Abstract
A swaying motion of thermal air plume arising from a horizontal line heat source in a stably and thermally stratified fluid is investigated experimentally. Flow and temperature visualizations of the plume were carried out. In the condition of an average heat rate from the line heat source, the amplitude of a swaying motion becomes larger and the plume transits laminar from turbulent state in the top region of the plume. In the condition of a large heat rate from the line heat source, a coherent vortex pair exists in a turbulent region of the plume. From the time-averaged temperature and the swaying spectrum of the plume, influences of the thermal stratification on the plume phenomenon were made clear. Temperature wave measurements are performed. A regular wave occurs in measured temperature profiles of laminar region. It is made clear that swaying spectrum gradients in laminar region are equal to -9/2 and -8.0. Turbulent spectrum gradients are equal to -5/3 and -3.0.
