*Article* **Scour Induced by Single and Twin Propeller Jets**

#### **Yonggang Cui 1, Wei Haur Lam 1,2,\*, Tianming Zhang 1, Chong Sun 1 and Gerard Hamill 3**


Received: 27 April 2019; Accepted: 23 May 2019; Published: 25 May 2019

**Abstract:** Single and twin ship propeller jets produce scour holes with deposition dune. The scour hole has a maximum depth at a particular length downstream within the propeller jet. Existing equations are available to predict maximum scour depth and the corresponding scour length downstream. Experiments conducted with various physical propeller models, rotational speeds, propeller-to-propeller distances and bed clearances are presented. The measurements allowed a better understanding of the mechanism of temporal scour and deposition formation for scour caused by single-propeller and twin-propeller. Results show that the propeller jet scour profiles can be divided into three zones, which are the small scour hole, primary scour hole and deposition dune. An empirical 2D scour model is proposed to predict the scour profile for both a single-propeller and twin-propeller using a Gaussian normal distribution.

**Keywords:** ship twin-propeller; jet; scour; 3D printing
