Characteristics of Turbulent Flow in Divergent Channels of Rectangular Section

Abstract

The characteristics of turbulent flow in divergent channels of rectangular section with comparatively small angle were experimentally investigated. The results were as follows: The velocity profiles were recognized as a composite structure consisting of those in the inner and outer layers. The inner layer was the region where the law of the wall could be applied independently of adverse pressure gradient. Its region decreased with increasing longitudinal distance x. The outer layer was the region which formed a plane jet relatively uninfluenced by the divergent walls. The effectiveness of Coles’ law of the wake was confirmed qualitatively, but the maximum deviation from present experimental data was from 10 to 20%. The skin-friction profiles with distance were classified into three patterns of variation in the downstream direction, and could be expressed by the relation of Reynolds number Reθ and shape factor H in the region where skin-friction coefficients decreased in the x-direction. The initial state of separation occurred at a divergence of 8°, and the region of back flow was limited very near the wall. Phenomena such as reattachment were observed at divergent angles of more than 4°. © 1983, The Society of Chemical Engineers, Japan. All rights reserved.