Numerical investigation of hydrogel deformation under rotational impact with application to traumatic brain injury

Rotational impact is a major cause of traumatic brain injury (TBI). In our previous work, we approximated the brain as a hydrogel sphere suspended in liquid-filled cylinder and conducted preliminary studies on hydrogel deformation under rotational impact, with good agreement between experiments and numerical simulations. In this talk, we present a comprehensive numerical study, aiming to deepen our understanding of hydrogel dynamics with implications for modeling TBI. The hydrogel is modeled as a poroelastic solid saturated with a Newtonian interstitial fluid and the rotational impact is achieved by varying the rotational speed of the cylinder. The evolution of the hydrogel-fluid interface, along with the elastic deformation within the hydrogel, is tracked using an arbitrary Lagrangian-Eulerian (ALE) method. The governing equations in both the hydrogel and the surrounding fluid are solved monolithically using a finite element method. We systematically investigate the effects of rotational acceleration and deceleration, density ratio, and the hydrogel's elastic moduli and permeability. Our results indicate that the hydrogel undergoes greater deformation during deceleration than during acceleration. Moreover, a smaller hydrogel with higher density experiences a greater angular displacement relative to the cylinder, which may suggest a more severe injury in cases of brain atrophy.