23.3.2 Particle Types

When you define a set of initial conditions (as described in Section  23.3.15), you will need to specify the type of particle. The particle types available to you depend on the range of physical models that you have defined.

• A massless particle is a discrete element that follows the flow and temperature of the continuous phase. As it has no mass, it has no associated physical properties, and no force is exerted on it. However, you can assign a User-Defined Law to be applied to the massless particle. The massless particle type is available with all ANSYS FLUENT models.

• An inert particle is a discrete phase element (particle, droplet, or bubble) that obeys the force balance ( this equation in the separate Theory Guide) and is subject to heating or cooling via Law 1 ( this section in the separate Theory Guide). The inert type is available for all ANSYS FLUENT models.

• A droplet particle is a liquid droplet in a continuous-phase gas flow that obeys the force balance ( this equation in the separate Theory Guide) and that experiences heating/cooling via Law 1 followed by vaporization and boiling via Laws 2 and 3 ( this section and this section in the separate Theory Guide). The droplet type is available when heat transfer is being modeled and at least two chemical species are active or the nonpremixed or partially premixed combustion model is active. You should use the ideal gas law to define the gas-phase density (in the Create/Edit Materials dialog box, as discussed in Section  8.3.5) when you select the droplet type.

• A combusting particle is a solid particle that obeys the force balance ( this equation in the separate Theory Guide) and experiences heating/cooling via Law 1 followed by devolatilization via Law 4 ( this section ), and a heterogeneous surface reaction via Law 5 ( this section in the separate Theory Guide). Finally, the nonvolatile portion of a combusting particle is subject to inert heating via Law 6. You can also include an evaporating material with the combusting particle by selecting the Wet Combustion option in the Set Injection Properties dialog box. This allows you to include a material that evaporates and boils via Laws 2 and 3 ( this section and this section in the separate Theory Guide) before devolatilization of the particle material begins. The combusting type is available when heat transfer is being modeled and at least three chemical species are active or the nonpremixed combustion model is active. You should use the ideal gas law to define the gas-phase density (in the Create/Edit Materials dialog box) when you select the combusting particle type.

• A multicomponent particle is, as the name implies, a mixture of droplet particles. These particles contain more than one component, which due to its complexity of assigning a whole particle to one process, have to be modeled by a law that integrates all processes of relevance in one equation. Law 7, the multicomponent law ( this section in the separate Theory Guide) is used for such systems. You should use the volume weighted mixing law to define the particle mixture density (in the Create/Edit Materials dialog box) when you select the particle-mixture material type.

Particle Type	Description	Laws Activated
Massless	-	-
Inert	inert/heating or cooling	1, 6
Droplet	heating/evaporation/boiling	1, 2, 3, 6
Combusting	heating; evolution of volatiles/swelling; heterogeneous surface reaction	1, 4, 5, 6
Multicomponent	multicomponent droplets/particles	7