Correction to: Influence of time interval on the water entry of two spheres in tandem configuration

In this paper, the influence of time interval on the cavity dynamics of two spheres entering into water in tandem configuration is experimentally studied. Cavity evolution and motion characteristic of the two spheres are evaluated through a high-speed camera system and advanced image process techniques. The relationship between the cavitation characteristics and Froude number ( Fr ) is quantified, and it is found that deep pinch-off time of the cavity formed by the second sphere is close to a constant value of 34.8 ms at different Fr s. Drag reduction effect when the second sphere passes through the bubbly flow associated with deep pinch-off of the cavity for the first sphere is also analyzed. The dimensionless number “Matryoshka number” ( Mt ), defined as the ratio of time interval between the two spheres and deep pinch-off time of the second cavity, is introduced as well. The result shows that decay rate of acceleration for the second sphere decreases with increasing Mt .