Second Order Difference- and Sum-Frequency Wave Loads in the Open-Source Potential Flow Solver NEMOH

Abstract

Theoretical and numerical aspects of the open-source potential flow boundary element solver, NEMOH, for the first order hydrodynamic coefficients computations in the frequency domain are described in [Babarit, A. and Delhommeau, G., 2015]. [Philippe, M. et al., 2015] described the implementation and verifications of the second order difference-frequency quadratic transfer functions (QTFs) in the NEMOH code. In the latter paper, the QTFs are verified for standard cases, a bottom-mounted cylinder and a hemisphere. The present study reports the implementation and verification of the complete QTFs, for difference- and sum-frequency loads. The QTFs are composed of quadratic and potential parts. The quadratic part depending on the first order hydrodynamic quantities, is implemented using the near-field approach. The potential part, which depends on the second order potential, is solved using the indirect method. Verification is achieved by comparing the NEMOH result with a commercial software HYDROSTAR for a hemisphere and the OC5-DeepCwind semisubmersible.