Visualization of fluid flowing through curved pipes. (1st report. Secondary flow in a circular pipe).

A new visualization method is devised for researching the secondary flow in curved pipes. The secondary flow in a circular curved pipe, having curvature ratio of 7.6, is visualized by this method in the range of Dean numbers from about 30 to about 500, which corresponds to laminar flow. In this method, the nylon particles suspended in water flowing through the pipe are lighted by a stroboscope and pictures of the nylon particles are taken. The experimental results, the flow patterns and the velocity vectors and profiles of the secondary flow, are compared with the results obtained by numerical analysis. The agreement is fairly good, so the present visualization method shows itself to be effective for the velocity measurement of the secondary flow in curved pipes.