Ships are getting larger and faster due to significant technological advancements. The increasing need for higher engine power in ships is leading to the use of twin-propeller systems. Local scour caused by ship propellers during berthing and unberthing operations has led to stability problems in structures. This study experimentally investigated the unconfined scour mechanism for six propeller distances (ap) varying between 1.5Dp and 4Dp caused by twin-propeller systems. In other words, this paper presents the effect of changing distances between two propellers’ axes on scour profiles for twin-propeller systems. For this purpose, a rectangular flume was used, with all sides made of glass, located at the Hydraulic Laboratory of the Civil Engineering Department at Istanbul Technical University (ITU). A ship propeller jet was simulated as a model propeller jet in the flume. Propeller rotation was controlled with an automation panel, allowing for speed of 355 rpm. The present study was carried out using twin propeller with a diameter of Dp = 10 cm, a constant height from the sand bed (gap) of G = 15 cm, and a constant water level of h = 70 cm. The results show that, the distance between propellers is an effective parameter on scour profiles for twin-propeller systems. Therefore, different scouring formations may be observed and while single hole were observed for the propeller distances of 1.5Dp, 2Dp, 2.5Dp, and 3Dp, two different holes were occurred at the distances for 3.5Dp, and 4Dp.

Scour, Twin Propeller, Single Propeller, Seabed Erosion.