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通讯作者:

陆泽琦,E-mail:luzeqi@shu.edu.cn

中图分类号:TB52

文献标识码:A

文章编号:1672-6553-2024-22(2)-053-006

DOI:10.6052/1672-6553-2024-001

参考文献 1
黄飞,何锃,彭伟才.大型二维稳态声场问题的一种预测方法[J].动力学与控制学报,2007,5(1):83-87.HUANG F,HE Z,PENG W C.A efficient prediction method for steady-state dynamic analysis of two dimensional large acoustic domain problem [J].Journal of Dynamics and Control,2007,5(1):83-87.(in Chinese)
参考文献 2
LIU Y J.On the BEM for acoustic wave problems [J].Engineering Analysis with Boundary Elements,2019,107:53-62.
参考文献 3
WU H J,LI D,YU L,et al.A boundary element method based near field acoustic holography in noisy environments [J].The Journal of the Acoustical Society of America,2020,147(5):3360.
参考文献 4
TADEU A,ANTÓNIO J.3D acoustic wave simulation using BEM formulations:closed form integration of singular and hypersingular integrals [J].Engineering Analysis with Boundary Elements,2012,36(9):1389-1396.
参考文献 5
DEHGHAN M,HOSSEINZADEH H.Calculation of 2D singular and near singular integrals of boundary elements method based on the complex space C [J].Applied Mathematical Modelling,2012,36(2):545-560.
参考文献 6
RONG J J,WEN L H,XIAO J Y.Efficiency improvement of the polar coordinate transformation for evaluating BEM singular integrals on curved elements [J].Engineering Analysis with Boundary Elements,2014,38:83-93.
参考文献 7
KOOPMANN G H,SONG L M,FAHNLINE J B.A method for computing acoustic fields based on the principle of wave superposition [J].The Journal of the Acoustical Society of America,1989,86(6):2433-2438.
参考文献 8
向宇,石梓玉,陆静,等.基于波叠加法的非共形近场声全息波函数的构造与选择[J].振动与冲击,2020,39(15):183-192.XIANG Y,SHI Z Y,LU J,et al.Construction and selection of nonconformal near-field acoustic holography wave function based on wave superposition method [J].Journal of Vibration and Shock,2020,39(15):183-192.(in Chinese)
参考文献 9
陈岩豪,石梓玉,向宇,等.基于波叠加法近场声全息的一种组合型射线波函数法[J].振动与冲击,2022,41(12):125-135.CHEN Y H,SHI Z Y,XIANG Y,et al.A combined ray wave function method for near-field acoustic holography based on the wave superposition method [J].Journal of Vibration and Shock,2022,41(12):125-135.(in Chinese)
参考文献 10
HE T J,HUMPHREY V F,MO S Q,et al.Three-dimensional sound scattering from transversely symmetric surface waves in deep and shallow water using the equivalent source method [J].The Journal of the Acoustical Society of America,2020,148(1):73.
参考文献 11
VALDIVIA N P.Advanced equivalent source methodologies for near-field acoustic holography [J].Journal of Sound and Vibration,2019,438:66-82.
参考文献 12
GAO C,LI Y N.Mechanical model of bio-inspired composites with sutural tessellation [J].Journal of the Mechanics and Physics of Solids,2019,122:190-204.
目录contents

    摘要

    波叠加法在求解声源外部辐射声场时,需要对所有离散单元进行数值积分计算导致计算效率较低,而等效源法由于过度简化单元始终存在较大的积分近似误差.针对以上缺陷,利用Helmholtz方程在球坐标系下的解构造了一种与单元积分等效且无需积分的波函数.受仿生复合材料三角形缝合结构启发,以适用范围最广的平面三角形单元为例,构造了波函数的一般形式和内推形式.最后,通过数值仿真对比了两种波函数与直接积分的计算声场的精度和效率.结果表明,两种波函数与直接积分的计算误差低于0.5%,且内推波函数的计算效率约为直接积分的6倍.

