Baldwin J T, Deutsch S, Geselowitz D B, Tarbell J M
Department of Chemical Engineering, Pennsylvania State University, University Park 16802.
ASAIO Trans. 1990 Jul-Sep;36(3):M274-8.
Fluid velocities were measured using a two-component laser Doppler anemometery (LDA) system at 129 locations within a Plexiglas model of a 70 cm3 Penn State electric Left Ventricular Assist Device (LVAD). The LVAD was driven by a pulsatile piston pump acting on an attached segmented polyurethane diaphragm. Bjork-Shiley tilting disc valves were used to provide unidirectional flow through the inlet and outlet ports. A seeded blood analog fluid, which matched the kinematic viscosity of blood at high shear rates and the refractive index of Plexiglas, was used to make the measurements. At each location, 250 instantaneous velocity realizations were collected at eight instances during the pump cycle. The maximum Reynolds shear and normal stresses were calculated for each pump cycle time and location after filtering the data. The results reveal that the highest Reynolds shear and normal stresses occur in the near wall region just proximal to the aortic valve during diastole, and reach values of 5,300 dynes/cm2 and 10,800 dynes/cm2, respectively. The elevated turbulent stresses are observed during the period of regurgitant flow through the aortic valve, with peak stress values arising during the period of peak regurgitant flow. This supports the hypothesis that a regurgitant turbulent jet is formed near the wall of the prosthetic aortic valve and may be contributing to blood damage.
使用双分量激光多普勒测速仪（LDA）系统，在一个70立方厘米的宾夕法尼亚州立大学电动左心室辅助装置（LVAD）的有机玻璃模型内的129个位置测量流体速度。LVAD由一个作用在连接的分段聚氨酯隔膜上的脉动活塞泵驱动。使用 Bjork-Shiley 倾斜盘式瓣膜来提供通过入口和出口端口的单向流动。一种种子血液模拟流体用于进行测量，该流体在高剪切速率下与血液的运动粘度匹配，并且与有机玻璃的折射率匹配。在每个位置，在泵循环的八个时刻收集250个瞬时速度数据。在对数据进行滤波后，计算每个泵循环时间和位置的最大雷诺切应力和法向应力。结果表明，在舒张期，最高的雷诺切应力和法向应力出现在主动脉瓣近端的近壁区域，分别达到5300达因/平方厘米和10800达因/平方厘米。在通过主动脉瓣的反流期间观察到湍流应力升高，峰值应力值出现在反流峰值期间。这支持了这样的假设，即在人工主动脉瓣壁附近形成了反流湍流射流，并且可能导致血液损伤。
