Impact of Prismatic-Shaped Obstacle on the Characteristics of Transverse Waves

Document Type : Research Paper

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Abstract

By passing water flow through obstacles (trees in rivers, piers of bridge and any hydraulic structure), vortex flows emerge at the downstream of them and by overlapping of these emerged vortexes, shallow waves with propagation direction perpendicular to the water flow direction are formed. In this study the impact of obstacles on the formation of transverse waves has been studied. For this purpose, cylindrical and triangular obstacles were used. For the triangular obstacle, two states of collision in corner and side of it were considered. Discharges of 5, 15 and 25 L s-1 and placement of barriers in parallel position with the arrangement of  60×60, 60×120, 120×120, 180×180 (mm×mm), were considered. Totally, 36 series of experiments were carried out. The results showed that the barrier had much impact on the formation of transverse waves. The maximum amount of relative amplitude () (: The maximum wave amplitude, : depth of flow) for the cylindrical obstacles with 60×120 (mm×mm) arrangement in the flow rate of 5 L s-1 and the minimum amount of it for the triangular obstacles with flow hitting its corner and the flow rate of 15 L s-1 at the arrangement of 60×120 (mm×mm) were achieved with the values of 61.1% and 3.46% , respectively. Also, in order to estimate the Strouhal number as a function of ,  and (: distance between obstacles, : diameter of obstacles and : number of obstacles in each row) for desired shape, some relationships were developed using SPSS software.
 
 

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Water and Soil Science
Volume 25, Issue 2 - Serial Number 2
October 2015
Pages 117-128

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