Flow visualization in turbulent free convection over horizontal smooth and grooved surfaces

The present paper discusses the flow visualization for turbulent free convection in a tank of water with the bottom surface being a smooth or a grooved surface and the top of the water surface exposed to ambient. The grooved surface is of parallel 90° V-grooves with groove height of 10 mm and groove width of 20 mm. The experiment is carried out with aspect ratio (AR) of 2.9 and Rayleigh number (Ra) in the range, 1.3 × 107 − 4 × 107. Here AR is the aspect ratio (= width of fluid layer/height of fluid layer). Heat flux at the bottom surface is from electrical heating. From the pH-dye visualization, interesting flow structures are observed and these structures are analyzed with the help of plumes dynamics and temperature variations with time.