Numerical investigation of haemodynamics in spiral-inducing grafts using Eulerian and Lagrangian frameworks

Soler, Andres Ruiz (2017) Numerical investigation of haemodynamics in spiral-inducing grafts using Eulerian and Lagrangian frameworks. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

A large range of vascular diseases require the replacement of blood vessels. Bypass grafting is a widely used treatment, in particular for high risk-patients, and consists of the connection of autologous/prosthetic graft and veins/arteries in order to repair the regular blood supply through occluded or damaged vessels. However, the development of stenosis due to thrombosis, atherosclerosis and intimal hyperplasia, linked to unfavourable haemodynamic patterns, reduces the long-term efficiency of the treatment. The identification of the natural blood motion as a swirling flow in the whole arterial system has resulted in new promising lines of research in cardiovascular devices in order to increase the patency rates of graft anastomoses by reproducing this physiological phenomenon. The impact of the proposed research lies in the numerical investigation of the influence of different design parameters of novel spiral-inducing grafts on haemodynamics, with the objective of understanding the physics of the problem and determinating the most relevant geometrical parameters. Conventional Eulerian metrics highlighted the effects of the ridge cross-sectional shape and, particularly, the position of the ridge around the perimeter of the graft on inducing an enhanced swirling blood flow. The Lagrangian approach, which assumes the blood as a heterogeneous solid-liquid suspension, allows to assess the individual behaviour and movement of representative particles travelling in the continuous phase and again highlighted the influence of the ridge orientation from this perspective. The correlation between distributions of friction forces and terminal locations of particles in the wall of the host artery showed a predominant deposition in regions of low wall shear stress, in agreement with those assumptions that were initially considered as optimisation criteria.