Gijsen F J, van de Vosse F N, Janssen J D
Department of Mechanical Engineering, Eindhoven University of Technology, The Netherlands.
Biorheology. 1998 Jul-Oct;35(4-5):263-79. doi: 10.1016/S0006-355X(99)80010-9.
An experimental investigation of the wall shear stress distribution downstream of a backward-facing step is carried out. The wall shear stress distribution was determined by measuring the deformation of a gel layer, attached to the wall downstream of the step. Speckle pattern interferometry was applied to measure the deformation of the gel layer. The measured deformation, combined with the properties of the gel layer, served as an input for a finite element solid mechanics computation to determine the stress distribution in the gel layer. The wall shear stress, required to generate the measured deformation of the gel layer, was determined from these computations. A Newtonian buffer solution and a non-Newtonian red blood cell suspension were used as measuring fluids. The deformation of the gel layer was determined for a Newtonian buffer solution to evaluate the method and to obtain the properties of the gel layer. Subsequently, the wall shear stress distribution for the non-Newtonian red blood cell suspension was determined for three different flow rates. The inelastic non-Newtonian Carreau-Yasuda model served as constitutive model for the red blood cell suspension. Using this model, the velocity and wall shear stress distribution were computed by means of a finite element fluid mechanics computation. From the comparison between the numerical and the experimental results, it can be concluded that wall shear stresses, induced by the red blood cell suspension, can be modeled accurately by employing a Carreau-Yasuda model.
对后向台阶下游的壁面剪应力分布进行了实验研究。壁面剪应力分布是通过测量附着在台阶下游壁面上的凝胶层的变形来确定的。应用散斑图案干涉测量法来测量凝胶层的变形。测得的变形与凝胶层的特性相结合，作为有限元固体力学计算的输入，以确定凝胶层中的应力分布。由这些计算确定产生凝胶层测得变形所需的壁面剪应力。使用牛顿缓冲溶液和非牛顿红细胞悬浮液作为测量流体。为评估该方法并获得凝胶层的特性，对牛顿缓冲溶液确定了凝胶层的变形。随后，针对三种不同流速确定了非牛顿红细胞悬浮液的壁面剪应力分布。非弹性非牛顿卡雷au - 亚苏达模型用作红细胞悬浮液的本构模型。使用该模型，通过有限元流体力学计算来计算速度和壁面剪应力分布。从数值结果与实验结果的比较可以得出结论，采用卡雷au - 亚苏达模型可以准确地模拟红细胞悬浮液引起的壁面剪应力。
