WAKE STRUCTURES OF A CANTILEVER BEAM EXCITED BY PIEZOELECTRIC ACTUATORS

摘要

In this paper, the wake structures of a cantilever beam in axial flows under the excitations of piezoelectric actuators are studied. It is assumed that the dynamic response of the cantilever beam is relatively small (i.e., linear) and the beam is modeled as an Euler-Bernoulli beam. The total force is divided into two parts: 1) the hydrodynamic loading, which changes beam's natural frequencies and damping ratios and 2) the piezoelectric induced part, which is the excitation force. Furthermore, the hydrodynamic loading can be separated into an added mass term and a fluid damping term and they are obtained with the hydrodynamic function; the excitation force induced by the converse piezoelectric effect is calculated with Love's control operator. In order to maximize wake generations, two specific types of piezoelectric actuators (i.e., modal actuators and segmented actuators) are used in this study. It is assumed that the mode shapes of the cantilever beam remain unchanged in fluids and the dynamic responses of the cantilever beam can be calculated by the modal expansion method. Once the dynamic responses of the cantilever beam are known, the panel method free-wake model is adopted to simulate the wake structures. In case studies, the wake structures excited by modal actuators and segmented actuators of the first four modes are compared. The effects of applied voltage and flow velocity to the wakes are also studied. Distinct wake roll-up phenomenon is observed in all simulation results. Higher applied voltage and lower flow speed make the wake easier to roll-up.