Salt fingers at low Rayleigh numbers

This is a laboratory study of salt fingers at low Rayleigh numbers. We report on the stability boundary in the (R _S, R _T)-plane (where R _S and R _T are the salt and heat Rayleigh numbers respectively), the wavenumber of the observed fingers, and the planform. In this low R _S, R _T range, fingers have width comparable to their height, as predicted by linear stability theory. The planform appears to be close-packed polygonal cells when they are formed on curved profiles of temperature and salinity. However, the planform is distinctly rolls when care is taken to approximate linear profiles.