Omnidirectional thermal-electric stealth cloak with double-layer elliptical core-shell structure and its design method

Abstract

The present invention discloses an omnidirectional thermoelectric stealth cloak with a double-layer elliptical core-shell structure and a design method thereof. The thermoelectric stealth cloak comprises, from the inside out, a confocal elliptical core region representing the stealth region, a double-layer confocal elliptical shell region representing the stealth cloak, and an outermost background matrix. Under different heat flow and current directions, the thermal conductivity and electrical conductivity of the background matrix are consistent with the anisotropic equivalent thermal conductivity and equivalent electrical conductivity of the confocal elliptical double-layer core-shell structure. The omnidirectional thermoelectric stealth cloak of the present invention can prevent external heat flow and current from any direction from entering the stealth region, reducing the temperature and potential gradients in the region to zero. Furthermore, the stealth cloak does not cause disturbances in the temperature and electric fields of the background matrix, thus achieving omnidirectional stealth in both thermal and electric fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of metamaterials and relates to an omnidirectional thermal-electric stealth cloak with a double-layer elliptical core-shell structure and a design method thereof. Background Art

[0002] Metamaterials achieve specialized functions not possessed by ordinary materials by engineering material parameters and structural features. Coordinate transformation and neutral inclusion methods are commonly used in material design. Specifically, by manipulating material parameters in specific regions, specialized physical field control functions are achieved. Examples include stealth, aggregation, camouflage, and detection. As research deepens, metamaterials designed for multi-field control—simultaneously controlling multiple physical fields using a single metamaterial—are gaining increasing interest. This allows devices with the same control function across different physical fields to be integrated, improving their efficiency and conserving resources.

[0003] Current research on thermoelectric dual-field cloaking has been limited to isotropic circular structures. Because circular structures are geometrically isotropic, they do not consider the directionality of the external physical field. However, due to practical applications, the geometric shape of the cloak is not limited to a circle. When the geometry of the thermoelectric dual-field cloak is anisotropic, achieving omnidirectional thermoelectric cloaking becomes an unresolved issue. Summary of the Invention

[0004] The purpose of this invention is to design an omnidirectional stealth cloak based on anisotropic geometry that is compatible with both thermal and electric fields. Regardless of the direction of the heat and electric current, the cloak prevents external heat and current from entering the cloaked region, reducing the temperature and potential gradients in that region to zero. This achieves omnidirectional stealth without disturbing the external temperature and electric field distributions. This dual-field thermoelectric stealth cloak has potential applications in aerospace and other related technologies.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a design method for an omnidirectional thermo-electric stealth cloak based on an anisotropic confocal elliptical double-layer core-shell structure. The omnidirectional thermo-electric stealth cloak based on the anisotropic confocal elliptical double-layer core-shell structure can realize an omnidirectional thermo-electric stealth function. The omnidirectional thermo-electric stealth cloak is divided into a first region, a second region, a third region and a fourth region from the inside to the outside. The first region is a region for realizing stealth, which is an anisotropic elliptical shape. The second region and the third region form a stealth cloak. The second region and the third region are hollow elliptical. The first region, the second region and the third region are combined to form a confocal elliptical double-layer core-shell structure. The confocal elliptical double-layer core-shell structure has a core-shell structure in which the dielectrics in the first, second and third regions are made of isotropic materials. The dielectric in the second region is a thermoelectric insulating material. The fourth region is a background matrix for realizing omnidirectional thermoelectric stealth function. Under different heat flow and current directions, the thermal conductivity and electrical conductivity of the background matrix are consistent with the anisotropic equivalent thermal conductivity and equivalent electrical conductivity of the confocal elliptical double-layer core-shell structure, so that no matter how the direction of the external temperature gradient and potential gradient changes, the objects in the first region are not disturbed by the external heat flow and current, and the temperature and potential in the first region remain at a constant value.

[0007] Preferably, the isotropic material of the first region and the third region may be copper, aluminum alloy, magnesium alloy, stainless steel, tungsten, etc. The material of the second region may be polydimethylsiloxane (PDMS).

[0008] In the present invention, the medium in the background matrix of the fourth region is composed of different isotropic base materials and circular inclusions with different radii.

