Study of vortex motions over an inclined plate with periodic oscillating microstructures

The surfaces of many animals and plants in nature are covered with deformable microstructures that engage in complex fluid–structure interactions and thereby control the flow. However, our understanding of the physical mechanisms by which these deformable microstructures regulate the flow remains limited. In this work, a bioinspired surface with periodically oscillating microstructures is designed to investigate how microstructures influence the flow over an inclined plate. The study employs a simplified model inspired by the dermal denticles of shark skin, and a method combining the immersed boundary method and the lattice Boltzmann flux solver is conducted for two-dimensional numerical simulations. The Reynolds number based on the plate chord and the incoming flow velocity is 2.0×104. The results show that changing the oscillation amplitude and frequency of the microstructures can effectively control the drag. With increasing frequency and amplitude, the drag reduction rate increases and reaches a maximum of 47.5%. The flow over different cases can be classified into two regimes, which are the coherent vortex shedding regime and the isolated vortex shedding regime. With large microstructure frequency and amplitude, the isolated vortex shedding regime appears and a substantial drag reduction is reached. In this regime, the microstructures periodically modulate the flow field near the leading edge, causing the characteristic frequency of the flow to become locked to the structural oscillation frequency. A parameter combining the microstructure frequency and amplitude is analyzed to predict the flow regime for different cases.