ID 376

Validating a Numerical Framework for Resolved Simulations of Vaporizing Droplets

 

Abstract:

Standard practice when simulating spray combustion is to represent the spray as a collection of droplets which vaporize and subsequently combust. Empirical models are used to approximate the process of droplet vaporization, however, these models were largely developed for isolated droplets in uniform flow. These models also typically neglect the influence of droplet deformation and internal heat transfer on vaporization. The impact of these assumptions on the accuracy of model predictions still needs to be evaluated. One natural way to study this, is the comparison of data from direct numerical simulations with that of spray models. The current work demonstrates a direct numerical simulation framework for simulating vaporizing liquid-gas flows with a focus towards spray combustion. The framework builds from first principles as the governing equations are developed directly from the principles of conservation of mass, momentum, and energy without the introduction of empirical models. A VOF method is used for interface transport, which is coupled with a robust momentum solver for high density ratio flows. Scalar transport is performed using BQUICK for advection and an unconditionally stable monotone scheme for diffusion. Thermodynamic equilibrium at the interface is handled using the Clausius-Clapeyron relation. This initial study focuses on validating the framework against known solutions for single droplet vaporization in simple flows. Numerical simulations in three dimensions are compared to analytical solutions and the accuracy of the framework is verified. Comparisons with experimental correlations for vaporizing droplets in uniform flow indicate a good match between numerical and experimental results.