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|Title:||Simulating Blood Flow in A Human Carotid Artery Model Using the Lattice Boltzmann Method||Contributor(s):||Boyd, Joshua (author); Buick, James Maxwell (supervisor); Green, Simon (supervisor)||Conferred Date:||2008||Copyright Date:||2008||Handle Link:||https://hdl.handle.net/1959.11/1586||Abstract:||In this thesis an application of the lattice Boltzmann method (LBM) to simulating blood flow in a human carotid artery geometry is presented, with a view towards developing a numerical method to aid in the study of the hemodynamical influences on the progression of atherosclerosis. Two different boundary schemes, namely the halfway bounceback and an extrapolation boundary scheme, are tested for the D3Q15 and D3Q19 lattices. It is verified that the LBM extrapolation boundary scheme, unlike the halfway bounceback scheme, retains the second order accuracy of the LBM when simulating geometries which are not parallel to the underlying lattice grid. The question of whether the assumption that human blood can be considered Newtonian for the purposes of arterial modelling is also questioned with a particular emphasis on the behaviour of the near wall shear. A non-Newtonian LBM was implemented and tested and the LBM is shown to retain second order accuracy for non-Newtonian flows in a 2D power law flow in a pipe with parallel walls. The difference between Newtonian and non-Newtonian flows is then examined in the context of steady and oscillatory flows using Casson and Carreau-Yasuda non-Newtonian blood models. Differences in both the velocity and the shear are examined. It is observed that relatively large differences occur for Reynold’s and Womersley numbers corresponding to the human carotid artery for both non-Newtonian models. The difference between the Newtonian and Carreau-Yasuda non-Newtonian blood flow is then investigated in realistic unstenosed and stenosed 2D carotid artery geometries. A physiologically accurate pulsatile waveform is implemented in this model and the differences in velocity and shear are examined, particularly near the walls of the artery, as the near wall velocity and shear characteristics are known to be important in the progression of atherosclerosis in the artery. It is found that small differences occur, but these differences are mainly confined to the central regions of the artery. Thus it is concluded that a Newtonian blood approximation is valid for this application, at least for the human carotid artery. A parallel implementation of the LBM code is demonstrated. A speed up of order o = 0.73 is achieved for both 2D and 3D lattices on the 16 node UNE Beowulf cluster. A 3D carotid artery model is then implemented and the observed flow characteristics are then examined. The velocity magnitude and shear rates are examined in the carotid artery bifurcation, and a novel method of examining the near wall shear rate is demonstrated. It is observed that low near wall velocity and shear rate occur on the outer walls of the bifurcation for large periods of the pulse cycle, which agrees with the literature results as well as previous results. Rotating flow is also observed in the region of the internal carotid artery (ICA) immediately after the bifurcation. This work demonstrates the suitability of the LBM for studying flow characteristics known to be important to the study of atherosclerotic progression. The results agree well with previous literature results and provide a new method for examining the near wall shear behaviour in an artery and identifying areas susceptible to atherosclerosis. This work provides a good foundation for further research into the use of the LBM for non-Newtonian flow simulation, artery modelling, atherosclerosis research and the study of the forces involved in plaque rupture.||Publication Type:||Thesis Doctoral||Field of Research Codes:||029901 Biological Physics||Rights Statement:||Copyright 2008 - Joshua Boyd||HERDC Category Description:||T2 Thesis - Doctorate by Research||Statistics to Oct 2018:||Visitors: 269
|Appears in Collections:||Thesis Doctoral|
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