Summary

This document describes how AquaSim models the combined effects of waves and current, focusing on how current modifies the wave propagation through Doppler shifting and wave action conservation.

When waves travel with the current, they become longer with decreased amplitude. When waves travel against the current, the waves become shorter with increased amplitude. AquaSim interprets the input wave period as valid for an observer moving with the current. Meaning, if the period relative to an earth fixed point is to remain constant, the input period must be adjusted depending on current direction and velocity.

A case study from (Faltinsen et. al., 2025) is reproduced with AquaSim analyses. The AquaSim results are compared with the test results. The results show how AquaSim captures the main physical effects correctly when Doppler corrections are applied.

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