ABSTRACT
In consideration of the pressure-flow relationships of oscillatory flow in Chapters 2 and 7, the artery is treated primarily as a cylindrical tube of constant (or non-varying) diameter. In reality, an artery is a viscoelastic tube consisting of three layers (Fig. 3.1) (Gasser et al., 2006) whose diameter varies with a pulsating pressure which is generated by a pulsating flow of blood (Sonesson et al., 1994); in addition, the arterial system will propagate pressure, flow and diameter waves, generated by the ejection of a viscous liquid (blood) from the ventricle, at a certain velocity, which is largely determined by the elastic properties of the arterial wall (Bramwell and Hill, 1922a; Bramwell and Hill, 1922b; Hardung, 1962; Cox, 1968; McDonald, 1968b; Nichols and McDonald, 1972; Farrar et al., 1978; Milnor and Bertram, 1978; Corte et al., 1979; Kelly and Fitchett, 1992; Saeki et al., 1995; Laurent et al., 2006). The model considered, therefore, was inconsistent in that the artery was treated partly as a straight rigid tube (its diameter was invariant) and partly as an elastic tube (the velocity of the pulse wave was given a realistic value corresponding to that found in vivo). For, in a rigid tube filled with an incompressible liquid, the wave velocity would be infinitely high, and filled with a real liquid it would be the velocity of sound in blood – about 1500 m/s.
