Settling regimes of inertial particles in isotropic turbulence
Settling regimes of inertial particles in isotropic turbulence
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DOI：
10.1017/jfm.2014.602
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发表时间：
2014-01-01
影响因子：
3.7
通讯作者：
Warhaft, Z.
中科院分区：
文献类型：
--
作者：
Good, G. H.;Ireland, P. J.;Warhaft, Z.
我们调查的建立速度和均方根（r.m.s.）惯性粒子在各向同性湍流中的速度与重力，使用32个扬声器射流和直接数值模拟（DNS）的空气湍流中的水滴实验。粒子的惯性，重力和最小和最大的湍流涡旋的尺度的依赖性进行了研究。我们分离的机制，湍流沉降修改，并发现在实验中的大颗粒的沉降速度降低是由于非线性阻力效应。我们证明了使用DNS降低了线性阻力的稳定速度（例如，参见Nielsen，J. Sedim.汽油，第63卷，1993年，第100页。835-838）仅出现在通过设计消除由涡流优先扫掠的人工流中。重力和惯性都会减小粒子的均方根值。速度和下落的颗粒对垂直波动的响应比对水平波动的响应更大。Wang & Stock的模型（J. Atmos。科学，第50卷，1993年，pp. 1897-1913年）抓住了这些趋势。
We investigate the settling speeds and root mean square (r.m.s.) velocities of inertial particles in isotropic turbulence with gravity using experiments with water droplets in air turbulence from 32 loudspeaker jets and direct numerical simulations (DNS). The dependence on particle inertia, gravity and the scales of both the smallest and largest turbulent eddies is investigated. We isolate the mechanisms of turbulence settling modification and find that the reduced settling speeds of large particles in experiments are due to nonlinear drag effects. We demonstrate using DNS that reduced settling speeds with linear drag (e.g. see Nielsen, J. Sedim. Petrol., vol. 63, 1993, pp. 835-838) only arise in artificial flows that, by design, eliminate preferential sweeping by the eddies. Gravity and inertia both reduce the particle r.m.s. velocities and falling particles are more responsive to vertical than to horizontal fluctuations. The model by Wang & Stock (J. Atmos. Sci., vol. 50, 1993, pp. 1897-1913) captures these trends.