基于聲學(xué)超常材料的聲能量調(diào)控研究
發(fā)布時(shí)間：2018-08-12 11:47
【摘要】：作為當(dāng)前聲學(xué)領(lǐng)域的熱門(mén)課題,聲學(xué)人工復(fù)合材料的設(shè)計(jì)和應(yīng)用正受到廣泛關(guān)注。聲學(xué)人工復(fù)合材料一般具有特殊的人工結(jié)構(gòu),這些經(jīng)過(guò)特殊設(shè)計(jì)的人工結(jié)構(gòu)使其擁有了超越天然材料本身的超常物理性質(zhì),這為聲學(xué)材料的研究開(kāi)辟了新思路。聲子晶體和聲超構(gòu)介質(zhì)是聲學(xué)人工復(fù)合材料研究領(lǐng)域中的兩類(lèi)典型,兩者在尺度結(jié)構(gòu)和物理機(jī)理上有所差別。聲子晶體的研究更關(guān)注于對(duì)聲波波動(dòng)在其中傳播過(guò)程的分析,因此對(duì)它的研究是多尺度的,既有布拉格散射型聲子晶體,其工作聲波波長(zhǎng)與晶格常數(shù)相當(dāng),同時(shí)也有局域共振型聲子晶體,其工作聲波波長(zhǎng)是晶格常數(shù)的上百倍。由于這類(lèi)材料中存在聲子帶隙,其在高性能聲學(xué)濾波和高精度隔振等方面有著潛在應(yīng)用。相比之下,聲超構(gòu)介質(zhì)更關(guān)注宏觀尺度下人工微結(jié)構(gòu)所表現(xiàn)出的等效聲學(xué)參數(shù)。通過(guò)引入亞波長(zhǎng)尺度的特殊微結(jié)構(gòu)單元可以實(shí)現(xiàn)天然材料中不存在的超常物理性質(zhì),如零折射率、密度各向異性、負(fù)密度和負(fù)體模量等,這些超常的物理性質(zhì)被應(yīng)用于亞波長(zhǎng)成像和聲隱身等諸多領(lǐng)域。本文基于聲子晶體和聲超構(gòu)介質(zhì)這兩種聲學(xué)人工復(fù)合材料,通過(guò)理論計(jì)算和有限元數(shù)值分析相結(jié)合的方法對(duì)兩種聲能量調(diào)控方法的特性和機(jī)理進(jìn)行了詳細(xì)研究。主要涉及基于固-流超晶格結(jié)構(gòu)的聲能量透射增強(qiáng)研究和基于非均勻各向異性零密度超構(gòu)介質(zhì)的聲能量流動(dòng)控制研究。第一章緒論部分簡(jiǎn)要回顧了本文相關(guān)的聲學(xué)人工復(fù)合材料的研究背景和研究進(jìn)展,并概述了本文研究工作的主要內(nèi)容。第二章作為對(duì)固-流超晶格結(jié)構(gòu)的初步研究,其基于傳遞矩陣法,從理論上推導(dǎo)了全向入射條件下固-流超晶格結(jié)構(gòu)的傳遞矩陣。在此理論的基礎(chǔ)上,分別計(jì)算了無(wú)限周期和有限周期的固-流超晶格結(jié)構(gòu)在全向入射條件下的能帶結(jié)構(gòu)和傳輸特性。計(jì)算結(jié)果證明了固-流超晶格結(jié)構(gòu)的能帶結(jié)構(gòu)中低頻聲裂隙的存在。第三章中,研究了基于固-流超晶格結(jié)構(gòu)的聲能量透射增強(qiáng)問(wèn)題。利用Green函數(shù)方法和傳遞矩陣方法分別得到固-流超晶格結(jié)構(gòu)的表面模式色散曲線和相應(yīng)的聲能量透射系數(shù)曲線。結(jié)果表明,聲能量透射增強(qiáng)現(xiàn)象是由固-流超晶格結(jié)構(gòu)的特定表面聲振動(dòng)模式引起的,其透射系數(shù)要遠(yuǎn)高于普通通帶的聲能量透射系數(shù)。隨后,為了進(jìn)一步理解這種聲能量透射增強(qiáng)效應(yīng)的機(jī)理,使用有限元方法研究了不同入射條件下超晶格結(jié)構(gòu)中的位移場(chǎng)分布。數(shù)值模擬結(jié)果證明,聲能量透射增強(qiáng)效應(yīng)可以歸因于在超晶格表面激發(fā)出的表面聲振動(dòng)共振態(tài)。基于此效應(yīng)設(shè)計(jì)的可調(diào)諧聲耦合器件,可用于實(shí)時(shí)匹配兩種聲阻抗相差巨大的流體,實(shí)現(xiàn)聲能量超常穿透。固-流結(jié)構(gòu)為所設(shè)計(jì)的聲耦合器件帶來(lái)的實(shí)時(shí)可調(diào)性有效地彌補(bǔ)了聲能量透射增強(qiáng)效應(yīng)有限帶寬的局限性。第四章中,研究了基于非均勻各向異性零密度超構(gòu)介質(zhì)的聲能量流動(dòng)控制問(wèn)題。利用嚴(yán)格的聲學(xué)理論分析,得到了非均勻各向異性零密度材料在正向入射條件下的等效密度和等效波長(zhǎng)。進(jìn)一步,結(jié)合理論計(jì)算和有限元數(shù)值模擬分析,證明了當(dāng)聲波在材料內(nèi)以垂直于零密度的方向傳播時(shí),零密度分量會(huì)對(duì)非零密度分量施加一種強(qiáng)平均作用。隨后,使用有限元法研究了該強(qiáng)平均效應(yīng)作用下材料內(nèi)部的聲能量流動(dòng)方式。借助于這種強(qiáng)平均效應(yīng),僅需通過(guò)設(shè)計(jì)非零密度分量的分布即可控制聲能量在任意路徑上流動(dòng)。最后,討論了非均勻各向異性零密度超構(gòu)介質(zhì)的具體物理實(shí)現(xiàn)方式。本章中所提出的利用非均勻各向異性零密度超構(gòu)介質(zhì)實(shí)現(xiàn)聲能量流動(dòng)任意控制,僅需簡(jiǎn)單地將流動(dòng)路徑上材料密度張量中的非零分量設(shè)計(jì)為較低值,有效地避免了利用變換聲學(xué)理論所帶來(lái)的極其復(fù)雜的各向異性和非均勻性。最后一章對(duì)全文主要工作做了總結(jié),并展望未來(lái)的研究方向。
[Abstract]:As a hot topic in acoustics, the design and application of acoustical artificial composites have attracted much attention. Acoustical artificial composites usually have special artificial structures, which make them possess extraordinary physical properties beyond the natural materials themselves. This opens up the way for the study of acoustical materials. Phononic crystals and acoustic superstructure media are two typical types of acoustical artificial composites. They are different in scale structure and physical mechanism. The study of phononic crystals is more concerned with the analysis of the propagation process of acoustic wave in them. Therefore, the study of phononic crystals is multi-scale, including Prague scattering phononic crystals. Because of the existence of phonon band gaps in these materials, they have potential applications in high-performance acoustic filtering and high-precision vibration isolation. In contrast, acoustic superstructure