Lecture+7

Lecture+7 - 2/1/12 1 Heart Valves 4-6 cm 2 3-4 cm 2...

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Unformatted text preview: 2/1/12 1 Heart Valves 4-6 cm 2 3-4 cm 2 www.heartcenteronline.com Calcified heart valve. Rosenhek et al. (2000) NEJM 2/1/12 2 www.echobyweb.com St. Louis University School of Medicine Mark Kittleson, UCD VMTH Ball and cage valve Bjork-Shiley valve Carpentier Edwards stented porcine valve Leeds polyurethane valve All images from Leeds University School of Mechanical Engineering 2/1/12 3 Native valve Valve prosthesis AXIAL VELOCITY PROFILES at systolic peak flow Native valve: "blunted" velocity profiles; Prosthetic valve: "two jet" velocity profiles Native valve Valve prosthesis Axial WSS is higher downstream of the aortic valve prosthesis when compared to the native configuration (note the difference is measurement scales!) 2/1/12 4 Velocity profile of flow through normal healthy heart valve Velocity profile of flow through mechanical heart valve Images courtesy of BIDMC, Boston, MA Blood vessels arent just tubes! 2/1/12 5 Dynamics of flow in the heart 2/1/12 6 Curved Vessels Re = = De R a Curved Vessels A scaling of the Re by the ratio of the tube radius (a) to the radius of curvature (R). velocity profile 2/1/12 7 Curved Vessels = + = = = 72 sin 4 and 73728 cos 1 4 2 De a v De a v a r r a r rz For De<34 and <<1: The wall shear stress rz due to the primary flow is greatest at the outer wall and lowest at the inner wall. r arises from the secondary flow and is smaller than the value for the main component. 2/1/12 8 Changes in flow at branches Flow separation areas that diverge from fully-developed flow, often presenting as regions in which some of the fluid moves in a reverse direction. Separation point the location at which flow first reverses direction. Conversely, the reattachment point is the location where all of the fluid again moves in the same direction....
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Lecture+7 - 2/1/12 1 Heart Valves 4-6 cm 2 3-4 cm 2...

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