Yongpu Wang , Yanyan Liu , Michael David Atkins , Tian Jian Lu , Tongbeum Kim
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引用次数: 0
Abstract
Contrary to previously known physics about fluid motion around two side-by-side circular cylinders, this study has demonstrated stably biased gap flow when excited by a flapping and stationary cantilever pair - the gap flow is only deflected towards the flapping cantilever (without switching). Mechanisms for this behavior were presented in this study. To this end, flow visualization and spectral analysis of time-resolved data from hot-wire anemometers and the piezoelectric mount of a flapping cantilever were carried out. Furthermore, particle image velocimetry was conducted to map instantaneous and time-averaged velocity and vorticity fields. During measurements, a center-to-center spacing normalized by cantilever diameter (T/D, pitch ratio) was systematically varied in the Reynolds number range of 1800 ≤ ReD ≤ 13,000. We demonstrated that the Kelvin-Helmholtz (K-H) instability of shear layers separated from the flappable cantilever was intensified due to flapping, consequently inciting the earlier onset of Kármán vortices (evolved from K-H vortices) than those behind the stationary cantilever. Thereafter, an earlier velocity recovery developed, generating a transverse pressure gradient towards the flapping cantilever and subsequent upstream penetration (i.e., potential effect). The gap flow then became stably pushed towards the flapping cantilever.
期刊介绍:
The Journal of Fluids and Structures serves as a focal point and a forum for the exchange of ideas, for the many kinds of specialists and practitioners concerned with fluid–structure interactions and the dynamics of systems related thereto, in any field. One of its aims is to foster the cross–fertilization of ideas, methods and techniques in the various disciplines involved.
The journal publishes papers that present original and significant contributions on all aspects of the mechanical interactions between fluids and solids, regardless of scale.