论文标题
由于碰撞和湍流内部凝结引起的粒子的径向分布功能的急剧消耗
Sharp depletion of radial distribution function of particles due to collision and coagulation inside turbulent flow
论文作者
论文摘要
我们执行直接的数值模拟（DNS），以研究经受湍流中碰撞凝集（即碰撞粒子总是凝结（凝聚）为大的小型，重，单分散的颗粒的聚类。我们发现，碰撞凝集会导致粒子的径向分布函数（RDF）在粒子分离距离$ r $接近粒子直径$ d $的情况下强烈减小。但是，RDF不会无限期地降低，而是在$ r \的限制中接近$ r \ d $的有限值。我们研究了该“耗尽区”的特征与粒子的数量（ST），粒子直径和湍流的雷诺数有关。碰撞引起的调制因子$γ_{C} $定义为表示由于碰撞凝集而导致的RDF耗竭程度。在$γ_c（r）$是准power-law的区域中，相应的幂律指数$ \ tilde {c} _1 $仅弱取决于$ st $。相对于$ st $，$ \ tilde {c} _1 $的总体趋势与经典的幂律指数$ c_ {1} $出现在非填料粒子的rdf中的总体趋势，即指数在小$ st $中增加，$ st $，大约$ st \ st \ s preep \ st \ of 0.7 $ and降低。对于$ r \ to d $的限制值$γ_c$的限制值也观察到了相同的定性趋势。对耗尽区中完整RDF的Stokes数量趋势进行了互补调查。 RDF的斜率对于$ st \ ll1 $而言似乎是恒定的，但是当$ st $变大时，正在发生变化。发现RDF开始降低的位置被认为是$ st $依赖的。耗尽区对雷诺的流不敏感，而不同的$re_λ$重叠的$γ_c$。随着粒子直径$ d $的变化，RDF的减少发生在相应移动的尺度上，并且始终起价为2.4d-3d $。 $γ_C（R）$的形状与$ D $中的变化无关。
We perform direct numerical simulation (DNS) to study the clustering of small, heavy, monodisperse particles subject to collision-coagulation in turbulent flow (i.e., colliding particles always coagulate (coalesce) into large ones). We find that collision-coagulation causes the radial distribution function (RDF) of the particles to decrease strongly at particle separation distances $r$ close to the particle diameter $d$. However, the RDF do not decrease indefinitely but approach a finite value in the limit of $r\to d$. We study how the characteristics of this "depletion zone" relate to the particle Stokes number (St), particle diameter, and the Reynolds number of the turbulent flow. A collision-induced modulation factor $γ_{c}$ is defined to represent the degree of RDF depletion due to collisions-coagulation. In the region where $γ_c(r)$ is a quasi-power-law, the corresponding power-law exponent $\tilde{c}_1$ only depends weakly on $St$. The overall trend of $\tilde{c}_1$ with respect to $St$ is similar to that of the classical power-law exponent $c_{1}$ appearing in the RDF of non-colliding particles, i.e., the exponent increase at small $St$, peak around $St \approx 0.7$, and decrease thereafter. The same qualitative trend is also observed for the limiting values of $γ_c$ at $r\to d$. A complementary investigation on the Stokes number trend of the full RDF in the depletion zone is conducted. The slope of RDF appears constant for $St\ll1$ but is changing when $St$ is getting large. The position where the RDF starts to decrease is found to be $St$-dependent. The depletion zone is insensitive to the flow Reynolds number and $γ_c$ of different $Re_λ$ overlap. With changing particle diameter $d$, the reduction of RDF occurs at scales that shift accordingly and always starts at around $2.4d-3d$. The shape of $γ_c(r)$ is independent of changes in $d$.
