Effects of initial stretches on wave speeds in thin orthotropic hyperelastic tubes containing fluid flow

Effects of longitudinal and circumferential initial stretch ratios (or stresses) on the speeds of wave propagation in orthotropic hyperelastic tubes containing viscous flow are investigated. Womersley's theory is used together with the long wavelength approximation, and numerical calculations are carried out for two models of natural arteries and for an artificial artery. It is found that the wave speeds increase with the circumferential stretch ratio in the natural arteries but decrease in the artificial artery. The effects of the inertia of the tube and the viscosity of the fluid are shown briefly. Comparisons with earlier work are made, in particular with the results of the simpler characteristic theory. In the latter case the influence of the Poisson ratio is noted