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Effects of Froude Number and Horizontal Blade Attachment on Scour under Submerged Pipelines
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  • Alireza Masjedi,
  • Farideh Karamzadeh,
  • Mohammad Heidarnejad,
  • Amin Bordbar
Alireza Masjedi
Islamic Azad University Ahvaz Branch

Corresponding Author:[email protected]

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Farideh Karamzadeh
Islamic Azad University Ahvaz Branch
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Mohammad Heidarnejad
Islamic Azad University Ahvaz Branch
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Amin Bordbar
Islamic Azad University Ahvaz Branch
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Abstract

A very large percentage of pipeline failures is attributed to scouring around pipelines. If the depth of scour becomes significant, the stability of the pipeline may be endangered, with a consequent risk of damage and failure. The effect of Froude number and horizontal blade installed under submerged pipelines on scour controlling at a direct laboratory flume was experimentally studied. Experiments were carried out on four pipe diameters, four blade lengths, and two horizontal placement modes for the lower blade at three Froude numbers were considered under clear-water conditions. At the end of each experiment, the length and depth of scour beneath the pipe were measured. According to the results, increased Froude number, the relative blade length and the location of the lower blade affect the scour depth around the pipe. The relative scour depth and length increase with the increase in Froude number. In all cases, the use of a longitudinal blade caused an increase in the percentage of scour depth reduction around the submerged pipe. For a pipe with a diameter of 3.1 cm, the use of a blade with a relative length of 0.81 at Fr=0.24 in the center and under of the pipe reduced the scour depth by 58% on average as compared to the pipe without a blade. Furthermore, with both the pipe and the blade under it, the maximum increase in the scour length by 19% was obtained with a relative blade length of 0.81 and a pipe diameter of 3.1 cm at Fr=0.24.