Model Tuning of a Vibrating Plate in Contact with Water

This paper presents the early results of a test designed and performed as part of the author's Ph.D. project, whose objective is the study of metamaterials in mitigating structural vibrations and underwater radiated noise from ships. An experiment was developed to investigate the effect of one or multiple devices called Acoustic Black Holes (ABH) installed on a plate vibrating in contact with water. The plate was hung using four ropes above a 3 x 3 meters water tank facility at the Memorial University of Newfoundland and excited using an electrodynamic shaker. This test was designed to simulate the condition of water's contact with one side of a metal structure, as in the case of ships. Aside from the test, a finite element model representing the same scenario was also created to validate it using the recorded experimental data. The described situation falls under the case of fluid-structure interaction problems. Fluid-structure interaction is challenging as it presents both experimental and numerical complications; the scope of the paper is to illustrate how these problems were addressed. Experimentally, the main uncertainties were encountered due to the complexity of replicating the very same water-structure interaction for each test. Numerically, the phenomenon is typically modeled through an approach that generally disregards fluid viscosity and hydrodynamics effects. These effects must, therefore, be included in the added water damping, a parameter generally unknown that must be tuned to match numerical results with experimental outcomes. The preliminary results shown in this paper are limited to the host plate without any ABH installed on it. The reported data include the measured experimental surface mean square velocity on the plate and underwater pressure in the tank facility. This data was eventually used to tune model parameters and validate the finite element model