An Immersed Boundary Method for flows with evaporating droplets

Abstract

We present a new Immersed Boundary Method (IBM) for the interface resolved simulation of spherical droplet evaporation in gas flow. The method is based on the direct numerical simulation of the coupled momentum, energy and species transport in the gas phase, while the exchange of these quantities with the liquid phase is handled through global mass, energy and momentum balances for each droplet. This approach, applicable in the limit of small spherical droplets, allows for accurate and efficient phase coupling without direct solution of the liquid phase fields, thus saving computational cost. We provide validation results, showing that all the relevant physical phenomena and their interactions are correctly captured, both for laminar and turbulent gas flow. Test cases include fixed rate and free evaporation of a static droplet, displacement of a droplet by Stefan flow, and evaporation of a hydrocarbon droplet in homogeneous isotropic turbulence. The latter case is validated against experimental data, showing the feasibility of the method towards the treatment of conditions representative of real life spray fuel applications.