TED-AJ03-147 EFFECTS OF ADVERSE PRESSURE GRADIENT ON MEAN AND FLUCTUATING TEMPERATURES IN TURBULENT BOUNDARY LAYER
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概要
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Characteristics of turbulent boundary layer flows with adverse pressure gradients (APG) differ flows with adverse pressure gradients (APG) differ significantly from those of canonical boundary layers. With respect to thermal fields in the turbulent boundary layer, classical experimental data under an equilibrium APG condition were, even now, discussed in order to validate proposed turbulence models and/or theory. In practical situations, however, the flow fields are usually encountered in a more complex situation, such as non-equilibrium pressure gradients. Unfortunately, there is little information on the corresponding thermal field in APG boundary layers. In order to improve the model predictions for practical usage, we have to provide trustworthy databases in such complex flow conditions. In the present study, an experimental investigation was made on non-equilibrium turbulent boundary layers subjected to adverse pressure gradients developing on a uniformly heated flat wall. Streamwise velocity and temperature fluctuations are simultaneously measured with hot- and cold-wire techniques. The experimental result showed that in the APG boundary layer the Stanton number follows the[figure] correlation curve for a flat plate, although the skin friction coefficient decreases drastically, in comparison with ZPG flow. The mean temperature profiles in APG flows lie below the conventional thermal law of the wall in the fully turbulent region. R.m.s. intensities of temperature fluctuation in the APG flows remain unchanged, in comparison with the ZPG flow. On the other hand, the turbulence intensities of the streamwise velocity component decrease n the near-wall region of APG flow. The reduction of the streamwise heat flux in an APG flow can be seen (Fig A-1), though the correlation coefficient remains consistently as high as 0.55 over most of the layer. Thus, the streamwise velocity and temperature fluctuations are still closely related to each other in the APG flow, as in the canonical wall flow. The time scale of the thermal field in the APG flow increases in the near-wall region. This characteristic conforms to the result of the velocity field. Moreover, the time scale ratio in the log region of APG flow decreases, thus indicating that the velocity-field time scale is more elongated than that for the thermal field (Fig. A-2).[figure]
- 一般社団法人日本機械学会の論文
著者
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Nagano Yasutaka
Department Of Mechanical Engineering Nagoya Institute Of Technology
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Nagano Yasutaka
Department Of Environmental Technology And Urban Planning Graduate School Of Engineering Nagoya Inst
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HOURA Tomoya
Department of Environmental Technology Nagoya Institute of Technology
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