Spectral analysis of temperature fluctuations in molten metals

Abstract

Spectral analysis techniques have been used to obtain the power spectrum of the thermal fluctuations which were reported (Hurle 1966) to occur in molten gallium contained in a horizontal boat on which was impressed a large axial temperature gradient. The fluctuations have components which form a harmonic series, the fundamental of which has the frequency of the sinusoidal signal obtained at low temperature gradients. The results suggest that the fluctuations are due to the phenomenon of ‘overstability’, rather than to the onset of turbulence in the melt.