Study on the drag reduction characteristics of non-equal height bionic surfaces of underwater vehicles

To enhance the range and reduce the energy consumption of marine equipment, inspired by the non-equal height ridge structures of the beluga whale and pilot whale body surfaces, we reconstructed analogous skin ridge features and designed a bionic non-smooth surface model for the Defense Advanced Research Projects Agency SUBOFF underwater vehicle. Four types of bionic surface structures, namely, V-shaped, circular arc, trapezoidal, and non-equal height trapezoidal, were evaluated using numerical simulations. The simulations employed the shear stress transport k–ω turbulence model to assess drag reduction performance under different flow conditions. The underlying drag reduction mechanisms were investigated based on velocity field, shear stress distribution, pressure field, and vortex structure analyses. The results indicate that the non-equal height trapezoidal structure exhibits the most effective drag reduction, achieving a local drag reduction rate of up to 6.7%. In addition, this structure shows reduced fluctuations in the friction coefficient and the smallest increase in pressure drag. Moreover, it also presents a lower shear stress gradient and a thicker boundary layer at the bottom, which contributes to decreased surface velocity and viscous drag.