a depth of a concave portion.
  • FIG. 11 is a view for explaining a process of deriving a depth of a concave portion in the graph of FIG. 10 .
  • FIG. 1 and 2 are perspective and cross-sectional views of a meta surface on which a smooth surface is exposed according to an embodiment of the present invention
  • FIG. 3 is an enlarged view of FIG. 2A in which a smooth surface according to an embodiment of the present invention is exposed.
  • It is a cross-sectional view of the unit cell of the metasurface.
  • 4 is a cross-sectional view of a state in which a meta-surface, on which a smooth surface is exposed, is attached to the surface of a moving means operating in a fluid medium according to an embodiment of the present invention.
  • the meta surface 100 on which a smooth surface is exposed includes a plurality of unit cells 110 in which a plurality of concave portions 111 having different depths are formed.
  • the other surface 101 of the metasurface including the dog, on which the concave portion 111 is formed is attached to the surface of the moving means 10 running in a fluid medium, and the smooth one surface 102 of the metasurface is exposed to the outside.
  • the metasurface 100 reflects the acoustic wave at an angle different from the incident angle with respect to the acoustic wave detection signal for the moving means 10 to perform a stealth function to conceal the moving means 10, It prevents the stealth function from being deteriorated by preventing foreign substances from getting caught during the operation of the vehicle because the exposed surface is smooth.
  • a plurality of identical unit cells 110 are arranged in one direction (the illustrated X-axis direction).
  • the unit cell 110 at least four or more concave portions 111 having different depths in the x-axis direction are formed on one surface with the same width and the same spacing. At this time, if the number of at least 4 or more is n, n is one of 4 or more natural numbers.
  • the metasurface 100 has a smooth surface 102 in which the surfaces of the unit cells 110 in which the concave portions 111 are not formed are continuously arranged and the surfaces of the unit cells 110 in which the concave portions 111 are formed are continuous. It has an arranged curved rudder surface 101 . In addition, the meta surface 100 is an edge portion ( 103) may have more.
  • the unit cell 110 has n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n having different depths in the x-axis direction on one surface have the same width and formed with equal spacing.
  • n is one of 4 or more natural numbers.
  • n is 10.
  • the n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n are grooves having a flat bottom surface and a rectangular cross-section, and each depth is formed differently.
  • each of the different depths of the n recesses 111-1, 111-2, 111-3, 111-4, ..., 111-n is incident on the smooth surface 102 of the metasurface and the recesses ( 111), the acoustic waves reflected from the flat bottom have an equally spaced phase gradient.
  • the acoustic wave reflected from each of the bottom surfaces of the ten concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-10 is equal to 36 degrees. It has a phase gradient of spacing.
  • the metasurface 100 has a physical structure for avoiding detection of acoustic waves of a specific frequency.
  • the unit cell 110 is processed from one material selected from among materials similar to the acoustic impedance of the medium through which the acoustic wave travels. This means that the metasurface 100 is applied to a moving means running in a fluid medium, prevents reflection of acoustic waves from the smooth surface 102 of the metasurface 100 and the sound incident into the metasurface 100 . for good penetration of waves.
  • the unit cell 110 is formed of ABS resin similar to the acoustic impedance of water.
  • the n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n formed in the unit cell 110 are acoustic waves of a medium through which the acoustic wave propagates. It is filled with a filler material made of a material selected from among the materials differing from the impedance. The supplementary material is different from the acoustic impedance of the material constituting the unit cell so that the acoustic wave incident into the metasurface 100 is well reflected from the bottom of the concave portion 111 .
  • the filler filling the recess 111 is made of air or aluminum which is different from the acoustic impedance of water.
  • FIG. 5 is a simulation diagram illustrating the behavior of an incident wave and a reflected wave with respect to a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
  • the detection is successful, but as in the present invention, if the acoustic wave is reflected at an angle different from the incident angle, When the acoustic incident wave incident on the metasurface 100 at 0 degrees is reflected and is reflected at a reflection angle corresponding to a predetermined angle other than 0 degrees, detection by reflection of the acoustic wave is not performed. Accordingly, the metasurface 100 has a stealth function to avoid detection of the acoustic wave by reflecting the acoustic wave at an angle different from the incident angle.
  • FIG. 6 is a flowchart of a method for designing a metasurface to which a smooth surface is exposed according to an embodiment of the present invention
  • FIG. 7 is a method for designing a unit cell of a metasurface to which a smooth surface is exposed according to an embodiment of the present invention. is a flowchart of
  • the design method (S100) of the metasurface 100 on which a smooth surface is exposed is attached to the surface of the moving means 10 operated in a fluid medium and the moving means ( 10)
  • a method of designing a metasurface 100 that avoids being detected by returning an acoustic wave detection signal for 10) the step of designing a unit cell 110 that is one unit of the metasurface 100 (S110), It includes a step of processing the metasurface 100 (S120), and attaching the metasurface 100 (S130).
  • the unit cell 110 designed in step S110 is one unit of the metasurface 100 and a unit cell in which n concave portions 111 having different depths in one direction on one side are formed with the same width and the same spacing ( 110) is the design stage.
  • n is a natural number equal to or greater than 4.
  • the step of designing the unit cell 110 includes the step of selecting the cycle of the unit cell 110 ( S111 ), the spacing between the concave portions 111 and the spacing of the concave portions 111 . It includes a step of selecting a width (S113), and a step of deriving the depth of each of the n concave portions 111 (S115).
  • FIGS. 8 and 9 are diagrams for explaining the principle of designing a unit cell of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
  • the unit cell 110 which is one unit of the metasurface 100, has a cross-section having a flat bottom surface on the other surface 101 opposite to the smooth one surface 102 of the metasurface 100.
  • Concave portions 111 corresponding to rectangular grooves have different depths and are formed with the same width and the same spacing.
  • step S111 first, a period M corresponding to the size in the X-axis direction of the unit cell 110, which is one unit of the metasurface 100, is selected.
  • the period M of the unit cell 110 is the wavelength of the acoustic wave corresponding to the detection signal so that the acoustic wave incident on the normal of the smooth surface 102 of the metasurface 100 is reflected at an angle ⁇ with respect to the normal line. ( ⁇ ) is selected as a value divided by sin ⁇ .
  • step S113 the number (n) of the concave portions 111 formed within the period M of the unit cell 110, the concave portions 111
  • the spacing (a) and the width (b) of the concave portion 111 are selected.
  • the spacing a of the concave portion 111 should be greater than or equal to the period M of the unit cell 110 divided by 4 . That is, the number of the concave portions 111 should be four or more.
  • the number n of the concave portions 111 is selected as a natural number of 4 or more, and the interval M of the concave portions 111 is calculated by dividing the period M by n.
  • n is 10.
  • the width b of the concave portion 111 is smaller than the spacing between the concave portions 111, an appropriate width that can act as a resistance to the acoustic wave is selected.
  • n is 10.
  • step S115 in order to derive different depths of each of the n concave portions 111, the curved other surface 101 of the metasurface 100 is attached to the surface of the moving means 10, and the smooth surface 102 is Referring to FIG. 9, which is exposed to the outside and shows in cross-sectional view that the acoustic wave is incident on a smooth surface, the concave portion 111 for the acoustic incident wave I incident on the concave portion 111 having a depth L
  • the reflection efficiency (R/I) of the reflected wave (R) reflected from the bottom is expressed as in Equation 1 below.
  • m is (a-b)/a
  • k is the wave number of the incident wave.
  • FIG. 10 is a graph illustrating a phase difference of acoustic reflected waves according to the depth of the concave portion
  • FIG. 11 is a view for explaining a process of deriving the depth of the concave portion from the graph of FIG. 10 .
