Enhanced extreme wave statistics of irregular waves due to accelerating following current over a submerged bar

We present experimental results of irregular long-crested waves propagating over a submerged trapezoidal bar with the presence background current in wave flume. investigate non-equilibrium phenomenon (NEP) induced by significant changes water depth and mean horizontal flow velocity as trains pass bar. Using skewness kurtosis proxies, we show evidence that an accelerating following could increase sea-state non-Gaussianity enhance both magnitude spatial extent NEP. also find below ‘saturation relative depth’ $k_p h_2 \approx 0.5$ ( $k_p$ being peak wavenumber shallow area $h_2$ ), although NEP manifests, decrease does not further maximum crest. This work highlights nonlinear physics according to which provoke higher freak risk coastal areas where modulation instability plays insignificant role.