12.1.1. Run control¶

12.1.1.1. RUN_NAME¶

Data Type: CHARACTER

required

Name used to create output files. The name should generate legal file names after appending extensions. Ex: Given the input, RUN_NAME = “bub01”, MFIX will generate the output files: BUB01.LOG, BUB01.OUT, BUB01.RES, etc.

12.1.1.2. DESCRIPTION¶

Data Type: CHARACTER

Problem description. Limited to 60 characters.

12.1.1.3. PROJECT_VERSION¶

Data Type: CHARACTER

Project version. Limited to 80 characters.

12.1.1.4. UNITS¶

Data Type: CHARACTER

required

Simulation input/output units.

Table 12.1 Valid Values¶
Name	Default?	Description
`SI`	◉	All input and output in SI units (kg, m, s, J).
`cgs`		All input and output in CGS units (g, cm, s, cal). DEPRECATED.

12.1.1.5. RUN_TYPE¶

Data Type: CHARACTER

required

Type of run.

Table 12.2 Valid Values¶
Name	Default?	Description
`new`		A new run. There should be no .RES, .SPx, .OUT, or .LOG files in the run directory.
`RESTART_1`		Traditional restart. The run continues from the last time the .RES file was updated and new data is added to the SPx files.
`RESTART_2`		Start a new run with initial conditions from a .RES file created from another run. No other data files (SPx) should be in the run directory.

12.1.1.6. PPO¶

Data Type: LOGICAL

Flag to run the preprocessing (mesh generation) only and exit.

12.1.1.7. TIME¶

Data Type: DOUBLE PRECISION

Simulation start time. This is typically zero.

12.1.1.8. TSTOP¶

Data Type: DOUBLE PRECISION

Simulation stop time.

12.1.1.9. OPTFLAG1¶

Data Type: DOUBLE PRECISION

Use NREL-CU optimization routines?.

12.1.1.10. NICE_DT¶

Data Type: LOGICAL

Flag to use nice time step value.

12.1.1.11. DT¶

Data Type: DOUBLE PRECISION

Initial time step size. If left undefined, a steady-state calculation is performed.

12.1.1.12. DT_MAX¶

Data Type: DOUBLE PRECISION

Maximum time step size.

12.1.1.13. DT_MIN¶

Data Type: DOUBLE PRECISION

Minimum time step size.

12.1.1.14. DT_FAC¶

Data Type: DOUBLE PRECISION

Factor for adjusting time step.

The value must be less than or equal to 1.0.
A value of 1.0 keeps the time step constant which may help overcome initial non-convergence.

12.1.1.15. PERSISTENT_MODE¶

Data Type: LOGICAL

Force a forward time-step if the maximum number of iterations, MAX_NIT, is reached. The forward time-step is only forced after reaching the minimum time-step, DT_MIN, for adjustable time-step simulations (DT_FAC /= 1). This option should be used with caution as unconverged time-steps may lead to poor simulation results and/or additional convergence issues.

Table 12.3 Valid Values¶
Name	Default?	Description
`.TRUE.`		Force forward time-step when DT=DT_MIN and the maximum number of iterations are reached.
`.FALSE.`	◉	Abort run when DT < DT_MIN.

12.1.1.16. AUTO_RESTART¶

Data Type: LOGICAL

Flag to restart the code when DT < DT_MIN.

12.1.1.17. MOMENTUM_X_EQ(PHASE)¶

Data Type: LOGICAL

\(0 \le Phase \le 10\)

Flag to enable/disable solving the X-momentum equations.

Table 12.4 Valid Values¶
Name	Default?	Description
`.TRUE.`	◉	Solve X-momentum equations.
`.FALSE.`		The X velocity initial conditions persist throughout the simulation.

12.1.1.18. MOMENTUM_Y_EQ(PHASE)¶

Data Type: LOGICAL

\(0 \le Phase \le 10\)

Flag to enable/disable solving the Y-momentum equations.