  • Equation 1 the acoustic incident wave I incident on the concave portion 111 having a depth L is reflected from the bottom surface of the concave portion 111 to generate a phase difference, and the phase difference ⁇ at that time is calculated by the following equation Same as Equation 2.
  • step S115 the phase difference ⁇ of the acoustic reflected wave according to the depth L of the concave portion 111 in order to derive different depths of each of the n concave portions 111 is calculated by Equation 1 and 2 are shown graphically.
  • step S115 different depths of n concave portions 111 are derived from a graph illustrating the phase difference ⁇ of the acoustic reflected wave according to the depth L of the concave portion 111 .
  • the different depths of each of the n concave portions 111 are, after drawing n equally spaced lines having the same phase difference in the range of the phase difference of 360 degrees in the graph curve, the depth of the coordinate values in the graph curve meeting the equal intervals It is derived through the value corresponding to (L).
  • each of the n concave portions 111 are incident on the smooth surface 102 of the metasurface 100 and the acoustic waves reflected from the bottom surface of each of the n concave portions 111 are equally spaced. It is derived to have a phase gradient.
  • n is selected as 10, and the acoustic waves reflected from the bottom surface formed at different depths of each of the ten concave portions 111 generate a phase difference of 36 degrees each. Since the n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n have different depths, the sound incident on the metasurface 100 has an incident angle of 0 degrees. The incident wave is reflected from the bottom surface of the concave portions 111 and is reflected at a reflection angle corresponding to a constant angle instead of 0 degree. Accordingly, the metasurface 100 has a physical structure for avoiding the detection of the acoustic wave of a specific frequency by reflecting the acoustic wave at an angle different from the incident angle.
  • step S120 the metasurface 100 is processed by arranging the unit cells 110 designed in step S110 in one direction. Prior to the processing of the concave portion 111 , the material of the unit cell and the material of the supplementary material inserted into the concave portion 111 are selected. The material selection is the same as described above in the description of the meta surface 100 . After processing the meta surface 100 on which the recess 111 is formed, a supplementary material is inserted into the recess 111 .
  • step S130 the meta surface 100 processed in step S120 is attached to the moving means 10 running in a fluid medium.
  • the curved other surface 101 of the meta surface 100 on which the recess 111 is formed is attached to the surface of the moving means 10 and the smooth surface 102 of the meta surface 100 is exposed to the outside. .

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  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
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  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

The present invention relates to a metasurface having a smooth and exposed surface, and provides a metasurface which is attached to a surface of a moving means operated in a fluid medium and has one smooth and exposed surface, the metasurface comprising a plurality of identical unit cells arranged in one direction, wherein each of the unit cells has n (n is a natural number greater than or equal to 4) concave parts which are formed in said one direction on one surface thereof, have different depths and identical widths, and are spaced an identical interval apart from each other, the different depths of the n concave parts enable acoustic waves, which are incident to the one smooth surface of the metasurface and reflected from the bottom surface of the n concave parts, respectively, to have phase gradients of an equal interval, and the other surface of the metasurface, on which the concave parts are formed, is attached to a surface of the moving means and the one smooth surface of the metasurface is exposed to the outside.

Description

매끈한 일면이 노출되는 메타표면 및 이의 설계 방법A metasurface with a smooth surface exposed and a design method therefor
본 발명은 매끈한 일면이 노출되는 메타표면 및 이의 설계 방법에 관한 것으로, 상세하게는 유체 매질에서 운행하는 이동 수단의 표면에 형성되어 음향파에 대해 상기 이동 수단을 은폐하는 매끈한 일면이 노출되는 메타 표면 및 이의 설계 방법에 관한 것이다.The present invention relates to a metasurface having a smooth surface exposed and a design method thereof, and more particularly, a metasurface formed on the surface of a moving means running in a fluid medium and having a smooth surface exposed to conceal the moving means from acoustic waves. and to a design method thereof.
메타물질은 주기적인 인공구조물을 이용하여 영(0) 굴절률 및 음의 굴절률과 같은 자연 물질이 가지기 어려운 파동 특성을 구현하는 것이다. 과거에는 전자기 분야에서 활발했던 메타물질의 연구가 최근 음향 분야로 빠르게 이동하면서 음향파(acoustic wave)의 파동 특성을 이용한 음향 메타 물질에 대한 연구가 활발해지고 있다. 예를 들어 소리를 파장보다 작은 영역에 극소적으로 집중시키거나, 진행경로를 자유자재로 바꾸거나, 음파 및 초음파 이미징 화질을 개선하는데 음향 메타 물질이 이용될 수 있다. 이를 위해서는 파장보다 작은 구조체를 주기적인 배열을 통해 탄성률, 밀도, 굴절률을 자유자재로 조절하는 인공 구조체 설계 기술이 필수적이다.Metamaterials use periodic artificial structures to implement wave characteristics that are difficult to have in natural materials, such as zero (0) refractive index and negative refractive index. As the study of metamaterials, which was active in the electromagnetic field in the past, has moved rapidly to the acoustic field, research on acoustic metamaterials using the wave characteristics of acoustic waves is becoming active. For example, acoustic metamaterials can be used to microscopically focus sound in a region smaller than a wavelength, freely change the path of travel, or improve sound wave and ultrasound imaging quality. For this, artificial structure design technology that freely adjusts the elastic modulus, density, and refractive index through periodic arrangement of structures smaller than the wavelength is essential.
최근에는 2차원 박막 위에 물리적인 원리를 통해 설계된 단위 구조들을 배열하여 만들어지는 메타표면(meta surface) 구조들에 대한 연구가 이루어지고 있으며, 음향파의 탐지 신호에 대항하는 은폐 기술, 즉 스텔스(stealth) 기능을 갖는 메타 표면의 개발이 요구된다.Recently, research on meta-surface structures made by arranging unit structures designed based on physical principles on a two-dimensional thin film has been conducted, and a concealment technology against the detection signal of acoustic waves, that is, stealth ), the development of metasurfaces with functionalities is required.
본 발명은 음향파를 입사각도와 다른 각도로 반사하는 매끈한 일면이 노출되는 메타표면 및 이의 설계방법을 제공하려는 것이다. An object of the present invention is to provide a metasurface that reflects an acoustic wave at an angle different from an angle of incidence and a metasurface exposed to a smooth surface, and a design method thereof.
본 발명에 따른 매끈한 일면이 노출되는 매타표면은, 유체 매질에서 운행되는 이동 수단의 표면에 부착되고 매끈한 일면이 노출되는 메타표면에 있어서, 일 방향으로 배열되는 동일한 단위 셀을 복수 개 포함하고, 상기 단위 셀은 일면에 상기 일 방향으로 서로 다른 깊이를 갖는 n(n은 4 이상인 자연수)개의 오목부가 동일한 폭 및 동일한 이격 간격으로 형성되고, 상기 n개의 오목부의 서로 다른 깊이는, 상기 메타표면의 매끈한 일면에 입사하고 상기 상기 n개의 오목부 각각의 바닥면에서 반사되는 음향파가 등간격의 위상 구배를 갖게 하고, 상기 오목부가 형성된 상기 메타표면의 타면이 상기 이동 수단의 표면에 부착되고, 상기 메타표면의 매끈한 일면은 외부로 노출된다. The metasurface to which a smooth surface according to the present invention is exposed includes a plurality of identical unit cells arranged in one direction in the metasurface that is attached to the surface of a moving means running in a fluid medium and has a smooth surface exposed, In the unit cell, n (n is a natural number equal to or greater than 4) concave portions having different depths in the one direction on one surface are formed with the same width and the same spacing, and the different depths of the n concave portions are the smoothness of the meta surface. Acoustic waves incident on one surface and reflected from the bottom surface of each of the n concave portions have a phase gradient at equal intervals, and the other surface of the meta surface on which the concave portions are formed is attached to the surface of the moving means, and the meta One smooth surface of the surface is exposed to the outside.