[0009] In the present invention, the base material and the circular inclusions of different radii in the background matrix are all made of isotropic materials. Preferably, the base material of the fourth region is the same as that of the first and third regions; the material of the circular inclusions in the fourth region can be air, PDMS, etc.

[0010] In the present invention, the background matrix structure adopts a multi-layer structure, and its construction method is as follows:

[0011] First, using the equivalent medium theory, the fourth region with anisotropic thermal conductivity and electrical conductivity is structured into a multilayer structure with alternating layers, where the material parameters of each layer are isotropic and arbitrary. Furthermore, using the single particle structure method for each layer, it is transformed into a new structure consisting of a matrix and circular inclusions, where the materials of the matrix and circular inclusions are isotropic materials already available in industrial production. Furthermore, preferably, in the multilayer structure, the thermal conductivity of any odd-numbered layer is defined as κ1, and the electrical conductivity is defined as σ1. The thermal conductivity of any even-numbered layer is defined as κ2, and the electrical conductivity is defined as σ2. The thermal conductivities of the matrix parts of the odd-numbered and even-numbered layered structures are κ and σ, respectively. 基体1 , κ 基体2 , the conductivity is σ基体1 ,σ 基体2 The thermal conductivity of the circular inclusion part of the odd-layer and even-layer structure is κ 圆夹1 , κ 圆夹2 , the conductivity is σ 圆夹1 ,σ 圆夹2 , should satisfy: κ 基体1 (κ 圆夹1 )<κ1<κ 圆夹1 (κ 基体1 ),σ 基体1 (σ 圆夹1 )<σ1<σ 圆夹1 (σ 基体1 ),κ 基体2 (κ 圆夹2 )<κ2<κ 圆夹2 (κ 基体2 ),σ 基体2 (σ 圆夹2 )<σ2<σ 圆夹2 (σ 基体2 ).

[0012] In the present invention, the geometric parameters of the third region are obtained by a parameter optimization method, and the optimization control condition is: by designing and optimizing the geometric parameters of this region, the geometric parameters of the odd-even layer circular inclusions in the fourth region solved in the future under the temperature field are equal to the geometric parameters of the odd-even layer circular inclusions in the fourth region solved under the electric field. That is, the geometric parameters of the odd-even layer circular inclusions in the fourth region are required to be applicable to both the thermoelectric and dual fields.

[0013] The present invention also provides an omnidirectional thermo-electric stealth cloak obtained by the above-mentioned design method.

[0014] The present invention is based on the theory of neutral inclusions. After fully considering the geometric anisotropy of the confocal elliptical double-layer core-shell structure, the anisotropic equivalent thermal conductivity and equivalent electrical conductivity of the confocal elliptical double-layer core-shell structure under different heat flow and current directions are theoretically solved. In order to meet the omnidirectional stealth function in the thermal and electric fields, the thermal conductivity and electrical conductivity of the background matrix need to be consistent with the derived anisotropic equivalent material parameters of the confocal elliptical double-layer core-shell structure. The present invention uses different base materials and circular inclusions to construct an anisotropic background matrix. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] The thermoelectric cloak of the present invention has an anisotropic geometry and is simultaneously applicable to temperature and electric fields in any direction. Current research on thermoelectric dual-field cloaking primarily focuses on circular core-shell structures, which have an isotropic geometry and therefore do not need to consider the direction of the temperature and electric fields. However, if the circular design principle is still used for anisotropic geometries, omnidirectional thermoelectric cloaking cannot be achieved. Therefore, the geometric anisotropy of the device must be fully considered. Based on this, the material parameters required for omnidirectional cloaking are determined. The present invention enables omnidirectional thermoelectric cloaking based on an anisotropic confocal elliptical double-layer core-shell structure. That is, when heat and current are transmitted in any direction, the cloak with anisotropic geometry can achieve thermoelectric cloaking. Furthermore, the thermoelectric cloak of the present invention achieves cloaking without disturbing the temperature and electric field distribution of the background environment. The present invention expands the geometry of the thermoelectric cloak from an isotropic circle to an anisotropic confocal ellipse, achieving omnidirectional thermoelectric cloaking. The thermoelectric omnidirectional stealth function has potential application value in aerospace and military fighter anti-reconnaissance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The geometric area distribution diagram of the omnidirectional thermoelectric stealth cloak with anisotropic confocal elliptical double-layer core-shell structure; in the figure, the thermal conductivity of the confocal elliptical core is κ c The conductivity is σ c The geometric dimensions of the major and minor axes are lc1 and lc2. The thermal conductivity of the inner shell of the confocal ellipse is κ s The conductivity is σ s The semi-major and semi-minor axis geometric dimensions are ls1 and ls2. The thermal conductivity of the outer shell of the confocal ellipse is κ e The conductivity is σ e The geometric dimensions of the major and minor axes are le1 and le2. The thermal conductivity of the background matrix is κ b The conductivity is σ b .

