THE EFFECT OF BLOOD VISCOELASTICITY ON PULSATILE FLOW IN STATIONARY AND AXIALLY MOVING TUBES

An analytical solution for pulsatile flow of a generalized Maxwell flu id in straight rigid tubes, with and without axial vessel motion, has been used to calculate the effect of blood viscoelasticity on velocity profiles and shear stress in flows representative of those in the lar ge arteries, Measured bulk flow rate a waveforms were used as starting points in the calculations for the aorta and femoral arteries, from w hich axial pressure gradient del P waves were derived that would repro duce the starting Q waves for viscoelastic flow, The del P waves were then used to calculate velocity profiles for both viscoelastic and pur ely viscous flow, For the coronary artery, published del P and axial v essel acceleration waveforms were used in a similar procedure to deter mine the separate and combined influences of viscoelasticity and vesse l motion, Differences in local velocities, comparing viscous flow to v iscoelastic flow, were in all cases less than about 2% of the peak loc al velocity, Differences in peak wall shear stress were less than abou t 3%. In the coronary artery, wall shear stress differences between vi scous and viscoelastic flow were small, regardless of whether axial ve ssel motion was included, The shape of the wall shear stress waveform and its difference, however, changed dramatically between the stationa ry and moving vessel cases, The peaks in wall shear stress difference corresponded with large temporal gradients in the combined driving for ce for the flow.