PULSATILE FLOW IN FLEXIBLE TUBES.

The high frequency, time periodic, pulsatile flow of an incompressible fluid in a straight flexible tube is considered in the context of blood flow in the larger arteries. The basic axisymmetric, hydraulic or pulsatile approximation to the Navier-Stokes equations is derived. The high frequency limit of these equations yields two nonlinear partial differential equations relating pressure, axial velocity and cross-sectional tube area. The system is completed by a rate dependent wall equation which models the interaction between the fluid flow and the tube wall. The first two terms of an asymptotic solution to this system, valid in the high frequency limit, are calculated. These are shown to predict effects which are consistent with known conditions in the arterial system. A high frequency boundary layer and a low frequency flow are investigated and the propagation of weak shocks is examined. Author