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Floodplain Vegetation Contribution to Velocity Distribution in Compound Channels Original Article, C52 HamidifarH. and Omid M.H Journal. Civil Eng. Urban. 3(6): 357-361. 2013 ABSTRACT:The flow in compound open-channel is characterized by a complex flow structure due to the interaction between the main channel and floodplain which is often home to a lot of kinds of vegetation. This paper describes the results of an experimental study on the influence of floodplain vegetation on velocity distribution in compound channels. For vegetation on the floodplain, rigid cylindrical rods 1 cm in diameter are used. The local flow velocities for different densities of vegetation were measured using a 3D acoustic Doppler velocimeter. The results showed that that after implanting the vegetation over the floodplain, the depth averaged velocity over the floodplain increases whereas it increases in the main channel. Also, the depth averaged velocity decreases in both the main channel and floodplain with an increase in the vegetation density. The maximum value of the streamwise velocity was found to decreases with vegetation density. While it was found that a major vortex forms in the main channel for smooth floodplain, two distinct vortexes (free surface and bottom vortexes) were observed for the tests with vegetated floodplain. Keywords: Compound channel, Vegetation, Floodplain, Velocity distribution, Secondary currents منبع: [Hidden Content] دانلود: [Hidden Content].,52-357-361.pdf J. Civil Eng. Urban.,52-357-361.pdf

Flow Visualization in Vortex Chamber Original Article, B5 Chapokpour J., Farhoudi J., Amiri Tokaldany E., Majedi-Asl M. Journal. Civil Eng. Urban. 2(1): 26-34. 2012 ABSTRACT: This paper presents the results of experimental study that was accomplished in a vortex settling chamber to observe the flow structures. A polar grid of data accusation was designed to trace the velocity characteristics of the flow. An ADV three dimensional velocity measuring equipment was utilized. The experiments were conducted under four different discharges and three dimensional flow velocities were then measured. The different type secondary currents were detected in 2D manner at radial sections of vortex chamber. Additionally, it was tried to show a 3D appearance of velocity components inside the basin. It was found that flow structure of basin is highly dependent on entrance velocity. Two types of clockwise and anticlockwise vortices and some sink points combined with each other were observed in radial sections of chamber where their configurations and role were varied with flow discharge. To understand sediment trapping process in these basins, the streamlines and velocity vectors in the horizontal superimposed sections were drawn and analyzed then for motion of sediment particles the spiral settling path were observed. The 3D analyzing of sediment motion path has exhibited a different outcome from 2D analysis Such that there was not only any especial sediment motion path in the horizontal sections but also it was oriented towards up and down in its spiral circulation. Keywords: Vortex basin, ADV velocity measuring equipment, Velocity distribution, Streamline, Sediment motion path. منبع: [Hidden Content] دانلود: [Hidden Content].,B5-26-34.pdf J. Civil Eng. Urban.,B5-26-34.pdf