Guidelines and procedure for tailoring high-performance, steady-state traveling waves for propulsion and solid-state motion

Abstract

Structure-Borne Traveling Waves (SBTWs) have significant promise as a means of underwater propulsion, solid-state motion, and drag reduction. However, there is limited understanding over how to tailor SBTWs for these applications. This study establishes guidelines and a procedure for tailoring SBTWs on thin-walled two-dimensional (2D) surfaces. These guidelines were specifically crafted to yield SBTWs favorable for propulsion and solid-state motion: propagation along a uniform direction and with consistent amplitude. SBTWs are steady-state traveling waves generated by taking advantage of a surface’s modal properties (i.e. mode shapes). This novel mechanism provides significant benefits including a minimal actuation footprint, a wide frequency bandwidth, and active variability (propagation direction, wavelength, etc). However, this mechanism also introduces a dependence on the mode shapes and actuator location. Thus, to tailor SBTWs favorable for propulsion the relationship between SBTWs, the mode shapes, and actuator locations must be understood. Eight Guidelines governing this relationship are established. These Guidelines are demonstrated using SBTWs generated on a previously validated model of a 2D plate. Among others, it is shown that the frequency bandwidth can be broken into distinct frequency regions, and each region can be classified as yielding favorable or unfavorable SBTWs. A multi-step procedure is then introduced that enables SBTWs to be tailored on any thin-walled surface. Numerically or experimentally applicable, the actuator configuration can be defined to tailor SBTWs with a specific propagation direction; all that is required is knowledge of the mode shapes. Finally, a case study is presented in which the guidelines and procedure are implemented to tailor SBTWs on a trapezoidal surface. Two different sets of SBTWs are tailored, each propagating in different directions and with various wavelengths. Thus, the established guidelines and procedure enable SBTWs to be tailored for specific applications, such as propulsion and solid-state motion.