또한, 상기 n개의 오목부의 서로 다른 깊이는, 상기 메타표면의 매끈한 일면의 법선으로 입사하는 음향파가 상기 법선에 대하여 일정한 각도로 가지고 반사되게 한다. In addition, the different depths of the n concave portions allow acoustic waves incident on the normal of the smooth surface of the metasurface to be reflected at a constant angle with respect to the normal.
또한, 상기 단위 셀은 상기 유체 매질의 음향 임피던스와 유사한 재료 중에서 선택된 하나의 재료로 가공된다. In addition, the unit cell is fabricated from one material selected from among materials similar to the acoustic impedance of the fluid medium.
또한, 상기 n개의 오목부는 상기 유체 매질의 음향 임피던스와 차이가 나는 재료 중에서 선택된 하나의 재료로 이루어진 보충재로 채워진다. Further, the n recesses are filled with a supplementary material made of a material selected from among materials different from the acoustic impedance of the fluid medium.
또한, 상기 유체 매질이 물인 경우, 상기 하나의 재료는 ABS 수지이다. Also, when the fluid medium is water, the one material is ABS resin.
또한, 상기 유체 매질이 물인 경우, 상기 보충재는 공기 또는 알루미늄이다. Also, when the fluid medium is water, the replenisher is air or aluminum.
본 발명에 따른 매끈한 일면이 노출되는 매타표면의 설계방법은, 유체 매질에서 운행되는 이동 수단의 표면에 부착되고 매끈한 일면이 노출되는 메타표면의 설계방법에 있어서, 상기 메타표면의 일 단위이며, 서로 다른 깊이를 갖는 n(n은 4 이상인 자연수)개의 오목부가 동일한 폭 및 동일한 이격 간격으로 형성되는 단위 셀을 설계하는 단계; 상기 단위 셀이 상기 일 방향으로 배열되도록 상기 메타표면을 가공하는 단계; 및 상기 오목부가 형성된 상기 메타표면의 타면이 상기 이동 수단의 표면에 부착되도록 상기 이동 수단의 표면에 상기 메타표면을 부착하는 단계를 포함한다. The method for designing a metasurface with a smooth surface exposed according to the present invention is a method for designing a metasurface in which a smooth surface is exposed and attached to the surface of a moving means operated in a fluid medium, one unit of the metasurface, designing a unit cell in which n (n is a natural number equal to or greater than 4) concave portions having different depths are formed with the same width and the same spacing; processing the meta surface so that the unit cells are arranged in the one direction; and attaching the metasurface to the surface of the moving means so that the other surface of the metasurface on which the recess is formed is attached to the surface of the moving means.
또한, 상기 단위 셀을 설계하는 단계는, 상기 이동 수단을 탐지하는 음향파의 파장 및 상기 메타표면의 매끈한 일면의 법선으로 입사하는 상기 음향파가 상기 n개의 오목부의 바닥에서 반사되어 진행하는 반사각으로 상기 단위 셀의 배열 주기를 선정하는 단계, 상기 n개의 오목부의 상기 폭 및 상기 이격 간격을 선정하는 단계, 및 상기 메타표면의 매끈한 일면에 입사하고 상기 상기 n개의 오목부 각각의 바닥면에서 반사되는 음향파가 등간격의 위상 구배를 갖도록 상기 n개의 오목부의 서로 다른 깊이를 도출하는 단계를 포함한다. In addition, the step of designing the unit cell includes the wavelength of the acoustic wave detecting the moving means and the reflection angle at which the acoustic wave incident to the normal of the smooth surface of the metasurface is reflected from the bottom of the n concave portions and travels. selecting the arrangement period of the unit cell, selecting the width and the spacing of the n concave portions, and being incident on a smooth surface of the metasurface and reflected from the bottom surface of each of the n concave portions and deriving different depths of the n concave portions so that the acoustic waves have equally spaced phase gradients.
또한, 상기 n개의 오목부의 서로 다른 깊이를 도출하는 단계는, 상기 오목부의 깊이에 따른 상기 음향파의 위상 차를 계산하는 단계를 포함한다. In addition, the step of deriving the different depths of the n concave portions includes calculating a phase difference of the acoustic wave according to the depth of the concave portions.
또한, 상기 메타표면을 가공하는 단계는, 상기 단위 셀의 재료 및 상기 n개의 오목부에 채워지는 보충재의 재료를 선정하는 단계, 및 상기 n개의 오목부를 가공하는 단계를 포함한다.In addition, the step of machining the metasurface includes selecting a material of the unit cell and a material of a supplementary material to be filled in the n recesses, and processing the n recesses.
본 발명에 따른 매끈한 일면이 노출되는 매타표면은 반사면의 각 지점의 깊이 변화에 따른 위상 구배 구현을 통해 상기 메타표면이 형성된 유체 매질에서 운행되는 이동 수단을 음향파의 탐지 신호에 대해 은폐시킬 수 있다. The metasurface with a smooth surface exposed according to the present invention can conceal the movement means running in the fluid medium in which the metasurface is formed from the detection signal of the acoustic wave through the implementation of a phase gradient according to the change in depth of each point of the reflective surface. have.
또한, 본 발명에 따른 매끈한 일면이 노출되는 매타표면은, 오목부가 형성된 면은 유체 매질에서 운행되는 이동 수단의 표면에 부착되고 굴곡없이 매끈하게 형성된 면은 외부에 노출됨으로써, 이동 시 표면에 의한 유체의 저항을 높이는 현상이 발생되지 않으며, 이물질이 끼어 스텔스 기능이 약화되는 현상이 발생되지 않고 표면의 관리가 용이하다. In addition, the matta surface on which a smooth surface according to the present invention is exposed, the surface on which the concave portion is formed is attached to the surface of the moving means operated in a fluid medium, and the surface formed smoothly without bending is exposed to the outside, so that when moving, the fluid by the surface The phenomenon of increasing the resistance does not occur, and the phenomenon of weakening of the stealth function due to foreign substances does not occur, and the management of the surface is easy.
본 발명에 따른 매끈한 일면이 노출되는 메타표면의 설계방법은, 반사면의 각 지점의 깊이 변화에 따른 위상 구배 구현을 통해 음향파를 입사각도와 다른 각도로 반사시켜 특정 주파수의 음향파의 탐지를 회피하기 위한 물리적 구조를 가지도록 설계될 수 있다. The method for designing a metasurface with a smooth surface exposed according to the present invention avoids the detection of acoustic waves of a specific frequency by reflecting the acoustic waves at an angle different from the incident angle through the implementation of a phase gradient according to the change in depth of each point of the reflective surface. It can be designed to have a physical structure for
본 발명에서 얻을 수 있는 효과는 이상에서 언급한 효과들로 제한되지 않으며, 언급하지 않은 또 다른 효과들은 아래의 기재로부터 본 발명이 속하는 기술 분야에서 통상의 지식을 가진 자에게 명확하게 이해될 수 있을 것이다.The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description. will be.
도 1은 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 사시도이다. 1 is a perspective view of a meta surface on which a smooth surface is exposed according to an embodiment of the present invention.
도 2는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단면도이다.2 is a cross-sectional view of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
도 3은 도 2의 A의 확대도로서 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단위 셀의 단면도이다. FIG. 3 is an enlarged view of FIG. 2A , and is a cross-sectional view of a unit cell of a metasurface having a smooth surface exposed according to an embodiment of the present invention.
