Numerical model and hydrodynamic performance of tuna finlets

Finlets, a series of small individual triangular fins located along the dorsal and ventral midlines of the body, are remarkable specializations of tuna and other scombrid fishes capable of high-speed swimming. In this study, a symmetric model containing nine finlets of tuna is proposed to overcome the limitation of measurement without losing authenticity. Hydrodynamic performance along with three-dimensional flow structures obtained by direct numerical simulation are demonstrated to disclose the underlying hydrodynamics mechanism of finlets. Complex interactions of leading-edge vortices(LEVs), trialing-edge vortices(TEVs), tip vortices(TVs) and root vortices(RVs) are observed from the three-dimensional vortical structures around the finlets. Two more cases consisting of the 3rd to 9th(without the first two) and the 3rd to 7th(without the first two and the last two) finlets are also simulated to examine the effects of the first two and the last two finlets.