The overflow duct is a key part of a trailing suction hopper dredger, which is directly related to the loading efficiency and overflow loss. However, the design of the overflow duct usually refers to the previous design drawings and lacks of guiding theories. This paper takes the hopper system of a 4500 m3 trailing suction hopper dredger as the research object and applies the Free Surface Model to simulate the water-air two-fluid flow during the overflow process. Aiming at reducing the thickness of the overflow layer and meanwhile decreasing the air entrainment through the overflow duct, two parameters, i.e., the inlet diameter of the upper conical structure and the diameter of the lower cylinder, are numerically analyzed and optimized for a given loading condition. The results show that appropriately increasing the inlet diameter of the conical structure is beneficial to reduce the thickness of the overflow layer on the premise of that the cylinder diameter is large enough to tolerate the overflow rate. The air entrainment linearly rises as the cylinder diameter increases, while it first rises and then falls as the inlet diameter of the conical structure increases. In summary, when the ratio of the inlet diameter of the conical structure to the cylinder diameter is 2.3, the comprehensive overflow effect is the best.
Trailing suction hopper dredgers (TSHD) are widely used in dredging engineering such as port construction and waterway maintenance. The main equipment on TSHD includes drag head, dredge pump, and hopper system. During construction, the dredge pump sucks the sands excavated by the drag head and transports them to the hopper. The hopper system is an unique equipment for TSHD, and it is not only closely related to the stability of the hull, but also affects the dredging performance. There is one or two overflow ducts in the hopper, which can discharge the upper low-concentration slurry into the sea. Since low-density dredged soil such as fine sands is difficult to completely settle down in the hopper, a part of sands that has been loaded into the hopper will be discharged overboard with the overflow water. Then overflow loss occurs.
