管内温度助走域の乱流諸量の分布とその生成, 拡散および散逸

概要

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Measurements have been made to investigate the mechanism of turbulent heat transport in the thermal entrance region of a pipe. To capture the interface between hot and ambient cold fluids, we have developed new detector functions based on the the time-derivative of temperature fluctuations. The instantaneous position of the interface fluctuates widely around the time-averaged position in conformity to a Gaussian probability distribution function. As a result, ambient cold fluids penetrate deeply into the near-wall hot region. From the analysis of both the developing processes and the energy budgets of temperature variance and radial turbulent heat flux, it is shown that peak values of the productions of these quantities become gradually larger as the thermal boundary layer develops, whereas their diffusive transports near the wall reach a fully developed state very rapidly. The distributions of the turbulent Prandtl number show no similarity throughout the entrance region ; furthermore, they are not constant within the thermal boundary layer. This means that the analogy between turbulent heat and momentum transfer, which is often assumed in conventional heat transfer analyses, does not hold in the thermal entrance region of a wall turbulent shear flow.
社団法人日本機械学会の論文
1992-09-25