EXPERIMENTAL STUDY OF 3-D TURBULENT BEND FLOWS IN OPEN CHANNEL

A generalized bend flow model, treating a 90° single bend and 60° continuous bends, was designed to quantitatively describe 3-D turbulence mechanism of circulating not-fully-developed flow in open channels with bends. The 3-D fluctuating velocities of turbulent flow were measured and analyzed with a 3-D acoustic-Doppler velocimeter. Formula for 3-D turbulent intensity was derived using the dimension analysis approach. Expressions of vertical turbulent-intensity distributions were obtained with the multivariant-regression theory, which agree with experiment data. Distributions of turbulent intensity and turbulent stress were characterized, and their relationships were concluded. In the bend-turbulent-flow core region, longitudinal and lateral turbulent-intensity distributions are coincident with linear distribution, but in near-wall region are coincident with the Gamma distribution. Vertical turbulent intensity distributions are coincident with the Rayleigh distribution. Herein, it is concluded that the bend turbulence is anisotropic.