3 - Flow patterns and wall shear stress in arteries

Summary

The next three chapters, which form the core of this monograph, have two main purposes. One is to give a theoretical explanation for some of the arterial velocity profiles described in § 1.2.4. The other, of greater potential importance in the analysis of arterial disease, is to make predictions of the detailed distribution of wall shear stress in arteries, which is related to the rate of mass transport across artery walls and hence (presumably) to atherogenesis (§ 1.2.6). The second purpose is particularly important because no method has yet been devised to measure wall shear stress accurately as a function of time in vivo. This is rather surprising, considering the probable importance of wall shear, and the first section of this chapter is devoted to an explanation of why it is so difficult to measure. The second section begins the analysis of viscous flow in arteries with a discussion of unsteady entry flow (with flow reversal) in a straight tube. In chapters 4 and 5 respectively, curved and branched tubes are considered, and chapter 5 concludes with a discussion of flow instability in arteries.

The difficulty of measuring wall shear stress

The need for a good frequency response

Since the mechanism by which the wall shear stress influences mass transport across the artery wall is unknown, with the consequence that the relevant features of the wall shear distribution cannot be identified, it is important to understand as many features as possible.