Speed of laminar flow in a pipe with an abrupt variation in cross-sectional area

Abstract

We determine flow speeds (laminar flow) inside a cylindrical pipe with an abrupt variation in cross-sectional area. Measurements are carried out using the laser doppler velocimetry setup developed in our laboratory. The results are in good agreement with the predictions of the continuity equation. Interesting results are found at region near the abrupt change in the cross-sectional area. At this region, the drop in flow speed exhibits a linear behavior. Furthermore, the relation between the rate of drop in flow speed (drop in speed per unit distance) and the initial flow speed (speed before the abrupt variation in crosssection) is found to be approximately linear. The experiment is suitable for undergraduate level and can help enhance the understanding of students on the subject matter involved.