Numerical Studies Of Falling Droplet

Particle - fluid two - phase flow exsits in industry process widely, such as, spray granulation, flue gas dedust, spray and fluidized drying. Because of numerous influencing factors and complicated mechanism of these processes, macroscopical empirical equations are widely used to estimate the transport parameter; however, the microcosmic transport characteristics are ignored. Moreover, most of the empirical equations are only applicable in specific system and operation range. The process parameters acquired from them usually deviate from practice largely. So the consumption of material and energy is increased, environmental pollution is aggravated. Especially, the technical design of spray granulation process needs the deformation and motion rules of granule. Under the demand of clean production, conserving energy and reducing consumption, it is significant for optimizing the design parameter of chemical processes to describe the transport characteristics of gas-liquid two-phase flow more exactly.The aim of this research is to simulate the dynamics and transport characteristics of a single droplet moving in the gas flow by the method of computational fluid dynamics and provide fundamental data for the design of spray granulation process.The simulation of droplet shape shows that, the droplet undergoes a vibrating course and finally becomes a quasi sphere. The pressure field and flow field of stretching droplet and constracting droplet are acquired .The shape of quasi-steady droplet and deformation conditions are obtained. The deformation parameter of quasi-steady droplet and pressure field and flow field of deforming droplet are also acquired. It is found that the inlet gas velocity does not influence the deformation of droplet markedly.The change of interphase drag coefficients with Reynolds number and Ac number is acquired ,at 300) is obviously smaller than that of steady moving droplet (dUr/dt =0).The maximal and minimal relative difference between them are respectively 33.1% and 16.8%.By using Colburn analogy law, the change law of Nusselt number and Sherwood number in the course of droplet accelerating is obtained from the information of interphase momentum transport, at 30