非阻塞性颗粒阻尼器内部的颗粒莱顿弗罗斯特现象

Granular Leidenfrost Effect in a Non-Obstructive Particle Damper

为了更好地揭示非阻塞性颗粒阻尼器(NOPD)的减振机理,基于振动颗粒物质的流变特性,研究了NOPD的阻尼效果和其内部阻尼颗粒运动形态之间的关系,通过实验确定了NOPD发挥最优阻尼效果时其内部颗粒的运动形态,使用离散元仿真分析了最优阻尼颗粒的耗散特性。研究表明:实验设计参数下的NOPD发挥最优阻尼效果时(激振强度Γ=3.3,f=21 Hz),其内部出现稳定的颗粒莱顿弗罗斯特现象;这种状态下的NOPD最优阻尼效果主要来自两方面,一方面是主系统的部分振动动能通过颗粒间或颗粒与容器壁间发生的碰撞和摩擦以热能的形式散发,是颗粒对主系统振动能量的直接耗散;另一方面是主系统的部分振动动能转化为浮动颗粒的势能以维持颗粒莱顿弗罗斯特效应的稳定,这可看作是颗粒对主系统振动能量的间接耗散。

To reveal the optimal damping mechanism of non-obstructive particle dampers （NOPDs）, the relationship between the damping performance of NOPDs and the motion mode of damping particles in NOPDs is deduced following the rheological behavior of vibrated granular particles. The motion mode of the damping particles giving the optimal damping effect is determined via cantilever system experiments, and the dissipation properties of the damping particles giving the optimal effect are analyzed numerically by the discrete element method （DEM）. It is found that when the NOPD gives the optimal damping effect （P=3.3, f=21 Hz）, the steady granular Leidenfrost phenomenon occurs. In this circumstance, the optimal damping performance of the NOPD results mainly from two aspects, i.e. the direct energy dissipation caused by collisions and frictions between particle-particle and particle-wall, and the energy conversion from the input vibration energy to the potential energy of levitated granular particles, which can be regarded as indirect energy dissipation.