Abstract
In this paper, the temperature inside an artificially generated young turbulent spot in a low free stream turbulence water tunnel were measured experimentally, using a digital particle image thermometry (DPIT) method by seeding slurry thermochromic liquid crystals to the flow. The measurements were conducted on both an elevation view at distances of 0, 10, 20mm from the central plane, and a plan view at distances of 3, 6mm from the flat plate at times of 0.8, 1.2, 1.6, and 2s after the spot initiation. During the test, the Reynolds number, turbulence intensity, and temperature of the mainstream was maintained at 75,000, 0.93%, and 23.6°C, respectively. Meanwhile, the temperature of the heated plate, considered as the heat source of the turbulent spot, was kept at 25.4°C. The results showed that this technique provides both an instantaneous temperature distribution throughout an entire spot structure and the spot parameters such as the spot celerities, the half spreading angles, and non-dimensional spot propagation parameter simultaneously. Moreover, the mechanism of the upward heat diffusion was observed and discussed. Finally, when the obtained structures were coincided with the temperature contour of the turbulent spot footprint, the heat convection characteristics of turbulent spot were, then, further clarified.
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