Second-order difference-frequency wave loads on a floating body in uniform current in the frequency domain

ABSTRACT

In this study, a formulation for the second-order difference-frequency wave load in the presence of steady uniform current (or forward speed) is presented, and a practical approximate approach is proposed. A potential flow-based solution is formulated to include terms up to the second-order in wave slope and first-order in current speed. In the uniform-flow approximation, the body disturbed and ship-generated steady flows are neglected, assuming slender bodies and low uniform flow speed. The free-surface integral is not included in evaluating the difference-frequency force quadratic transfer function (QTF) considering its relatively unimportant contribution compared to other terms, which significantly reduces the cost of the computational implementation. The present numerical results compare well against published experimental and numerical result. The importance of directly calculating off-diagonal terms of the QTF in the presence of uniform flow is investigated by comparing the present model with other existing approximation methods and with cases without uniform flow.

KEYWORDS:

• Quadratic transfer function (QTF)
• uniform flow
• direct pressure integration
• second-order load
• drift force
• wave-current interaction

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2017R1A5A1014883). This work was also supported by the Indonesia Endowment Fund for Education or also known as LPDP grant No: PRJ-4038/LPDP.3/2016.