    Abstract

    The wave superposition method requires numerical integration of all discrete elements when solving the external radiation sound field of the sound source, resulting in low computational efficiency. However, the equivalent source method always has significant integration approximation errors due to excessively simplifying the elements. In response to the above shortcomings, a wave function that is equivalent to element integration and does not require integration was constructed using the Helmholtz equation in a spherical coordinate system. Inspired by the triangular stitching structure of biomimetic composite materials, taking the most widely applicable planar triangular element as an example, the general and internal forms of the wave function were constructed. Finally, the accuracy and efficiency of the two wave functions and the direct integration calculation of the sound field were compared through numerical simulation. The results show that the calculation error between the two wave functions and direct integration is less than 0.5%, and the calculation efficiency of the extrapolated wave function is about 6 times that of direct integration.

  • 引言

  • 在声场计算中,边界元法(Boundary element method,BEM)是一种被广泛使用的计算方法[1-3].边界元法通过边界积分方程在分析域边界上离散,可以将问题的维数降低一维,且不用像有限元法那样将区域离散化,这可以显著减少单元数,从而减少数据量和计算时间.边界元法作为一种半解析半数值方法,计算精度虽然高,但是由于积分面与声源表面重合,会产生奇异性问题[4],需要采用额外的处理方法[56].

  • 为了避免边界元法存在的问题,可将积分面设置在声源内部的虚拟面上,即可避免奇异积分的处理,这种方法被称为波叠加法(Wave superposition approach,WSA)[7-9].该方法在求解声源外部辐射声场时,需要对虚拟面进行单元离散.当离散单元数量较多、求解规模较大时,计算效率较低.若用单极子点源替代离散单元的辐射声场,可得到无需积分计算的等效源法(Equivalent source method,ESM)[10].但该方法是对单元辐射声场的过度简化,在面源简化为点源的过程中,始终存在较大积分近似误差,一定程度上影响了计算精度[11].

  • 针对以上问题,本文利用球Hankel函数与球谐波函数乘积的加权和构造一种波函数,替代波叠加法中Green函数在单元区域的积分,避免在求解声源外部辐射声场中复杂的积分计算.受仿生复合材料三角形缝合结构启发[12],由于三角形单元拥有更好的形状逼近性,可以更好地描述复杂的几何结构.以平面三角形单元为例,推导了替代平面三角形单元积分声场一般形式和内推形式波函数,对比了两种波函数与直接积分计算平面三角形单元外部声场的计算精度和计算效率.

  • 1 平面三角形单元波函数的构造

  • 1.1 离散形式的波叠加积分方程

  • 由波叠加法积分方程可知,声源外部声场可由置于其内部虚拟面S′上分布的等效源辐射的声场叠加得到:

  • p(r)=S' qrEGr,rEdS'rE
    (1)
  • 其中,pr)为振动体外部场点r处的声压,qrE)为虚拟面上rE点的源强;GrrE)为自由空间Green函数:

  • Gr,rE=eikr-rE/4πr-rE
    (2)
  • 其中,r-rE表示源强点rE与场点r之间的距离,k为波数,i=-1.

  • 若将虚拟面S′进行离散,可得到M个节点单元Si,式(1)可写为:

  • p(r)=i=1M S' qirEGr,rEdS'rE
    (3)
  • 其中,qirE)表示第i个单元的源强,若Si足够小,单元源强qirE)可近似为常数,此时可得:

  • p(r)=i=1M qirES' Gr,rEdS'rE
    (4)
  • 由式(4)可知,要计算声源外部辐射声场,需要根据场点r的位置进行多次积分,当单元数目较多时,辐射声场的计算效率较低.为提高计算效率,等效源法将上式中单元积分近似为格林函数,即令S' Grr'dS'r'Grr'.该方法虽然提高了计算效率,但由于对物理模型过度简化,始终存在较大的积分误差,一定程度上影响了计算精度.为此,本文提出构造一种等效波函数代替波叠加法中Green函数在单元区域的积分,并以适用范围最广的平面三角形单元为例,详细推导了单元积分等效波函数的构造.

