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Turbulence and Shear Flow Phenomena -1 First International Symposium

ISBN:
1-56700-135-1 (Print)

MEASUREMENT OF DEVELOPING TURBULENT FLOW IN A U-BEND OF CIRCULAR CROSS-SECTION

Young Don Choi
Department of Mechanical Engineering, Korea University, 1, Anam-dong, Sungbuk-ku, Seoul 136-701, Korea

Gun Hyee Lee
Department of Mechanical Engineering, Wonkwang University, Shinyoungdong, Iksansi, Chullabukdo, 570-749, Korea

Abstract

A full mapping of the velocity and Reynolds stress distributions of the 3-dimensional turbulent flow in a strongly 180 degree curved pipe and its tangents was obtained by hot-wire anemometer. Slanted wire is rotated into 6 orientations and the voltage outputs from them are combined to obtain the mean velocity and Reynolds stress components. It was found that the strength of the secondary flow reaches up to the 35% of bulk mean velocity. The strong counter-rotating vortex pair induced by the transverse pressure gradient and centrifugal force imbalance grows up to θ = 67.5° into bend. But the counter-rotating vortex pair breaks down into two cell pattern after θ = 90° of bend. Significant double maxima in the streamwise velocity profiles appear in the bend region due to the breakdown of counter-rotating vortex pair.