Experimental study of boundary layer transition with elevated freestream turbulence on a heated flat plate
Experimental study of boundary layer transition with elevated freestream turbulence on a heated flat plate
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加热平板上自由流湍流边界层转变的实验研究
DOI：
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发表时间：
1991
期刊：
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通讯作者：
E. Reshotko
中科院分区：
文献类型：
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作者：
K. Sohn;E. Reshotko
详细研究了在加热平板上进行自然过渡的边界层的动量和热发展。给出了层流、过渡和低雷诺数湍流边界层的总体和条件采样特性的实验结果。测量是在一个低速闭环风洞中进行的，风洞的自由流速度为100英尺/秒，压力梯度为零，自由流湍流强度（TI）为0.4%至6%。表面摩擦、换热率和雷诺数剪应力的分布均与前人发表的数据一致。当R（sub θ）小于2300时，通过层流和湍流的相关关系可以很好地预测雷诺数类比因子。所测得的雷诺数类比系数层流值比Pr（sup -2/3）高53%。观察到湍流结果对TI的依赖性很小。在过渡边界层中进行的条件采样表明，间歇性存在近壁下降，在某些低间歇性时明显存在，这与其他人观察到的湍流斑的横截面形状一致。观察到非湍流区间具有较大的近壁不稳定性，湍流区间的峰值比在完全湍流站测量的值高50%。过渡边界层中的非湍流型和湍流型不能简单地分别视为Blasius型和完全湍流型。边界层光谱表明，TI对T-S波的预测选择性放大约为0.4%。然而，当TI约为0.8%和1.1%时，T-S波定位在非常靠近壁的地方，在转变过程中不起主导作用。
A detailed investigation to document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were acquired in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft/s and zero pressure gradient over a range of freestream turbulence intensities (TI) from 0.4 to 6 percent. The distributions of skin friction, heat transfer rate and Reynolds shear stress were all consistent with previously published data. Reynolds analogy factors for R(sub theta) is less than 2300 were found to be well predicted by laminar and turbulent correlations which accounted for an unheated starting length. The measured laminar value of Reynolds analogy factor was as much as 53 percent higher than the Pr(sup -2/3). A small dependence of turbulent results on TI was observed. Conditional sampling performed in the transitional boundary layer indicated the existence of a near-wall drop in intermittency, pronounced at certain low intermittencies, which is consistent with the cross-sectional shape of turbulent spots observed by others. Non-turbulent intervals were observed to possess large magnitudes of near-wall unsteadiness and turbulent intervals had peak values as much as 50 percent higher than were measured at fully turbulent stations. Non-turbulent and turbulent profiles in transitional boundary layers cannot be simply treated as Blasius and fully turbulent profiles, respectively. The boundary layer spectra indicate predicted selective amplification of T-S waves for TI is approximately 0.4 percent. However, for TI is approximately 0.8 and 1.1 percent, T-S waves are localized very near the wall and do not play a dominant role in transition process.