3 Most Innovative Applications of FSI in Biomechanical Systems
Fluid-Structure Interaction or FSI is a complex phenomenon involving the interaction of fluid flow with the structure, causing it to deform. While it is often very difficult to solve such problems analytically, they are usually solved using experiments and numerical simulations. Thankfully, the research advancements in the field of computational fluid dynamics and structural dynamics have led to the possibility of solving FSI problems more precisely. In everyday life, there are numerous physical examples that involve fluid-solid interaction. The best example could be an automobile air bag, which undergoes deformation when interacts with the passenger head. Too much deformation is obviously not required in this case, as it may lead to injury. Apart from the airbags, FSI can be observed in many mechanical applications such as tire hydroplaning, aerodynamic flutter, sloshing, etc. Although, these problems have been widely addressed using modern solver capabilities, its application in the field of biomechanical systems is what seems to be more interesting. Human body itself consists of parts that involve fluid-structure interaction, and applying simulation technology to study these parts opens a new set of opportunities for the medical industry.
Some of the most interesting applications of FSI in biomechanical systems are described here. These studies were conducted using ADINA FSI, which utilizes one single program for the solution of problems involving fluids and structures undergoing non-linear deformation.
1. Human Coughing Mechanism:
The human coughing mechanism was studied to compare the deformation and collapsibility of the human tracheal wall during normal breathing and coughing. This study is useful to improve endotracheal tube implants since the simulation provides better understanding of the coughing process. Figures below show the deformation of the tracheal wall during normal breathing and coughing respectively. It can be seen that during coughing, the deformation is higher along with an increase in flow rate.
2. Red Blood Cell :
This study was conducted to study the mechanical properties of the red blood cell using numerical simulation. A transient dynamic analysis was performed, considering that the cell was subjected to axial tension along one of its diameter. Two-way coupling of the hyperelastic membrane and incompressible cytoplasm fluid was considered. The figure shows deformation in the RBC due to tensile forces.
3. Brain Dynamics :
FSI can be applied to understand the cerebrospinal fluid dynamics and its interaction with the brain tissues. The study shown here was aimed to understand the dynamics of the cerebrospinal fluid to identify different abnormalities in the central nervous system. The animation shows the variation of cerebrospinal fluid velocity and pressure fields during the cardiac cycle. The subsequent image compares the fluid flow pattern between a normal and hydrocephalus subjects. Hydrocephalus is a medical condition in which there an abnormal accumulation of the cerebrospinal fluid in the brain ventricles. The fluid velocity and pressure were calculated using Navier-Stokes and Darcy flow equations, which were then coupled with equations of motion of the solid.
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