SECOND ORDER DIFFERENCE- AND SUM-FREQUENCY WAVE LOADS IN THE OPEN-SOURCE POTENTIAL FLOW SOLVER NEMOH

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 nearfield 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.