Kozlovsky Pavel, Rosenfeld Moshe, Jaffa Ariel J, Elad David
Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel.
School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel.
J Biomech. 2015 Jun 25;48(9):1652-61. doi: 10.1016/j.jbiomech.2015.03.001. Epub 2015 Mar 12.
The physical mechanism that drives blood flow in the valveless tubular embryonic heart is still debatable whether it is peristaltic flow or valveless dynamic suction. Previous studies of valveless pumping were concerned with either the role of the excitation parameters or the mechanisms that generate the unidirectional outflow. In this study, a dimensionless one-dimensional (1D) analysis of the valveless pumping due to local excitation at an asymmetric longitudinal location was performed for non-uniform thick-wall elastic tubes, including tubes with local bulging and tapering. A general tube law that accounts for wall thicknesses was implemented for describing the physically realistic dynamics of the tube and the two-step MacCormack algorithm was utilized for the numerical analysis. A comprehensive analysis was conducted to explore the affecting roles of the system (e.g., tube geometry) and the working (e.g., Strouhal number and flow friction parameter) parameters on the net outflow of the pump. The maximal positive net outflow in all the tested cases always occurred when the natural Strouhal number was about π. Flow reversals were observed only for relatively low friction parameters. A local bulging at the site of excitation and thick walls contributed to larger outflows, while tube tapering reduced the net outflow.
驱动无瓣膜管状胚胎心脏中血液流动的物理机制究竟是蠕动流还是无瓣膜动态抽吸，仍存在争议。先前对无瓣膜泵血的研究要么关注激发参数的作用，要么关注产生单向流出的机制。在本研究中，针对非均匀厚壁弹性管，包括具有局部凸起和逐渐变细的管，对在不对称纵向位置处的局部激发引起的无瓣膜泵血进行了无量纲一维（1D）分析。实施了考虑壁厚的通用管定律来描述管的实际物理动态，并采用两步MacCormack算法进行数值分析。进行了全面分析，以探究系统参数（如管几何形状）和工作参数（如斯特劳哈尔数和流动摩擦参数）对泵净流出量的影响作用。在所有测试案例中，当自然斯特劳哈尔数约为π时，总是会出现最大正净流出量。仅在相对较低的摩擦参数下观察到了流动逆转。激发部位的局部凸起和厚壁有助于产生更大的流出量，而管的逐渐变细则会减少净流出量。
