On the scale diffusivity of a 2-D liquid atomization process analysis

Liquid atomization processes are mechanisms during which the shape of the liquid system continuously varies. This can be evidenced and quantified by measuring the surface-based scale distribution that continuously evolves from the nozzle exit down to the spray region. The description of this evolution is associated to a time- and scale-dependent fractal dimension and can be modeled by the scale entropy diffusion model developed to treat the evolution of turbulent interface. This model introduces the scale diffusivity parameter that characterizes the diffusion of scale entropy through scale space. In a previous investigation, scale diffusivity was measured from the 2-D analysis of an atomization process. The present paper is an extension of that investigation. First, the experiment is completed to address the question of the aerodynamic force effects on the atomization process. Second, using the present experimental conclusions, an analysis of the scale diffusivity is conducted and a mathematical expression for this characteristic is established. It is similar to the one estimated in turbulence, the Reynolds number in turbulence being replaced by a Weber number in atomization. Furthermore, the diffusivity expression returns a critical Weber number which is found to be a characteristic feature of the atomizer. The results presented in this paper confirm the relevance of the scale entropy diffusion model to apprehend and characterize liquid atomization processes. (C) 2011 Elsevier B.V. All rights reserved.