Experimental analysis of turbulence measurements in a new dissipator structural (cross beams) in abruptly expanding channels

Abstract

In order to mitigate the flood, weirs were also used as the flood mitigating structures but no study has been found in which efficacy of energy dissipators downstream of weirs is checked either experimentally. Present work is an attempt to study the efficacy of weirs under the flood conditions. Turbulence characteristics of a new device dissipator as series of crossbeams to control the spatial jump of an abrupt expanding channel are presented in this work. Experiments were conducted in a 12 m flume in the hydraulic lab of Shahid Chamran of Ahvaz University. First, Experiments were conducted on Froude numbers 7.4, 8.7, and 9.5. After regression analysis, it found 3 Configurations that had the best results on velocity distribution and control the destructive effects of the jump based on experimental data. So, an Electronic Magnetic Velocity meter (EMV (was used to obtain measurements of 3D velocities to analyze the velocity distributions, α and β Coefficient, Turbulent kinetic energy, turbulent intensities, and Reynolds stresses, which investigated on three best configurations for Fr = 9.5 and for the percentage of tail water of 0.7hs 0.8hs 0.9hs and hs. In general, maximum energy dissipation occurs at 0.7hs. Velocity distribution analysis showed that energy cascades reach the surface of the water and break there, so more stable and uniform conditions in terms of streamlines in this state could be considered. Also, for tailwater depth ratios of hs and 0.7hs, the layers of flow show a more uniform energy transfer rate and a decrease in the turbulent kinetic energy values of the flow (TKE). Configuration 2 with 0.7hs and Configuration 1 with 0.8hs tail water have the most suitable flow conditions due to the reduction of turbulent intensities (TI) caused by the use of the device and the approximate length of the basin presented as a suggestion. In Reynolds's stresses (RS) u'v'‾ for 0.7hs tail water, two stress sources of - 0.025 and +0.0126 were observed from the beginning of the flow.