Numerical Study on Haemodynamics and Biomechanics in the Valve Diseases and Polyurethane Prosthetic Heart Valves

• Main Authors: VU HA HAI, 武河海
• Other Authors: Hsu, Cheung-Hwa
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/tg6dz7

博士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 100 === This study aims to investigate haemodynamicss and biomechanics in the aortic valve with diseases and polyurethane prosthetic heart valves by using numerical approach. The dissertation consists of five main parts. Part 1 proposed a numerical approach based on quasi-steady method to investigate fluid-structure interaction (FSI) problems in the aortic valve during systolic phase. This approach assumed that the valve suffers only transvalvular pressure during systole, and coupled the computational fluid dynamic code FLUENT and the finite element analysis code ABAQUS to solve the FSI problems. The data exchange between two codes has been performed via commercial pre-processing software including Hypermesh, Solidworks and Gambit. The valve model was developed with the diameter of 23.5 mm, height 10 mm, and the valve leaflet thickness was 0.2 mm. The interaction between the valve leaflets and surrounding fluid resulted in a complex flow field according to the valve orifice alterations during systole. By utilizing proposed approach, an insight of haemodynamicss and biomechanics of the valve during systole has been revealed. Part 2 investigated haemodynamicss and biomechanics of the aortic valves with abnormally thickened leaflets during systole using the numerical technique that was proposed in part 1. This study assumed two cases of valve diseases including one thickened leaflet and two thickened leaflets with thickness of the diseased leaflet was thicker than normal one of 50%, 100% and 150%, respectively. The results have provided an insight about the diseased valves which is difficult to acquire by experiment or other simulation methods. Part 3 also utilized numerical approach proposed in part 1 to investigate haemodynamicss and biomechanics of the bicuspid aortic valves during systole. The valve model was developed with valve height of 12.5 mm, free edge angle of 40 degree, leaflet thickness of 0.3 mm, and the valve diameter of 23.5 mm. To simulate the bicuspid condition of the valve this study has applied tie constraint to two leaflets. The results indicated that the geometric parameters could significantly affect performance of the valve. The study showed that bicuspid valve caused decrease of blood circulating into circulation system, and induced high cyclic shear stress that might lead to other severe issues to the valve. Mechanical valves utilize mechanical concepts or mechanisms to design the valves so that even the best design provides performances are still far from the native valve. Polyurethane prosthetic heart valve imitates the geometry of native valve that is expected to provide performances close to natural valve. However, the geometry of natural valve is very complex and there are variety of parameters can affect performances of the valves. This study has simplified the geometry of natural valve so that only four parameters needs to be considered, including the fundamental curve, the free edge angle, the valve height, and the leaflet thickness. The study investigated the influence of these four parameters on biomechanics of the polyurethane prosthetic valves. Part 5 investigated an appropriate approach to manufacture polyurethane prosthetic heart valves, and established an experiment loop to test the samples. The manufacture approaches included Assembly and Singe-piece forming methods. In Assembly method, support frames and valve leaflets were separately manufactured and then attached together by an adhesive substance. Meanwhile two main components of the valve were simultaneously fabricated by using molding technique in Single-piece forming method. The experiment loop tried to mimic the haft side of natural recirculation from the left ventricle through the aortic valve to the aorta. In addition, a testing loop was also established to measure the Effective Orifice Area of manufactured valves. Keywords: Valve diseases, PU prosthetic heart valve, Numerical technique, Haemodynamics, Biomechanics