中文摘要：

在三维内波水槽中制备两层流体,利用粒子图像测速技术（PIV）,研究了小球在跃层、跃层上部与跃层下部三个位置运动时的表面流场特征,对图像进行处理后得到表面的速度场、散度场、涡度场。当小球在不同深度以不同速度运动时,散度场的锋线均有类似Kelvin波峰线的形状,辐散的角度（内Kelvin角）随着速度的增加而减小。特别地,当小球以在跃层处运动时,辐聚辐散强度的极值随着速度的增加先增加后减小,此时的表面流场近乎于无旋场。

英文摘要：

We put experiment in a 3D tank filled with two--layer fluid to investigate the characteristics of surface velocity field of internal waves generated by a shphere moving horizontally at, on andunder the pycnocline. The velocity vorticity by the picture of CCD. When the sphere moves in different depth, the surface crest lines shape as Kelvincrestlines and the angle decreases with the increasing of velocity of the sphere. When the sphere moves at the pycnocline. When the sphere moves at the pycno- cline, the absolute value of divergence increases first and then decreases with the velocity of the sphere, and vorticity of surface velocity field is close to zero.