도 4는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면이 유체 매질에서 운행되는 이동 수단의 표면에 부착된 상태의 단면도이다. 4 is a cross-sectional view of a state in which a metasurface having a smooth surface exposed is attached to the surface of a moving means operating in a fluid medium according to an embodiment of the present invention.
도 5는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면에 대한 입사파 및 반사파의 거동을 나타내는 시뮬레이션 도면이다. 5 is a simulation diagram illustrating the behavior of an incident wave and a reflected wave with respect to a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
도 6은 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 설계방법의 순서도이다.6 is a flowchart of a method for designing a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
도 7은 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단위 셀을 설계하는 방법의 순서도이다.7 is a flowchart of a method of designing a unit cell of a metasurface to which a smooth surface is exposed according to an embodiment of the present invention.
도 8은 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단위 셀을 설계하는 원리를 설명하는 도면이다.8 is a view for explaining the principle of designing a unit cell of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
도 9는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단위 셀을 설계하는 원리를 설명하는 도면이다.9 is a view for explaining the principle of designing a unit cell of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
도 10은 오목부의 깊이에 따른 음향 반사파의 위상 차를 도시한 그래프이다. 10 is a graph illustrating a phase difference of an acoustic reflected wave according to a depth of a concave portion.
도 11은 도 10의 그래프에서 오목부의 깊이를 도출하는 과정을 설명하는 도면이다.11 is a view for explaining a process of deriving a depth of a concave portion in the graph of FIG. 10 .
이하, 첨부된 도면을 참조하여 본 발명에 따른 매끈한 일면이 노출되는 메타표면 및 이의 설계 방법을 설명한다. Hereinafter, a metasurface to which a smooth surface is exposed and a design method thereof according to the present invention will be described with reference to the accompanying drawings.
본 문서의 다양한 실시 예들 및 이에 사용된 용어들은 본 문서에 기재된 기술적 특징들을 특정한 실시 예들로 한정하려는 것이 아니며, 해당 실시 예의 다양한 변경, 균등물, 또는 대체물을 포함하는 것으로 이해되어야 한다. 도면의 설명과 관련하여, 유사한 또는 관련된 구성요소에 대해서는 유사한 참조 부호가 사용될 수 있다. 아이템에 대응하는 명사의 단수 형은 관련된 문맥상 명백하게 다르게 지시하지 않는 한, 상기 아이템 한 개 또는 복수 개를 포함할 수 있다. 본 문서에서, "A 또는 B", "A 및 B 중 적어도 하나","A 또는 B 중 적어도 하나,""A, B 또는 C," "A, B 및 C 중 적어도 하나,"및 "A, B, 또는 C 중 적어도 하나"와 같은 문구들 각각은 그 문구들 중 해당하는 문구에 함께 나열된 항목들 중 어느 하나, 또는 그들의 모든 가능한 조합을 포함할 수 있다. "제 1", "제 2", 또는 "첫째" 또는 "둘째"와 같은 용어들은 단순히 해당 구성요소를 다른 해당 구성요소와 구분하기 위해 사용될 수 있으며, 해당 구성요소들을 다른 측면(예: 중요성 또는 순서)에서 한정하지 않는다. The various embodiments of this document and the terms used therein are not intended to limit the technical features described in this document to specific embodiments, and should be understood to include various modifications, equivalents, or substitutions of the embodiments. In connection with the description of the drawings, like reference numerals may be used for similar or related components. The singular form of the noun corresponding to the item may include one or more of the item, unless the relevant context clearly dictates otherwise. As used herein, "A or B", "at least one of A and B", "at least one of A or B," "A, B or C," "at least one of A, B and C," and "A , B, or C" each may include any one of the items listed together in the corresponding one of the phrases, or all possible combinations thereof. Terms such as “first”, “second”, or “first” or “second” may simply be used to distinguish the component from other components in question, and may refer to components in other aspects (e.g., importance or order) is not limited.
도 1 및 도 2는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 사시도 및 단면도이고, 도 3은 도 2의 A의 확대도로서 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단위 셀의 단면도이다. 도 4는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면이 유체 매질에서 운행되는 이동 수단의 표면에 부착된 상태의 단면도이다.1 and 2 are perspective and cross-sectional views of a meta surface on which a smooth surface is exposed according to an embodiment of the present invention, and FIG. 3 is an enlarged view of FIG. 2A in which a smooth surface according to an embodiment of the present invention is exposed. It is a cross-sectional view of the unit cell of the metasurface. 4 is a cross-sectional view of a state in which a meta-surface, on which a smooth surface is exposed, is attached to the surface of a moving means operating in a fluid medium according to an embodiment of the present invention.
도 1 내지 도 4를 참조하면, 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면(100)은, 서로 다른 깊이를 갖는 복수 개의 오목부(111)가 형성된 단위 셀(110)을 복수 개 포함하고, 오목부(111)가 형성된 메타표면의 타면(101)이 유체 매질에서 운행하는 이동 수단(10)의 표면에 부착되고, 메타표면의 매끈한 일면(102)은 외부로 노출된다. 이로써, 상기 메타표면(100)은, 상기 이동 수단(10)에 대한 음향파 탐지 신호에 대해 상기 음향파를 입사각도와 다른 각도로 반사시켜 상기 이동 수단(10)을 은폐시키는 스텔스 기능을 수행하고, 노출되는 표면이 매끈하여 이동 수단의 운행 중 이물질이 끼는 것을 방지함으로써 스텔스 기능이 열화되는 것을 막는다.1 to 4 , the meta surface 100 on which a smooth surface is exposed according to an embodiment of the present invention includes a plurality of unit cells 110 in which a plurality of concave portions 111 having different depths are formed. The other surface 101 of the metasurface including the dog, on which the concave portion 111 is formed is attached to the surface of the moving means 10 running in a fluid medium, and the smooth one surface 102 of the metasurface is exposed to the outside. Thus, the metasurface 100 reflects the acoustic wave at an angle different from the incident angle with respect to the acoustic wave detection signal for the moving means 10 to perform a stealth function to conceal the moving means 10, It prevents the stealth function from being deteriorated by preventing foreign substances from getting caught during the operation of the vehicle because the exposed surface is smooth.
메타표면(100)에서, 복수 개의 동일한 단위 셀(110)은 일 방향(도시된 X축 방향)으로 배열된다. 단위 셀(110)은 일면에 x축 방향으로 서로 다른 깊이를 갖는 적어도 4개 이상인 개수의 오목부(111)가 동일한 폭 및 동일한 이격 간격으로 형성된다. 이 때, 적어도 4개 이상인 개수를 n이라하면, n은 4 이상인 자연수 중에서 하나이다.In the metasurface 100 , a plurality of identical unit cells 110 are arranged in one direction (the illustrated X-axis direction). In the unit cell 110, at least four or more concave portions 111 having different depths in the x-axis direction are formed on one surface with the same width and the same spacing. At this time, if the number of at least 4 or more is n, n is one of 4 or more natural numbers.
메타표면(100)은 오목부(111)가 형성되지 않은 단위 셀(110)의 면이 연속적으로 배열된 매끈한 일면(102) 및 오목부(111)가 형성된 단위 셀(110)의 면이 연속적을 배열된 굴곡진 타면(101)을 가진다. 또한, 메타표면(100)은, 굴곡진 타면(101)을 이동 수단(10)의 표면에 단단히 부착시키기 위하여 단위 셀(110)의 배열의 양측으로 굴곡진 타면(101)에서 연장된 엣지부(103)을 더 가질 수 있다. The metasurface 100 has a smooth surface 102 in which the surfaces of the unit cells 110 in which the concave portions 111 are not formed are continuously arranged and the surfaces of the unit cells 110 in which the concave portions 111 are formed are continuous. It has an arranged curved rudder surface 101 . In addition, the meta surface 100 is an edge portion ( 103) may have more.
