Numerical simulation of KVLCC2 self-propulsion with ducted propeller in head waves

Abstract

In order to meet the Energy Efficiency Design Index (EEDI) requirements, consideration of reducing added power in waves is important for large tankers operating in ocean environments. In this study, the Reynolds-averaged Navier-Stokes (RANS) solver is employed in Computational Fluid Dynamics (CFD) method to simulate the self-propulsion of KVLCC2 model with a ducted KP458 propeller in head waves, especially for comparison with the non-ducted cases. Two methods are adopted for simulating the ducted propeller: the discretized propeller method and the improved body force ducted propeller method. The latter method incorporates an improved principle of momentum conservation to solve the advance speed of the ducted virtual disk precisely in real time, resulting in similar accuracy and higher efficiency compared to the former method. For some wavelengths, the ducted cases display higher propulsive efficiency and lower power than the non-ducted cases, especially under very short wavelength condition, where negative thrust deduction fraction is observed in the ducted case. With the increase of wave height, the effect of the duct becomes more pronounced, resulting in an increase in propulsive efficiency and a reduction in power, both of which can exceed 10%. Moreover, this research carefully analyzes the added values of self-propulsion factors in head waves, as well as flow fields, providing useful insights to inform the application of ducted propellers in ultra-large ocean-going tankers.