Reduction of propeller jet flow scour around a pile structure by using collar plate

In this study, the effect of the collar plate usage on local scour around a pile due to propeller jet flow was investigated experimentally. Experiments were carried out for unconfined conditions, only existence of a pile and a pile with collar plate. Three different collar plate widths (W) and two different locations of the collar plate with respect to the seabed (hc) were used to determine the effect of the collar plate on scour. Three different rotational speeds were used and scour around a pile was measured by using an Acoustic Doppler Velocimeter Profiler (ADVP). Since the experiments were completed before reaching the equilibrium state, present study can be considered as a short-term study. The results of the experimental studies show that the amount of reduction of scour around a pile is sensitive to the collar plate width and location of the collar plate. A collar plate application is an effective way for reducing scour around a pile. The most effective type of collar plate was determined as a condition in which W/D and hc/y0 are equal to 3 and 0, respectively. The amount of reduction in scour around a pile was observed as 75%.