Computational Study on Fluid Flexible-Solid Interaction-based Chaotic Mixing Characteristics in a Cavity Flow

In our previous work, it was observed that the addition of an elliptic-shaped deformable solid in a simple cavity flow has induced chaotic mixing while the no-solid case showed linear mixing. This work aims to understand the reason behind mixing enhancement due to the presence of a deformable solid. The work focuses on the optimum solid parameters i.e, Aspect Ratio 0.5 and Volume Fraction 10% as obtained from our earlier work, at a constant Capillary number 0.05 and Reynolds number 100. To this end, a detailed investigation was done using non-linear lagrangian dynamical tools, such as Poincare Map Analysis (PMA), Periodic Point Analysis (PPA), and Adaptive Material Tracking (AMT).  PMA revealed three clearly visible islands at the core, apart from islands near the stationary walls. PPA revealed the lowest order hyperbolic/elliptic periodic points to be third. AMT gave the physical picture of the deforming material blob revealing its exponential stretch with steep folds. Additionally, unstable /stable manifolds corresponding to lowest order hyperbolic points have been identified. Further study confirmed the existence of heteroclinic connections and tangles in the system.