Study on 2nd-Order Wave Loads With Forward Speed Through Aranha’s Formula and Neumann-Kelvin Linearization

The 2nd-order wave loads consist of difference frequency, sum frequency components and a steady drift component that is also called the mean drift load. The first two components are usually not of interest, because of their small amplitudes compared with the 1st-order wave loads. The remaining mean drift load should be taken into consideration due to its steady effect on floating bodies. In the previous research, the full derivation and expression of the 2nd-order wave loads applied to a floating structure was presented. Moreover, numerically estimated quadratic transfer function was also illustrated with both off-diagonal elements and diagonal elements called the mean drift coefficients. Most research topics in this scenario consider the wave only case. In this paper, the mean drift wave loads applied to a floating structure with forward speed or current velocity has been numerically estimated through Aranha’s formula, a far field method and Neumann-Kelvin linearization, a near field method. Therefore, the effect of the floating structure’s forward speed or current velocity on the 2nd-order mean drift loads that is also called the wave drift damping has been discussed through these two methods. This work will provide a meaningful reference and numerical basis for the ongoing projects of the floating structure’s seakeeping and maneuvering problems.