The Reynolds number based on inlet diameter was 7600, and the measurement plane was perpendicular to the leaflet axes at the centerline of the aortic sinus. The typical formation of three jets was observed: the upper and lower lateral orifice jets, and the central jet. Flow separation from the valve ring was seen, and large scale vortices were identified in both the upper and lower sinus regions. An asymmetry in the reverse flow was found, and possible causes were discussed. All three jets were seen to decay similarly to free rectangular jets, with zero decay initially, followed by a 'linear' decay rate in which U max 2 ∝ X. The central jet was also seen to be self similar in the linear decay region. Analysis of the out-of-plane velocity yielded two alternate explanations of streamwise vortex (i.e. Ω x ) structure, with either a four-cell or an eight-cell streamwise vortex structure being present in the mean velocity field. Organization of large scale three dimensional flow structures was thus apparent. Calculation of in-plane Reynolds stresses showed that values were highest in the outer shear layers of the lateral orifice jets. Elevated Reynolds shear stress values were also found in the leaflet wake regions, and the shear layers of the central jet.iii

Computational modeling of bileaflet heart valve (BiMHV) flow requires experimentally validated datasets and improved knowledge of BiMHV fluid mechanics. In this study, flow was studied downstream of a model BiMHV in an axisymmetric aortic sinus using stereoscopic particle image velocimetry. The inlet flow was steady and the Reynolds number based on the aortic diameter was 7600. Results showed the outof-plane velocity was of similar magnitude as the transverse velocity. Although additional studies are needed for confirmation, analysis of the out-ofplane velocity showed the possible presence of a four-cell streamwise vortex structure in the mean velocity field. Spatial data for all six Reynolds stress components were obtained. Reynolds normal stress profiles revealed similarities between the central jet and free jets. These findings are important to BiMHV flow modeling, though clinical relevance is limited due to the idealized conditions chosen. To this end, the dataset is publicly available for CFD validation purposes.

Cracking at the trailing edge of a heavy duty industrial gas turbine blade has been observed on a number of serviced parts. The cracking usually occurs within 1.0″ of the platform. The trailing edge (TE) cracks have been found to propagate through the airfoil, leading to airfoil separation and severe engine damage. Liburdi Turbine Services has undertaken an independent metallurgical and stress analysis of the blade to determine the cause of the cracking. This paper covers the stress and low cycle fatigue (LCF) analysis of a platform undercut modification designed to mitigate crack initiation and thus increase part life. A finite element model of the blade was developed. Thermal loading was applied from a conjugate heat and mass transfer analysis between the blade, gas path flow and internal cooling flow. Base load conditions were used at turbine inlet temperature 2482°F. Results showed that the peak stress was present in the TE cooling slot corner, and was large enough to cause local yielding and LCF. The geometry of the modification was shown to strongly influence stress in the TE airfoil region and in the undercut region. Thus a balance was found to provide sufficiently low stresses in both regions and still be practical for machining. The modification was found to decrease stress in the TE cooling slot by a factor of 0.71 relative to that of the current OEM design, and increase life by 1.79 times. A viable modification has been demonstrated to extend blade life by reducing local stress and thus mitigating crack initiation at the airfoil TE.

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