Table 12.5 Valid Values¶
Name	Default?	Description
`.TRUE.`	◉	Solve Y-momentum equations.
`.FALSE.`		The Y velocity initial conditions persist throughout the simulation.

12.1.1.19. MOMENTUM_Z_EQ(PHASE)¶

Data Type: LOGICAL

\(0 \le Phase \le 10\)

Flag to enable/disable solving the Z-momentum equations.

Table 12.6 Valid Values¶
Name	Default?	Description
`.TRUE.`	◉	Solve Z-momentum equations.
`.FALSE.`		The Z velocity initial conditions persist throughout the simulation.

12.1.1.20. JACKSON¶

Data Type: LOGICAL

Flag to enable Jackson form of momentum equations. See Anderson and Jackson, (1967), IECF, 6(4), p.527.

Table 12.7 Valid Values¶
Name	Default?	Description
`.TRUE.`		Solve Jackson form of momentum equations.
`.FALSE.`	◉	Default form.

12.1.1.21. ISHII¶

Data Type: LOGICAL

Flag to enable Ishii form of momentum equations. See Ishii, (1975), Thermo-fluid dynamic theory of two-phase flow.

Table 12.8 Valid Values¶
Name	Default?	Description
`.TRUE.`		Solve Ishii form of momentum equations.
`.FALSE.`	◉	Default form.

12.1.1.22. ENERGY_EQ¶

Data Type: LOGICAL

Solve energy equations.

Table 12.9 Valid Values¶
Name	Default?	Description
`.TRUE.`	◉	Solve energy equations.
`.FALSE.`		Do not solve energy equations.

12.1.1.23. SPECIES_EQ(PHASE)¶

Data Type: LOGICAL

\(0 \le Phase \le 10\)

Solve species transport equations.

Table 12.10 Valid Values¶
Name	Default?	Description
`.TRUE.`	◉	Solve species equations.
`.FALSE.`		Do not solve species equations.

12.1.1.24. TURBULENCE_MODEL¶

Data Type: CHARACTER

Gas phase turbulence model. [“NONE”]

For K_EPSILON (K-epsilon turbulence model for single-phase flow):

Numerical parameters (like underrelaxation) are the same as the ones for SCALAR (index = 9).
All walls must be defined (NSW, FSW or PSW) in order to use standard wall functions. If a user does not specify a wall type, the simulation will not contain the typical turbulent profile in wall-bounded flows.

Table 12.11 Valid Values¶
Name	Default?	Description
`NONE`	◉	No turbulence model.
`MIXING_LENGTH`		Turbulent length scale must be specified for the full domain using keyword IC_L_SCALE.
`K_EPSILON`		K-epsilon turbulence model (for single-phase flow) using standard wall functions.

12.1.1.25. MU_GMAX¶

Data Type: DOUBLE PRECISION

Maximum value of the turbulent viscosity of the fluid, which must be defined if any turbulence model is used. A value MU_GMAX =1.E+03 is recommended. (see calc_mu_g.f)

12.1.1.26. DRAG_TYPE¶

Data Type: CHARACTER

Available gas-solids drag models. Note: The extension _PCF following the specified drag model indicates that the polydisperse correction factor is available. This option is available for TFM solids only. For PCF details see:

Van der Hoef MA, Beetstra R, Kuipers JAM. (2005) Journal of Fluid Mechanics.528:233-254.
Beetstra, R., van der Hoef, M. A., Kuipers, J.A.M. (2007). AIChE Journal, 53:489-501.
Erratum (2007), AIChE Journal, Volume 53:3020

