Dynamic Response of Wall-Mounted Flaps in an Oscillating Crossflow

摘要

The coupled interactions between fluids and slender structures play a number of critical roles in a broad range of physical processes. In flow control applications, poroelastic coatings consisting of arrays of passive slender structures have been shown to provide beneficial aerodynamic characteristics when applied to bluff bodies. This effect has been linked to the appearance of a travelling wave through the array which locks in to the shedding frequency of the wake. Through a simplified test case, which reduces the problem complexity while retaining the essential physics of the behaviour, the present work aims to further elucidate this phenomenon via numerical simulations. A range of array lengths are tested and the appearance and propagation of the travelling waves are monitored. The results show that for small arrays there exists one clearly defined wave, which is attributed to the advection of the primary bulk vortex over the array. However, for larger arrays, secondary vortices are generated at the tips which also induce a wave-like behaviour. These secondary vortices are smaller in size and intensity than the primary vortex and induce a smaller deflection in the flaps which dissipates quicker as it propagates though the array.