An investigation of flow structure interactions on a finite compliant surface using computational methods

Abstract

A study of the interaction of one-sided flow over a compliant surface is presented. When fluid passes over a flexible surface the simultaneous interaction between the flow and structure gives rise to vibrations and instabilities on the surface as well as in the fluid. The fluid-structure interaction (FSI) has potential to be used in the control of boundary layer dynamics to achieve drag reduction through transition delay. The modelling and control of FSI systems apply to many fields of engineering beyond drag reduction, for example: the modelling and analysis of biomechanical systems; natural environmental systems; aero-elastics; and other areas where flow interacts moving or compliant boundaries. The investigation is performed through numerical simulation. This returns more detail than could be resolved through experiments, while also permitting the study of finite compliant surfaces that are prohibitively difficult, or impossible, to study with analytical techniques. In the present work, novel numerical modelling methods are developed from linear system analysis through to nonlinear disturbances and viscous effects.Two numerical modelling techniques are adopted to approach the analysis of the FSI system. A potential-flow method is used for the modelling of flows in the limit of infinite Reynolds numbers, while a grid-free Discrete Vortex Method (DVM) is used for the modelling of the rotational boundary-layer flow at moderate Reynolds numbers. In both inviscid and viscous studies, significant contributions are made to the numerical modelling techniques. The application of these methods to the study of flow over compliant panels gives new insight to the nature of the FSI system. In the linear inviscid model, a novel hybrid computational/theoretical method is developed that evaluates the eigenvalues and eigenmodes from a discretised FSI system. The results from the non-linear inviscid model revealed that the steady-state of the non-linear wall motion is independent of initial excitation. For the viscous case, the first application of a DVM to model the interaction of a viscous, rotational flow with a compliant surface is developed. This DVM is successfully applied to model boundary-layer flow over a finite compliant surface.