Table 12.12 Valid Values¶
Name	Default?	Description
`BVK`		Beetstra, van der Hoef, Kuipers (2007). Chemical Engineering Science 62:246-255
`DIFELICE`		Di Felice, The voidage function for fluid-particle interaction systems, Int. J. Multiph. Flow 20 (1994) 153-159.
`DIFELICE_GANSER`		G.H. Ganser, A rational approach to drag prediction of spherical and nonspherical particles, Powder Technol. 77 (1993) 143-152. This model requires specification of a sphericity and a reference length (typically the bed diameter)
`GAO`		Gao, X., Li, T., Sarkar, A., Lu, L., Rogers, W.A. Development and Validation of an Enhanced Filtered Drag Model for Simulating Gas-Solid Fluidization of Geldart A Particles in All Flow Regimes. Chemical Engineering Science, 184, 33-51, 2018.
`GIDASPOW`		Ding J, Gidaspow D (1990). AIChE Journal 36:523-538
`GIDASPOW_PCF`		(TFM only). see GIDASPOW
`GIDASPOW_BLEND`		Lathouwers D, Bellan J (2000). Proceedings of the 2000 U.S. DOE Hydrogen Program Review NREL/CP-570-28890.
`GIDASPOW_BLEND_PCF`		(TFM only). see GIDASPOW_BLEND
`HYS`		Yin, X, Sundaresan, S. (2009). AIChE Journal 55:1352-1368 This model has a lubrication cutoff distance, LAM_HYS, that can be specified. (TFM only).
`KOCH_HILL`		Hill RJ, Koch DL, Ladd JC (2001). Journal of Fluid Mechanics, 448: 213-241. and 448:243-278.
`KOCH_HILL_PCF`		(TFM only). see KOCH_HILL
`QKQY`		Qi, S.B. Kuang, T.S. Qiu, A.B. Yu, Lattice Boltzmann investigation on fluid flows through packed beds: Interaction between fluid rheology and bed properties, Powder Technology 369 (2020) 248-260 and S. Benyahia, Simulation of heavy particles fluidized with non-Newtonian fluids, Powder Technology 433 (2024) 119261
`RADL`		Radl, S., Sundaresan, S., 2014. A drag model for filtered Euler-Lagrange simulations of clustered gas-particle suspensions. Chem. Eng. Sci., 117, 416-425.
`SARKAR`		Sarkar, A., Milioli, F.E., Ozarkar, S., Li, T., Sun, X.,Sundaresan, S., 2016. Filtered sub-grid constitutive models for fluidized gas-particle flows constructed from 3-D simulations. Chem. Eng. Sci., 152, 443-456.
`SQP_DIFELICE_GANSER`		Xi Gao, Jia Yu, Liqiang Lu, Cheng Li and William A Rogers, Development and validation of SuperDEM-CFD coupled model for simulating non-spherical particles hydrodynamics in fluidized beds, Chemical Engineering Journal, 2021,420: 127654. and G.H. Ganser, A rational approach to drag prediction of spherical and nonspherical particles, Powder Technol. 77 (1993) 143-152. This model requires specification of a sphericity and a reference length (typically the bed diameter)
`SQP_DIFELICE_HOLZER_SOMMERFELD`		Xi Gao, Jia Yu, Liqiang Lu, Cheng Li and William A Rogers, Development and validation of SuperDEM-CFD coupled model for simulating non-spherical particles hydrodynamics in fluidized beds, Chemical Engineering Journal, 2021,420: 127654. and A. Hölzer, M. Sommerfeld, New simple correlation formula for the drag coefficient of nonspherical particles, Powder Technology 184 (2008) 361-365.
`SYAM_OBRIEN`	◉	Syamlal M, OBrien TJ (1988). International Journal of Multiphase Flow 14:473-481. Two additional parameters may be specified: DRAG_C1, DRAG_D1
`WEN_YU`		Wen CY, Yu YH (1966). Chemical Engineering Progress Symposium Series 62:100-111.
`TGS`		Tenneti, S., Garg, R., Subramaniam, S., 2011. Drag law for monodisperse gas solid systems using particle-resolved direct numerical simulation of flow past fixed assemblies of spheres. Int. J. Multiph. Flow, 37(9), 1072-1092.
`TPKKV`		Tang, Peters, Kuipers, Kreibitzsch, & van der Hoef. AIChE J., 61(2), pp.688-698 (2015).
`WEN_YU_PCF`		(TFM only). see WEN_YU
`USER_DRAG`		Invoke user-defined drag law. (usr_drag.f)

12.1.1.27. DRAG_C1¶

Data Type: DOUBLE PRECISION

Quantity for calibrating Syamlal-O’Brien drag correlation using Umf data. This is determined using the Umf spreadsheet.

