23.2.5 Physical Models for the Discrete Phase Model

This section provides instructions for using the optional discrete phase models available in ANSYS FLUENT. All of them can be enabled in the Physical Models tab of the Discrete Phase Model dialog box (Figure  23.2.2).

Models Discrete Phase Edit...

Figure 23.2.2: The Discrete Phase Model Dialog Box and the Physical Models

Including Radiation Heat Transfer Effects on the Particles

If you want to include the effect of radiation heat transfer to the particles ( this equation in the separate Theory Guide), you must enable the Particle Radiation Interaction option under the Physical Models tab, in the Discrete Phase Model dialog box (Figure  23.2.2). You will also need to define additional properties for the particle materials (emissivity and scattering factor), as described in Section  23.5.2. This option is available only when the P-1 or discrete ordinates radiation model is used.

Including Thermophoretic Force Effects on the Particles

If you want to include the effect of the thermophoretic force on the particle trajectories ( this equation in the separate Theory Guide), enable the Thermophoretic Force option under the Physical Models tab, in the Discrete Phase Model dialog box. You will also need to define the thermophoretic coefficient for the particle material, as described in Section  23.5.2.

Including Brownian Motion Effects on the Particles

For sub-micron particles in laminar flow, you may want to include the effects of Brownian motion (described in this section in the separate Theory Guide) on the particle trajectories. To do so, enable the Brownian Motion option under the Physical Models tab. When Brownian motion effects are included, it is recommended that you also select the Stokes-Cunningham drag law in the Drag Law drop-down list under Drag Parameters, and specify the Cunningham Correction ( $C_c$ in this equation in the separate Theory Guide).

Including Saffman Lift Force Effects on the Particles

For sub-micron particles, you can also model the lift due to shear (the Saffman lift force, described in this section in the separate Theory Guide) in the particle trajectory. To do this, enable the Saffman Lift Force option under the Physical Models tab, in the Discrete Phase Model dialog box.

Monitoring Erosion/Accretion of Particles at Walls

Particle erosion and accretion rates can be monitored at wall boundaries. These rate calculations can be enabled in the Discrete Phase Model dialog box when the discrete phase is coupled with the continuous phase (i.e., when Interaction with Continuous Phase is selected). Enabling the Erosion/Accretion option will cause the erosion and accretion rates to be calculated at wall boundary faces when particle tracks are updated. You will also need to set the Impact Angle Function ( $f(\alpha)$ in this equation in the separate Theory Guide), Diameter Function ( $C(d_p)$ in this equation ), and Velocity Exponent Function ( $b(v)$ in this equation ) in the Wall boundary conditions dialog box for each wall zone (as described in Section  23.4.1).

Including the Effect of Particles on Turbulent Quantities

Particles can damp or produce turbulent eddies [ 53]. In ANSYS FLUENT, the work done by the turbulent eddies on the particles is subtracted from the turbulent kinetic energy using the formulation described in [ 21] and [ 6].

If you want to consider these effects in the chosen turbulence model, you can enable this using Two-Way Turbulence Coupling, under the Physical Models tab.