Secondary Flows in Curved Ducts of Rectangular Cross-Section

Abstract

Secondary flows generated in curved ducts of rectangular cross-section are experimentally investigated. The velocity gradient of the uniform inlet shear flow and the duct width are taken as parameters to investigate their influences on the distortions of the velocity distribution, of the streamline, and of the kinetic energy distribution which are due to the secondary flow. When the inlet flow is uniform excluding thin wall boundary layers, a pair of secondary vortices is seen to roll up along the inner wall. As the inlet velocity gradient increases, the secondary motion due to this shear becomes apparent and the kinetic energy of the secondary flow increases. On the other hand, as the duct becomes wider, the rated at which the inlet kinetc energy is converted into that of the secondary flow increases. A rather simple solution for the channel theory is derived and comparisons with experimental results are made.