arXiv subjects

Hibah Saddal

Publications and source records attributed to Hibah Saddal.

2 recordsLinked to original sources

arXiv2026

Effects of Plunging Acceleration on the Passive Morphing of Avian-Inspired Flexible Foils

This study investigates the dynamics of passively morphing foils under accelerated plunging, establishing mechanistic links between transient kinematics, structural compliance, and aerodynamic performance. Two-way coupled simulations are performed for three wing geometries: a symmetric NACA0012 foil and two bio-inspired geometries based on falcon and owl wing sections, across non-dimensional bending rigidity values, chordwise flexible segment extents from the trailing-edge (25%, 50%, and 75%), and transition speed parameters. The present findings reveal that flexible trailing-edge configurations exhibit improved aerodynamic performance relative to stiffer foils, and the aerodynamic benefit of trailing-edge compliance is strongly influenced by wing geometry. A geometry-specific optimal bending stiffness exists beyond which additional flexibility degrades performance. The extent of the chordwise flexible segment critically governs the aeroelastic response. Whilst a 25% flexible segment produces behaviour indistinguishable from a rigid wing, extending flexibility to 75% of the chord induces highly unsteady lift fluctuations, particularly for the NACA0012 foil, for which the root-mean-square lift coefficient increases sharply. The bio-inspired foils, in contrast, exhibit a moderate reduction in root-mean-square lift coefficient for the 50% and 75% cases, reflecting the stabilising influence of their cambered geometry. Increasing the transition speed parameter monotonically amplifies trailing-edge deflection, strengthens the leading- and trailing-edge vortices, and intensifies the coupling between structural deformation and instantaneous lift. These findings provide new physical insight into bio-inspired propulsion and manoeuvring strategies, with implications for the design of passively adaptive lifting surfaces in unsteady environments.

physics.flu-dyn↗

arXiv2026

Efficacy of the Weak Formulation of Sparse Nonlinear Identification in Predicting Vortex-Induced Vibrations

Vortex-induced vibrations (VIV) remain a canonical yet complex manifestation of fluid-structure interactions, where coupled nonlinear dynamics govern the motion of bluff bodies. For several years, we have relied on traditional reduced-order mathematical models derived from empirical and oscillator-based formulations; however, such models often fail to reproduce the quantitative dynamics observed in realistic flow environments. In this study, we explore a data-driven framework that leverages sparse identification of nonlinear dynamics (SINDy) and its weak formulation to uncover the governing equations of a single-degree-of-freedom cylinder undergoing VIV, using both data generated from previously developed reduced-order models and high-fidelity simulation results to assess the interpretation and efficacy of models discovered from a purely data-driven approach, particularly when the underlying dynamics are not fully known. The weak formulation (WSINDy), which replaces numerical differentiation with an integral-based representation, demonstrates marked robustness for aperiodic dynamics in particular. A complementary analysis using proper orthogonal decomposition (POD) is employed to extract the dominant spatio-temporal structures of the flow and to assess whether the temporal evolution of the wake can be represented on a reduced-dimensional manifold. The findings establish that data-driven identification can recover interpretable, quantitatively reliable models of VIV, providing a robust and computationally efficient pathway for modelling fluid-structure interactions directly from data. In particular, WSINDy is shown to be a more robust and interpretable alternative to standard SINDy for discovering VIV equations from aperiodic response dynamics, paving the way for predictive, data-informed design of fluid-structure interaction systems.

physics.flu-dyn↗