Abstract
The thermal convection in the large water body has not yet clarified sufficiently. In this paper the development of convection is visualized by means of the Schlieren method, the dye injecting method, the aluminium powder method and so on. At the beginning of convection many polygonal patterns appear on the bottom plate and vortex rings appear from the vertexes of them.
The nature of convection in an equilibrium state is classified into two regions, according to the Rayleigh number, or the Reynolds number in a strict sence. In the region where the flux type Rayleigh number is smaller than 2×105, the convection is in a turbulent state. but where the Rayleigh number is larger than 2×106, the convection is a turbulent state.
By photographs obtained with the use of the vertical slit beam and the horizontal slit beam, relations between the convection and the external parameters are derived.
