The aortic sinus vortex is a classical flow structure of significant importance to aortic valve dynamics and the initiation and progression of calcific aortic valve disease. We characterize the spatiotemporal characteristics of aortic sinus vortex dynamics in relation to the viscosity of blood analog solution as well as heart rate. High-resolution time-resolved (2 kHz) particle image velocimetry was conducted to capture 2D particle streak videos and 2D instantaneous velocity and streamlines along the sinus midplane using a physiological but rigid aorta model fitted with a porcine bioprosthetic heart valve. Blood analog fluids used include a water–glycerin mixture and saline to elucidate the sensitivity of vortex dynamics to viscosity. Experiments were conducted to record 10 heart beats for each combination of blood analog and heart rate condition. Results show that the topological characteristics of the velocity field vary in timescales as revealed using time bin-averaged vectors and corresponding instantaneous streamlines. There exist small timescale vortices and a large timescale main vortex. A key flow structure observed is the counter vortex at the upstream end of the sinus adjacent to the base (lower half) of the leaflet. The spatiotemporal complexity of vortex dynamics is shown to be profoundly influenced by strong leaflet flutter during systole with a peak frequency of 200 Hz and peak amplitude of 4 mm observed in the saline case. While fluid viscosity influences the length and timescales as well as the introduction of leaflet flutter, heart rate influences the formation of counter vortex at the upstream end of the sinus. Higher heart rates are shown to reduce the strength of the counter vortex that can greatly influence the directionality and strength of shear stresses along the base of the leaflet. This study demonstrates the impact of heart rate and blood analog viscosity on aortic sinus hemodynamics.

中文翻译：

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主动脉窦涡的时空复杂性

主动脉窦涡是一种经典的流动结构，对主动脉瓣动力学和钙化性主动脉瓣疾病的发生和发展具有重要意义。我们描述了与血液模拟溶液粘度和心率相关的主动脉窦涡流动力学的时空特征。使用配备猪生物人工心脏瓣膜的生理但刚性主动脉模型，进行高分辨率时间分辨 (2 kHz) 粒子图像测速，以捕获 2D 粒子条纹视频和 2D 瞬时速度和沿窦中平面的流线。使用的血液模拟流体包括水-甘油混合物和盐水，以阐明涡流动力学对粘度的敏感性。进行实验以记录血液模拟和心率状况的每种组合的 10 次心跳。结果表明，速度场的拓扑特征在时间尺度上变化，如使用时间区间平均矢量和相应的瞬时流线所揭示的那样。存在小时间尺度涡和大时间尺度主涡。观察到的一个关键流动结构是靠近瓣叶基部（下半部分）的窦上游端的反涡流。涡流动力学的时空复杂性被证明受到收缩期强烈单张颤动的深刻影响，在盐水情况下观察到的峰值频率为 200 Hz，峰值振幅为 4 mm。虽然流体粘度影响长度和时间尺度以及瓣叶颤动的引入，但心率会影响窦上游端反涡的形成。较高的心率被证明会降低反涡的强度，这会极大地影响沿着小叶底部的剪切应力的方向性和强度。这项研究证明了心率和血液模拟粘度对主动脉窦血流动力学的影响。