The influence of a side wall on rotating flow over bottom topography

Abstract

We describe laboratory observations of the flow of a homogeneous fluid over three-dimensional obstacles that are towed along the bottom of one vertical wall of a wide rotating channel. The behaviour of the viscous-inertial flow, for a given direction of rotation, depends strongly upon whether the wall is on the right- or left-hand side when looking downstream (in the direction of flow relative to the obstacle). There are a number of flow regimes, with a blocked region occurring above the topography at low Rossby numbers when the wall is on the right of the flow (for anticlockwise rotation), but a large blocked region developing downstream of the obstacle when the wall is on the left. Blocking on the left-hand wall occurs at larger Rossby numbers than on the right-hand wall, contrary to theoretical predictions for slowly varying topography or linearised disturbances. When the influence of viscosity is sufficiently small the blocked region against a left-hand wall gives way to a train of cyclonic eddies. No wake is seen when the wall is on the right of the flow and there are no anticyclonic eddies. At large Rossby numbers the disturbance takes the form of a system of standing inertial lee waves.