Development and evaluation of a high resolution photochromic dye method for pulsatile flow studies

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Abstract
Major improvements in the resolution of the photochromic dye method for measuring the instantaneous velocity profile for pulsatile flow are described. Specifically, improvements in the optical design have reduced the trace width from approximately 1.2 to 0.2 mm. Detailed studies were conducted using a 2.9 Hz sinusoidal flow superimposed on a steady flow through a straight rigid tube of 4.85 mm inside diameter. Velocity profiles were measured throughout the flow cycle and these, together with the wall shear stresses, were compared with those predicted from the Womersley rigid-tube flow equations. The excellent agreement between the experimental and predicted values illustrates the accuracy of the experimental technique. The authors have also developed a split-beam measurement method whereby the velocity profiles at three different positions along a flow vessel can be measured simultaneously. This technique provides an instantaneous description of the spatial relationship of the flow field, and is illustrated for pulsatile flow through a constricted tube.