Inlet Regions

Inlet regions differ from the standard inlets in two important and practical aspects – they can be defined anywhere inside the domain and they can be of arbitrary shape. This is of enormous help in the pre-processing phase and circumvents some of the nastiest elements from the previous chapter.

Inlet regions can be defined in rectangular, circular or custom shape. While the first two require just 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 simply contains the coordinates (x, y, z) of the particles which are to be 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.

More substantial information about the regions can be found in Theory and Advanced Features.

inletregions
{
    inletregion
    {
        inletregion_type            INREG_CIRCULAR              
        inletregion_phase           1
        inletregion_motphs          7                           
        inletregion_nrm             "0.0 0.0 -1.0"              
        inletregion_vel             2.0                         
        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_tvs_file        time-velocity-series.txt    
        inletregion_tvs_offset      1.5                         
        inletregion_tvs_latch       true                        
    }
}

inletregion_type: Specifying the type of the outlet region.; There are five options: INREG_CIRCULAR, INREG_RECTANGULAR, INREG_CUSTOM, INREG_CIRCULAR_ARBOR, and INREG_RECTANGULAR_ARBOR.; When specifying INERG_CUSTOM, the user must provide the stencil file (inletregion_stf_file).
inletregion_phase: Phase ID of the fluid spawned by the inlet region.
inletregion_motphs: This option is applicable only to *_ARBOR (arbitrary orientation) inlets.; It specifies the MOVINGWALL phase number which the probe is supposed to follow.
inletregion_nrm: Direction vector of the inlet region (can only point in +/- X, Y, Z).
inletregion_vel: Velocity magnitude of the inlet region.; Using a varying velocity file supersedes this value.
inletregion_stf_file: Inlet region stencil file containing X, Y and Z coordinates of the seed inlet particles.; Using the stencil file, the shape of the inlet can be an arbitrary 2-dimensional shape.
inletregion_prefilled: This command 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.; Options: true/false; Default: true
inletregion_indexsim: Setting this value to true will result in the particles introduced by this inlet to follow the particle ID numbering in accordance with particle ID’s present in the domain at the time.; This command has no influence on the particle spawning or other related inlet parameters.; Options: true/false; Default: false
inletregion_extend: In order 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). Setting this command to true automatically creates that impose region.; This option is not necessary in a single phase case, assuming that the inlet is located in a particle vacuum.; Options: true/false; Default: true
inletregion_extlen: Defines the absolute length of the impose region in front of the inlet region (in the direction of the inlet normal).; Unit: [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).; Unit: [m]
inletregion_circle_rad: Radius of the circular inlet region.; Not applicable to rectangular or custom inlet regions.; Unit: [m]
inletregion_rectangle_len: Length of the sides of the rectangular inlet region in each direction.; The length along the inletregion_nrm direction is ignored.; Unit: [m]
inletregion_time_start: Time at which the inlet region becomes active.; Unit: [s]
inletregion_time_end: Time at which the inlet region becomes inactive.; Unit: [s]
inletregion_time_rampup: Time during which the inlet velocity values goes from zero to the specified peak value.; Unit: [s]
inletregion_time_rampdn: Time during which the inlet velocity values goes down from a specified peak value to zero.; Unit: [s]
inletregion_tvs_file: For the inlet region there can be a Time Velocity Series file provided in .txt format, specifying an arbitrary shape of the inlet velocity magnitude as a function of time.; The form of it simply a 2-column format specifying time (column 1) and velocity magnitude (column2) with a space as delimiter.
inletregion_tvs_offset: Provided that the TVS file is used for the inlet region, this values offsets the beginning of the TVS file in time.; For example, specifying a value of 2.0 for this command will offset the TVS file by two seconds, such that the starting time of the TVS file effect is two seconds.; Unit: [s]
inletregion_tvs_latch: Assuming that TVS file for the inlet region is provided, this command extends the last specified value in the TVS file until the end of the simulation.; Example: TVS file specifies the magnitude of 5 m/s at two seconds and that is the last entry in the TVS file. Total specified simulation duration is five seconds (t_end = 5). When this command is set to true, the velocity magnitude will remain 5 m/s until the simulation ends even though the TVS file ends at t = 2 s.