[0017] Figure 2 Schematic diagram of the structure of the omnidirectional thermoelectric stealth cloak with anisotropic confocal elliptical double-layer core-shell structure.

[0018] Figure 3 The following images show the artifacts of the omnidirectional thermoelectric cloak with a confocal elliptical double-layer core-shell structure and the control group. 1 represents the confocal elliptical core, 2 represents the confocal elliptical inner shell, 3 represents the confocal elliptical outer shell, 4 represents the circular inclusion in the odd-numbered layered structure, 5 represents the circular inclusion in the even-numbered layered structure, 6 represents the matrix material in the odd-numbered layered structure, and 7 represents the matrix material in the even-numbered layered structure.

[0019] Figure 4The temperature field simulation results distribution diagram of the anisotropic double-layer confocal elliptical stealth cloak of Example 1 and the control group in the horizontal and vertical temperature gradient directions.

[0020] Figure 5 The distribution diagram of the electric field simulation results of the anisotropic double-layer confocal elliptical invisible cloak of Example 1 and the control group under the horizontal and vertical potential gradient directions. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 The geometric area distribution diagram of the omnidirectional thermoelectric cloaking device with anisotropic confocal elliptical double-layer core-shell structure; in the figure, the thermal conductivity of the confocal elliptical core is κ c The conductivity is σ c The geometric dimensions of the major and minor axes are lc1 and lc2. The thermal conductivity of the inner shell of the confocal ellipse is κ s The conductivity is σ s The semi-major and semi-minor axis geometric dimensions are ls1 and ls2. The thermal conductivity of the outer shell of the confocal ellipse is κ e The conductivity is σ e The geometric dimensions of the major and minor axes are le1 and le2. The thermal conductivity of the background matrix is κ b The conductivity is σ b .

[0023] Figure 2 Schematic diagram of the structure of the omnidirectional thermoelectric stealth cloak with an anisotropic confocal elliptical double-layer core-shell structure in the embodiment. The materials of the first, second and third regions are 316 stainless steel, PDMS and 6061 aluminum alloy. The temperature gradient is 273-293K, and the potential gradient is 0-5V. The fourth region is the background matrix for realizing the omnidirectional thermoelectric stealth function. Under different heat flow and current directions, the thermal conductivity and electrical conductivity of the background matrix are consistent with the anisotropic equivalent thermal conductivity and equivalent electrical conductivity of the confocal elliptical double-layer core-shell structure, so that no matter how the direction of the external temperature gradient and potential gradient changes, the object in the first region is not disturbed by the external heat flow and current, and the temperature and potential in the first region remain at a constant value. The material parameters of the background matrix in the fourth region are realized by a composite structure made of isotropic material, which is composed of a matrix material and a circular inclusion material with different pore sizes. The relevant process of constructing the composite structure is as follows:

[0024] First, using the equivalent medium theory, the fourth region with anisotropic thermal conductivity and electrical conductivity is structured into a multilayer structure with alternating layers, where the material parameters of each layer are isotropic and arbitrary, which is not easy to implement in engineering (here, the arbitrary thermal conductivity of the odd-numbered layer is defined as κ1, and the electrical conductivity is defined as σ1; the arbitrary thermal conductivity of the even-numbered layer is defined as κ2, and the electrical conductivity is defined as σ2). We further use the single-particle structure method for each layer structure to transform it into a new structure consisting of a matrix and circular inclusions, and the materials of the matrix and circular inclusions are common isotropic ordinary materials. It should be noted that the matrix part of the odd-numbered and even-numbered layered structures (κ 基体1 , κ 基体2 ,σ 基体1 ,σ 基体2 ) and the circular inclusion part (κ 圆夹1 , κ 圆夹2 ,σ 圆夹1 ,σ 圆夹2 ) can be any material parameter, but must satisfy κ 基体1 (κ 圆夹1 )<κ1<κ 圆夹1 (κ 基体1 ),σ 基体1 (σ 圆夹1 )<σ1<σ 圆夹1 (σ 基体1 ),κ 基体2 (κ 圆夹2 )<κ2<κ 圆夹2 (κ 基体2 ),σ 基体2 (σ 圆夹2 )<σ2<σ 圆夹2 (σ 基体2 ). The circular inclusions in odd-numbered and even-numbered layers have different aperture geometries.

