Laboratory–Numerical Model Comparisons of Flow over a Coastal Canyon

Abstract

Different modeling approaches are applied to the same geophysical flow in order to assess the ability of laboratory models to provide useful benchmarks in the development of oceanic numerical models. The test case considered here?that of the flow driven by an oscillatory forcing over a submarine canyon?involves background rotation, density stratification, and steep topography. Velocity fields measured by particle-tracking velocimetry and time series of density fluctuations are directly compared to the corresponding outputs from a high-order finite-element numerical ocean model. Quantitative comparison of the laboratory and numerical models shows good overall agreement in the structure and magnitude of the strongest residual currents, which occur at the level of the shelf break in the configuration presented here. The associated residual vorticity field is also structurally consistent between the two models, although the residual divergence is not. Residual currents higher up and lower down in the water column are weaker than at the shelf break, and the agreement between the laboratory and numerical models is less good at these levels, possibly indicative of the controlling influence of the surface and bottom boundary layers.