Select ishii to use the fluid-fluid drag function described by Equation 14–516 in the Theory Guide. This option is available when the boiling model is enabled.

Select schiller-naumann to use the fluid-fluid drag function described by Equation 14–215 in the Theory Guide. The Schiller and Naumann model is the default method, and it is acceptable for general use in all fluid-fluid multiphase calculations. When using the homogeneous population balance models you can also select schiller-naumann-pb in which case the interfacial area will be calculated directly from the population balance variables.

Select morsi-alexander to use the fluid-fluid drag function described by Equation 14–219 in the Theory Guide. The Morsi and Alexander model is the most complete, adjusting the function definition frequently over a large range of Reynolds numbers, but calculations with this model may be less stable than with the other models.

Select symmetric to use the fluid-fluid drag function described by Equation 14–225 in the Theory Guide. The symmetric model is recommended for flows in which the secondary (dispersed) phase in one region of the domain becomes the primary (continuous) phase in another. For example, if air is injected into the bottom of a container filled halfway with water, the air is the dispersed phase in the bottom half of the container; in the top half of the container, the air is the continuous phase. The symmetric drag law is the default method for the Multi-Fluid VOF Model, which is available with Eulerian multiphase model.

Select grace to use the fluid-fluid drag function described by Equation 14–230 in the Theory Guide. The Grace model is recommended for gas-liquid flows in which the bubbles can have a range of shapes such as spherical, elliptical, or cap.

In the Grace Swarm Correction dialog box that opens automatically when you first select this model, you can specify Coefficient: Cexp ( in Equation 14–230 in the Fluent Theory Guide) as constant or user-defined. Depending on the flow regime and the bubble size, the following values should be used:

See Grace et al. Model in the Fluent Theory Guide for more information.

Select tomiyama to use the fluid-fluid drag function described by Equation 14–236 in the Theory Guide. Like the Grace model, the Tomiyama model is recommended for gas-liquid flows in which the bubbles can have a range of shapes such as spherical, elliptical, or cap.

Select ishii-zuber to use the fluid-fluid drag function described in Ishii-Zuber Drag Model in the Fluent Theory Guide. The model automatically accounts for swarms of bubbles moving together in high gas volume fractions. Like the Grace and Tomiyama drag models, the Ishii-Zuber drag law is recommended for gas-liquid flows in which bubbles may have a range of shapes such as spherical, elliptical, or cap.

Select anisotropic to use the fluid-fluid drag function described in Multi-Fluid VOF Model in the Theory Guide. The anisotropic drag law is recommended for free surface modeling. It is based on higher drag in the normal direction to the interface and lower drag in the tangential direction to the interface.

Select universal-drag for bubble-liquid and/or droplet-gas flow when the characteristic length of the flow domain is much greater than the averaged size of the droplets/bubbles. It is suitable for flows in which the bubbles/droplets may have a range of shapes. The universal drag law is described using Equation 14–247 in the Theory Guide. When universal-drag is selected, you will need to set a value for the Surface Tension Coefficient. This value will apply to the primary phase and the secondary phase.

Select wen-yu to use the fluid-solid drag function described by Equation 14–282 in the Theory Guide. The Wen and Yu model is applicable for dilute phase flows, in which the total secondary phase volume fraction is significantly lower than that of the primary phase. When using the homogeneous population balance models you can also select wen-yu-pb in which case the interfacial area will be calculated directly from the population balance variables.

Select gidaspow to use the fluid-solid drag function described by Equation 14–284 in the Theory Guide. The Gidaspow model is recommended for dense fluidized beds.

Select syamlal-obrien to use the fluid-solid drag function described by Equation 14–269 in the Theory Guide. The Syamlal-O’Brien model is recommended for use in conjunction with the Syamlal-O’Brien model for granular viscosity.

Select syamlal-obrien-para to use the parameterized formulation of the Syamlal-O’Brien model described by Equation 14–279 in the Theory Guide. This model addresses under/over-prediction of bed expansion that can arise with syamlal-obrien. When you first select this model, you will be presented with the Syamlal Obrien Model dialog box.

Figure 26.58: Syamlal Obrien Model Dialog Box

There are two inputs:

Once you have input these values, click Validate/Apply to compute the coefficients c1 and d1 used in Equation 14–280 in the Fluent Theory Guide. A message will also be printed to the text user interface summarizing the fluid and flow properties used in the computation and the resulting values. You should check that these property values are consistent with the properties set elsewhere.

Select syamlal-obrien-symmetric to use the solid-solid drag function described by Equation 14–292 in the Theory Guide. The symmetric Syamlal-O’Brien model is appropriate for a pair of solid phases.

Select huilin-gidaspow to use the fluid-solid drag function described by Equation 14–286 in the Theory Guide. This option provides a better blending function for the Gidaspow model when moving from the dense packing limit to the dilute flow limit.

Select gibilaro to use the fluid-solid drag function described by Equation 14–288 in the Theory Guide. This option is used for circulating fluidized beds.

Select emms drag model for gas-solid flow where heterogeneous meso-scale flow structures are dominant and such structures cannot be adequately resolved using fine grid resolution in commercial scale fluidized bed simulation. The fluid-solid drag function is described by Equation 14–290 in the Fluent Theory Guide. The EMMS drag model is applicable only to monodispersed two-phase granular flows without axisymmetric swirl.

Note that this option is not available for non-granular flows.

