Laminar streak growth above a spanwise oscillating wall
Laminar streak growth above a spanwise oscillating wall
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展向振荡壁上方的层流条纹生长
DOI：
10.1017/jfm.2015.98
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发表时间：
2015
影响因子：
3.7
通讯作者：
Hicks P
中科院分区：
文献类型：
--
作者：
Hicks P
研究了利用展向壁振动来减弱不可压缩 Blasius 边界层内层流条纹的生长。正如 Leib 等人研究的固定平板上方流动的情况一样。 （J. Fluid Mech.，第 380 卷，1999 年，第 169-203 页），自由流对流阵风与边界层相互作用以驱动条纹生长。展向壁振动可以减少或增加层流条纹的总能量，具体取决于壁振动幅度和频率以及自由流阵风特性。条纹能量降低高达 90%，表明翼展壁振动是减弱层流条纹生长的有效技术。因此，它们可以抑制二次边界层不稳定性并延迟转变。层流边界层基流在流向和壁法向方向上与 Blasius 剖面相匹配，而在翼展方向上，会出现经典斯托克斯层剖面的广义版本（由静止流体下方的壁面振荡生成），该剖面由于非平行流效应而向下游演化。通过 Wentzel-Kramers-Brillouin-Jeffreys 分析，该广义斯托克斯层在大下游距离或高频板块振荡的限制下接近经典斯托克斯层。广义斯托克斯流和经典斯托克斯流所强制的层流条纹显着不同，这意味着展向基流的选择可能会影响该流的二次不稳定和转变。分析还证明，Hack & Zaki (Phys. Fluids. vol. 24 (3), 2012, 034101) 采用的经典斯托克斯层作为展向基流是不合适的。
The use of spanwise wall oscillations to attenuate the growth of laminar streaks within the incompressible Blasius boundary layer is investigated. As in the case of the flow above a stationary flat plate, studied by Leib et al. (J. Fluid Mech., vol. 380, 1999, pp. 169–203), free-stream convected gusts interact with the boundary layer to drive the streak growth. Spanwise wall oscillations can either reduce or increase the total energy of the laminar streaks, depending upon the wall oscillation amplitude and frequency, as well as the free-stream gust properties. Reductions in streak energies of up to 90 % are obtained, indicating that spanwise wall oscillations are an effective technique for attenuating the laminar streak growth. Therefore they may suppress secondary boundary-layer instabilities and delay transition. The laminar boundary-layer base flow matches the Blasius profile in the streamwise and wall-normal directions, while in the spanwise direction a generalized version of the classical Stokes layer profile (generated by a wall oscillating beneath a quiescent fluid) occurs, which evolves downstream due to non-parallel flow effects. Via a Wentzel–Kramers–Brillouin–Jeffreys analysis, this generalized Stokes layer is shown to approach the classical Stokes layer in the limit of large downstream distances or high-frequency plate oscillations. The laminar streaks forced by the generalized and the classical Stokes flows differ significantly, which implies that the choice of the spanwise base flow may affect the secondary instability and transition in this flow. The analysis also proves that the use of the classical Stokes layer as spanwise base flow, as employed by Hack & Zaki (Phys. Fluids. vol. 24 (3), 2012, 034101), is inappropriate.
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