TEMPERATURE-FLUCTUATION PROPERTIES IN SODIUM CONVECTION

Experimental investigations have been carried out on some aspects of t emperature field in sodium convection. Using spectra, histograms, and structure functions the properties of the temperature fluctuations wer e analyzed. It was found that, at Ra similar or equal to 5 x 10(6), th e maximum Rayleigh number reached in this experiment; the temperature field behavior was mainly diffusive. The frequency spectra showed a ve ry clear scaling with a slope of -4. It was also found that, over the whole range of Rayleigh numbers checked, the probability density funct ions (PDF's) of the temperature fluctuations were Gaussian shaped, whe reas the PDF's of the temperature differences were well fitted by stre tched exponential tails.