UC San Diego

This dissertation describes key contributions in Fluid-- Structure Interaction (FSI) simulations using Isogeometric Analysis (IGA). We first describe the state of the art in both FSI and IGA. Several new contributions to these fields are developed, which enable novel simulations in the fields of cardiovascular fluid flow and shock hydrodyanmics. In our first application, a hyperelastic material model is integrated with the FSI solver and applied to bloodflow through a Fontan surgical conduit. These conduits are created in patients with otherwise fatal congenital heart defects. The junction is comprised of the native venous vessels which return blood to the heart, the vena cava, which are anastamosed directly to the pulmonary arteries, resulting in a junction with several material regions. A hyperelastic material model is applied to the disparate native tissues, and FSI simulations are performed which respect unique material regions. Parameters of clinical interest, such as efficiency, flow split, and wall shear are presented. FSI was required to accurately predict wall shear, but did not significantly impact other hemodynamic properties. In a second application, we simulate physiologic operation of a Pulsatile Ventricular Assist Device (PVAD). Patients with severe congenital or acquired heart diseases may require cardiac transplantation to ensure survival. In critical cases, a PVAD is implanted in a bridge-to-transplant scenario. This device is a mechanical displacement pump which delivers blood systemically to the patient. PVADs exhibit large structural deformations, creating significant modeling difficulties. IGA is used to model the structural membrane, which is a key component of PVAD performance. Physiologic simulations are carried out for the first time, and results are analyzed for thrombogenic risks, such as residence time. Preliminary results indicate pediatric models have higher thrombotic risks than adult models, matching clinical experience. The use of IGA without FSI is also explored, and is applied to several classic shock hydrodynamics problems in the axisymmetric frame. The retention of radially symmetric solutions are crucial in this field, and difficult to obtain. Simulations of the Noh problem, Coggeshall problem, and a 'multi-material' problem are presented, and in each case IGA exhibits the best known symmetric performance