The laminar boundaxy layer and the position of the transition point were investigated on a heated flat plate. It was found that the Reynolds number of transition decreases as the temperature of the plate is increased. It is shown from simple qualitative analytical considerations that the effect of variable viscosity in the boundary layer due to the temperature difference produces a velocity profile with an inflection point if the wall temperature is higher than the free-stream temperature. This profile is confirmed by measurements. Furthermore, it is confirmed that even with large deviation from the Blasius condition, the velocity and temperature profiles are very nearly identical, as predictable theoretically for a Prandtl number [sigma] of the order of 1.0 (for air, [sigma] = 0.76). The instability of inflection-point profiles is discussed. ududStudies of the flow in the wake of large, two-dimensional roughness elements are presented. It is shown that a boundary layer can separate and reattach itself to the wall without having transition take place.
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机译:在加热的平板上研究层状边界层和转变点的位置。已经发现,随着板的温度升高,转变的雷诺数减小。从简单的定性分析考虑表明,如果壁温高于自由流温度,则由于温度差异而在边界层中产生的粘度变化会产生带有拐点的速度分布。该轮廓通过测量得到确认。此外,已经证实,即使与布拉索斯条件有较大偏差,速度和温度分布也几乎几乎相同,如理论上对于1.0的数量级的普朗特数σ可预测的(对于空气,σ= 0.76)。 。讨论了拐点轮廓的不稳定性。 ud ud介绍了大型二维粗糙度元素后的流动研究。结果表明,边界层可以分离并重新附着到墙壁上,而不会发生过渡。
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