Abstract: The instability and transition process of the natural-convection boundary layer around a vertical heated isothermal flat plate was investigated experimentally. It demonstrates that the characteristics of the unstable wave, measured at the flexion point in the velocity profile, consist with the results of linear stability theory. After an initial growth of its low frequency components, the comparatively higher frequency components develop and become to be turbulentized subsequently with a buoyancy subrange in its power spectra. In the inner sublayer, a new disturbance signal and its subharmonics in a much higher frequency domain were discovered near the wall and an inertial subrange was observed by its high frequency side in the spectra at Gr≈378.6.

Key words: natural-convection boundary layer, instability, transition, buoyancy subrange

摘要： 对恒壁温竖直加热平板的自然对流边界层的流动稳定性与转捩过程进行了试验研究，研究结果表明在外层速度剖面拐点处测得的线性不稳定波的特性与Brewster和Gebhart的计算基本一致。在低频成分首先增长后，随着Grashof数的增加高频成分迅速发展，在湍流化过程中逐渐形成浮力子区；与此同时，在内层近壁处的测量发现，在更高频段存在一种具有较强选频特性的不稳定波及其亚谐波，并在转捩后期 Gr≈378.6 时于其频谱的高频一侧逐渐形成惯性子区。

关键词: 自然对流边界层, 稳定性, 转捩, 浮力子区