media pay more attention to macro-scale. By introducing special microstructural units at sub-wavelength scale, supernormal physical properties, such as zero refractive index, density anisotropy, negative density and negative modulus, can be realized in natural materials. These supernormal physical properties are applied to sub-wavelength imaging and acoustic stealth. Fields. Based on phononic crystals and acoustic superstructure media, the characteristics and mechanism of the two acoustic energy modulation methods are studied in detail by means of theoretical calculation and finite element numerical analysis. In the first chapter, the background and research progress of the related acoustical artificial composites are briefly reviewed, and the main contents of the research work are summarized. In the second chapter, as a preliminary study of the structure of solid-fluid superlattices, the transfer matrix method is used. On the basis of this theory, the band structure and transmission characteristics of infinite-period and Finite-Period solid-flow superlattices under the condition of omnidirectional incidence are calculated respectively. In Chapter 3, the problem of sound energy transmission enhancement based on solid-fluid superlattices is studied. The surface mode dispersion curves and the corresponding sound energy transmission coefficient curves of solid-fluid superlattices are obtained by Green function method and transfer matrix method, respectively. In order to understand the mechanism of the enhancement effect of acoustic energy transmission, the finite element method was used to study the displacement field distribution in the superlattice structure under different incident conditions. A tunable acoustical coupler device based on this effect can be used to match two fluids with large acoustic impedance difference in real-time to achieve supernormal acoustic energy penetration. In Chapter 4, the control of acoustic energy flow in nonhomogeneous anisotropic zero-density superstructure media is studied. The equivalent density of nonhomogeneous anisotropic zero-density materials under forward incidence is obtained by using strict acoustic theory analysis. Furthermore, it is proved that the zero-density component exerts a strong average effect on the non-zero-density component when the sound wave propagates in the direction perpendicular to zero-density by combining theoretical calculation and finite element numerical simulation analysis. By means of this strong averaging effect, the flow of sound energy in any path can be controlled only by designing the distribution of non-zero-density components. Finally, the physical realization of inhomogeneous anisotropic zero-density superstructure media is discussed. In order to avoid the extremely complex anisotropy and inhomogeneity caused by the theory of transform acoustics, the non-zero component of the material density tensor in the flow path is simply designed as a lower value.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TB33
本文編號(hào)：2178962
