Mpemba effect in an anisotropically driven granular gas

Mpemba effect in anisotropically driven inelastic Maxwell gases

Through an exact analysis, we show the existence of Mpemba effect in an anisotropically driven inelastic Maxwell gas, a simplified model for granular gases, in two dimensions. Mpemba effect refers to the couterintuitive phenomenon of a hotter system relaxing to the steady state faster than a cooler system, when both are quenched to the same lower temperature. The Mpemba effect has been illustrated in earlier studies on isotropically driven granular gases, but its existence requires non-stationary initial states, limiting experimental realisation. In this paper, we demonstrate the existence of …

Mpemba effect in driven granular gases: role of distance measures

Mpemba effect refers to the counterintuitive effect where a system which is initially further from the final steady state equilibrates faster than an identical system that is initially closer. The closeness to the final state is defined in terms of a distance measure. For driven granular systems, the Mpemba effect has been illustrated in terms of an ad-hoc measure of mean kinetic energy as the distance function. In this paper, by studying four different distance measures based on the mean kinetic energies as well as velocity distribution, we show that the Mpemba effect depends on the definitio…

Mpemba effect in driven granular Maxwell gases

Mpemba effect refers to the counterintuitive result that, when quenched to a low temperature, a system at higher temperature may equilibrate faster than one at intermediate temperatures. This effect has recently been demonstrated in driven granular gases, both for smooth as well as rough hard-sphere systems based on a perturbative analysis. In this paper, we consider the inelastic driven Maxwell gas, a simplified model for a granular gas, where the rate of collision is assumed to be independent of the relative velocity. Through an exact analysis, we determine the conditions under which a Mpemb…

When the Hotter Cools More Quickly: Mpemba Effect in Granular Fluids

Under certain conditions, two samples of fluid at different initial temperatures present a counterintuitive behavior known as the Mpemba effect: it is the hotter system that cools sooner. Here, we show that the Mpemba effect is present in granular fluids, both in uniformly heated and in freely cooling systems. In both cases, the system remains homogeneous, and no phase transition is present. Analytical quantitative predictions are given for how differently the system must be initially prepared to observe the Mpemba effect, the theoretical predictions being confirmed by both molecular dynamics …

sheared granular gas中速度依赖性恢复系数的Mpemba效应

Mpemba effect in a sheared granular gas with velocity-dependent restitution

研究了速度依赖性恢复系数的稀疏剪切颗粒气体中的Mpemba效应，通过基于Grad的矩方法的动能理论分析了剪切速率突然变化后的弛豫动力学，发现初始温度较高但起始状态为各向同性的系统比起始处于剪切稳态的系统弛豫更快，展示了温度演变中的明显Mpemba效应，并进一步展示了粘度Mpemba效应，通过弛豫曲线的交叉现象，多交叉现象由恢复系数的速度依赖性引入的额外内在时间尺度导致，为驱动颗粒气体中的多重Mpemba效应提供了最小的动能机制。

Mpemba-like effect in driven binary mixtures

The Mpemba effect occurs when two samples at different initial temperatures evolve in such a way that the temperatures cross each other during the relaxation towards equilibrium. In this paper we show the emergence of a Mpemba-like effect in a molecular binary mixture in contact with a thermal reservoir (bath). The interaction between the gaseous particles of the mixture and the thermal reservoir is modeled via a viscous drag force plus a stochastic Langevin-like term. The presence of the external bath couples the time evolution of the total and partial temperatures of each component allowing …