非均匀平面波声场中质点运动的椭圆度

Ellipticity of Motion for Particle in Field of Inhomogeneous Plane Wave

当均匀平面声波入射在液—固介质分界面上产生非均匀平面波时，场中质点将在其平衡位置附近作椭圆振动。计算表明：对于场中固体界面上的质点，当入射角比纵波临界角小得多时，其椭圆度近似为１，质点基本上作直线振动；当入射角比横波临界角大得多时，纵波场中质点运动的椭圆度接近于０，质点运动轨迹近于圆，而横波场中质点运动的椭圆度最小；当入射角在纵波临界角或横波临界角附近时，质点运动的椭圆度有较大的变化。文中指出固体粘滞系数对场中质点运动椭圆度的影响不大，且仅仅表现在临界角附近。在瑞利角入射下，界面法线方向上的固体质点，其运动的椭圆度呈周期性变化，当深度为瑞利波半波长整数倍时，椭圆度为１；当深度为瑞利波半波长的奇数倍时。

Locus of mation for particle in the field of inhomogeneous plane wave will be elliptic when the homogeneous plane wave incidents upon the interface of liquid thermoviscoelastic and generates the inhomogeneous plane waves.Calculations show:for the particles which are located in the fields of longitudinal and transversal wave,the ellipticity will be 1 if the incidence is much smaller than their critical angle;the ellipticity will be the smallest if the incidence is much bigger than their critical angles;the ellipticity will change much if the incidence is near their critical angles.For the particles which are located in the field of entropic or reflective wave,the ellipticity of the former will diminish linearly approximately versus angle of incidence;the ellipticity of the latter is totally 1.The ellipticity will change periodically versus depth of interface under the incidence of Rayleigh angle.The ellipticity will be 1 if the depths are the integer times of wavelength of Rayleigh wave and the ellipticity will be the smallest if the depths are the odd times of half wavelength of Rayleigh wave.