We develop a monolithic solver for simulating strongly coupled fluid–structure interaction (FSI) problems involving flexible structures immersed in incompressible flows. The solver is based on the immersed boundary (IB) method, which enables the handling of large structural deformations without the need for body-fitted meshes. By coupling the Navier–Stokes equations with nonlinear structural dynamics within a unified framework, the solver provides a robust and efficient tool for capturing complex FSI behaviors. The method is validated through the simulation of a flapping filament, demonstrating its ability to reproduce self-sustained oscillations and flow-induced deformations. The method is validated through simulations of a flapping filament in a uniform flow, demonstrating its ability to capture self-sustained oscillations, symmetry breaking, and flow-induced deformations. These results highlight the capability of the monolithic immersed boundary framework to accurately model two-dimensional FSI phenomena. Furthermore, the solver exhibits good scalability and is readily extensible to more complex 3D configurations, such as flag dynamics and bio-inspired propulsion systems.
 

Fluid-structure interaction (FSI),Immersed boundary (IB) method,Monolithic solver