Mechanisms of drag reduction by semidilute inertial particles in turbulent channel flow
Mechanisms of drag reduction by semidilute inertial particles in turbulent channel flow
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DOI：
10.1103/physrevfluids.8.084305
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发表时间：
2023-03
影响因子：
2.7
通讯作者：
H. Dave;M. H. Kasbaoui
中科院分区：
文献类型：
--
作者：
H. Dave;M. H. Kasbaoui
我们研究了在半稀释条件下分散的惯性粒子在 $\mathrm{Re}_\tau = 180$ 时导致湍流通道流显着减阻的机制。我们考虑一系列四向耦合的欧拉-拉格朗日模拟，其中摩擦斯托克斯数 $\mathrm{St}^+ = 6$ 或 30 的粒子以逐渐增加的质量载荷从 $M=0.2$ 到 1.0 引入。模拟表明，$\mathrm{St}^+ = 30$ 粒子在 $M=1.0$ 时导致阻力大幅减少高达 19.74\%，而 $\mathrm{St}^+ = 6$ 粒子在 $M=1.0$ 时导致阻力大幅增加高达 16.92\%。为了揭示减阻或增阻的机制，我们研究了通道内的应力分布以及分散颗粒对近壁相干结构的影响。我们发现减阻颗粒的一个显着特征是形成极长的簇，称为绳索。这些结构优先与低速条纹对齐，有助于其稳定和抑制爆发。尽管颗粒产生了额外的应力，但近壁相干结构的调制导致雷诺剪切应力的更大减少和近壁流的部分再层化。在$\mathrm{St}^+ = 6$的增阻颗粒的情况下，还观察到雷诺剪切应力的减少，但是，这种减少不足以克服导致阻力增加的额外颗粒应力。
We investigate the mechanisms by which inertial particles dispersed at semi-dilute conditions cause significant drag-reduction in a turbulent channel flow at $\mathrm{Re}_\tau = 180$. We consider a series of four-way coupled Euler-Lagrange simulations where particles having friction Stokes number $\mathrm{St}^+ = 6$ or 30 are introduced at progressively increasing mass loading from $M=0.2$ to 1.0. The simulations show that $\mathrm{St}^+ = 30$ particles cause large drag-reduction by up to 19.74\% at $M=1.0$, whereas $\mathrm{St}^+ = 6$ particles cause large drag increase by up to 16.92\% at $M=1.0$. To reveal the mechanisms underpinning drag-reduction or drag-increase, we investigate the stress distribution within the channel and the impact of the dispersed particles on the near-wall coherent structures. We find a distinctive feature of drag-reducing particles which consists in the formation of extremely long clusters, called ropes. These structures align preferentially with the low-speed streaks and contribute to their stabilization and suppression of bursting. Despite the additional stresses due to the particles, the modulation of the near-wall coherent structures leads to a greater reduction of Reynolds shear stresses and partial relaminarization of the near-wall flow. In the case of the drag-increasing particles with $\mathrm{St}^+ = 6$, a reduction in Reynolds shear stresses is also observed, however, this reduction is insufficient to overcome the additional particle stresses which leads to drag increase.