Experimental investigation of scour beneath a pipeline due to tidal currents in a Strait

This study presents an investigation of the impact of tidal currents on scouring beneath pipelines. To elucidate the role of parameters such as current velocity, time period of each cycle, depth of flow, and number of tidal cycles required to attain equilibrium, 38 tests were conducted in a bidirectional flume for a pipeline. The geometry of pipeline and the flow characteristics of the Persian Gulf were scaled down to a ratio of 1:30 based on the Froud law and used for this study. The tests were carried out in clear water conditions. The experimental findings reveal that a significant portion of the scour depth occurs during the mid-range of each half cycle. This is the case regardless of ebb or flood conditions, and when the current velocity is at its maximum value. Also, the scour hole resulting from bidirectional flow exhibits a symmetrical shape with two dunes on either side. Furthermore, the relative scour depths in daily and semi-daily tidal tests are greater by factors of 1.40 and 1.1, respectively, compared to unidirectional tests when the root mean square values from steady current scenarios are considered. Finally, a series of formulae have been developed based on the experimental results.