Adaptive Nonlinear Structures for Flow Regulation: Modelling Fluid-Structure Interactions with Coupled Eulerian-Lagrangian Meshes

A design concept for an adaptive, variable geometry fluid inlet is presented. The inlet’s shape adapts passively in response to varying flow conditions. In contrast to traditional designs, the inlet does not rely on separate mechanisms for actuation. Instead, the novelty of the present approach is that a variety of adaptive responses are obtained by exploiting the nonlinear behaviour of post-buckled structures. In fact, due to this distinction, the device is better described as variable shape, rather than variable geometry. The concept is not presented as an ad hoc solution to a specific engineering problem, but rather as a demonstration of the value in exploiting structural nonlinearities in engineering design. Because of this generality, the concept promises to benefit many applications where fluid-structure interactions (FSI) and shape adaptation are key, e.g., biomedical, automotive and aerospace. The proposed device comprises a deformable post-buckled section, interposed between two interfacing parts. The deformable section changes shape depending on the pressure field applied by the fluid flow, thereby regulating the inlet aperture. By tailoring the stress field in the post-buckled state, the deformable section can snap through to close (or open, depending on the initial configuration) the inlet completely. In addition, the snap-through behaviour can be designed so that either one or both of the open and closed states are stable with respect to variations in pressure. The fluid-structure interaction is modelled with a Coupled Eulerian-Lagrangian (CEL) approach that allows for large deformations and divisions in the fluid domain.