中文摘要：

通过高速摄像的方法观测了玻璃颗粒组成的准二维气态颗粒流的冷凝耗散过程,并和理想情况下的均匀耗散的颗粒流体理论作了比较,实验发现气态颗粒部分在耗散堆积过程中近似地满足高斯分布;从动能的结果来看,实际耗散过程和流体理论所预测的不同.实验发现冷凝分为两个阶段：当动能的贡献以气体颗粒为主时,发现颗粒以恒定的速度堆积,动能耗散主要由其中以气态分布的颗粒的沉积速率α,颗粒温度T和气态部分的平动速度νg决定;当气态颗粒数目趋向于0,能量耗散主要来自于密堆颗粒的表面层部分,耗散速度和表面层的“黏性”有关,堆积速率和能量耗散速度都会随着时间呈指数的衰减.

英文摘要：

Granular gas is a far from equilibrium discrete system.Due to intrinsic energy dissipation,the system will cool down when there is no energy input.In this paper we report our experimental study on this cooling process in a quasi 2-D granular gas system under gravity.By using fast video photography,particles excited by air flow from the bottom of the container were traced during cooling.The cooling process contains two regimes：One of them is when inelastic collisions of particles in the gas phase is dominant.In this regime condensation at the bottom will occur at a rate determined by three factors,namely the constant piling rate α,granular temperature T and vertical mass velocity v_g.The second regime is near the end of the cooling,the energy dissipation is mainly contributed from the surface area of the condensation region.This time the piling rate and the dissipation rate both show exponential dependence.