Numerical analysis on the buckling instability of a soft rod under fluid-structure interaction

Soft structures are usually slow to respond under external load. However, recent development in soft matter and robotics makes use of buckling mechanism to introduce interesting and fast morphing or locomotion patterns. We aim to explore the combined effect of fluid-structure interaction (FSI) and structural instability on underwater soft structures.

We report the numerical analysis of a buckled soft rod fixed at both ends, and we explore the nonlinear interplay between geometric nonlinearity and vortex shedding. The rod is actuated at the center via periodic loads. The large deformation of soft rod is coupled with the incoming fluid flow via the Arbitrary Lagrangian-Eulerian (ALE) method. The dimensionless parameters affecting the dynamics of the FSI problem are derived. The critical dimensionless parameters that lead to the sudden buckling phenomena are compared in air and in water. The corresponding deformation patterns, hydrodynamic force distributions, and vortex shedding patterns are discussed.