단위 셀(110)은 일면에 x축 방향으로 서로 다른 깊이를 갖는 n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n)가 동일한 폭 및 동일한 이격 간격으로 형성된다. 여기서, n은 4 이상인 자연수 중에서 하나이다. 도 3에 도시된 실시 예에서, n은 10이다. n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n)는 평평한 바닥면을 가지는 단면이 직사각형인 홈으로 각각의 깊이는 서로 다르게 형성된다. The unit cell 110 has n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n having different depths in the x-axis direction on one surface have the same width and formed with equal spacing. Here, n is one of 4 or more natural numbers. In the embodiment shown in FIG. 3 , n is 10. The n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n are grooves having a flat bottom surface and a rectangular cross-section, and each depth is formed differently.
n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n)의 각각의 서로 다른 깊이는 메타표면의 매끈한 일면(102)에 입사되고 오목부(111)들의 평평한 바닥면에서 반사되는 음향파가 등간격의 위상 구배를 갖게 한다. 도 3에 도시된 실시 예에서, 10개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-10)의 바닥면 각각에서 반사되는 음향파는 36도의 등간격의 위상 구배를 갖는다. Each of the different depths of the n recesses 111-1, 111-2, 111-3, 111-4, ..., 111-n is incident on the smooth surface 102 of the metasurface and the recesses ( 111), the acoustic waves reflected from the flat bottom have an equally spaced phase gradient. In the embodiment shown in FIG. 3 , the acoustic wave reflected from each of the bottom surfaces of the ten concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-10 is equal to 36 degrees. It has a phase gradient of spacing.
n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n) 각각의 서로 다른 깊이는 메타표면(100)의 매끈한 일면(102)의 법선으로 입사하는 음향파가 상기 법선에 대하여 일정한 각도를 가지고 반사되게 한다. 즉, n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n)가 서로 다른 깊이를 가짐으로 인해 입사각이 0도로 메타표면(100)에 입사한 음향 입사파는 오목부(111)들의 바닥면에서 반사되어 0도가 아닌 일정한 각도에 해당하는 반사각으로 반사하게 된다. 이로써, 메타표면(100)은 특정 주파수의 음향파의 탐지를 회피하기 위한 물리적 구조를 가지게 된다. Different depths of each of the n recesses 111-1, 111-2, 111-3, 111-4, ..., 111-n are incident on the normal of the smooth surface 102 of the metasurface 100 The acoustic wave is reflected at a certain angle with respect to the normal. That is, because the n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n have different depths, the incident angle is 0 degrees incident on the metasurface 100 One acoustic incident wave is reflected from the bottom surface of the concave portions 111 and is reflected at a reflection angle corresponding to a constant angle instead of 0 degree. Accordingly, the metasurface 100 has a physical structure for avoiding detection of acoustic waves of a specific frequency.
n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n)의 서로 다른 깊이를 포함하여 상기 메타표면(100)의 물리적 구조를 설계하는 원리는 후술한다. The principle of designing the physical structure of the metasurface 100 including the different depths of the n recesses 111-1, 111-2, 111-3, 111-4, ..., 111-n is It will be described later.
단위 셀(110)은, 음향파가 진행하는 매질의 음향 임피던스와 유사한 재료 중에서 선택된 하나의 재료로 가공된다. 이는, 유체 매질에서 운행하는 이동 수단에 메타표면(100)이 적용되고, 메타표면(100)의 매끈한 일면(102)에서 음향파의 반사가 일어나는 것을 막고 메타표면(100)의 내부로 입사한 음향파를 잘 투과시키기 위함이다. 예를 들어, 이동 수단(10)이 수중에서 운행되는 경우, 단위 셀(110)은 물의 음향 임피던스와 유사한 ABS 수지로 형성된다.The unit cell 110 is processed from one material selected from among materials similar to the acoustic impedance of the medium through which the acoustic wave travels. This means that the metasurface 100 is applied to a moving means running in a fluid medium, prevents reflection of acoustic waves from the smooth surface 102 of the metasurface 100 and the sound incident into the metasurface 100 . for good penetration of waves. For example, when the moving means 10 is operated in water, the unit cell 110 is formed of ABS resin similar to the acoustic impedance of water.
일 실시 예에서, 단위 셀(110)에 형성된 n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n)는 음향파가 진행하는 매질의 음향 임피던스와 차이가 나는 재료 중에서 선택된 재료로 이루어진 보충재로 채워진다. 보충재는 단위 셀을 이루는 재료의 음향 임피던스와 차이가 나서 메타표면(100)의 내부로 입사한 음향파가 오목부(111)의 바닥에서 잘 반사되도록 하기 위함이다. 예를 들어, 이동 수단(10)이 수중에서 운행되는 경우, 오목부(111)를 채우는 보충재는 물의 음향 임피던스와 차이가 나는 공기 또는 알루미늄으로 이루어진다.In an embodiment, the n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n formed in the unit cell 110 are acoustic waves of a medium through which the acoustic wave propagates. It is filled with a filler material made of a material selected from among the materials differing from the impedance. The supplementary material is different from the acoustic impedance of the material constituting the unit cell so that the acoustic wave incident into the metasurface 100 is well reflected from the bottom of the concave portion 111 . For example, when the moving means 10 is operated in water, the filler filling the recess 111 is made of air or aluminum which is different from the acoustic impedance of water.
도 5는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면에 대한 입사파 및 반사파의 거동을 나타내는 시뮬레이션 도면이다. 5 is a simulation diagram illustrating the behavior of an incident wave and a reflected wave with respect to a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
도 5를 참조하면, 본 발명의 일 실시 예에 따른 매끈한 일면(102)이 노출되는 메타표면(100)에 대한 시뮬레이션을 통해 상기 일면(102)의 법선 방향으로, 즉, 수직으로 또는 입사각 0도로 입사하는 음향 입사파가 동일한 반사각도로 반사되지 않고, 일정한 각도로 반사하는 반사파를 확인할 수 있다. 탐지물의 평면에 대해 음향파를 입사시키고 입사방향의 반대 방향으로 반사되는 음향파를 감지하게 되면 탐지가 성공적이지만, 본 발명과 같이, 음향파를 입사각도와 다른 각도로 반사하게 되면, 예들 들어 입사각이 0도로 메타표면(100)에 입사한 음향 입사파가 반사되어 0도가 아닌 일정한 각도에 해당하는 반사각으로 반사하게 되면 음향파의 반사에 의한 탐지가 이루어지지 않는다. 따라서, 메타표면(100)은 음향파를 입사각도와 다른 각도로 반사시켜 음향파의 탐지를 회피하는 스텔스 기능을 가지게 된다.Referring to FIG. 5 , in the normal direction of the one surface 102 through simulation of the meta surface 100 to which the smooth one surface 102 is exposed according to an embodiment of the present invention, that is, vertically or at an incident angle of 0 degrees It can be confirmed that the incident acoustic wave is not reflected at the same reflection angle, but is reflected at a constant angle. If an acoustic wave is incident on the plane of the target and the acoustic wave reflected in the opposite direction to the incident direction is detected, the detection is successful, but as in the present invention, if the acoustic wave is reflected at an angle different from the incident angle, When the acoustic incident wave incident on the metasurface 100 at 0 degrees is reflected and is reflected at a reflection angle corresponding to a predetermined angle other than 0 degrees, detection by reflection of the acoustic wave is not performed. Accordingly, the metasurface 100 has a stealth function to avoid detection of the acoustic wave by reflecting the acoustic wave at an angle different from the incident angle.
