DECELERATING OPEN-CHANNEL FLOW IN A GRADUAL EXPANSION

ABSTRACT: The velocity and turbulence distributions of decelerating open-channel flow in a gradual expansion were measured using LDV equipment. The results show that the logarithmic law can describe the mean velocity in the bottom region well while the Coles ’ law can be applied to the outer region. The shear velocity can be determined both by the logarithmic fit of the mean velocity and by the fit of the Reynolds stress distributions. The turbulence intensities reach their maximum values at z/h = 0.1 to z/h = 0.15. The turbulence intensities do increase along the expansion, especially in the outer region. This is more pronounced for larger Reynolds numbers. Both turbulence intensity and Reynolds stress distributions are found to deviate from the theoretical and empirical curves reported for uniform flow. This can be attributed to the secondary currents generated in the relatively narrow channel