Stability of boundary-layer flow over a skin made of porous compliant wall and micro floating raft arrays

Abstract

ABSTRACT To improve the drag reduction performance of underwater vehicles, a skin composed of a porous compliant wall and micro floating raft elements is proposed. A two-dimensional stability model of boundary-layer flow over the compliant skin is established, and the effect of structural parameters on the flow stability is investigated. It is found that enlarging the spacing l attenuates the Tollmien-Schlichting Instability (TSI) mode but promotes the occurrence of the Compliance-Induced Flow Instability (CIFI) mode, while the permeability coefficient a presents an opposite effect on the instability modes. Moreover, the CIFI mode is stabilised by increasing the stiffness ratio β, damping ratio γ and intermediate mass m, within limits. The skin proposed in this paper with specific parameters can better reduce the arising of TSI and CIFI modes in boundary-layer flow compared with the corresponding rigid and compliant walls, leading to a favourable performance for delaying boundary-layer transition.