도 6은 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 설계방법의 순서도이고, 도 7는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단위 셀을 설계하는 방법의 순서도이다. 6 is a flowchart of a method for designing a metasurface to which a smooth surface is exposed according to an embodiment of the present invention, and FIG. 7 is a method for designing a unit cell of a metasurface to which a smooth surface is exposed according to an embodiment of the present invention. is a flowchart of
도 6을 참조하면, 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면(100)의 설계방법(S100)은 유체 매질에서 운행되는 이동 수단(10)의 표면에 부착되어 상기 이동 수단(10)에 대한 음향파 탐지 신호가 되돌아가 감지되는 것을 회피시키는 메타표면(100)을 설계하는 방법으로서, 메타표면(100)의 일 단위가 되는 단위 셀(110)을 설계하는 단계(S110), 메타표면(100)을 가공하는 단계(S120), 및 메타표면(100)을 부착하는 단계(S130)을 포함한다.Referring to Figure 6, the design method (S100) of the metasurface 100 on which a smooth surface is exposed according to an embodiment of the present invention is attached to the surface of the moving means 10 operated in a fluid medium and the moving means ( 10) A method of designing a metasurface 100 that avoids being detected by returning an acoustic wave detection signal for 10), the step of designing a unit cell 110 that is one unit of the metasurface 100 (S110), It includes a step of processing the metasurface 100 (S120), and attaching the metasurface 100 (S130).
단계 S110에서 설계되는 단위 셀(110)은 메타표면(100)의 일 단위이고 일면이 일 방향으로 서로 다른 깊이를 갖는 n 개의 오목부(111)가 동일한 폭 및 동일한 이격 간격으로 형성되는 단위 셀(110)을 설계하는 단계이다. 여기서, n은 4 이상인 자연수이다. The unit cell 110 designed in step S110 is one unit of the metasurface 100 and a unit cell in which n concave portions 111 having different depths in one direction on one side are formed with the same width and the same spacing ( 110) is the design stage. Here, n is a natural number equal to or greater than 4.
도 7을 참조하면, 단위 셀(110)을 설계하는 단계(S110)는, 단위 셀(110)의 주기를 선정하는 단계(S111), 오목부(111)의 이격 간격 및 오목부(111)의 폭을 선정하는 단계(S113), 및 n 개의 오목부(111) 각각의 깊이를 도출하는 단계(S115)를 포함한다. Referring to FIG. 7 , the step of designing the unit cell 110 ( S110 ) includes the step of selecting the cycle of the unit cell 110 ( S111 ), the spacing between the concave portions 111 and the spacing of the concave portions 111 . It includes a step of selecting a width (S113), and a step of deriving the depth of each of the n concave portions 111 (S115).
도 8 및 도 9는 본 발명의 일 실시 예에 따른 매끈한 일면이 노출되는 메타표면의 단위 셀을 설계하는 원리를 설명하는 도면이다.8 and 9 are diagrams for explaining the principle of designing a unit cell of a meta surface to which a smooth surface is exposed according to an embodiment of the present invention.
도 8 및 도 9를 참조하면, 메타표면(100)의 일 단위인 단위 셀(110)은 메타표면(100)의 매끈한 일면(102)의 반대편인 타면(101)에 평평한 바닥면을 가지는 단면이 직사각형인 홈에 해당하는 오목부(111)가 서로 다른 깊이를 가지고 동일한 폭 및 동일한 이격 간격으로 형성되어 있다. 단계 S111에서, 먼저 메타표면(100)의 일 단위인 단위 셀(110)의 X축 방향으로의 크기에 해당하는 주기(M)를 선정한다. 단위 셀(110)의 주기(M)는, 메타표면(100)의 매끈한 일면(102)의 법선으로 입사하는 음향파가 상기 법선에 대하여 θ 각도를 가지고 반사되도록 탐지 신호에 해당하는 음향파의 파장(λ)에 sinθ로 나눈 값으로 선정된다. 8 and 9, the unit cell 110, which is one unit of the metasurface 100, has a cross-section having a flat bottom surface on the other surface 101 opposite to the smooth one surface 102 of the metasurface 100. Concave portions 111 corresponding to rectangular grooves have different depths and are formed with the same width and the same spacing. In step S111, first, a period M corresponding to the size in the X-axis direction of the unit cell 110, which is one unit of the metasurface 100, is selected. The period M of the unit cell 110 is the wavelength of the acoustic wave corresponding to the detection signal so that the acoustic wave incident on the normal of the smooth surface 102 of the metasurface 100 is reflected at an angle θ with respect to the normal line. (λ) is selected as a value divided by sinθ.
단계 S111에서 단위 셀(110)의 주기(M)가 선정되면, 단계 S113에서, 단위 셀(110)의 주기(M) 내에 형성되는 오목부(111)의 개수(n), 오목부(111)의 이격 간격(a) 및 오목부(111)의 폭(b)을 선정한다. 오목부(111)의 이격 간격(a)은 단위 셀(110)의 주기(M)를 4로 나눈 것보다 크거나 같아야 한다. 즉, 오목부(111)의 개수가 4개 이상하여야 한다. 따라서, 단계 S113에서, 오목부(111)의 개수(n)는 4개 이상인 자연수로 선정하고 주기(M)을 n으로 나누어 오목부(111)의 이격 간격(a)을 계산한다. 도시된 실시 예에서, n은 10이다. 오목부(111)의 폭(b)은 오목부(111)의 이격 간격 보다는 작지만 음향파에 대해 저항으로 작용할 수 있는 적정한 폭으로 선정한다. 도시된 실시 예에서, n은 10이다. When the period M of the unit cell 110 is selected in step S111, in step S113, the number (n) of the concave portions 111 formed within the period M of the unit cell 110, the concave portions 111 The spacing (a) and the width (b) of the concave portion 111 are selected. The spacing a of the concave portion 111 should be greater than or equal to the period M of the unit cell 110 divided by 4 . That is, the number of the concave portions 111 should be four or more. Accordingly, in step S113, the number n of the concave portions 111 is selected as a natural number of 4 or more, and the interval M of the concave portions 111 is calculated by dividing the period M by n. In the illustrated embodiment, n is 10. Although the width b of the concave portion 111 is smaller than the spacing between the concave portions 111, an appropriate width that can act as a resistance to the acoustic wave is selected. In the illustrated embodiment, n is 10.
단계 S115에서, n 개의 오목부(111) 각각의 서로 다른 깊이를 도출하기 위해, 이동 수단(10)의 표면에 메타표면(100)의 굴곡진 타면(101)이 부착되고 매끈한 일면(102)이 외부로 노출되어 음향파가 매끈한 일면으로 입사되는 것을 단면도로 도시한 도 9을 참조하면, 깊이(L)인 오목부(111)에 입사되는 음향 입사파(I)에 대한 오목부(111)의 바닥면에서 반사되는 반사파(R)의 반사 효율(R/I)은 아래 수학식 1과 같이 나타낸다.In step S115, in order to derive different depths of each of the n concave portions 111, the curved other surface 101 of the metasurface 100 is attached to the surface of the moving means 10, and the smooth surface 102 is Referring to FIG. 9, which is exposed to the outside and shows in cross-sectional view that the acoustic wave is incident on a smooth surface, the concave portion 111 for the acoustic incident wave I incident on the concave portion 111 having a depth L The reflection efficiency (R/I) of the reflected wave (R) reflected from the bottom is expressed as in Equation 1 below.
Figure PCTKR2021003748-appb-img-000001
Figure PCTKR2021003748-appb-img-000001
여기서, m은 (a-b)/a 이고, k는 입사파의 파수(wave number)이다.Here, m is (a-b)/a, and k is the wave number of the incident wave.
