LAUSR

Abstract Structure-Borne Traveling Waves (SBTWs) can replicate the combined undulatory and oscillatory motions utilized by body and/or caudal fin (BCF) aquatic swimmers. However, when SBTWs are generated in a dense fluid media, such as water, there is poor understanding of the Fluid–Structure Interactions (FSI). There is also limited understanding of how to achieve the full undulatory motions. This study demonstrates the effect of FSI on SBTWs and investigates the relationship between SBTW quality (undulatory vs. oscillatory motion) and forcing input. SBTWs function by leveraging a surface’s structural properties (mode shapes and natural frequencies) to deform a surface into a dynamic waveform. SBTWs are a combination of traveling and standing waves, and can range in quality from pure traveling wave (undulatory) to pure standing wave (oscillatory). SBTWs require a small number of actuators, can be generated on any thin-walled surface (flat or curved), and have customizable parameters (direction, frequency, wavelength). However, SBTWs are sensitive to FSI due to their dependence on the structural properties. In this study, an electro-hydro-elastic (EHE) model is developed to capture the effect of FSI on SBTWs and investigate how the forcing input affects the resultant waveform (undulatory vs. oscillatory). The EHE model consists of a clamped-free beam with discrete, piezoelectric actuators in a quiescent fluid. Slender beam theory and the hydrodynamic function are used to capture the added fluid mass and viscous damping, assuming small displacement amplitudes. The model accurately replicates experimental SBTWs in quiescent water across a range of parameters and is able to predict the SBTW quality. It is shown that the quality is maximized (i.e. pure traveling wave/undulatory motion) when the actuators provide equal forcing to the structure. This can be achieved through judicious actuator placement and control of the relative voltage inputs. This study demonstrates that SBTWs can be generated in quiescent water and they can replicate the combined undulatory and oscillatory motions seen in BCF swimming. This represents a critical step towards implementing SBTWs for underwater propulsion, and future studies should evaluate the propulsive capabilities (i.e. thrust).