The laminar free surface boundary layer of a solitary wave

The laminar free surface boundary layer beneath a solitary wave is investigated using numerical simulations. Across the boundary layer $\partial {u}_{s} / \partial {x}_{n} $ and $\partial {u}_{n} / \partial {x}_{s} $ are comparable in magnitude, where $u$ is the velocity, $x$ position and subscripts $s$ and $n$ refer to components tangential and normal to the free surface. In this region $\partial {u}_{n} / \partial {x}_{s} $ is approximately constant across the boundary layer while $\partial {u}_{s} / \partial {x}_{n} $ varies with ${x}_{n} $ and outside the boundary layer tends to ${\ensuremath{-} } \mathop{ (\partial {u}_{s} / \partial {x}_{n} )} \nolimits _{n= 0} $. The numerical results are compared to analytical models and good agreement is found.