12.1.1.28. DRAG_D1¶

Data Type: DOUBLE PRECISION

Quantity for calibrating Syamlal-O’Brien drag correlation using Umf data. This is determined using the Umf spreadsheet.

12.1.1.29. LAM_HYS¶

Data Type: DOUBLE PRECISION

The lubrication cutoff distance for HYS drag model. In practice this number should be on the order of the mean free path of the gas for smooth particles, or the RMS roughness of a particle if they are rough (if particle roughness is larger than the mean free path).

12.1.1.30. SPHERICITY_DG¶

Data Type: DOUBLE PRECISION

Particle sphericity (between zero and one) used in the DIFELICE_GANSER drag law.

12.1.1.31. REF_LENGTH_DG¶

Data Type: DOUBLE PRECISION

Reference length (typically the bed diameter) used in the DIFELICE_GANSER drag law.

12.1.1.32. SUBGRID_TYPE¶

Data Type: CHARACTER

Applies to solids model(s): TFM

Subgrid models.

Table 12.13 Valid Values¶
Name	Default?	Description
`Igci`		Igci, Y., Pannala, S., Benyahia, S., and Sundaresan S. (2012). Industrial & Engineering Chemistry Research, 2012, 51(4):2094-2103
`Milioli`		Milioli, C.C., Milioli, F. E., Holloway, W., Agrawal, K. and Sundaresan, S. (2013). AIChE Journal, 59:3265-3275.

12.1.1.33. FILTER_SIZE_RATIO¶

Data Type: DOUBLE PRECISION

Applies to solids model(s): TFM

Ratio of filter size to computational cell size.

12.1.1.34. SUBGRID_WALL¶

Data Type: LOGICAL

Applies to solids model(s): TFM

Flag for subgrid wall correction.

Table 12.14 Valid Values¶
Name	Default?	Description
`.FALSE.`	◉	Do not include wall correction.
`.TRUE.`		Include subgrid wall correction.

12.1.1.35. MODEL_B¶

Data Type: LOGICAL

Shared gas-pressure formulation. See Syamlal, M. and Pannala, S. “Multiphase continuum formulation for gas-solids reacting flows,” chapter in Computational Gas-Solids Flows and Reacting Systems: Theory, Methods and Practice, S. Pannala, M. Syamlal and T.J. O’Brien (editors), IGI Global, Hershey, PA, 2011.

Table 12.15 Valid Values¶
Name	Default?	Description
`.FALSE.`	◉	Use Model A. See J.X. Bouillard and R.W. Lyczkowski (1991), Powder Tech, 68:31-51.
`.TRUE.`		Use Model B. See Bouillard, J.X., Lyczkowski, R.W., Folga, S., Gidaspow, D., Berry, G.F. (1989). Canadian Journal of Chemical Engineering 67:218-229.

12.1.1.36. NSCALAR¶

Data Type: INTEGER

The number of user-defined scalar transport equations: to solve.

12.1.1.37. PHASE4SCALAR(SCALAR EQUATION)¶

Data Type: INTEGER

\(1 \le Scalar Equation \le 100\)

The phase convecting the indexed scalar transport equation.

12.1.1.38. KEYFRAME(KEYFRAME FILE ID)¶

Data Type: LOGICAL

\(1 \le Keyframe file ID \le 100\)

Read a keyframe data file. Example: KEYFRAME(3) = .TRUE. will read the keyframe file keyframe_0003.csv. The first column of keyframe_0003.csv stores the independent variable. The next columns of keyframe_0003.csv store the dependent variables.

