This study is devoted to laboratory experiments on the coalescence of two lenticular anticyclones in a linearly stratified rotating fluid. These anticyclones are generated by injecting small volumes of fluid at the centre of a rotating tank where a linearly stratified layer was previously prepared with salt. The characteristics of the interaction between the vortices are studied by visualisation and Particle Image Velocimetry (PIV) as a function of the initial separation distance between the vortices, the Coriolis parameter of the rotating table and the Brünt-Väisälä frequency of the density stratification. Our results show that the merging critical distance depends drastically on the Rossby radius of deformation of the vortices and are in complete agreement with previous numerical modelling of vortex coalescence. We have also observed that mergers involve three-dimensional processes as the vortices intertwine together possibly because of the presence of an elliptic instability that tilts the vortex cores. They are also accompanied by the emission of vorticity filaments and internal gravity waves radiation although we cannot prove that in our experiments these waves are solely due to the merging process.

中文翻译：

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线性分层旋转流体中透镜状反气旋的合并

本研究致力于线性分层旋转流体中两个透镜状反气旋合并的实验室实验。这些反气旋是通过在旋转罐的中心注入少量流体而产生的，在那里，线性分层层事先用盐制备。通过可视化和粒子图像测速 (PIV) 研究涡流之间相互作用的特性，作为涡流之间的初始分离距离、旋转台的科里奥利参数和密度分层的 Brünt-Väisälä 频率的函数。我们的结果表明，合并临界距离在很大程度上取决于涡旋的 Rossby 变形半径，并且与先前涡旋合并的数值模拟完全一致。我们还观察到合并涉及三个维度的过程，因为涡旋交织在一起可能是因为存在倾斜涡旋核心的椭圆不稳定性。它们还伴随着涡度丝和内部重力波辐射的发射，尽管我们无法证明在我们的实验中这些波完全是由于合并过程。