A systematic study of the local thermal dissipation rate in turbulent thermal convection is carried out in the aspect-ratio-one and aspect-ration-0.5 cells filled with water. Four small thermistors are used to make a multi-sensor temperature probe to simultaneously measure the local temperature gradient in three directions. Systematic measurements of the local thermal dissipation rate are carried out over varying Rayleigh numbers and spatial positions across the entire convection cell. The experiment reveals the spatial distribution of the local thermal dissipation rate in a closed convection cell. Large values of the thermal dissipation rate are found mainly along the cell periphery and they are determined primarily by the thermal plumes in the system....[ Read more ]

A systematic study of the local thermal dissipation rate in turbulent thermal convection is carried out in the aspect-ratio-one and aspect-ration-0.5 cells filled with water. Four small thermistors are used to make a multi-sensor temperature probe to simultaneously measure the local temperature gradient in three directions. Systematic measurements of the local thermal dissipation rate are carried out over varying Rayleigh numbers and spatial positions across the entire convection cell. The experiment reveals the spatial distribution of the local thermal dissipation rate in a closed convection cell. Large values of the thermal dissipation rate are found mainly along the cell periphery and they are determined primarily by the thermal plumes in the system.

The statistical properties of the normalized local thermal dissipation rate are also studied at three typical positions in aspect-ratio-one convection cell. It is found that the thermal dissipation field in the bulk region does not change much with Rayleigh number.