23.1 Introduction

In addition to solving transport equations for the continuous phase, ANSYS FLUENT allows you to simulate a discrete second phase in a Lagrangian frame of reference. This second phase consists of spherical particles (which may be taken to represent droplets or bubbles) dispersed in the continuous phase. ANSYS FLUENT computes the trajectories of these discrete phase entities, as well as heat and mass transfer to/from them. The coupling between the phases and its impact on both the discrete phase trajectories and the continuous phase flow can be included.

ANSYS FLUENT provides the following discrete phase modeling options:

• calculation of the discrete phase trajectory using a Lagrangian formulation that includes the discrete phase inertia, hydrodynamic drag, and the force of gravity, for both steady and unsteady flows

• prediction of the effects of turbulence on the dispersion of particles due to turbulent eddies present in the continuous phase

• heating/cooling of the discrete phase

• vaporization and boiling of liquid droplets

• combusting particles, including volatile evolution and char combustion to simulate coal combustion

• optional coupling of the continuous phase flow field prediction to the discrete phase calculations

• droplet breakup and coalescence

• consideration of particle/particle collisions and voidage of discrete phase

These modeling capabilities allow ANSYS FLUENT to simulate a wide range of discrete phase problems including particle separation and classification, spray drying, aerosol dispersion, bubble stirring of liquids, liquid fuel combustion, and coal combustion. The physical equations used for these discrete phase calculations are described in this section - this section in the separate Theory Guide , and instructions for setup, solution, and postprocessing are provided in Sections  23.2- 23.7.