Department of Biomedical Engineering, The Ohio State University, 473W 12th Ave., Columbus, OH, 43210, USA.
Ann Biomed Eng. 2019 Jan;47(1):85-96. doi: 10.1007/s10439-018-02128-6. Epub 2018 Sep 12.
Blood damage and platelet activation are inherent problems with present day bi-leaflet mechanical heart valve designs. Passive flow control through different arrangements of vortex generators (VG) as means of improving pressure gradients and reducing turbulence are investigated. Rectangular VG arrays were mounted on the downstream surfaces of a 23 mm 3D printed mechanical valve. The effect of VGs on the resulting flow structures were assessed under pulsatile physiological flow conditions where high resolution particle image velocimetry measurement was performed. The co-rotating VGs showed lower Reynolds shear stresses and improved pressure gradients (PG) compared with the counter-rotating ones and the no-VG control one (that showed higher turbulence). RSS was found 38.13 ± 0.89, 12.95 ± 0.32, 15.75 ± 0.71, 24.54 ± 0.84 and 16.33 ± 0.58 Pa for the control, co-rotating VGs, 8 counter-rotating VGs, 4 far-spaced VGs and 4 closely-spaced VGs, respectively. PG of 10.45 ± 0.94 mmHg was obtained with co-rotating VGs and the difference was significant compared with the other configurations (control 14.88 ± 0.4 mmHg; 8 counter-rotating VGs 13.76 ± 0.51 mmHg; 4 far-spaced VGs 13.84 ± 0.09 mmHg; and 4 closely-spaced VGs 15.37 ± 0.16 mmHg). Co-rotating VGs for this application induce a more delayed flow separation and a more homogenized and streamlined transition of flow compared with the counter-rotating VGs. Passive flow control techniques deployed on BHMVs is potentially beneficial as significant control of flow at small length scales without inducing large-scale design modifications of the valve.
目前的双叶机械心脏瓣膜设计存在血液损伤和血小板激活等固有问题。本研究通过不同涡旋发生器（Vortex Generator，VG）的布置来改善压力梯度并减少湍流，以此对被动式流量控制进行了研究。矩形 VG 阵列安装在 23mm 3D 打印机械瓣膜的下游表面。在脉动生理流动条件下，使用高分辨率粒子图像测速法进行了测量，以评估 VG 对流动结构的影响。与反向旋转 VG 和无 VG 对照组（显示出更高的湍流）相比，共旋转 VG 显示出更低的雷诺剪切应力和更高的压力梯度（PG）。共旋转 VG 的 RSS 为 38.13±0.89、12.95±0.32、15.75±0.71、24.54±0.84 和 16.33±0.58 Pa，而对照组、共旋转 VG、8 个反向旋转 VG、4 个远距间隔 VG 和 4 个近距离间隔 VG 的 RSS 分别为 38.13±0.89、12.95±0.32、15.75±0.71、24.54±0.84 和 16.33±0.58 Pa。共旋转 VG 可获得 10.45±0.94 mmHg 的 PG，与其他构型相比差异显著（对照组为 14.88±0.4 mmHg；8 个反向旋转 VG 为 13.76±0.51 mmHg；4 个远距间隔 VG 为 13.84±0.09 mmHg；4 个近距离间隔 VG 为 15.37±0.16 mmHg）。与反向旋转 VG 相比，这种应用中的共旋转 VG 会导致更迟的流动分离，并使流动的过渡更加均匀和流线化。在 BHMV 上部署被动式流量控制技术具有潜在的益处，因为它可以在不引起瓣膜大规模设计修改的情况下，对小尺度的流量进行有效控制。
