On the two staggered swimming fish

We characterised the hydrodynamics of the two staggered swimming fish using vortex dynamic method. Based on the theoretical model, we showed that the horizontal spacing between the two fish plays a crucial role in affecting the fluid dynamics around two fish, while the vertical spacing between the two fish merely affects the value of propulsive force individually generated by the two fish. Furthermore, we revealed that there are two horizontal spacing thresholds for the holding and breaking of the spatial configurations of the two fish, indicating that two fish would swim at the stable status: the synchronous acceleration or deceleration.