Surface tension barrier for juvenile flying fish

Flying fish penetrate the air-water surface before they fly. Due to the surface tension, the juvenile flying fish measured within 0.4 mm in length fail to leap out of the water surface (Yang et al., APS DFD, 2013)[1]. In this experimental study, we use styrofoam spheres to mimic juvenile flying fish and investigate the process of penetrating air-water surface. The penetrating process depends on the size of the sphere: About 20 mm is the critical diameter. Spheres smaller than this diameter can not break the water surface. Our analytical model suggests that this critical diameter of spheres is around 6 mm, which is one-third of the experimental results. The inconsistency is possibly due to the surface properties of the styrofoam spheres. Understanding the leaping process of juvenile flying fish may shed light on the design of micro aero-hydro vehicles.

[1] https://meetings.aps.org/Meeting/DFD13/Event/202874