[0025] In the present invention, the method for selecting and setting the material and geometric parameters of the invisible cloak is as follows:

[0026] 1. Material parameters

[0027] First of all, the first area is the area for achieving stealth, and the material parameters of this area need to be selected according to the actual application requirements and can be arbitrary. The material of the second area is a thermoelectric insulating material, and PDMS can be used. The material selection of the third area is also arbitrary, for example, stainless steel, copper, aluminum alloy, magnesium alloy, etc. can be selected. The selection of the base material and the circular inclusion material of the odd and even layers of the composite structure in the fourth area is also arbitrary. Taking into account the possible resistance at the splicing interface of different materials, the base material selection of the odd and even layers of the composite structure of the present invention is consistent with that of the third area, but it is arbitrary in principle. The circular inclusions of the odd and even layers of the composite structure in the fourth area are selected as air to simplify the workpiece preparation process and save costs.

[0028] 2. Geometric Parameters

[0029] The geometric parameters of the first and second regions need to be designed based on actual application requirements and can be arbitrary. The geometric parameters of the third region are obtained through parameter optimization. The optimization control condition is: by optimizing the geometric parameters of this region, the geometric parameters of the odd- and even-layer circular inclusions in the fourth region, calculated under the temperature field, are equal to those calculated under the electric field; that is, by optimizing the geometric parameters of this region, the geometric parameters of the odd- and even-layer circular inclusions in the fourth region, calculated under the electric field, are compatible with both the thermoelectric and electric fields. The widths of the odd and even-layer substrates in the fourth region are equal. Given the known outer length, the more layers, the more accurate the calculation. The geometric dimensions of the odd and even-layer circular inclusions in the fourth region are determined by the anisotropic background matrix, the widths of the odd and even-layer substrates, and the materials of the substrates and the circular inclusions. Once these parameters are known, the geometric dimensions of the circular inclusions corresponding to the odd and even layers can be calculated, which are compatible with both the thermoelectric and electric fields.

[0030] Next, an example analysis of the thermoelectric stealth cloak device will be conducted.

[0031] Example 1

[0032] The confocal elliptical double-layer core-shell structure was placed in a background matrix, and temperature gradients and electric potential gradients were applied in the horizontal and vertical directions respectively. At the same time, a control group was set up (i.e., the elliptical core without the double-layer stealth cloak was placed in the background matrix) to compare and verify the omnidirectional thermoelectric stealth function of the stealth cloak. Figure 3 The workpiece of the omnidirectional thermoelectric stealth cloak with a confocal elliptical double-layer core-shell structure [ Figure 3 (b)] and the control group [ Figure 3(a)] Workpiece diagram. Among them, the background matrix is composed of 36 layers of alternating layered structures. The matrix parts of the odd-numbered and even-numbered layered structures are both made of 6061 aluminum alloy, and the circular inclusion parts of the odd-numbered and even-numbered layered structures are both made of air. It should be noted that the material parameters of the matrix parts and circular inclusion parts of the odd-numbered and even-numbered layered structures can be arbitrary. The aperture geometry of different circular inclusions needs to be determined based on the derived anisotropic background matrix and the width of each layer of the layered structure. The numerical simulation method is used for verification, and the corresponding temperature field and electric field finite element simulation results are shown in Figure 2. Figure 4 and Figure 5 The analysis shows that in the control group without the invisibility cloak, no matter whether the temperature gradient is applied horizontally or vertically, the elliptical core causes a temperature field disturbance in the external background matrix, and a temperature gradient exists inside the elliptical core [see Figure 4 (a1), 4(a2)]. When the elliptical core is covered by the invisible cloak, the external temperature field disturbance is automatically eliminated, and the temperature gradient inside the elliptical core becomes zero, and the isotherms bypass the central elliptical core [see Figure 4 (b1), 4(b2)]. The simulation results of the electric field show the same trend of change, that is, the existence of the invisible cloak can eliminate the electric field disturbance in the background matrix and make the electric potential gradient inside the elliptical core become zero [see Figure 5 (b1), 5(b2)]. In this way, the omnidirectional stealth function of the confocal elliptical double-layer stealth cloak in the thermoelectric dual field is realized.