  • 1.2 平面三角形单元一般形式波函数构造

  • 在离散边界积分方程时,平面三角形单元具有网格划分灵活等特点,所以被广泛使用.本节以平面三角形单元为例,分析三角形单元等效波函数具体构造方法.

  • 如图1所示,在球坐标系下考虑单元积分.该单元积分表示一个空间声场,假设该积分可以用一个无需积分的函数Krθφ)来表示:

  • K(r,θ,ϕ)=S Gr,r'dSr'
    (5)
  • 其中,r为场点坐标,r′为单元上的点坐标,r为三角形单元中心点ξ到场点r的距离,θrz轴正方向之间的夹角,φrx轴正方向逆时针方向的夹角,S为三角形单元所在区域.

  • 图1 三角形单元球坐标示意图

  • Fig.1 Schematic diagram of spherical coordinates of triangular elements

  • 利用Helmholtz方程在球坐标系下的解将Krθφ)展开为如下波函数形式:

  • K(r,θ,ϕ)=n=0 m=-nn Cnmhn(1)(kr)Ynm(θ,ϕ)
    (6)
  • 其中,Cnm为展开系数,hn1kr为第一类球Hankel函数,Ynmθϕ为不同阶次的球谐函数,它可以表示为:

  • Ynm(θ,ϕ)=(2n+1)(n-m)!4π(n+m)!Pnmcos(θ)eimϕ
    (7)
  • 其中,mn为球谐函数的阶数,其中n=0,1,···,∞,m=-n,···,nPnmcosθ为连带的Legendre函数.

  • 由于单元积分S Grr'dSr'与波函数Krθφ)均满足Helmholtz方程和Sommerfeld辐射条件,则由微分方程的定解理论可知,只要两者在某个边界上等效,它们在整个空间中的声场分布都等效.为求解展开系数Cnm,在三角形单元外部任选一个半径为r=R的球形人工边界,利用球谐函数的正交性可得到:

  • Cnm=1hn(1)krR02π 0π frR,θR,ϕRY-nmθR,ϕRsinθRdθRdϕR
    (8)
  • 其中,Y-nmθRϕRYnmθRϕR的复共轭.frRθRφR)为该人工边界上的声场分布:

  • frR,θR,ϕR=S GrR,r'dSr'
    (9)
  • 由于式(9)的积分边界S为任意平面常数三角形,不便于积分,现对任意三角形进行坐标变换,使得xy坐标下的三角形单元在参数坐标系ηξ下变为直角边长为1的等腰直角三角形,如图2所示,图中两三角形对应的单元节点编号均记为1,2,3,式(9)变为:

  • frR,θR,ϕR=01 01-η GrR,ξ,η|J(ξ,η)|dξdη
    (10)
  • 其中,Jξη)为雅可比矩阵,对于三角形单元,|Jξη)|=2AA为变换前三角形单元的面积.

  • 图2 任意平面三角形单元及其坐标变换

  • Fig.2 Arbitrary planar triangular element and its coordinate transformation

  • 将式(9)代入式(8)中,可求得展开系数Cnm为:

  • Cnm=2Ahn(1)krR02π 0π 01 01-η GrR,ξ,ηY-nmθR,ϕRsinθRdηdξdθRdϕR
    (11)
  • 为便于后文分析,令C-nm=Cnmhn1krR,可得波函数的具体表达式:

  • K(r,θ,ϕ)=n=0 m=-nn C-nmhn(1)(kr)hn(1)krRYnm(θ,ϕ)
    (12)
  • 由于式(12)的人工边界为任意选取,本文将该式构造的波函数称为三角形单元一般形式波函数.但由式(12)可知,形成波函数时需计算四重积分,较为复杂,计算效率不高.

