Inlet Regions

Defines inlet region parameters.

Inlet regions differ from standard inlets in two ways. They can be defined anywhere inside the domain and they can be of arbitrary shape. They can also be prescribed through specified velocity of the flow, mass or volumetric flow (in units of m/s, kg/s or m3/s).

Inlet regions can be defined in rectangular, circular or custom shape. While the first two only require the geometric description of the region as an input, the custom shaped region requires a “stencil” of particles in form of a separate .txt file. The .txt file for the custom shaped inlet region contains the coordinates (X, Y, Z) of the particles which are inserted into the domain. The stencil, in that case, behaves as a source of particles.

The only limitation to the inlet regions is that they must be planar, even in the custom shape or arbitrary orientation scenario.

For more information, refer to Inlet Regions in the Theory Manual.


        inletregion_type            INREG_CIRCULAR              
        inletregion_phase           1
        inletregion_motphs          7                           
        inletregion_nrm             "0.0 0.0 -1.0"   
        inletregion_stttyp          vel
        inletregion_sttval          0.0                      
        inletregion_stf_file        "stencil-file.txt"          
        inletregion_prefilled       true                       
        inletregion_indexsim        false                       
        inletregion_extend          true                        
        inletregion_extlen          0.1                         
        inletregion_extlenodx       4                           
        inletregion_cnt             "0.04 0.0105 0.03"          
        inletregion_circle_rad      0.015                       
        inletregion_rectangle_len   "0.03 0.04 0.0"             
        inletregion_time_start      0.0                         
        inletregion_time_end        0.05                        
        inletregion_time_rampup     0.01                        
        inletregion_time_rampdn     0.025
        inletregion_tss_file        time-state-series.txt
        inletregion_tss_offset      0.0
        inletregion_tss_latch       false
        inletregion_temp            0.0
        inletregion_extpre          false
        inletregion_extpst          false


Command Contents SI Unit Example
inletregion_type Specifies the type of inlet region.
Attention: When specifying INREG_CUSTOM, you must provide the stencil file (inletregion_stf_file).
inletregion_phase Phase ID of the fluid spawned by the inlet region.  
inletregion_motphs specifies the MOVINGWALL phase number which the probe is supposed to follow.
Attention: This command is only applicable to *_ARBOR (arbitrary orientation) inlets.
inletregion_nrm Direction vector of the inlet region (can only point in the positive or negative X, Y, or Z direction).  
inletregion_stttyp Type of inlet region state.
  • vel (Default) - Velocity
  • vfl - Volume flow rate
  • mfl - Mass flow rate
Note: This command is optional.
inletregion_sttval State magnitude of the inlet region.
Attention: If defined, inletregion_tss_file takes precedence over this command.

Default = 0.0

[m/s] or [kg/s] or [m3/s]
inletregion_stf_file Inlet region stencil file containing X, Y and Z coordinates of the seed inlet particles.
Note: When you use the stencil file, the shape of the inlet can be an arbitrary two-dimensional shape.
inletregion_prefilled Notifies the solver that at the time of the inlet region activation, there are fluid particles overlapping at the seeding coordinates of the inlet. If so, the command should be set to true.
  • true (Default)
  • false
inletregion_indexsim When this command is set to true, the particles introduced by this inlet will follow the particle ID numbering relative to the particle IDs present in the domain at that time.
  • true
  • false (Default)
Note: This command has no influence on the particle spawning or other related inlet parameters.
inletregion_extend For the inlet region to function properly in a multiphase environment and reduce potential local instabilities, an impose region should be created in front of the inlet stencil particles (in the direction of the inlet normal). When this command is set to true, the solver creates the impose region.
  • true (Default)
  • false
Note: This command is not necessary in a single phase case, assuming that the inlet is located in a particle vacuum.
inletregion_extlen Defines the absolute length of the impose region in front of the inlet region (in the direction of the inlet normal). [m]
inletregion_extlenodx Defines the relative length of the impose region in front of the inlet region (in the direction of the inlet normal) as a function of dx (particle pitch).  
inletregion_cnt X, Y and Z coordinates of the inlet region center. The center is defined for both circular and rectangular inlet regions (not needed for the custom file). [m]
inletregion_circle_rad Radius of the circular inlet region.
Attention: Not applicable to rectangular or custom inlet regions.
inletregion_rectangle_len Length of the sides of the rectangular inlet region in each direction.
Note: The length along the inletregion_nrm direction is ignored.
inletregion_time_start Time at which the inlet region becomes active. [s]
inletregion_time_end Time at which the inlet region becomes inactive. [s]
inletregion_time_rampup Time during which the inlet velocity value goes from zero to the specified peak value. [s]
inletregion_time_rampdn Time during which the inlet velocity value goes down from a specified peak value to zero. [s]
inletregion_tss_file For the inlet region there can be a Time State Series (TSS) file provided in ASCII format, specifying an arbitrary shape of the inlet flow magnitude as a function of time. TSS file has a two-column format specifying time (column 1) and magnitude of the velocity/mass/volume flow (column2) with a space as delimiter.  
inletregion_tss_offset Provided that the TSS file is used for the inlet region, this value offsets the beginning of the TSS file in time.
Note: For example, specifying a value of 2.0 for this command will offset the TSS file by two seconds, such that the starting time of the TSS file effect is two seconds.

Default = 0.0

inletregion_tss_latch Provided that the TSS file for the inlet region is provided, this command extends the first and/or last specified value in the TSS file until start and/or end of the simulation, respectively.
  • true
  • false (Default)
Note: For example, the last entry in the TSS file specifies a magnitude of 5 m/s at two seconds. The total specified simulation duration is six seconds (t_end = 6 s). When this command is set to true, the velocity magnitude will remain 5 m/s until the simulation ends even though the TSS file ends at t = 2 s.
inletregion_temp Temperature of the inlet region. Specifies the inlet region fluid temperature.
Attention: The specified temperature spawned by the inlet region overrides the fluid phase temperature defined in the phases section. Leaving the value blank or excluding this keyword, reverts back to using temperature from phases section.

Default = temp_0 of phase

inletregion_extpre Notifies the solver about inlet region extension status before the inlet start time.
  • true
  • false (Default)
inletregion_extpst Notifies the solver about inlet region extension status after the inlet start time.
  • true
  • false (Default)