[0033] The above description of the embodiments is intended to facilitate understanding and application of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments can be readily made, such as by changing the parameters of the base materials for the odd- and even-numbered multilayer structures and the circular inclusions in the background matrix, and by applying the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments; improvements and modifications made by those skilled in the art based on the present disclosure without departing from the scope of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A design method for an omnidirectional thermo-electric stealth cloak based on an anisotropic confocal elliptical double-layer core-shell structure, characterized in that: The omnidirectional thermo-electric stealth cloak based on the anisotropic confocal elliptical double-layer core-shell structure can realize an omnidirectional thermoelectric stealth function, which is divided into a first region, a second region, a third region and a fourth region from the inside to the outside; the first region is the region for realizing stealth, which is an anisotropic elliptical shape, the second region and the third region form a stealth cloak, the second region and the third region are hollow elliptical, and the first region, the second region and the third region are combined to form a confocal elliptical double-layer core-shell structure, the medium in the first region, the second region and the third region adopts an isotropic material, and the medium in the second region is a thermoelectric insulating material, and the fourth region is a background matrix for realizing the omnidirectional thermoelectric stealth function. Under different heat flow and current directions, the thermal conductivity and electrical conductivity of the background matrix are consistent with the anisotropic equivalent thermal conductivity and equivalent electrical conductivity of the confocal elliptical double-layer core-shell structure, so that no matter how the direction of the external temperature gradient and the electric potential gradient changes, the object in the first region is not disturbed by the external heat flow and electric current, and the temperature and electric potential in the first region remain at a constant value; The medium in the background matrix of the fourth region is composed of isotropic different matrix materials and circular inclusions of different radii. The background matrix structure adopts a multilayer structure. In the multilayer structure, the thermal conductivity of any odd-numbered layer is defined as κ1, and the electrical conductivity is defined as σ1. The thermal conductivity of any even-numbered layer is defined as κ2, and the electrical conductivity is defined as σ2. The thermal conductivity of the matrix part of the odd-numbered and even-numbered layered structures is κ, respectively. 基体1 , κ 基体2 , the conductivity is σ 基体1 ,σ 基体2 The thermal conductivity of the circular inclusion part of the odd-layer and even-layer structure is κ 圆夹1 , κ 圆夹2 , the conductivity is σ 圆夹1 ,σ 圆夹2 , should satisfy: κ 基体1 (κ 圆夹1 )<κ1<κ 圆夹1 (κ 基体1 ),σ 基体1 (σ 圆夹1 )<σ1<σ 圆夹1 (σ 基体1 ),κ 基体2 (κ 圆夹2 )<κ2<κ 圆夹2 (κ 基体2 ),σ 基体2 (σ 圆夹2 )<σ2<σ 圆夹2 (σ 基体2 ); The geometric parameters of the third region are obtained through parameter optimization. The optimization control condition is: by designing and optimizing the geometric parameters of this region, the geometric parameters of the odd- and even-layer circular inclusions in the fourth region solved in the future under the temperature field are equal to the geometric parameters of the odd- and even-layer circular inclusions in the fourth region solved under the electric field. That is, the geometric parameters of the odd- and even-layer circular inclusions in the fourth region are required to be applicable to both the thermoelectric and dual fields.

2. The design method according to claim 1, characterized in that: The background matrix structure adopts a multi-layer structure, and its construction method is as follows: First, the equivalent medium theory is used to structure the fourth region with anisotropic thermal and electrical conductivity into a multilayer structure with alternating layers, where the material parameters of each layer are isotropic and arbitrary. Then, the single-particle structure method is used for each layer structure to transform it into a new structure consisting of a matrix and circular inclusions. The materials of the matrix and circular inclusions are isotropic materials already used in industrial production.

3. An omnidirectional thermo-electric stealth cloak obtained according to the design method according to any one of claims 1-2.

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