도 10은 오목부의 깊이에 따른 음향 반사파의 위상 차를 도시한 그래프이고, 도 11은 도 10의 그래프에서 오목부의 깊이를 도출하는 과정을 설명하는 도면이다.10 is a graph illustrating a phase difference of acoustic reflected waves according to the depth of the concave portion, and FIG. 11 is a view for explaining a process of deriving the depth of the concave portion from the graph of FIG. 10 .
상기 수학식 1을 통해 깊이(L)인 오목부(111)에 입사되는 음향 입사파(I)가 오목부(111)의 바닥면에서 반사됨으로써 위상 차가 생기고 그때의 위상 차(φ)는 다음 수학식 2와 같다. Through Equation 1 above, the acoustic incident wave I incident on the concave portion 111 having a depth L is reflected from the bottom surface of the concave portion 111 to generate a phase difference, and the phase difference φ at that time is calculated by the following equation Same as Equation 2.
Figure PCTKR2021003748-appb-img-000002
Figure PCTKR2021003748-appb-img-000002
도 10을 참조하면, 단계 S115에서, n 개의 오목부(111) 각각의 서로 다른 깊이를 도출하기 위해 오목부(111)의 깊이(L)에 따른 음향 반사파의 위상 차(φ)를 수학식 1 및 2를 통해 그래프로 도시한다. Referring to FIG. 10 , in step S115 , the phase difference φ of the acoustic reflected wave according to the depth L of the concave portion 111 in order to derive different depths of each of the n concave portions 111 is calculated by Equation 1 and 2 are shown graphically.
도 11을 참조하면, 단계 S115에서, 오목부(111)의 깊이(L)에 따른 음향 반사파의 위상 차(φ)를 도시한 그래프에서 n 개의 오목부(111) 각각의 서로 다른 깊이를 도출한다. n 개의 오목부(111) 각각의 서로 다른 깊이는, 상기 그래프 곡선에서 360도의 위상 차의 범위에서 동일한 위상 차를 갖는 n 개의 등간격선을 그린 후 상기 등간격선과 만나는 그래프 곡선 내의 좌표값 중 깊이(L)에 해당하는 값을 통해 도출된다. 즉, n 개의 오목부(111) 각각의 서로 다른 깊이는, 메타표면(100)의 매끈한 일면(102)에 입사하고 n개의 오목부(111) 각각의 바닥면에서 반사되는 음향파가 등간격의 위상 구배를 가지도록 도출된다. Referring to FIG. 11 , in step S115 , different depths of n concave portions 111 are derived from a graph illustrating the phase difference φ of the acoustic reflected wave according to the depth L of the concave portion 111 . . The different depths of each of the n concave portions 111 are, after drawing n equally spaced lines having the same phase difference in the range of the phase difference of 360 degrees in the graph curve, the depth of the coordinate values in the graph curve meeting the equal intervals It is derived through the value corresponding to (L). That is, the different depths of each of the n concave portions 111 are incident on the smooth surface 102 of the metasurface 100 and the acoustic waves reflected from the bottom surface of each of the n concave portions 111 are equally spaced. It is derived to have a phase gradient.
일 실시 예에서, n이 10으로 선정되고, 10 개의 오목부(111) 각각의 서로 다른 깊이로 형성된 바닥면에서 반사된 음향파는 각각 36도씩 위상 차가 발생한다. n개의 오목부(111-1, 111-2, 111-3, 111-4,..., 111-n)가 서로 다른 깊이를 가짐으로 인해 입사각이 0도로 메타표면(100)에 입사한 음향 입사파는 오목부(111)들의 바닥면에서 반사되어 0도가 아닌 일정한 각도에 해당하는 반사각으로 반사하게 된다. 이로써, 메타표면(100)은 음향파를 입사각도와 다른 각도로 반사시켜 특정 주파수의 음향파의 탐지를 회피하기 위한 물리적 구조를 가지게 된다. In an embodiment, n is selected as 10, and the acoustic waves reflected from the bottom surface formed at different depths of each of the ten concave portions 111 generate a phase difference of 36 degrees each. Since the n concave portions 111-1, 111-2, 111-3, 111-4, ..., 111-n have different depths, the sound incident on the metasurface 100 has an incident angle of 0 degrees. The incident wave is reflected from the bottom surface of the concave portions 111 and is reflected at a reflection angle corresponding to a constant angle instead of 0 degree. Accordingly, the metasurface 100 has a physical structure for avoiding the detection of the acoustic wave of a specific frequency by reflecting the acoustic wave at an angle different from the incident angle.
단계 S120에서, 단계 S110에서 설계된 단위 셀(110)을 일 방향으로 배열시켜 메타표면(100)을 가공한다. 오목부(111)의 가공에 앞서 단위 셀의 재료 및 오목부(111)에 삽입되는 보충재의 재료를 선정한다. 상기 재료 선정을 상기 메타표면(100)에 대한 설명에서 상술한 바와 같다. 오목부(111)가 형성된 메타표면(100)을 가공한 후 오목부(111)에 보충재를 삽입한다.In step S120, the metasurface 100 is processed by arranging the unit cells 110 designed in step S110 in one direction. Prior to the processing of the concave portion 111 , the material of the unit cell and the material of the supplementary material inserted into the concave portion 111 are selected. The material selection is the same as described above in the description of the meta surface 100 . After processing the meta surface 100 on which the recess 111 is formed, a supplementary material is inserted into the recess 111 .
단계 S130에서, 단계 S120에서 가공한 메타표면(100)을 유체 매질에서 운행되는 이동 수단(10)에 부착한다. 이 때, 오목부(111)가 형성된 메타표면(100)의 굴곡진 타면(101)이 이동 수단(10)의 표면에 부착되고 메타표면(100)의 매끈한 일면(102)이 외부로 노출되도록 한다.In step S130, the meta surface 100 processed in step S120 is attached to the moving means 10 running in a fluid medium. At this time, the curved other surface 101 of the meta surface 100 on which the recess 111 is formed is attached to the surface of the moving means 10 and the smooth surface 102 of the meta surface 100 is exposed to the outside. .

Claims (10)

  1. 유체 매질에서 운행되는 이동 수단의 표면에 부착되고 매끈한 일면이 노출되는 메타표면에 있어서,In the meta surface attached to the surface of the moving means running in a fluid medium and the smooth surface is exposed,
    일 방향으로 배열되는 동일한 단위 셀을 복수 개 포함하고,including a plurality of identical unit cells arranged in one direction,
    상기 단위 셀은 일면에 상기 일 방향으로 서로 다른 깊이를 갖는 n(n은 4 이상인 자연수)개의 오목부가 동일한 폭 및 동일한 이격 간격으로 형성되고,In the unit cell, n (n is a natural number equal to or greater than 4) concave portions having different depths in the one direction on one surface are formed with the same width and the same spacing,
    상기 n개의 오목부의 서로 다른 깊이는, 상기 메타표면의 매끈한 일면에 입사하고 상기 상기 n개의 오목부 각각의 바닥면에서 반사되는 음향파가 등간격의 위상 구배를 갖게 하고, The different depths of the n concave portions make the acoustic waves incident on the smooth surface of the metasurface and reflected from the bottom surface of each of the n concave portions have a phase gradient at equal intervals,
    상기 오목부가 형성된 상기 메타표면의 타면이 상기 이동 수단의 표면에 부착되고, 상기 메타표면의 매끈한 일면은 외부로 노출되는, 매끈한 일면이 노출되는 메타표면.The other surface of the meta surface on which the recess is formed is attached to the surface of the moving means, and the smooth surface of the meta surface is exposed to the outside, the smooth surface of which is exposed.