  • 1.3 平面三角形单元内推波函数构造

  • 由于理论上人工边界位置可任意选取,当其半径rR远大于单元尺寸时,可利用格林函数远场近似表达式获得单元积分S GrRr'dSr'的解析表达式,进一步简化展开系数Cnm,以此提高波函数构造效率.若将人工边界设于远场,人工边界半径rF远大于单元尺寸,此时格林函数的远场近似表达式为:

  • GrF,r'=e-ikrFeiksinθx'cosϕ+y'sinϕ/4πrF
    (13)
  • 其中,x′,y′表示平面三角形单元上点的坐标.

  • 为简化单元积分,对平面三角形常数单元进行坐标变换,如图2所示.记σ=[cosθsinθ]T1T2=x1-x3x2-x3y1-y3y2-y3B=x3y3,其中x1y1x2y2x3y3为三角形单元节点在xy平面下的坐标,变换至参数坐标系ηξ下得到远场格林函数表达式:

  • GrF,r'=eiksinθσT1ζ+σT2η+σB/4πrF
    (14)
  • 将式(14)代入式(10),可得:

  • frF,θF,ϕF=α01 01-η eβξ+γηdξdη
    (15)
  • 其中,α=Ae-ikrF-sinθσB2πrFβ=iksinθσT1γ=iksinθσT2.根据参数取值的不同,frFθFφF)的积分结果如表1所示.

  • 表1 frFθFφF)在参数不同取值的积分结果

  • Table1 Integration results of f (rF, θF, φF) under different parameter values

  • 将式(15)代入式(8),得到远场人工边界波函数的展开系数Cnm

  • Cnm=1hn(1)krF02π 0π frF,θF,ϕFY-nmθF,ϕFsinθFdθFdϕF
    (16)
  • 将式(16)代入式(6)得到远场人工边界波函数:

  • KF(r,θ,ϕ)=n=0 m=-nn C-nm-hn(1)(kr)hn(1)krFYnm(θ,ϕ)
    (17)
  • 其中,C-nm=Cnmhn1krF.

  • 由于式(17)的人工边界选为远场,本文将其称为三角形单元内推波函数.式(17)将展开系数由式(12)的四重积分简化为二重积分,进一步地了计算效率.

  • 2 数值仿真

  • 任意选取一个三角形单元的质心为原点,记三角形所在平面为xy平面,建立直角坐标系.该三角形单元的顶点坐标分别为(-0.0433m,-0.0250m,0m)、(-0.0132m,0.0816m,0m)、(0.0566m,-0.0566m,0m),最长边长L=0.0826m.近场人工球面半径为1.5L,远场人工球面半径为105L,计算的声场球面半径为2L,计算的场点数量为1.44×105个.

  • 为保证计算结果的精度,当划分的单元为三角形常数单元时,每个声波波长一般包含3~4个声学单元,也就是说,单元的最大边长L应满足π/2≤kL≤2π/3的条件.需要注意的是,波函数最高阶数的选择对计算结果影响很大.图3为中各阶波函数对应的重建声压相对误差,其中,相对误差由下式计算:

  • Error =pn-p2p2×100%
    (18)
  • 其中,pn为第n阶波函数重建声压向量,p为解析声压向量.

  • 为了验证本文所构造的两种波函数的准确性,如表3所示,φ=π/2时,本文构造的波函数与直接积分单元直接积分在kL分别为π/2、2π/3、π的情况下的拟合图像与相对误差.从表中可以看出,在kL分别为π/2、2π/3、π的情况下,两种波函数与直接积分计算的声场高度拟合,相对误差均低于0.3 %,证明了波函数的计算精度非常高.

