CAJ | 학술논문

以刚性/液体颗粒和气泡为例,开展椭球颗粒声散射数值研究。运用边界元法研究刚性颗粒的声散射特性,验证该方法的可行性,计算并分析在长短轴比2∶1和3∶1,无因次尺寸参量ka小于10条件下刚性椭球颗粒散射声压。鉴于边界元法的局限性,对液体颗粒和气泡,则采取一种声散射函数近似计算方法。以液体椭球算例验证计算程序,之后预测椭球气泡随不同无因次尺寸参量、长短轴比、入射角的散射声压变化趋势,比较椭球和球形气泡散射声压分布,并对散射截面变化进行探讨。结果表明：对于刚性颗粒,在无因次参量ka大于4后前向散射效应占主要地位,随长短轴比值增加散射旁瓣增强。对于气泡,当椭球趋近于球体时,将本文结果与球体散射声压比较,发现入射角90°时吻合度最高。此外,当无因次参量和入射角不变时,前向散射随长短轴比的增大而增强。表现出与刚性颗粒类似的散射旁瓣随长短轴比的增加而增强,能量向前集中的特征,但散射截面减小。
이강성/액체과립화기포위례,개전타구과립성산사수치연구。운용변계원법연구강성과립적성산사특성,험증해방법적가행성,계산병분석재장단축비2∶1화3∶1,무인차척촌삼량ka소우10조건하강성타구과립산사성압。감우변계원법적국한성,대액체과립화기포,칙채취일충성산사함수근사계산방법。이액체타구산례험증계산정서,지후예측타구기포수불동무인차척촌삼량、장단축비、입사각적산사성압변화추세,비교타구화구형기포산사성압분포,병대산사절면변화진행탐토。결과표명：대우강성과립,재무인차삼량ka대우4후전향산사효응점주요지위,수장단축비치증가산사방판증강。대우기포,당타구추근우구체시,장본문결과여구체산사성압비교,발현입사각90°시문합도최고。차외,당무인차삼량화입사각불변시,전향산사수장단축비적증대이증강。표현출여강성과립유사적산사방판수장단축비적증가이증강,능량향전집중적특정,단산사절면감소。
The purpose of this paper is to investigate acoustic scattering by a prolate spheroid particle.As a verification of the feasibility,the BEM (Boundary Element Method )is first introduced for calculating acoustic scattering by a rigid spherical particle,which yields consist results with the theoretical values.Then the acoustic pressure distributions of the rigid prolate spheroid particle are presented when the aspect ratio and non-dimensional parameter change.However,due to the limitation of BEM,another method is introduced for calculating acoustic scattering of weak and gas fluid spheroid,which is characterized by approximating the acoustic scattering function. To validate the accuracy,the calculated reduced target strength of weak fluid is compared with the results shown in a previous paper.Then the acoustic scattering pressure distributions of bubbles(i.e.gaseous particles)are illustrated, corresponding to varied incident angles,aspect ratiosand non-dimensional parameters.The variation trends of the scattering cross section are discussed too.In the case of bubbles,it is found that when the incident angle and non-di-mensional parameter remain unchanged,the forward scattering grows as the axial ratio increases.When the non-di-mensional parameter is far below 1 ,the scattering pressure distributes uniformly at each angle.For rigid particles and bubbles,it is shown that the forward scattering would gradually dominate when the non-dimensional parameter exceeds 4,the scattering side lobes will be enhanced when the axial ratio increases,while the scattering cross-section will decrease.