[Abstract]:As a hot topic in acoustics, the design and application of acoustical artificial composites have attracted much attention. Acoustical artificial composites usually have special artificial structures, which make them possess extraordinary physical properties beyond the natural materials themselves. This opens up the way for the study of acoustical materials. Phononic crystals and acoustic superstructure media are two typical types of acoustical artificial composites. They are different in scale structure and physical mechanism. The study of phononic crystals is more concerned with the analysis of the propagation process of acoustic wave in them. Therefore, the study of phononic crystals is multi-scale, including Prague scattering phononic crystals. Because of the existence of phonon band gaps in these materials, they have potential applications in high-performance acoustic filtering and high-precision vibration isolation. In contrast, acoustic superstructure media pay more attention to macro-scale. By introducing special microstructural units at sub-wavelength scale, supernormal physical properties, such as zero refractive index, density anisotropy, negative density and negative modulus, can be realized in natural materials. These supernormal physical properties are applied to sub-wavelength imaging and acoustic stealth. Fields. Based on phononic crystals and acoustic superstructure media, the characteristics and mechanism of the two acoustic energy modulation methods are studied in detail by means of theoretical calculation and finite element numerical analysis. In the first chapter, the background and research progress of the related acoustical artificial composites are briefly reviewed, and the main contents of the research work are summarized. In the second chapter, as a preliminary study of the structure of solid-fluid superlattices, the transfer matrix method is used. On the basis of this theory, the band structure and transmission characteristics of infinite-period and Finite-Period solid-flow superlattices under the condition of omnidirectional incidence are calculated respectively. In Chapter 3, the problem of sound energy transmission enhancement based on solid-fluid superlattices is studied. The surface mode dispersion curves and the corresponding sound energy transmission coefficient curves of solid-fluid superlattices are obtained by Green function method and transfer matrix method, respectively. In order to understand the mechanism of the enhancement effect of acoustic energy transmission, the finite element method was used to study the displacement field distribution in the superlattice structure under different incident conditions. A tunable acoustical coupler device based on this effect can be used to match two fluids with large acoustic impedance difference in real-time to achieve supernormal acoustic energy penetration. In Chapter 4, the control of acoustic energy flow in nonhomogeneous anisotropic zero-density superstructure media is studied. The equivalent density of nonhomogeneous anisotropic zero-density materials under forward incidence is obtained by using strict acoustic theory analysis. Furthermore, it is proved that the zero-density component exerts a strong average effect on the non-zero-density component when the sound wave propagates in the direction perpendicular to zero-density by combining theoretical calculation and finite element numerical simulation analysis. By means of this strong averaging effect, the flow of sound energy in any path can be controlled only by designing the distribution of non-zero-density components. Finally, the physical realization of inhomogeneous anisotropic zero-density superstructure media is discussed. In order to avoid the extremely complex anisotropy and inhomogeneity caused by the theory of transform acoustics, the non-zero component of the material density tensor in the flow path is simply designed as a lower value.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TB33
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