Experimental study of oscillatory flow in a rigid and a compliant tubular bulge

Abstract

Blood flow hemodynamics plays an important role in the localized deformation of arterial lumen and progression of atherosclerosis. To understand the flow details, the present study examines the possibility of chaotic flow in rigid and compliant deformed tubes. The geometries selected mimic the diseased portion in a human body and the oscillatory flow conditions are similar to the vascular flow rates in terms of Reynolds and Womersley numbers. An experimental set up is established through a set of controlled solenoid valves to produce the required oscillatory waveform. The working fluid used is a mixture of glycerin and water. Three components of velocity are determined by recording an image sequence of particle motion using a two-camera system. The particle is density matched with the working fluid. Coordinates of the particle position and velocity are determined using the image sequences recorded by each camera. The overall approach to velocity measurement is similar to particle tracking velocimetry. The frequency of oscillation considered is 1.2 Hz. The experiment represents realistic blood flow conditions in the human aorta with Womersley number in the range of 10–12 while the Reynolds number is lower, being in the range of 500–800. Since particle motion is followed, it is possible to detect Lagrangian chaos in terms of the positive largest Lyapunov exponent. Results show that the Lyapunov exponent of a compliant model is slightly greater than that of the rigid. In addition, it increases uniformly with Reynolds number.