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چکیده
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Bridges are among the most important structures in the hydraulics and river engineering science. Local scour around bridge piers are among the major dangers to these structures. Many bridges are destructed every year due to erosion. Hence, studies on reducing scour and determining flow patterns is of significant importance.
This thesis is a numerical investigation of flow and scour patterns around vertical seies peir on 180 degree bend . The computational software SSIIM1 was used to this end. For this purpose, downstream facing bridge piers are simulated in SSIIM1 with two arrangements: the first time transverse peir in three different positions and four different Froude numbers; and the second time parallel peir in different positions (the first half head, and the second half arc) with four different Froude numbers. The arc’s relative radius of curvature was 2 which is classified as sharp bend.
The results of the laboratory model by Tabib Nejad et al. was used for model verification.
The most important results of this research are as follows:
Maximum scouring for transverse piers in the first half, head, and the second half were 1.2, 1.3, and 1.5 times the flow depth at the end of the upstream direction, respectively. The locations were at 160-180 degrees 91% of the distance between the channel width and the internal bank in the first half of the arc, 53% of the channel width from the internal bank after the head of the bridge pier touching the middle pier at the head of the arc, and 67% of the channel width from the internal bank, exactly tangent to the pier close to the external bank, respectively.
The locations were at the first half of the arc, at the end of the arc, and 92% of the distance between the channel width and the internal bank in the first half of the arc 53% of the channel width from the internal bank and tangent to the middle pier and at the second half of the arc, and 92% of the channel width from the internal bank, between 130-150 degrees at the
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