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首页> 外文学位 >Analysis of low Reynolds number blood flow in a rectangular microchannel utilizing a two-phase Eulerian-Eulerian model and including a steady state oxygen-hemoglobin reaction approximation.
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Analysis of low Reynolds number blood flow in a rectangular microchannel utilizing a two-phase Eulerian-Eulerian model and including a steady state oxygen-hemoglobin reaction approximation.

机译：使用两相欧拉-欧拉模型并包括稳态氧-血红蛋白反应逼近分析矩形微通道中的低雷诺数血流。

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摘要

The evolution of oxygenator design has culminated in the current strategy of utilizing micro-porous membranes to separate blood and oxygen phases while utilizing extra-luminal blood flow orientations to promote passive and active secondary mixing of the blood to inhibit the build up of concentration boundary layers near oxygen transfer surfaces that impede efficiency. Advances in fabrication techniques could allow for the manufacturing of oxygenators employing microchannels to decrease the diffusion path between oxygen and the red blood cells, more closely mimicking the strategy employed by the body. Because blood is actually a complex suspension, it is difficult to model. Furthermore, as channel dimensions decrease below about 500 micometers, the particulate nature of blood becomes increasingly important. The Fahraeus effect and the Fahraeus-Lindquist effect indicate that blood flow in channels comprising dimensions smaller than this exhibit a decrease in hematocrit and apparent viscosity respectively within the microchannel as compared with the feed or discharge hematocrit or viscosity. Additionally, blood is a reactive fluid. Oxygen-hemoglobin binding increases the oxygen carrying capacity of the blood multifold.;The objective of the this work was to develop a CFD model to simulate blood flow in a rectangular microchannel in order to predict the appropriate Reynolds number (Re) or range of Re's to achieve optimal O2 transfer into the blood. It was imperative to include both the particulate nature of blood and the oxygen-hemoglobin binding effects in the model especially within the proposed microchannel dimensions.;Ansys CFX version 11.0 was employed to develop a Eulerian-Eulerian multiphase blood model consisting of a continuous plasma phase and a dispersed red blood cell phase, each possessing independent velocity fields and each phase interacting through friction drag forces. Oxygen diffusion and oxygen-hemoglobin reaction effects were included through the use of volumetric, scalar variables representing oxygen, hemoglobin, and oxyhemoglobin. Hemoglobin and oxyhemoglobin were limited to the dispersed red blood cell phase while oxygen was included as a component of both phases. Oxygen was allowed to transfer between phases as a function of the driving concentration gradient and a membrane resistance value quoted by previous experimenters. The oxygen-hemoglobin binding reaction was modeled using a non-linear source term in the red blood cell phase that adjusted oxygen, hemoglobin, and oxyhemoglobin concentrations to reflect saturation levels predicted by the Hill equilibrium curve which predicts hemoglobin saturation levels based on unbound oxygen concentrations. Simulations were conducted under 4 different velocity loads spanning Re from 0.2 to 9. A simplified passive Newtonian model was also employed under matching continuous phase velocity loads for comparison.;The multiphase model exhibited attenuated hematocrit and apparent viscosity levels within the microchannel as predicted. In addition, the multiphase model showed an attenuated hydraulic resistance when compared with the Newtonian simulations. The oxygen-hemoglobin binding kinetics of the multiphase model led to increases in Sherwood numbers as a result of the hemoglobin sink maintaining higher driving concentration gradients. Flux to flow rate ratios (N/Q) indicated a peak volumetric gain in oxygen around a Re of 0.2. Furthermore there was up to a 5-fold increase in the volumetric addition of oxygen in the multiphase model as opposed to the Newtonian control.;The model indicates that the microchannel might operate most efficiently under convective loads resulting in Re near 0.1 or 0.2.
机译：充氧器设计的发展最终达到了当前的策略，即利用微孔膜分离血液和氧气相，同时利用腔外血流方向促进血液的被动和主动二次混合，从而抑制浓度边界层的建立阻碍效率的氧气传输表面附近。制造技术的进步可能允许使用微通道制造充氧器，以减少氧气与红血球之间的扩散路径，从而更紧密地模仿人体采用的策略。由于血液实际上是复杂的悬浮液，因此很难建模。此外，随着通道尺寸减小到约500微米以下，血液的颗粒性质变得越来越重要。 Fahraeus效应和Fahraeus-Lindquist效应表明，与进料或排出血细胞比容或粘度相比，尺寸小于此范围的通道中的血流分别显示微通道内的血细胞比容和表观粘度降低。另外，血液是反应性流体。氧与血红蛋白的结合增加了血液的氧携带能力。;这项工作的目的是建立一个CFD模型来模拟矩形微通道中的血流，以预测合适的雷诺数（Re）或Re的范围。以实现最佳的O2传输到血液中。必须在模型中同时包括血液的颗粒性质和氧-血红蛋白结合效应，尤其是在建议的微通道尺寸内。; Ansys CFX版本11.0用于开发由连续血浆相组成的Eulerian-Eulerian多相血液模型一个分散的红细胞相，每个相具有独立的速度场，并且每个相都通过摩擦阻力相互作用。通过使用代表氧气，血红蛋白和氧合血红蛋白的体积标量变量，包括了氧扩散和氧合血红蛋白的反应效果。血红蛋白和氧合血红蛋白仅限于分散的红细胞相，而氧则是两个相的组成部分。根据驱动浓度梯度和先前实验人员所引用的膜电阻值，允许氧气在各相之间转移。氧合血红蛋白结合反应是在红细胞阶段使用非线性源项进行建模的，该项可以调整氧，血红蛋白和氧合血红蛋白的浓度以反映饱和度水平，该饱和度水平由希尔平衡曲线预测，希尔平衡曲线根据未结合的氧浓度预测血红蛋白饱和度水平。在跨越Re的从0.2到9的4种不同速度负荷下进行了仿真。在匹配连续相速度负荷的情况下，还使用了简化的被动牛顿模型进行比较。；多相模型显示微通道内的血细胞比容和表观粘度水平如预期的那样衰减。此外，与牛顿模拟相比，多相模型的水力阻力减小。多相模型的氧合血红蛋白结合动力学导致Sherwood数增加，这是因为血红蛋白池保持较高的驱动浓度梯度。流量与流量之比（N / Q）表明，Re的氧气峰值体积增益为0.2。此外，与牛顿控制相比，多相模型中氧气的体积添加增加了多达5倍。该模型表明，微通道在对流负载下可能最有效地运行，导致Re接近0.1或0.2。

著录项

  • 作者

    Wright, Jamie.;

  • 作者单位

    The University of Texas at Arlington.;

  • 授予单位 The University of Texas at Arlington.;
  • 学科 Engineering Biomedical.
  • 学位 M.S.
  • 年度 2009
  • 页码 105 p.
  • 总页数 105
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生物医学工程;
  • 关键词

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