Statistical mechanical description and modelling of turbulent collision of inertial particles
Statistical mechanical description and modelling of turbulent collision of inertial particles
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DOI：
10.1017/s0022112000008661
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发表时间：
1998-11
影响因子：
3.7
通讯作者：
Lian-Ping Wang;A. Wexler;Yong Zhou
中科院分区：
文献类型：
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作者：
Lian-Ping Wang;A. Wexler;Yong Zhou
单分散固体颗粒在紊流气体中的碰撞率受流动中各种运动尺度的影响。近年来的研究表明，大尺度高能涡旋是影响碰撞粒子相对速度的主要因素（湍流输运效应），而小尺度耗散涡旋则通过诱导粒子局部不均匀分布（积累效应）显著提高碰撞率。当质点惯性响应时间τp与流动积分时间尺度相当时，紊流输运效应最为显著；当质点惯性响应时间τp与流动Kolmogorov时间相当时，累积效应最为显著。我们通过直接数值模拟分别研究了这两种贡献。用独立于平均碰撞率计算的数值方法对这两种效应进行了量化。这不仅有助于研究碰撞核的统计描述，而且有助于研究两种物理效应的相对贡献和建模。在几个雷诺数下进行了模拟，以提出累积效应的模型。数据表明，累积效应与流动泰勒微尺度雷诺数Rλ呈线性关系，而充分发展的湍流理论表明，湍流输运效应的最大水平与R1/2λ呈线性关系。最后，建立了一个综合模型来预测任意流雷诺数和粒子惯性下的碰撞率。
The collision rate of monodisperse solid particles in a turbulent gas is governed by a wide range of scales of motion in the flow. Recent studies have shown that large-scale energetic eddies are the dominant factor contributing to the relative velocity between two colliding particles (the turbulent transport effect), whereas small-scale dissipative eddies can enhance the collision rate significantly by inducing local non-uniform particle distribution (the accumulation effect). The turbulent transport effect is most noticeable when the particle inertial response time τp is of the order of the flow integral timescale and the accumulation effect is most pronounced when τp is comparable to the flow Kolmogorov time. We study these two contributions separately through direct numerical simulations. The two effects are quantified carefully with a numerical procedure that is independent of the computation of average collision rate. This facilitates the study of not only the statistical description of the collision kernel, but also the relative contributions and modelling of the two physical effects. Simulations at several flow Reynolds numbers were performed to suggest a model for the accumulation effect. The data show that the accumulation effect scales linearly with flow Taylor microscale Reynolds number Rλ, while the theory for fully developed turbulence indicates that the maximum level of the turbulent transport effect scales with R1/2λ. Finally, an integrated model has been developed to predict the collision rate at arbitrary flow Reynolds numbers and particle inertia.