Topology optimization for fluid-structure interaction with precise evolving boundaries using iso geometric analysis

We present a novel body-fitted iso geometric topology optimization framework for fluid–structure interaction problems. Using a spline-based parametric representation of the fluid and solid domains as well as their interface, the method enables consistent evaluation of flow and structural quantities on geometrically accurate boundaries throughout the optimization process. When verified on various benchmark problems, the underlying iso geometric analysis exhibited higher accuracy and superior convergence rates in comparison to standard finite element methods. A shape optimization stage is introduced after the optimized topology is obtained, alleviating geometric artifacts arising from trimming and untrimming operations and reducing computational effort while preserving geometric smoothness and convergence. Several numerical examples demonstrate the capabilities of the framework to optimize fluid-structure interactions involving challenging functionals such as lift, drag, pressure drop, interfacial stress and fluid-to-solid traction distribution. Overall, the framework provides an accurate and physically consistent approach for shape and topology optimization in fluid–structure interaction systems.