MODULATION OF HYDRODYNAMIC FORCES ON OSCILLATING SUBMERGED STRUCTURES IN VISCOUS FLUIDS
AuthorAhsan, Syed Nazmul
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The study of the dynamical behavior of ﬂexible submerged cantilever-like structures subjected to underwater vibration is of primary importance in a wide range of scientiﬁc and engineering ﬁelds. In the context of such applications, the performance of submerged devices primarily depends on the hydrodynamic forces experienced by the submerged structure resulting from the ﬂuid-structure interactions. In turn, such forces are correlated to power dissipation occurring during underwater oscillations. The added mass and hydrodynamic damping eﬀect that arise due to the interaction between the ﬂuid and the structure are of practical relevance to design, fabrication, and control of devices operating in viscous ﬂuids. Modulation of the forces and dissipated power by manipulating the hydrodynamics in the vicinity of the structure can thus improve the performance of these devices. In this dissertation, we discuss several ﬂuid-structure interaction problems concerning oscillating submerged bodies in viscous ﬂuids with the overarching target ofmodulating hydrodynamic forces and power dissipation for optimal dynamic behavior. Towards this goal, we propose the novel paradigm of “shape-morphing” structures, whereby time-varying structural deformations are considered to manipulate vortex shedding and viscous forces. For a comprehensive set of vibration scenarios, including ﬂexural and torsional vibrations in an unbounded ﬂuid, as well as transverse oscillations in the vicinity of a solid wall, we conduct a thorough numerical and semi-analytical study to estimate the forces applied to the submerged structure and characterize the forces in the form of a manageable hydrodynamic function depending on diﬀerent governing parameters. The completed research activity thus elucidates the potential of the novel shape-morphing strategy to control and modulate hydrodynamic forces and power dissipation and its applicability in diﬀerent research and application ﬁelds. The capability to adapt to varying dynamical conditions and complex vibration scenarios will make this novel ﬂuid-structure interaction control paradigm an attractive solution for applications in atomic force microscopy, micromechanical sensors and actuators, piezoelectric fan systems, biomimetic robotic propulsion, and smart material-based energy harvesting devices.