论文标题
通过跨度壁强迫减少湍流阻力。第1部分：大型模拟
Turbulent drag reduction by spanwise wall forcing. Part 1: Large-eddy simulations
论文作者
论文摘要
在广泛的雷诺数字中研究了通过流向跨度壁振荡的流动流动波的湍流减少。在这里，在第1部分中，进行了通道流中的壁挂式大涡模拟模拟，以检查波动波的频率和波数如何影响摩擦雷诺数$re_τ= 951 $和$ 4000 $的阻力减少。致动参数空间仅限于内部刻度致动（ISA）途径，在该途径中，通过直接衰减近壁尺度来实现阻力减少。因此，发现湍流衰减的水平，因此减少阻力，随着近壁stokes layer lodrusion高度$ \ ell_ {0.01} $而改变。确定了一系列频率，其中stokes层减弱了湍流，提高了湍流的产生周期并增厚粘性的子层。在此范围内，减少拖动随着$ \ ell_ {0.01} $的增加而增加，最高可达$ 30 $粘稠的单位。在此范围之外，强烈的Stokes剪切应变可增强近壁湍流的产生，从而随着$ \ ell_ {0.01} $的增加而减少阻力。我们进一步发现，在我们的参数和雷诺数空间中，ISA路径的功率成本始终超过任何减少拖动节省的费用。这激发了对第2部分的外部刻度致动（OSA）途径的研究，在该途径中，通过驱动外部刻度运动来实现阻力减少。
Turbulent drag reduction through streamwise travelling waves of spanwise wall oscillation is investigated over a wide range of Reynolds numbers. Here, in Part 1, wall-resolved large-eddy simulations in a channel flow are conducted to examine how the frequency and wavenumber of the travelling wave influence the drag reduction at friction Reynolds numbers $Re_τ= 951$ and $4000$. The actuation parameter space is restricted to the inner-scaled actuation (ISA) pathway, where drag reduction is achieved through direct attenuation of the near-wall scales. The level of turbulence attenuation, hence drag reduction, is found to change with the near-wall Stokes layer protrusion height $\ell_{0.01}$. A range of frequencies is identified where the Stokes layer attenuates turbulence, lifting up the cycle of turbulence generation and thickening the viscous sublayer; in this range, the drag reduction increases as $\ell_{0.01}$ increases up to $30$ viscous units. Outside this range, the strong Stokes shear strain enhances near-wall turbulence generation leading to a drop in drag reduction with increasing $\ell_{0.01}$. We further find that, within our parameter and Reynolds number space, the ISA pathway has a power cost that always exceeds any drag reduction savings. This motivates the study of the outer-scaled actuation (OSA) pathway in Part 2, where drag reduction is achieved through actuating the outer-scaled motions.
