The advent of modern supercomputers and numerical methods has made it possible to simulate physiological flows and improve our understanding of pathology and pathophysiology of various conditions in the human body. Physiological flows, in spite of low Reynolds number of < 500, can exhibit turbulent like activity due to the complexity of the underlying physiological mechanisms. This thesis investigates the aspect of the onset of flow-transition in blood flow in intracranial aneurysms and the cerebrospinal fluid (CSF) flow in the spinal canal. The studies are carried out by conducting numerical simulations using the Lattice Boltzmann Method (LBM) in subject specific cases. The first part of the thesis describes the basics of transition to turbulence, briefs the LBM and aspects related to High Performance Computing. The methodology is validated by simulating transition to turbulence in pulsatile stenotic flows and comparing the results against literature. The work is then extended to explore transition in oscillatory flow. The second part elaborates the prevalence and pathophysiology of intracranial aneurysms and reports simulations of transitional hemodynamics in aneurysms. The geometrical, morphological and fluid dynamical aspects that lead to flow-transition in aneurysms are discussed and implications from a physiological point of view are drawn. The third part of the thesis is devoted to a description of pathology and pathophysiology of the CSF and presents simulations of CSF hydrodynamics in the subarachnoid spaces of one healthy subject and two patients suffering from Chiari malformation type I. The CSF hydrodynamics exhibit transitional like characteristics in one of the Chiari patients, the flow is highly disturbed in the other Chiari patient while it stays laminar in the healthy subject. Clinical implications of transitional CSF hydrodynamics are discussed in detail.
|Qualification||Doctor of Philosophy|
|Award date||22 Aug 2016|
|Place of Publication||Siegen|
|Publication status||Published - Sep 2016|