An experimental investigation on salt-finger convection

Abstract

This work investigates the vertical and horizontal characteristic velocities of salt-finger convection over different density ratios by experimentally adding various concentrations of salty, hot water into cold, fresh water in a water tank. salt fingers are visualized by dye and its displacement over time is obtained by recording and analysing video. These experiments effectively generate the phenomena resembling salt-finger micro-structure in the ocean. The vertical velocity is significantly increased by lowering the density ratio corresponding to a larger salinity difference between the top and bottom showing a stronger destabilizing effect. Tilted fingers that resemble the experimental and oceanography observations are also observed. We also observe a non-zero horizontal velocity implying the presence of staircases. Finger widths obtained from the experiments are compared with that predicted from the linear stability analysis, which is within the same order of magnitude.