The flow field around a twin-paddle high-speed ship with shaft support and shaft sleeve is simulated and analyzed based on CFD method, taking into account the effects of hydrostatic state and free surface. The flow around full-scale ship is directly simulated and its law is explored in order to study the scale effect of appendage resistance. The results demonstrate that the total resistance coefficient of the ship appendage can be obtained by adding the residual resistance coefficient of the experimental results in the tank and the friction resistance coefficient of the ship appendage predicted by the ITTC1957 formula.
The ship appendage is a general term for the protruding objects of the hull below the waterline. The appendage resistance means the resistance increase due to the appendage, which can be divided into the appendage itself resistance and the resistance increment caused by the appendage and hull interference. The appendage resistance can be obtained by subtracting the experimental results of ship model with appendage and the results of bare-hull at the same size from a model test. The main component of the appendage resistance is the viscous force, and the Reynolds number of the model ship is not equal to that of the full-scale ship. When the appendage is in the wake flow field of the ship, the local Reynolds number is quite different. Therefore when the traditional method is used to extrapolate the resistance of the appendage to the full-scale ship, the conversion error is large. The flow around the high-speed ship changes more violently because of the high speed, so its appendage resistance can not be ignored. Therefore the scale effect of the appendage resistance of the high-speed ship is more obvious. Shariati and Mousavizadegan (2017) studied the submarine with appendages and concluded that the appendages increased the resistance by 16%, mainly due to the viscous action and the interference of the hull and appendages.