Table 12.16 Valid Values¶
Name	Default?	Description
`.TRUE.`		Read keyframe data file.
`.FALSE.`	◉	Do not read keyframe data file.

12.1.1.39. KF_KEYWORD(KEYFRAME FILE ID, COLUMN NUMBER IN CSV KEYFRAME FILE)¶

Data Type: CHARACTER

\(1 \le Keyframe file ID \le 100\)
\(1 \le Column number in CSV keyframe file \le 20\)

Name of keyword controlled by a Keyframe datafile. Example: KF_KEYWORD(3,1)=’bc_v_g’ First index (3) means the keyframe data file is keyframe_0003.csv. Second index (1) means the first dependent variable (second column) controls keyword bc_v_g. See documentation for list of keywords that can be controlled by a keyframe.

12.1.1.40. KF_IV(KEYFRAME FILE ID)¶

Data Type: INTEGER

\(1 \le Keyframe file ID \le 100\)

Dependent variable identifier for a Keyframe datafile. Example: KF_IV(3)=0 Means the first column (independent variable) of keyframe data file keyframe_0003.csv represents time.

Table 12.17 Valid Values¶
Name	Default?	Description
`0`	◉	Keyframe file dependent variable is time.
`1`		Keyframe file dependent variable is x-coordinate.
`2`		Keyframe file dependent variable is y-coordinate.
`3`		Keyframe file dependent variable is z-coordinate.

12.1.1.41. KF_INTERP(KEYFRAME FILE ID)¶

Data Type: CHARACTER

\(1 \le Keyframe file ID \le 100\)

Keyframe interpolation method (applies to all variables in a Keyframe datafile. Example: KF_INTERP(3)=’LINEAR’ First index (3) means the keyframe data file is keyframe_0003.csv.

Table 12.18 Valid Values¶
Name	Default?	Description
`LINEAR`	◉	Linearly interpolate data between keyframes (default).
`STEP`		Keep data constant between keyframes.

12.1.1.42. OMEGA_UNIT¶

Data Type: CHARACTER

Angular velocity unit. This is only meant to be used for granular DEM, CGP, SQP or GSP models to move STL files or group of particles. Example: OMEGA_UNIT = ‘REV/S’ means the angular velocity is expressed in revolutions per second.

Table 12.19 Valid Values¶
Name	Default?	Description
`RAD/S`	◉	Radian per second
`DEG/S`		Degree per second
`REV/S`		Revolution per second
`RAD/MIN`		Radian per minute
`DEG/MIN`		Degree per minute
`REV/MIN`		Revolution per minute

12.1.1.43. DES_RIGID_MOTION(PHASE)¶

Data Type: LOGICAL

\(1 \le Phase \le 10\)

Applies to solids model(s): DEM

Prescribe rigid body motion to particles belonging to this phase. Default value is .FALSE., meaning the particle motion is computed by integrating acceleration to velocity and velocity to position.

12.1.1.44. DES_RIGID_MOTION_VEL(PHASE, COMPONENT)¶

Data Type: DOUBLE PRECISION

\(1 \le Phase \le 10\)
\(1 \le Component \le 3\)

Particle rigid motion translational velocity. The first index is the phase ID, the second index is the component (1=x, 2=y, 3=z)

12.1.1.45. DES_RIGID_MOTION_OMEGA(PHASE, COMPONENT)¶

Data Type: DOUBLE PRECISION

\(1 \le Phase \le 10\)
\(1 \le Component \le 3\)

Particle rigid motion angular velocity. The first index is the phase ID, the second index is the component (1=x, 2=y, 3=z)

12.1.1.46. DES_RIGID_MOTION_ROT_CENTER(PHASE, COMPONENT)¶

Data Type: DOUBLE PRECISION

\(1 \le Phase \le 10\)
\(1 \le Component \le 3\)

Particle rigid motion center of rotation. The first index is the phase ID, the second index is the component (1=x, 2=y, 3=z)