A study of oscillatory flow in curved pipes. 3rd report. Visualization and velocity measurement of secondary flow.

Visualization, by the tracer method, was made of the secondary flow in the fully-developed region of a curved pipe under oscillatory laminar flow conditions. In the experiment, photographs were taken systematically of traces on nylon particles suspended in water flowing in the range of Womersley number α=5.5 to 28 and oscillatory Dean numbers D= 40 to 500. The experimental results, i. e. the instantaneous or time-averaged velocity profiles, and the locations of the center of vortices, are compared with those of the numerical analysis and descriptions are given for the transition of the secondary flow pattern due to Dean and Womersley numbers.