Vortices in a Layered Fluid

A fluid that consists of a thin layer lying on top of a thicker and denser layer of water is a laboratory model of the upper ocean. Water at the surface of the ocean is usually warmer than water in the depth and this variation of temperature results in a density difference. Different forces acting on the surface of the ocean generate vortices. A wind pulse, for example, can induce a vortex dipole or a mushroom-type flow. A vortex dipole is a jet with a system of two vortices of opposite signs at its front. It resembles a sliced mushroom - hence the name. The flow in the photograph shows several dipoles induced by a small object moving in the upper layer. The flow was made visible with a pH indicator in an acid/base water solution rather than a regular dye. The areas of fluid that were initially of different acidity are colored differently and, when deformed by the flow, show the pattern of vortices.

Iakov Afanassiev
Memorial University of Newfoundland
Category 2 (Open) 3rd prize

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