Division of Physical Chemistry, Lund University, Box 124, S-221 00 Lund, Sweden.
Soft Matter. 2019 Oct 9;15(39):7747-7756. doi: 10.1039/c9sm00774a.
Collective behaviour in suspensions of microswimmers is often dominated by the impact of long-ranged hydrodynamic interactions. These phenomena include active turbulence, where suspensions of pusher bacteria at sufficient densities exhibit large-scale, chaotic flows. To study this collective phenomenon, we use large-scale (up to N = 3 × 106) particle-resolved lattice Boltzmann simulations of model microswimmers described by extended stresslets. Such system sizes enable us to obtain quantitative information about both the transition to active turbulence and characteristic features of the turbulent state itself. In the dilute limit, we test analytical predictions for a number of static and dynamic properties against our simulation results. For higher swimmer densities, where swimmer-swimmer interactions become significant, we numerically show that the length- and timescales of the turbulent flows increase steeply near the predicted finite-system transition density.
微泳者悬浮液中的集体行为通常受长程水动力相互作用的影响。这些现象包括活性湍流，在足够密度的推式细菌悬浮液中会出现大规模混沌流动。为了研究这种集体现象，我们使用了由扩展应力张量描述的模型微泳者的大规模（高达 N = 3 × 106）颗粒分辨格子玻尔兹曼模拟。这种系统大小使我们能够获得关于活性湍流转变和湍流状态本身特征的定量信息。在稀溶液极限下，我们根据模拟结果对一些静态和动态特性的分析预测进行了测试。对于泳者密度更高的情况，泳者-泳者相互作用变得显著，我们数值显示，在预测的有限系统转变密度附近，湍流流动的长度和时间尺度急剧增加。
