Correlation of restitution coefficient : experiment and computational fluid dynamics simulation

Abstract

The computational fluid dynamics with the discrete element method (CFD-DEM) is widely used to predict the hydrodynamics profile of the multiphase flow of fluid-solid or fluidization process. The coefficient of restitution (COR) is one of the most important parameters which is vital for CFD-DEM simulation. This parameter denotes the ratio of the relative velocity after the collision to the relative velocity before the collision. The appropriate value of the coefficient of restitution must receive attention to obtain the realistic collision and hydrodynamics profile. However, this parameter is still selected by trial and error in traditional CFD-DEM due to the lacking of the standard reference for this collision parameter. In this study, the significance of COR in multiphase flow systems was investigated. In addition, the effect of solid materials, impact velocity and temperature on the COR were investigated by the free-fall experiment. The collision behaviour was captured by a high-speed camera and the image analysis was employed to interpret the result. The new correlation was then proposed in terms of impact velocity, elastic modulus, Poisson's ratio, and temperature. The CFD-DEM simulations using a constant value of COR were compared with the CFD-DEM simulation using the correlation of the coefficient of restitution in the various systems such as three interconnected fluidized bed reactors, spouted bed reactor, internal circulating fluidized bed (ICFB) and rotating drum. The obtained results showed the importance of the correlation of dynamics COR and the guideline for further using this collision parameter.