Computational modelling of cardiovascular flows heart valves and carotid bifurcation
Raoul van Loon (Swansea University)
Thursday 4th March, 2010 02:00-03:00 326, Maths Department
heart valves Aortic valves are flexible structures that experience large deformations and large rotations inside the blood stream. There is a strong interaction between the valve and blood that is not trivial to solve computationally. A fictitious domain approach is applied to capture the interaction between the blood and the valve. This method couples the unsteady Navier Stokes equations for the fluid and the Neo-Hookean description for the solid implicitly using a Lagrange multiplier that represents the traction forces required to impose the kinematic condition on the fluid-solid interface. Coupling in this manner allows the solid and fluid meshes to “overlap” and interact without alignment of the meshes at the interface, which is particularly beneficial when the solid undergoes large translations, rotations and/or deformations. Aortic stenosis is an aortic valve disease where the valve is prohibited from opening freely. A cardiologist determines the severity of the stenosis based on aortic valve area (AVA) or transvalvular pressure gradient (PG). Three-dimensional finite element models of the aortic valve are proposed to assess how sensitive AVA and PG are as a function of geometry, material distribution or flow. carotid bifurcation Blood ﬂow modelling within a carotid artery bifurcation is of interest with regards to the genesis and diagnosis of atherosclerotic plaques. Haemodynamic parameters within the artery are highly inﬂuenced by its geometry and, hence, ideally geometries are used that are specific to the patient assessed. This “patient-specific” modelling is possible by integrating image processing using CT or MRI scans with the mesh reconstruction required for the CFD. A framework is being developed using in-house computing tools to segment cardiovascular structures from clinical scans, to reconstruct the mesh based on the segmented objects and to perform patient-specific CFD studies for a carotid bifurcation. There is a particular focus on resolving the high near-wall velocity gradients. Flow convergence studies are performed to assess what the minimum mesh requirements are for capturing the different criteria proposed in the literature.