Stereoscopic PIV of Steady Flow Through a Bileaflet Mechanical Heart Valve

Abstract

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

Measurements of steady flow through a bileaflet mechanical heart valve using stereoscopic PIV

“…Error analysis between a conventional 2 nd order polynomial method and an unconventional local weighted mean (LWM) method is discussed extensively in [15]. It was found that the non-linear image distortions present in the images resulted in unacceptable errors (maximum 5.5 pixels, average 0.9 pixels) using the 2 nd order polynomial transformation.…”

“…Flow visualization experiments were also performed at a range of Reynolds numbers, and the images are found in [15].…”

“…The flow was seeded with silver coated hollow glass spheres (Potters Industries, Malvern, PA) having density 1650 kg/m 3 and diameter 15 m, ensuring that the particles responded to the flow with high fidelity [15]. Flow visualization experiments were also performed at a range of Reynolds numbers, and the images are found in [15].…”

“…Laser pulse time separation was optimized to take advantage of the system dynamic range of 16 pixels for all three datasets obtained [15]. The laser pulse time separation for the SPIV measurements in the Full Aortic Sinus Dataset was 400 s.…”

“…A recirculating flow loop was constructed for the experiment, as described fully in [15]. A centrifugal pump provided steady flow to an axisymmetric flow conditioning chamber upstream of the test section.…”