Fig 1.
Experimental setup and aortic root scheme.
Schematic of the flow loop (a). Test cell (b) containing the AVBP and the silicone phantom (B, immersed in blood analog fluid). Experimental setup (c) showing the CCD Cameras for TOMO PIV (C) and POA measurements (F); the piston pump (D) controlling the contraction and expansion of the silicone ventricle (E); elements of the flow loop: the compliance chamber with air volume VC, the peripheral resistance Rp, and the tank (I); a light guide for volume illumination with a Nd:YAG laser (J); and the mirror setup for view-doubling (K). Parametrization of the aortic root (d) in axial plane at X = 0. Parametrization of SOV (e) in a cross-section at β1ra above the annulus.
Table 1.
Parameter values for the aortic root phantom geometry.
Fig 2.
Pressure and projected orifice area.
Ventricular pressure pLV (solid bold lines) and aortic pressure pa (solid thin line) pressure curves (averaged over five subsequent pulses) and projective orifice area POA, measured during experiments with different aortic root phantoms.
Fig 3.
Mean flow fields in the AAo and in the SOV.
Mean velocity magnitude |〈U〉| in the NS (a), S (b), M (c) and L (d) aortic root configuration during valve opening (t = 0.09 s. Each panel (a)—(d) shows axial and cross-sectional slices in the bulk flow downstream of the AVBP and a vertical and horizontal slice centered in the front-facing of the SOV.
Fig 4.
Mean flow fields in the AAo and in the SOV.
Mean velocity magnitude |〈U〉| in the NS (a), S (b), M (c) and L (d) aortic root configuration during mid-systole (t = 0.18 s. Each panel (a)—(d) shows axial and cross-sectiononal slices in the bulk flow downstream of the AVBP and a vertical and horizontal slice centered in the front-facing of the SOV.
Fig 5.
Mean flow fields in the AAo and in the SOV.
Mean velocity magnitude |〈U〉| in the NS (a), S (b), M (c) and L (d) aortic root configuration during valve closure (t = 0.30 s. Each panel (a)—(d) shows axial and cross-sectiononal slices in the bulk flow downstream of the AVBP and a vertical and horizontal slice centered in the front-facing of the SOV.
Fig 6.
Flow field in the medium sized aortic root (M) at t = 0.12 s: RMS velocity fluctuations urms (a); instantaneous velocity magnitude field |〈U〉| (b); 3D maximum shear rate γ3D (c).
Fig 7.
General organization of the mid-systolic flow shown for the results obtained in M. Mean velocity field 〈U〉 in the XY-plane (a) and in the cross-sectional XZ-plane (b) past the valve at peak systole. The mean velocity field in the front-facing SOV (aligned with positive Z-axis) for the same instance is depicted in the enlarged images to the right (velocity vectors and streamlines). Notice, that the orientation of the flow field (i.e. its reference frame) is the same for all representations. Indicated are the potential core (PC), the retrograde flow (RF) near the wall, and the circumferential flow (CF) pattern in the SOV.
Fig 8.
Flow rates and mean streamwise flow field.
Net flow rate (a) and RF flow rate (b) (computed form 〈Uy〉 at Y = 0) at the time points tj = 0.0, 0.03, …, 0.36 s together with the piston pump induced flow rate (dashed line). Mean streamwise velocity component |〈Uy〉| (c) in aortic root size M after valve opening (t4 = 0.12 s), at peak-systole (t7 = 0.21 s), during flow deceleration (t9 = 0.27 s), and during valve closing (t10 = 0.30 s). Cross-sections are shown at Y = −20, −10, 0, 10, 20 mm.
Fig 9.
Properties of aortic jet shear layer.
RMS velocity fluctuation field urms (a, c, e) and 3D shear rate γ3D (b, d, f) at t = 0.21 s for small (S), medium (M), and large (L) aortic root size.
Fig 10.
Above: Mean kinetic energy (a, c, e) and fluctuating kinetic energy
(b, d, f) in function of time for the domains Ω1, Ω2 past the valve and the sinus flow domain ΩS (as indicated in the aortic root sketches in the center). Note the different scales for (e) and (f). Below: Scatter plots of integrals
(g),
(h), and
(i) in function of the δSOV and δAAo (NS red, S violet, M blue, L black) with the sizes of circles corresponding to the parameter integral values calculated using Eq (8)).