论文标题
超音速湍流中惯性颗粒的凝结
Coagulation of inertial particles in supersonic turbulence
论文作者
论文摘要
超音速湍流驱动的凝血主要是一个天体物理问题，因为地球上的凝结过程通常与低马赫数下的不可压缩的流体流有关，而星际介质（ISM）中的尘埃聚集是相反方案的一个例子。我们使用高分辨率的直接和冲击的数值模拟研究了可压缩湍流中惯性颗粒的凝结，并具有从几乎不可压缩到中度超音速的广泛的马赫数。粒子动力学通过代表性粒子进行模拟，并探索了由于马赫数增加而对大小分布和凝血率的影响。我们表明，粒度分布的时间演变主要取决于可压缩性（MACH数）。我们发现，平均凝血核$ \ langle c_ {ij} \ rangle $与平均马赫数$ \ Mathcal {m} _ {\ rm rm rms} $线性缩放，乘以colliding粒子的组合大小，即$ \ langle c_i + sim + sim + sim a_j）^3 \ rangle \，\ Mathcal {m} _ {\ rm rms}τ_η^{ - 1} $，这与分析估计值的期望在质量上是一致的。定量校正$ \ langle c_ {ij} \ rangle \ sim \ langle（a_i + a_j）^3 \ rangle（v _ {\ rm p，rm p，rms}/c _ {\ rm s}）我们认为，凝血率$ \ langle r_c \ rangle $也通过可压缩性诱导的颗粒压实增强。
Coagulation driven by supersonic turbulence is primarily an astrophysical problem because coagulation processes on Earth are normally associated with incompressible fluid flows at low Mach numbers, while dust aggregation in the interstellar medium (ISM) for instance is an example of the opposite regime. We study coagulation of inertial particles in compressible turbulence using high-resolution direct and shock-capturing numerical simulations with a wide range of Mach numbers from nearly incompressible to moderately supersonic. The particle dynamics is simulated by representative particles and the effects on the size distribution and coagulation rate due to increasing Mach number is explored. We show that the time evolution of particle size distribution mainly depends on the compressibility (Mach number). We find that the average coagulation kernel $\langle C_{ij}\rangle$ scales linearly with the average Mach number $\mathcal{M}_{\rm rms}$ multiplied by the combined size of the colliding particles, that is, $\langle C_{ij}\rangle \sim \langle (a_i + a_j)^3\rangle\, \mathcal{M}_{\rm rms}τ_η^{-1}$, which is qualitatively consistent with expectations from analytical estimates. A quantitative correction $\langle C_{ij}\rangle \sim \langle(a_i + a_j)^3\rangle(v_{\rm p,rms}/c_{\rm s})τ_η^{-1}$ is proposed and can serve as a benchmark for future studies. We argue that the coagulation rate $\langle R_c\rangle$ is also enhanced by compressibility-induced compaction of particles.
