title: Identification of peak stresses in cardiac prostheses. A comparison of two-dimensional versus three-dimensional principal stress analyses.
abstract: This study assessed the accuracy of using a two-dimensional principal stress analysis compared to a three-dimensional analysis in estimating peak turbulent stresses in complex three-dimensional flows associated with cardiac prostheses. Three-component, coincident laser Doppler anemometer measurements were obtained in steady flow downstream of three prosthetic valves: a St. Jude bileaflet, Bjork-Shiley monostrut tilting disc, and Starr-Edwards ball and cage. Two-dimensional and three-dimensional principal stress analyses were performed to identify local peak stresses. Valves with locally two-dimensional flows exhibited a 10-15% underestimation of the largest measured normal stresses compared to the three-dimensional principal stresses. In nearly all flows, measured shear stresses underestimated peak principal shear stresses by 10-100%. Differences between the two-dimensional and three-dimensional principal stress analysis were less than 10% in locally two-dimensional flows. In three-dimensional flows, the two-dimensional principal stresses typically underestimated three-dimensional values by nearly 20%. However, the agreement of the two-dimensional principal stress with the three-dimensional principal stresses was dependent upon the two velocity-components used in the two-dimensional analysis, and was observed to vary across the valve flow field because of flow structure variation. The use of a two-dimensional principal stress analysis with two-component velocity data obtained from measurements misaligned with the plane of maximum mean flow shear can underpredict maximum shear stresses by as much as 100%.
authors.affiliation: Department of Chemical Engineering, Georgia Institute of Technology, Atlanta 30332-0100, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Fontaine
authors.forename: J T
authors.initials: JT
authors.lastname: Ellis
authors.forename: T M
authors.initials: TM
authors.lastname: Healy
authors.forename: J
authors.initials: J
authors.lastname: Hopmeyer
authors.forename: A P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D006350:Heart Valve Prosthesis; D006801:Humans; D008962:Models, Theoretical; D012212:Rheology; D013314:Stress, Mechanical