  • 图3 不同波函数对应的计算声压相对误差

  • Fig.3 The relative error of calculated sound pressure corresponding to different wave functions

  • 表2 kL分别为π/2、2π/3、π时两种波函数与直接积分计算声压对比

  • Table2 Comparison of two wave function and direct integration calculation sound pressure when kL is respectively π/2、2π/3、π

  • 表3 kL=π/2时两种波函数与直接积分计算声场CPU耗时

  • Table3 Two types of wave functions and direct integration calculation of sound field CPU time at time kL=π/2

  • 为了进一步验证本文构造的两种波函数的计算效率,如表3所示,φ=π/2时,两种波函数与直接积分计算场点声压的CPU耗时(计算场点声压均采用for循环).从表中可以看出,由于一般形式波函数的展开系数较为复杂,求解展开系数耗时较大,所以导致计算声压的总时长超过直接积分.但是,当求出展开系数后,波函数的计算声压效率约为直接积分的6倍.当采用远场人工边界构造的内推波函数计算单元外部场点声压时,求解展开系数的时间大幅度缩短,即便加上计算展开系数的时间,波函数计算声压的总时长也低于直接积分.

  • 3 结论

  • 针对波叠加法在求解声源外部辐射声场时,需要对所有离散单元进行数值积分计算导致计算效率较低,而等效源法由于过度简化单元始终存在较大的积分近似误差.受仿生复合材料三角形缝合结构启发,本文提出用更符合实际声源的三角形单元将替换单极子点源,并利用Helmholtz方程在球坐标系下的解构造一种高度近似单元积分的波函数.本文详细推导了平面三角形单元波函数的一般形式和内推形式,并对比了两种波函数与直接积分计算声场的精度和效率.结果表明,波函数与直接积分计算的声场拟合得非常好,计算精度在99.5%以上,并且两种波函数的计算效率都高于直接积分,其中内推波函数计算声场的速度约为直接积分的6倍.

  • 参考文献

    • [1] 黄飞,何锃,彭伟才.大型二维稳态声场问题的一种预测方法[J].动力学与控制学报,2007,5(1):83-87.HUANG F,HE Z,PENG W C.A efficient prediction method for steady-state dynamic analysis of two dimensional large acoustic domain problem [J].Journal of Dynamics and Control,2007,5(1):83-87.(in Chinese)

    • [2] LIU Y J.On the BEM for acoustic wave problems [J].Engineering Analysis with Boundary Elements,2019,107:53-62.

    • [3] WU H J,LI D,YU L,et al.A boundary element method based near field acoustic holography in noisy environments [J].The Journal of the Acoustical Society of America,2020,147(5):3360.

    • [4] TADEU A,ANTÓNIO J.3D acoustic wave simulation using BEM formulations:closed form integration of singular and hypersingular integrals [J].Engineering Analysis with Boundary Elements,2012,36(9):1389-1396.

    • [5] DEHGHAN M,HOSSEINZADEH H.Calculation of 2D singular and near singular integrals of boundary elements method based on the complex space C [J].Applied Mathematical Modelling,2012,36(2):545-560.

    • [6] RONG J J,WEN L H,XIAO J Y.Efficiency improvement of the polar coordinate transformation for evaluating BEM singular integrals on curved elements [J].Engineering Analysis with Boundary Elements,2014,38:83-93.

    • [7] KOOPMANN G H,SONG L M,FAHNLINE J B.A method for computing acoustic fields based on the principle of wave superposition [J].The Journal of the Acoustical Society of America,1989,86(6):2433-2438.

