Application of discrete multiphysics to fluid-structure-interaction simulation of vascular flows

Mohammed, Adamu Musa ORCID: 0000-0003-4947-965X (2022). Application of discrete multiphysics to fluid-structure-interaction simulation of vascular flows. University of Birmingham. Ph.D.

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Abstract

The advent of computer simulation has not only reduced the cost and time for testing a suitable design or product through expensive experiments but also become a potential tool for an in-silico and in-vitro research. With computer simulations different solutions can be evaluated numerically and only promising designs are sent to laboratory or production line for scale-up production. In this thesis, flow problems related to cardiovascular disorders in humans were studied using a mesh-free particle modelling technique. Since cardiovascular disease is the main cause of death worldwide, study into its causes, progression, and treatment is necessary. Therefore, the diseased cardiovascular organs (aortic valve and coronary artery) which are solid, and the blood (liquid) are represented as particles, constituting the full geometry that is employed for this study. This takes us to the use of a framework known as Discrete Multiphysics, which integrates two particle approaches, notably the Lattice Spring Model for solid mechanics and Smooth Particle Hydrodynamics for fluid mechanics. Employing this approach therefore, the mesh-free particle method in the form of discrete multiphysics was used to simulate the two cardiovascular problems with complex geometries, (i) effect of aortic valve calcification on blood flow and deformation of the valve (ii) the interaction between fluid (blood) and solid (arterial wall and stent) within a coronary artery implanted with a metal stent. In the case of aortic valve, the effects of various calcification stages (ranging from mild to severe) on cardiac output were simulated and evaluated. It was found that increasing levels of calcification result in a reduction in heart flow rate, and a critical threshold of calcification exists below which the flow rate drastically declines. Additionally, in the case of coronary stents, the key factors that affect how much the stent deforms are sorted according to dimensionless numbers, and a connection between the elastic forces of the stent and the pressure forces of the fluid is formed. The blood flow and stiffness of the stent material were subsequently found to considerably contribute to the stent's deformation and to have an impact on its rate of deformation. In both cases however, mechanical stresses were analysed and how the severity of calcification as well as the elastic and pressure forces affect the rate of deformation of the valve and the stent respectively were investigated. Therefore, it will be convincingly concluded that despite the complexity of these biological organ’s geometries, we were able to achieve the solid-liquid mechanics analyses with little difficulty, thanks to Discrete Multiphysics modelling approach.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):