Qamar Adnan, Bull Joseph L
a Biomedical Engineering , University of Michigan , Ann Arbor , MI , USA .
Comput Methods Biomech Biomed Engin. 2017 Aug;20(11):1195-1211. doi: 10.1080/10255842.2017.1340467. Epub 2017 Jun 28.
Mass transport and fluid dynamics characteristics in the vicinity of an oscillating cylindrical fiber with an imposed pulsatile inflow condition are computationally investigated in the present study. The work is motivated by a recently proposed design modification to the Total Artificial Lung (TAL) device, which is expected to provide better gas exchange. Navier-Stokes computations, coupled with convection-diffusion equation are performed to assess flow dynamics and mass transport behavior around the oscillating fiber. The oscillations and the pulsatile free stream velocity are represented by two sinusoidal functions. The resulting non-dimensional parameters are Keulegan-Carpenter number (KC), Schmidt number (Sc), Reynolds number (Re), pulsatile inflow amplitude ([Formula: see text]), and amplitude of cylinder oscillation ([Formula: see text]). Results are computed for [Formula: see text], Sc = 1000, Re = 5 and 10, [Formula: see text] and 0.7 and 0.25 [Formula: see text][Formula: see text][Formula: see text] 5.25. The pulsatile inflow parameters correspond to the flow velocities found in human pulmonary artery while matching the operating TAL Reynolds number. Mass transport from the surface of the cylinder to the bulk fluid is found to be primarily dependent on the size of surface vortices created by the movement of the cylinder. Time-averaged surface Sherwood number (Sh) is dependent on the amplitude and KC of cylinder oscillation. Compared to the fixed cylinder case, a significant gain up to 380% in Sh is achieved by oscillating the cylinder even at the small displacement amplitude (AD = 0.75D). Moreover, with decrease in KC the oscillating cylinder exhibits a lower drag amplitude compared with the fixed cylinder case. Inflow pulsation amplitude has minor effects on the mass transport characteristics. However, an increase in [Formula: see text] results in an increase in the amplitude of the periodic drag force on the cylinder. This rise in the drag amplitude is similar to that measured for the fixed cylinder case. Quantifications of shear stress distribution in the bulk fluid suggest that the physiological concerns of platelet activation and injury to red blood cells due to cylinder oscillation are negligible.
本研究通过计算研究了在施加脉动流入条件下振荡圆柱纤维附近的传质和流体动力学特性。这项工作的动机来自最近对全人工肺（TAL）装置提出的设计改进，预计该改进将提供更好的气体交换。进行了纳维 - 斯托克斯计算，并结合对流扩散方程来评估振荡纤维周围的流动动力学和传质行为。振荡和脉动自由流速度由两个正弦函数表示。得到的无量纲参数为柯列根 - 卡朋特数（KC）、施密特数（Sc）、雷诺数（Re）、脉动流入幅度（[公式：见原文]）和圆柱振荡幅度（[公式：见原文]）。针对[公式：见原文]、Sc = 1000、Re = 5和10、[公式：见原文]以及0.7和0.25 [公式：见原文][公式：见原文][公式：见原文] 5.25计算了结果。脉动流入参数对应于在人体肺动脉中发现的流速，同时匹配运行中的TAL雷诺数。发现从圆柱表面到主体流体的传质主要取决于圆柱运动产生的表面涡旋的大小。时间平均表面舍伍德数（Sh）取决于圆柱振荡的幅度和KC。与固定圆柱情况相比，即使在小位移幅度（AD = 0.75D）下振荡圆柱，Sh也能显著提高高达380%。此外，随着KC的减小，与固定圆柱情况相比，振荡圆柱的阻力幅度更低。流入脉动幅度对传质特性影响较小。然而，[公式：见原文]的增加会导致圆柱上周期性拖曳力幅度的增加。这种阻力幅度的增加与固定圆柱情况测量的结果相似。对主体流体中剪应力分布的量化表明，由于圆柱振荡导致的血小板激活和红细胞损伤的生理问题可以忽略不计。
