Abstract
The influence of bottom roughness on the development of lock-release gravity currents is investigated through laboratory experiments using Particle Image Velocimetry. The bottom roughness is represented by arrays of vertical LEGO bricks with a constant spacing while varying lambda , the relative height of the roughness elements to the gravity current depth. Depending on lambda , the roughness elements may affect the gravity current propagation: for small lambda the current behaves like moving over a smooth bottom, while for larger lambda the propagation speed is reduced and the internal structure of the current, including both the head and the tail, is significantly modified. As lambda increases, stronger recirculation areas between the roughness elements develop interacting with the overlying layer and giving rise to small-scale vortical structures of opposite sign within the whole depth of the current. The additional drag force induced by the bottom roughness adds significant complexity to the flow dynamics and modifies the characteristics of the current.
Highlights
Gravity currents are geophysical flows resulting from differences in temperature, salinity, or caused by suspended sediment particles
Attention has been paid to topographic features and how they affect the propagation of dense bottom gravity currents
Several studies analyze gravity currents interacting with a single large isolated structure [16–20] showing how a topographic discontinuity, as an obstacle placed on a horizontal bottom, deeply modifies the structure of the gravity current and enhances dilution
Summary
Gravity currents are geophysical flows resulting from differences in temperature, salinity, or caused by suspended sediment particles. These flows develop mainly in the horizontal direction and can occur spontaneously in nature or result from anthropic intervention. Gravity currents have been studied extensively by means of theoretical investigations, laboratory experiments, and numerical simulations. Most of these studies focused on gravity currents travelling along a flat, horizontal surface [2–7] or flowing over a sloping bottom [8–15]. Several studies analyze gravity currents interacting with a single large isolated structure [16–20] showing how a topographic discontinuity, as an obstacle placed on a horizontal bottom, deeply modifies the structure of the gravity current and enhances dilution
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