Select filtered drag model for gas-solid flow cases with coarse meshes. The fluid-solid drag function is computed by Equation 14–290 and Equation 14–488 in the Fluent Theory Guide. Once you click Apply, the following settings are automatically applied to the granular phase properties in the Phases tab:

For information about how these parameters are calculated, see The Filtered Two-Fluid Model in the Fluent Theory Guide.

In case of convergence issues, you can first run the case with homogeneous drag before switching to the filtered model.

The filtered drag model is applicable only to monodispersed two-phase flows involving gas and granular phases without axisymmetric swirl and is well suited for predicting flow hydrodynamics in fluidized beds.

Select constant to specify a constant value for the drag function, and then specify the value in the text field.

Select user-defined to use a user-defined function for the drag function (see the Fluent Customization Manual for details).

If you want to temporarily ignore the interaction between two phases, select none.

Select none (the default) to ignore the effect of lift forces.

Select constant to specify a constant lift coefficient, and then specify the value in the text field.

Select moraga to use the Moraga lift model (Moraga Lift Force Model in the Theory Guide). The Moraga lift model is applicable to spherical solid particles, drops, and bubbles.

Select saffman-mei to use the Saffman-Mei lift model (Saffman-Mei Lift Force Model in the Theory Guide). The Saffman-Mei lift model is applicable to spherical solid particles, and to drops and bubbles that are not significantly distorted.

Select legendre-magnaudet to use the Legendre—Magnaudet lift model (Legendre-Magnaudet Lift Force Model in the Theory Guide). The Legendre-Magnaudet model is applicable to small diameter spherical fluid particles, though it can be applied to non-distorted liquid drops and bubbles. It accounts for momentum transfer between the flow around the particle and the inner recirculation flow inside the fluid particle caused by fluid friction/stresses at the fluid interface.

Select tomiyama to use the Tomiyama lift model (Tomiyama Lift Force Model in the Theory Guide). The Tomiyama model is applicable to larger-scale deformable bubbles in the ellipsoidal and spherical cap regimes. Its main feature is the prediction of the cross-over point in bubble size at which particle distortion causes a reversal in the sign of the lift force.

Select hessenkemper-et-al to use the Hessenkemper et al. lift model (Hessenkemper et al. Lift Force Model in the Fluent Theory Guide). The Hessenkemper et al. lift model is applicable to small diameter spherical fluid particles and large-scale deformable fluid particles in the ellipsoidal and spherical cap regimes.

Select user-defined to use a user-defined function for the lift coefficient (see the Fluent Customization Manual for details).

Select none (the default) to ignore the effect of wall lubrication forces.

Select lubchenko to use the Lubchenko model (Lubchenko Model in the Fluent Theory Guide). This model is available only either burns-et-al or lopez-de-bertodano is selected for the Turbulent Dispersion. If lift is considered in your simulation, you should use the shaver-podowski lift correction.

Select antal-et-al to use the Antal et al. model (Antal et al. Model in the Theory Guide). You can edit the model parameters in the Antal Model dialog box (Figure 26.59: Antal et al. Model Dialog Box).

Figure 26.59: Antal et al. Model Dialog Box

The following model parameters are available:

Select tomiyama to use the Tomiyama model (Tomiyama Model in the Theory Guide). This model is only applicable for pipe geometries. You can enter the Hydraulic Diameter for your geometry in the Tomiyama Model dialog box (Figure 26.60: Tomiyama Model Dialog Box).

Figure 26.60: Tomiyama Model Dialog Box

The following model parameters are available:

Select frank to use the Frank et al. model (Frank Model in the Theory Guide). You can edit the model parameters in the Frank Model dialog box (Figure 26.61: Frank Model Dialog Box).

Figure 26.61: Frank Model Dialog Box

The following model parameters are available:

Select hosakawa to use the Hosokawa model (Hosokawa Model in the Theory Guide). You can edit the model parameters in the Hosokawa Model dialog box (Figure 26.62: Hosokawa Model Dialog Box).

Figure 26.62: Hosokawa Model Dialog Box

The following model parameters are available:

Select user-defined to use a user-defined function for the wall lubrication coefficient (see DEFINE_EXCHANGE_PROPERTY in the Fluent Customization Manual for details).

Select none (the default) to ignore the effects of turbulent dispersion.

Select lopez-de-bertodano to use the Lopez de Bertodano model (Lopez de Bertodano Model in the Theory Guide). You can edit the model parameters in the Lopez de Bertodano Model dialog box (Figure 26.63: Lopez de Bertodano Model Dialog Box).

Figure 26.63: Lopez de Bertodano Model Dialog Box

The following model parameters are available:

Select simonin to use the Simonin model (Simonin Model in the Theory Guide).

You can specify the model parameters in the Simonin Model dialog box (Figure 26.64: Simonin Model Dialog Box).

Figure 26.64: Simonin Model Dialog Box

The following model parameters are available:

Select burns-et-al to use the Burns et al. model (Burns et al. Model in the Theory Guide). You can edit the model parameters in the Burns-et-al Model dialog box (Figure 26.65: Burns et al. Model Dialog Box).

Figure 26.65: Burns et al. Model Dialog Box

The following model parameters are available:

Select diffusion-in-vof to use the Diffusion in VOF model (Diffusion in VOF Model in the Theory Guide). You can edit the model parameters in the Diffusion-in-vof Model dialog box (Figure 26.66: Diffusion—in—vof Model Dialog Box).

Figure 26.66: Diffusion—in—vof Model Dialog Box

The following model parameters are available:

Select user-defined to use a user-defined function for the turbulent dispersion (see DEFINE_VECTOR_EXCHANGE_PROPERTY in the Fluent Customization Manual for details).