  2. 청구항 1에 있어서,The method according to claim 1,
    상기 n개의 오목부의 서로 다른 깊이는,The different depths of the n recesses are,
    상기 메타표면의 매끈한 일면의 법선으로 입사하는 음향파가 상기 법선에 대하여 일정한 각도로 가지고 반사되게 하는, 매끈한 일면이 노출되는 메타표면.A metasurface with a smooth surface exposed so that an acoustic wave incident on the normal of the smooth surface of the metasurface is reflected at a predetermined angle with respect to the normal.
  3. 청구항 1에 있어서,The method according to claim 1,
    상기 단위 셀은 상기 유체 매질의 음향 임피던스와 유사한 재료 중에서 선택된 하나의 재료로 가공되는, 매끈한 일면이 노출되는 메타표면.The unit cell is processed from one material selected from among materials similar to the acoustic impedance of the fluid medium, the smooth surface of which is exposed metasurface.
  4. 청구항 1에 있어서,The method according to claim 1,
    상기 n개의 오목부는 상기 유체 매질의 음향 임피던스와 차이가 나는 재료 중에서 선택된 하나의 재료로 이루어진 보충재로 채워지는, 매끈한 일면이 노출되는 메타표면.Wherein the n recesses are filled with a replenishing material made of a material selected from among materials different from the acoustic impedance of the fluid medium, the smooth surface of which is exposed.
  5. 청구항 3에 있어서,4. The method according to claim 3,
    상기 유체 매질이 물인 경우, 상기 하나의 재료는 ABS 수지인, 매끈한 일면이 노출되는 메타표면.When the fluid medium is water, the one material is ABS resin, a metasurface with a smooth surface exposed.
  6. 청구항 4에 있어서,5. The method according to claim 4,
    상기 유체 매질이 물인 경우, 상기 보충재는 공기 또는 알루미늄인, 매끈한 일면이 노출되는 메타표면.When the fluid medium is water, the supplementary material is air or aluminum, the smooth surface of which is exposed metasurface.
  7. 유체 매질에서 운행되는 이동 수단의 표면에 부착되고 매끈한 일면이 노출되는 메타표면의 설계방법에 있어서,In the design method of a metasurface that is attached to the surface of a moving means running in a fluid medium and a smooth surface is exposed,
    상기 메타표면의 일 단위이며, 서로 다른 깊이를 갖는 n(n은 4 이상인 자연수)개의 오목부가 동일한 폭 및 동일한 이격 간격으로 형성되는 단위 셀을 설계하는 단계; designing a unit cell in which n (n is a natural number equal to or greater than 4) concave portions that are one unit of the metasurface and have different depths are formed with the same width and the same spacing;
    상기 단위 셀이 상기 일 방향으로 배열되도록 상기 메타표면을 가공하는 단계; 및processing the meta surface so that the unit cells are arranged in the one direction; and
    상기 오목부가 형성된 상기 메타표면의 타면이 상기 이동 수단의 표면에 부착되도록 상기 이동 수단의 표면에 상기 메타표면을 부착하는 단계를 포함하는, 매끈한 일면이 노출되는 메타표면의 설계방법.Comprising the step of attaching the metasurface to the surface of the moving means so that the other surface of the metasurface on which the recess is formed is attached to the surface of the moving means, a method for designing a metasurface with a smooth surface exposed.
  8. 청구항 7에 있어서,8. The method of claim 7,
    상기 단위 셀을 설계하는 단계는,The designing of the unit cell comprises:
    상기 이동 수단을 탐지하는 음향파의 파장 및 상기 메타표면의 매끈한 일면의 법선으로 입사하는 상기 음향파가 상기 n개의 오목부의 바닥에서 반사되어 진행하는 반사각으로 상기 단위 셀의 배열 주기를 선정하는 단계,Selecting the arrangement period of the unit cells by the wavelength of the acoustic wave detecting the moving means and the reflection angle at which the acoustic wave incident on the normal of the smooth surface of the meta surface is reflected from the bottom of the n concave portions,
    상기 n개의 오목부의 상기 폭 및 상기 이격 간격을 선정하는 단계, 및selecting the width and the spacing of the n concave portions; and
    상기 메타표면의 매끈한 일면에 입사하고 상기 상기 n개의 오목부 각각의 바닥면에서 반사되는 상기 음향파가 등간격의 위상 구배를 갖도록 상기 n개의 오목부의 서로 다른 깊이를 도출하는 단계를 포함하는, 매끈한 일면이 노출되는 메타표면의 설계방법.Including the step of deriving different depths of the n concave portions so that the acoustic wave incident on the smooth surface of the metasurface and reflected from the bottom surface of each of the n concave portions has a phase gradient at equal intervals. A design method for a metasurface with one side exposed.
  9. 청구항 8에 있어서,9. The method of claim 8,
    상기 n개의 오목부의 서로 다른 깊이를 도출하는 단계는,The step of deriving different depths of the n concave portions includes:
    상기 오목부의 깊이에 따른 상기 음향파의 위상 차를 계산하는 단계를 포함하는, 매끈한 일면이 노출되는 메타표면의 설계방법.Comprising the step of calculating the phase difference of the acoustic wave according to the depth of the concave portion, the design method of a metasurface in which a smooth surface is exposed.
  10. 청구항 7에 있어서,8. The method of claim 7,
    상기 메타표면을 가공하는 단계는, The step of processing the meta surface comprises:
    상기 단위 셀의 재료 및 상기 n개의 오목부에 채워지는 보충재의 재료를 선정하는 단계, 및 selecting the material of the unit cell and the material of the supplementary material to be filled in the n recesses, and
    상기 n개의 오목부를 가공하는 단계를 포함하는, 매끈한 일면이 노출되는 메타표면의 설계방법.A method of designing a metasurface in which a smooth surface is exposed, comprising the step of processing the n concave portions.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005098067A (en) * 2003-08-26 2005-04-14 Sekisui Chem Co Ltd Sound absorbing panel and sound absorbing method
CN104751841A (en) * 2015-04-14 2015-07-01 南京大学 Acoustic material capable of achieving ultra-wide-band sound wave redirection
US20190139529A1 (en) * 2015-10-30 2019-05-09 Massachusetts Institute Of Technology Subwavelength Acoustic Metamaterial With Tunable Acoustic Absorption
US20190266992A1 (en) * 2018-02-26 2019-08-29 Toyota Motor Engineering & Manufacturing North America, Inc. Acoustic absorber
WO2020056337A1 (en) * 2018-09-15 2020-03-19 Baker Hughes, A Ge Company, Llc Stealth applications of acoustic hyperabsorption by acoustically dark metamaterial cells

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104505085A (en) * 2014-12-03 2015-04-08 南京大学 Ultra-wideband acoustic absorber
CN110880311B (en) * 2018-09-05 2023-08-15 湖南大学 Underwater sub-wavelength space coiling type acoustic metamaterial

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005098067A (en) * 2003-08-26 2005-04-14 Sekisui Chem Co Ltd Sound absorbing panel and sound absorbing method
CN104751841A (en) * 2015-04-14 2015-07-01 南京大学 Acoustic material capable of achieving ultra-wide-band sound wave redirection
US20190139529A1 (en) * 2015-10-30 2019-05-09 Massachusetts Institute Of Technology Subwavelength Acoustic Metamaterial With Tunable Acoustic Absorption
US20190266992A1 (en) * 2018-02-26 2019-08-29 Toyota Motor Engineering & Manufacturing North America, Inc. Acoustic absorber
WO2020056337A1 (en) * 2018-09-15 2020-03-19 Baker Hughes, A Ge Company, Llc Stealth applications of acoustic hyperabsorption by acoustically dark metamaterial cells

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