    • [8] 向宇,石梓玉,陆静,等.基于波叠加法的非共形近场声全息波函数的构造与选择[J].振动与冲击,2020,39(15):183-192.XIANG Y,SHI Z Y,LU J,et al.Construction and selection of nonconformal near-field acoustic holography wave function based on wave superposition method [J].Journal of Vibration and Shock,2020,39(15):183-192.(in Chinese)

    • [9] 陈岩豪,石梓玉,向宇,等.基于波叠加法近场声全息的一种组合型射线波函数法[J].振动与冲击,2022,41(12):125-135.CHEN Y H,SHI Z Y,XIANG Y,et al.A combined ray wave function method for near-field acoustic holography based on the wave superposition method [J].Journal of Vibration and Shock,2022,41(12):125-135.(in Chinese)

    • [10] HE T J,HUMPHREY V F,MO S Q,et al.Three-dimensional sound scattering from transversely symmetric surface waves in deep and shallow water using the equivalent source method [J].The Journal of the Acoustical Society of America,2020,148(1):73.

    • [11] VALDIVIA N P.Advanced equivalent source methodologies for near-field acoustic holography [J].Journal of Sound and Vibration,2019,438:66-82.

    • [12] GAO C,LI Y N.Mechanical model of bio-inspired composites with sutural tessellation [J].Journal of the Mechanics and Physics of Solids,2019,122:190-204.

  • 参考文献

    • [1] 黄飞,何锃,彭伟才.大型二维稳态声场问题的一种预测方法[J].动力学与控制学报,2007,5(1):83-87.HUANG F,HE Z,PENG W C.A efficient prediction method for steady-state dynamic analysis of two dimensional large acoustic domain problem [J].Journal of Dynamics and Control,2007,5(1):83-87.(in Chinese)

    • [2] LIU Y J.On the BEM for acoustic wave problems [J].Engineering Analysis with Boundary Elements,2019,107:53-62.

    • [3] WU H J,LI D,YU L,et al.A boundary element method based near field acoustic holography in noisy environments [J].The Journal of the Acoustical Society of America,2020,147(5):3360.

    • [4] TADEU A,ANTÓNIO J.3D acoustic wave simulation using BEM formulations:closed form integration of singular and hypersingular integrals [J].Engineering Analysis with Boundary Elements,2012,36(9):1389-1396.

    • [5] DEHGHAN M,HOSSEINZADEH H.Calculation of 2D singular and near singular integrals of boundary elements method based on the complex space C [J].Applied Mathematical Modelling,2012,36(2):545-560.

    • [6] RONG J J,WEN L H,XIAO J Y.Efficiency improvement of the polar coordinate transformation for evaluating BEM singular integrals on curved elements [J].Engineering Analysis with Boundary Elements,2014,38:83-93.

    • [7] KOOPMANN G H,SONG L M,FAHNLINE J B.A method for computing acoustic fields based on the principle of wave superposition [J].The Journal of the Acoustical Society of America,1989,86(6):2433-2438.

    • [8] 向宇,石梓玉,陆静,等.基于波叠加法的非共形近场声全息波函数的构造与选择[J].振动与冲击,2020,39(15):183-192.XIANG Y,SHI Z Y,LU J,et al.Construction and selection of nonconformal near-field acoustic holography wave function based on wave superposition method [J].Journal of Vibration and Shock,2020,39(15):183-192.(in Chinese)

    • [9] 陈岩豪,石梓玉,向宇,等.基于波叠加法近场声全息的一种组合型射线波函数法[J].振动与冲击,2022,41(12):125-135.CHEN Y H,SHI Z Y,XIANG Y,et al.A combined ray wave function method for near-field acoustic holography based on the wave superposition method [J].Journal of Vibration and Shock,2022,41(12):125-135.(in Chinese)

    • [10] HE T J,HUMPHREY V F,MO S Q,et al.Three-dimensional sound scattering from transversely symmetric surface waves in deep and shallow water using the equivalent source method [J].The Journal of the Acoustical Society of America,2020,148(1):73.

    • [11] VALDIVIA N P.Advanced equivalent source methodologies for near-field acoustic holography [J].Journal of Sound and Vibration,2019,438:66-82.

    • [12] GAO C,LI Y N.Mechanical model of bio-inspired composites with sutural tessellation [J].Journal of the Mechanics and Physics of Solids,2019,122:190-204.

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