Compressible laminar streaks with wall suction
Compressible laminar streaks with wall suction
复制标题
带壁吸力的可压缩层流条纹
DOI：
10.1063/1.4807066
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发表时间：
2013
影响因子：
4.6
通讯作者：
P. Hicks
中科院分区：
文献类型：
--
作者：
P. Ricco;D. Shah;P. Hicks
研究了受自由流涡旋扰动和稳定平均流壁吸力影响的可压缩层流边界层的响应。 Leib 等人的理论框架。 [J。流体机械.380, 169–203 (年份: 1999)10.1017/S0022112098003504] 和 Ricco 和 Wu [J. Fluid Mech.587, 97–138 (Year: 2007)10.1017/S0022112007007070]基于线性化非定常边界区域方程，研究了吸力对自由流涡扰动与边界层相互作用产生的运动学和热条纹的影响。在与边界层厚度相比展向波长较小的渐近极限下，即当扰动流可以方便地用稳态可压缩边界区域方程描述时，吸力对速度波动的影响很轻微，对温度波动的影响可以忽略不计。当展向波长与边界层厚度相当时，较小的吸力值会增强超音速条纹，而较高的蒸腾水平始终会稳定所有马赫数下的扰动。在较大的展向波长下，非常小的壁蒸腾幅度对所有边界层波动具有显着的稳定作用，这可以采取瞬时增长的热条纹、大幅度流向振荡或倾斜指数增长的托尔米恩-施利希廷波的形式，具体取决于马赫数和波长。发生指数增长的波数范围变得更窄，并且不稳定的位置通过轻微吸力显着向下游移动，表明当这些不稳定扰动促进层流破坏时，壁蒸腾可以成为延迟转变的合适工具。这些扰动的典型流向波长反而不受吸力的影响，渐近三层甲板理论预测在较大的下游距离和较小的展向波数的限制下，增长率的强烈变化和流向波数的非常轻微的变化。
The response of a compressible laminar boundary layer subject to free-stream vortical disturbances and steady mean-flow wall suction is studied. The theoretical frameworks of Leib et al. [J. Fluid Mech.380, 169–203 (Year: 1999)10.1017/S0022112098003504] and Ricco and Wu [J. Fluid Mech.587, 97–138 (Year: 2007)10.1017/S0022112007007070], based on the linearized unsteady boundary-region equations, are adopted to study the influence of suction on the kinematic and thermal streaks arising through the interaction between the free-stream vortical perturbations and the boundary layer. In the asymptotic limit of small spanwise wavelength compared with the boundary layer thickness, i.e., when the disturbance flow is conveniently described by the steady compressible boundary region equations, the effect of suction is mild on the velocity fluctuations and negligible on the temperature fluctuations. When the spanwise wavelength is comparable with the boundary layer thickness, small suction values intensify the supersonic streaks, while higher transpiration levels always stabilize the disturbances at all Mach numbers. At larger spanwise wavelengths, very small amplitudes of wall transpiration have a dramatic stabilizing effect on all boundary layer fluctuations, which can take the form of transiently growing thermal streaks, large amplitude streamwise oscillations, or oblique exponentially growing Tollmien-Schlichting waves, depending on the Mach number and the wavelengths. The range of wavenumbers for which the exponential growth occurs becomes narrower and the location of instability is significantly shifted downstream by mild suction, indicating that wall transpiration can be a suitable vehicle for delaying transition when the laminar breakdown is promoted by these unstable disturbances. The typical streamwise wavelength of these disturbances is instead not influenced by suction, and asymptotic triple deck theory predicts the strong changes in growth rate and the very mild modifications in streamwise wavenumber in the limit of larger downstream distance and small spanwise wavenumber.