Volume 16, Issue 1 (2016)                   MCEJ 2016, 16(1): 1-11 | Back to browse issues page

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Experimental study of flow around spur dike with side slope. MCEJ 2016; 16 (1) :1-11
URL: http://mcej.modares.ac.ir/article-16-4199-en.html
Abstract:   (8583 Views)
Experimental study on effect of single spur dike side slope on flow structure carried out. In the study, 3D flow dynamics around the single spur dike with side slope of 75 degree has been studied experimentally in straight fixed bed channel. In order to analysis of flow characteristics, turbulence parameters flow around the scour have been measured using Acoustic Doppler Velocimeter (ADV). In behind of the spur dike, due to reduction of flow velocity that leads to formation of stationary zone, flow velocity will be increased in central zones. Therefore, a part of the flow is conducted upward and another part will be directed downward, where the pressure is lower. Downward flow is the cause of horseshoe vortex formation. Two velocity intensifier zones is formed, one is located in the main core of flow which is caused by reduction of flow width and the other one is a high velocity zone that is related to local velocity intensifying in outer layer of shear zone in the downstream of the spur dike. This is stemmed from increase in velocity of flow caused by reduction in flow width and leads to scour initiation from this zone. The maximum amount of “-ρ(u^' v^' ) ̅” stress element in shearing layer direction is occurred. Regarding to negative amounts of “-ρ(v^' w^' ) ̅” and “-ρ(u^' w^' ) ̅” stress elements, accumulation of deposits is happened in circular zone behind the spur dikes. Increases in both the speed, a core area to increase the speed of the flow and reduce the width of the high-speed flow and other areas related to the intensification of local rapidly down the breakwater and in the area the outer layer the shear is formed. The maximum mean flow velocity at the bottom of the breakwater 55/1 is the mean flow velocity is approaching. In the upstream region of the breakwater a rotating flow in the leg is shaped breakwater. It has small dimensions and rotational flow near the breakwater body rotation power was concentrated in the can be high. Upstream of the nose, the lines of the horseshoe vortex, the rotation around the nose, the hands move downward and adjacent layers come to be intertwined with the shear. The average flow field, the maximum kinetic energy in the central part of the channel and away from the shear layer form is the maximum kinetic energy of turbulence along the shear layer will occur. Increase in kinetic energy along the shear layer plays an important role in the sediment bed holds it down, so that the kinetic energy due to the formation of vortex turbulence the total flow depth have been developed. In behind of the spur dike, due to reduction of flow velocity that leads to formation of stationary zone, flow velocity will be increased in central zones. Therefore, a part of the flow is conducted upward and another part will be directed downward, where the pressure is lower.
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Article Type: Original Manuscript | Subject: -------
Received: 2013/05/20 | Accepted: 2015/04/7 | Published: 2016/03/20

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