Engineering Mechanics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore 560064, India.
Multi-Scale Mechanics, MESA+, University of Twente, Enschede, Netherlands.
Phys Rev E. 2018 Jan;97(1-1):012911. doi: 10.1103/PhysRevE.97.012911.
We report patterns consisting of coexistence of synchronous and asynchronous states [for example, a granular gas co-existing with (i) bouncing bed, (ii) undulatory subharmonic waves, and (iii) Leidenfrost-like states] in experiments on vertically vibrated binary granular mixtures in a Hele-Shaw cell. Most experiments have been carried out with equimolar binary mixtures of glass and steel balls of same diameter by varying the total layer height (F) for a range of shaking acceleration (Γ). All patterns as well as the related phase diagram in the (Γ,F) plane have been reproduced via molecular dynamics simulations of the same system. The segregation of heavier and lighter particles along the horizontal direction is shown to be the progenitor of such phase-coexisting patterns as confirmed in both experiment and simulation. At strong shaking we uncover a partial convection state in which a pair of convection rolls is found to coexist with a Leidenfrost-like state. The crucial role of the relative number density of two species on controlling the buoyancy-driven granular convection is demonstrated. The onset of horizontal segregation can be explained in terms of an anisotropic diffusion tensor.
我们报告了在 Hele-Shaw 细胞中垂直振动二元颗粒混合物实验中存在同步和异步状态共存的模式[例如，颗粒气体与（i）反弹床、（ii）波动次谐波和（iii）莱顿弗罗斯特状态共存]。大多数实验都是通过改变总层高度（F）和振动加速度（Γ）范围来进行等摩尔二元玻璃和钢球混合物的实验。通过对相同系统的分子动力学模拟，重现了所有模式以及（Γ，F）平面中的相关相图。实验和模拟都证实了，较重和较轻颗粒沿水平方向的分离是这种相共存模式的先驱。在强烈的振动下，我们发现了一种部分对流状态，其中一对对流卷与莱顿弗罗斯特状态共存。证明了两种物质的相对数密度对控制浮力驱动的颗粒对流的关键作用。可以根据各向异性扩散张量来解释水平分离的开始。
