跃层中运动小球产生的内波对表层流场的影响

Surface Effects of Internal Wave Generated by a Towed Sphere in Mid-Pycnocline

在实验室条件下制备三层流体,运用激光片光源的粒子图像和测速技术(PIV),研究了当小球沿着密跃层中心线匀速运动时产生的内波对表层流场的影响。实验表明:内波在表层产生的辐聚辐散导致了表层流场的变化,形成了辐散场,其峰线有类似于Kelvin波峰线的形状,用散度来描述;当小球以不同速度运动时,辐散场以散波形式呈现,而没有看到横波;辐散的角度随着内Froude数呈现先增后减。

Internal gravity waves generated by a sphere which is towed horizontally at the middle of pycnocline in three-layer fluid are studied by using PIV(Particle Image Velocimetor) technology in experiment.Internal waves give rise to divergence fields at the free surface due to effects on surface velocity fields.The divergence fields at the free surface are obtained,which plays an important role in the SAR image.Experimental results show that:surface crestlines have the same shape as kelvein crestlines.We only see the diverging wave crests despite of velosities about the sphere.The angles and intensity of divergence vary with internal Froude number accordingly.Especially,the angles increase first and then decrease second with the internal Froude number.