PLANFORM STRUCTURE OF TURBULENT RAYLEIGH-BENARD CONVECTION

The planform structure of turbulent Rayleigh-Benard convection is obtained from visualising a liquid crystal sheet stuck to the bottom hot surface. The bottom plate of the convection cell is Plexiglas and the top plate is glass. Water is the test liquid and the Rayleigh number is 4 x 10(7). The planform pattern reveals randomly moving hot streaks surrounded by cold regions suggesting that turbulent Rayleigh-Benard convection is dominated by quasi-two-dimensional randomly moving plumes. Simultaneous temperature traces from two vertically separated thermocouples indicate that these plumes may be inclined forward in the directon of horizontal motion. The periodic eruption of thermals observed by Sparrow et al [3] and which forms the basis of Howard's model is not observed.