The cavity dynamics and trajectories of twin spheres vertically entering water side-by-side are investigated experimentally for different time intervals and several lateral distances at initial velocities from 14.1 m/s to 15.2 m/s, with the diameter (D) based Froude number varying from 37.1 to 40.0. A high-speed photograph system and an image processing method are employed to obtain the features of cavity flow and the position of twin spheres. We firstly investigate the cavity shapes and sphere trajectories with lateral distance being 1.5D between the spheres. Results show that the contact lines of two cavities are obliquely pinned on the twin spheres in synchronous water entry, and a molar-shaped cavity is formed by the overlap of the two cavities. Subsequently, the motion characteristics of the second water-entry sphere (Sphere II) are studied as the increase of time interval between the twin spheres. It is found that the influence on Sphere II increases as the decrease of the time interval at lateral distance of a = 1.5D, except a certain condition, i.e. Δt = 2.5 ms. As we change the lateral distance in synchronous water entry, the disturbance introduced by adjacent sphere is weakened with the increase of the distance. The results demonstrate that both the cavity dynamics and trajectories of Sphere II are similar to that of single water entry when the lateral distance increases to 5.5D. As for the combined effects of lateral distance and time interval on twin water entry, it is found that Sphere II is attracted horizontally to Sphere I at moderate time intervals with the lateral distance of a = 1.5D, while the interaction acted on Sphere II in cases of a = 2.5D and 3.5D changes from repulsion to attraction gradually as the increase of time interval from 3.5 ms to 8.4 ms and then to 13.1 ms.

实验研究了在初始速度从14.1 m / s到15.2 m / s的不同时间间隔和若干横向距离下，垂直并排进入水中的双球体的腔动力学和轨迹，其中直径（D）为Froude数从37.1到40.0。利用高速照相系统和图像处理方法获得腔流和双球体位置的特征。我们首先研究横向距离为1.5 D的腔体形状和球轨迹在球体之间。结果表明，在同步进水过程中，两个空腔的接触线倾斜地钉在双球体上，两个空腔的重叠形成了臼齿状空腔。随后，随着双球之间时间间隔的增加，研究了第二水进入球（球II）的运动特性。可以发现，除了一定条件Δt以外，在a  = 1.5 D的横向距离上，随着时间间隔的减小，对球体II的影响增加。 = 2.5毫秒。当我们改变同步进水的横向距离时，相邻球体引入的扰动随着距离的增加而减弱。结果表明，当横向距离增加到5.5 D时，球体II的腔动力学和轨迹与单水进入的相似。关于横向距离和时间间隔对双水进入的综合影响，发现球体II以中等的时间间隔水平吸引到球体I，横向距离为a  = 1.5 D，而相互作用作用于球体II中。的情况下，一个 = 2.5 d和3.5 d 时间间隔从3.5毫秒增加到8.4毫秒，然后又增加到13.1毫秒，从排斥力逐渐变为吸引力。