Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session J46: Focus Session: Fluids Next - Fluid Dynamics of InjuryInvited
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Chair: Anne Staples, Virginia Tech Room: 209BC |
Sunday, November 19, 2023 4:35PM - 5:01PM |
J46.00001: Flows of cerebrospinal fluid during brain injury Invited Speaker: Douglas H Kelley During stroke, cardiac arrest, and traumatic brain injury, a primary cause of irreversible tissue damage is the severe swelling that ensues as fluid rushes into the brain. That fluid was long believed to come from the bloodstream. Though much does eventually come from blood, my collaborators and I recently showed that in the first half hour, nearly all comes instead from the cerebrospinal fluid (CSF) that surrounds the brain and fills the perivascular spaces around its blood vessels. In vivo particle tracking revealed that during injury, CSF reverses its flow direction and rushes into the tissue, concomitant with a spreading wave of sudden constrictions of nearby arteries. A simple fluid dynamical model reproduced much of the observed dynamics. MRI imaging and radiolabeled tracers confirmed that CSF is the source of swelling. Knowing that swelling is caused by pathological CSF circulation leads to new ideas for treatment during brain injury, such as promoting clearance of CSF from the brain, not only in the first half-hour but throughout the recovery period. |
Sunday, November 19, 2023 5:01PM - 5:27PM |
J46.00002: Biomimetic Studies of Concussive Brain Injuries Invited Speaker: Ji Lang Traumatic brain injury (TBI), a prevalent global health challenge, is associated with profound health and economic implications. TBI occurs due to a series of fluid-structure interactions (FSI) among the rigid skull, the cerebrospinal fluid (CSF), and the soft brain matter. This study has developed a novel and unique biomimetic approach, with the assistance of modern manufacturing and biological sciences, to examine two fundamental problems in bio-fluid mechanics. (1) the flow and pressurization of the CSF in the subarachnoid space (SAS) and (2) the response as well as the deformation of the brain matter as the head is exposed to sudden external impacts. The goal is to elucidate the critical role of the CSF in transmitting and mitigating external impacts and hence understand the mechanism of concussive brain injury. |
Sunday, November 19, 2023 5:27PM - 5:40PM |
J46.00003: Computational modeling of the effects of mechanosensory feedback on the locomotion of lampreys with spinal injuries Christina L Hamlet, Lisa J Fauci, Jennifer R Morgan, Eric Tytell Lampreys are basal fish that serve as model systems for locomotion and neurophysiology studies. While spinal cord injuries in mammals often result in a permanent loss of function, other vertebrates, such as lampreys, can partially or wholly recover locomotor functions such as swimming. The exact mechanism by which recovery occurs is not well understood. One hypothesis is that swimming in lampreys may recover through amplified proprioceptive (body-sensing) feedback. We employ a multiscale, integrative, computational neuromechanical model of an anguilliform (eel-like) swimmer fully coupled to a viscous, incompressible fluid in an immersed boundary framework to study the relations between neural signaling and swimming. This model, driven by coupled phase oscillators, can receive sensory feedback from changes in the body. We use this model to perform computational experiments which examine the effects of mechanosensory feedback on swimming performance. Our results show that feedback amplification below a spinal lesion is sometimes sufficient to partially or entirely restore normal swimming behavior. |
Sunday, November 19, 2023 5:40PM - 5:53PM |
J46.00004: Shear wave excitation in tissue phantom through non-spherical bubble collapse Saber Izak Ghasemian, Fabian Reuter, Yuzhe Fan, Georg Rose, Claus-Dieter Ohl Tissue exposed to a rapid acceleration, for example from traumatic impact, form voids that expand and collapse. The collapse of these cavitation bubbles has been made responsible for the damage to nearby cells through shear and strain. Bubbles collapsing non-spherically are known to launch shear waves. We present detailed measurements of how these shear waves are emitted from a well-controlled single laser-induced cavitation bubble. The bubbles are generated in a transparent tissue-mimicking hydrogel embedded with tracer particles. High-speed imaging of the tracer particles and the bubble shape allow quantifying the shear wave and relate it to the bubble dynamics. It is found that different stages of the bubble dynamics contribute to the shear wave generation and the mechanism of shear wave emission, its direction and the efficiency of energy converted into the shear wave depend crucially on the bubble to wall stand-off distance. These shear waves may travel far from the site of generation and could thus transport energy from the impact site, damaging remote delicate cellular structures. |
Sunday, November 19, 2023 5:53PM - 6:06PM |
J46.00005: Concussions and hydrodynamic origins of injuries Caroline Cohen, Juliette Amauger, Thibault Guillet, Philippe Decq, David Quere, Christophe Clanet In many sports (combat, team or speed sports), Traumatic Brain Injury (TBI) has become a major healthcare problem, particularly because it is difficult to properly diagnose. The occurrence of TBI is generally defined by symptoms observed by doctors or empirical criteria related to the acceleration and the duration of the shock undergone by the head. In this work, we investigate hydrodynamics possible origins of destroying mechanisms causing concussions. One of the possible causes of TBI is the formation of cavitation bubbles in the cerebro-spinal fluid (CSF). To investigate the link between TBI and cavitation bubbles, we built a model experiment to induce cavitation bubbles through an impact. A tank, filled with water and hermetically closed with a flexible membrane is impacted on a damper, designed to vary acceleration and contact time. The formation and dynamics of cavitation bubbles is observed and studied inside the tank. Modeling those confined cavitation bubbles induced by a shock in the model experiment allows us to compute their damaging capacities and finally make a link to the real fields and conclude on the dangerousness of shocks received by athletes. |
Sunday, November 19, 2023 6:06PM - 6:19PM |
J46.00006: Rotation-induced Traumatic Brain Injury: A fluid mechanical study Qifu Wang, Jiaqi Zhang, James J Feng, Pengtao Yue, Qianhong Wu Traumatic brain injury (TBI) is a serious health issue. Studies have highlighted the severity of rotation-induced TBI. However, the role of cerebrospinal fluid (CSF) in transmitting the impact from the skull to the soft brain matter remains unclear. Herein, we use experiments and computations to define and probe this role in a simplified setup. A spherical hydrogel ball, serving as a soft brain model, was subjected to controlled rotation within a water bath, emulating the CSF, and filling a transparent cylinder. The cylinder and ball velocities, as well as the ball's deformation over time, were measured. We found that acceleration and deceleration were more likely to cause brain damage. A finite-element code is written to simulate the process. The hydrogel ball is modeled as a poroelastic material infused with fluid and its coupling with the suspending fluid is handled by an arbitrary Lagrangian-Eulerian method. The results indicate that the ball-fluid density contrast, as well as the rotational velocity difference, play a central role in the ball’s deformation due to centrifugal forces. This approach contributes to a deeper understanding of brain injuries and may portend the development of preventive measures and improved treatment strategies. |
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