Abstract

This thesis presents an experimental study of jets emitted from flexible orifices of different configurations and is aimed at understanding the effects of a repair procedure for a malfunctioning mitral valve known as Edge-to-Edge repair. This study looks at simplified orifice geometries referred to as no-clip, middle-clip, and side-clip configurations. The flow is generated through a piston-cylinder setup. Time-resolved Particle Image Velocimetry (TR-PIV) is used for flow measurements. The velocity data is extracted using a commercial software, and is then processed with custom codes to analyze and reveal different flow characteristic features once the jets have interacted.
The results were obtained from analysing the average velocity fields, and it was noted that while the no-clip configuration would only be affected by the boundary layer roll-up produced at the exit of the orifice, the middle-clip configuration would strongly resemble the behaviour of two closely-spaced parallel jets. The two velocity profiles would gradually merge into one “plug-like” profile spreading radially. For the side-clip configuration, it was noted that while the proportional difference between the two velocity maxima did not exhibit dependence on the Reynolds number, the difference would be affected by the entrainment of the secondary jet into the primary jet. As a result, maximum velocity of the side-clip configuration’s primary jet at the end of the tested region was equivalent to that of the overall middle-clip velocity maximum. The entrainment of the secondary jet also resulted in the profile shifting in the direction of the primary jet. From the Proper Orthogonal Decomposition of the flow data, it was concluded that the highest energy consumption for the middle and side-clip configurations was attained through the first two modes, whose proportional difference is positively correlated with the piston stroke used. Reynolds Shear Stresses, as well as Turbulent Kinetic Energy is also assessed in order to have insight into the turbulent quantities affecting the hemodynamics. Although the side-clip configuration was discovered to be dominated by higher Reynolds Shear Stresses, it is believed that the longer duration of such stresses, combined with higher energy fluctuations of the Turbulent Kinetic Energy may produce more blood damage in the middle-clip configuration setting.