Two-Way Fluid-Structure Interaction Hydroelastic Simulation of Vibrating Membranes with Applications in Marine Renewable Wave Power

Abstract

Modern ocean engineering is developing quickly, and floating cities, new energy harvesting methods and novel marine systems are unfolding in the 21st century. The intelligent design of many such systems is exploiting “compliant” structures that deform under fluid dynamic loading, yet retain their function and integrity. These include floating solar membrane panels, breakwaters, OTEC systems and marine robotic inspection devices, e.g., Mantadroid and MIT’s Soft robotic fish. The nature of the ocean is unpredictable, and such systems must be designed for a range of loading conditions. Conventional rigid designs are now being superseded by compliant, flexible systems largely due to the development of novel materials. These structures interact with the hydrodynamic environment and perform “hydroelastically”. This involves two-way fluid structure interaction (FSI) between the fluid and the deforming structure and requires advanced analysis methods. The process is generally nonlinear and commercial computational fluid dynamics/finite element codes are presently the most robust method for conducting such simulations. Indeed, other loads may also arise including ice, tidal, earthquake, debris impact, etc. All these loadings can be accommodated reasonably with FSI analysis. In this work, motivated by examining in greater detail the mechanics of deformable membranes (for submerged ocean energy systems), a detailed analysis of the FSI behaviour of a vertical membrane structure is conducted. The analysis is performed on a thin plate acting as a membrane, experiencing under damped oscillatory motion within a still marine environment (wave effects are ignored). Linear elastic material behaviour is considered, and extensive visualization of pressure, velocity and Von Mises (equivalent) stress contours are provided. Mesh independence is conducted, and validation of the tip deflection with COMSOL multiphysics software is included. Extensive interpretation of the results is included and future modification pathways for more complex analysis are outlined including wave effects with different order theories. A major novelty of this work is the full 3-D visualization of FSI with both flow fields and stress fields analysed.