This computer simulation shows stable and unstable temperature fields 10,000 years after heat was applied to the boundary. The left side shows heat conduction in a stable state where heat is applied to the top so water density is lower at the top. The right side shows free convection cells in an unstable state where heat is applied to the bottom so water density is lower at the bottom. (7 minutes)
A discussion of the material in this video is provided in Section 4.2 ‘Stable and Unstable Density Configurations’ of the Groundwater Project book ‘Variable Density Groundwater Flow’, the PDF can be downloaded or the online version can be read at that link.
Citation: Post, V.E.A. & Simmons, C.T. (2022). Variable Density: Computer simulation of stable and unstable temperature fields 10,000 years after heat was applied to the boundary. Video of The Groundwater Project, Guelph, Ontario, Canada.