Effects of Froude Number and Horizontal Blade Attachment on Scour under
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.