Optimization of drag-reduction microstructure parameters and study of the drag reduction mechanism in a rotating flow field

Fluid drag greatly lowers the efficiency and increases the energy consumption of underwater vehicles and devices working in similar environments. Therefore, drag reduction has become a major topic in fluids research. Inspired by the high drag-reduction effect of shark skin, this paper experimentally and numerically investigates the drag-reduction performance of a bionic shark skin microstructure with a triangular cross section. The structural parameters are optimized through numerical simulations. The microstructure reduces the drag by reducing the velocity gradient near the wall and changes the turbulent kinetic energy distribution in the flow field near the wall. Next, samples of microstructures were prepared using the template method. Experimental rheometer tests revealed a drag reduction rate of 14.29% on the microstructure surface under the set experimental conditions. Experiments and simulations have demonstrated the high drag-reduction effect of the microstructures within a rotating flow field. The developed method and theoretical basis for numerical simulations of rotating flow fields can be utilized in pump machinery such as magnetic levitation centrifugal flow pumps.