Inlet Definitions

Since version 2.03, nanoFluidX has a separate inlets parameter section which allows to define multiple inlets in a single domain, inserting if desired multiple different fluid phases.

inlets
{
    inlet
    {
        inlet_type                 RECTANGULAR
        min_inlet_domain           "-0.02 -0.001 -0.02"    
        max_inlet_domain           "0.02 0.001 0.02"       
        inlet_phase                1                      
        inlet_vel                  "0.0 -0.05 0.0"          
        t_damp_inletvel_start      0.0
        t_damp_inletvel_end        0.0
        surrounding_ghost_cells    false
        BC_max		        "OUTLET INLET  OUTLET"   
        BC_min		        "OUTLET OUTLET OUTLET"               
    }
    inlet
    {
        inlet_type                 CIRCULAR			    
        inlet_center               "-0.02 -0.001 -0.02"    	 
        inlet_radius               0.02 		       	
        inlet_phase                1                      
        inlet_vel                  "0.0 -0.05 0.0"          
        t_damp_inletvel_start      0.0
        t_damp_inletvel_end        0.0
        surrounding_ghost_cells    false
        BC_max		        "OUTLET INLET  OUTLET"   
        BC_min                     "OUTLET OUTLET OUTLET"               
    }
}

Starting with version 2.03, nanoFluidX has a separate inlets parameter section which allows you to define multiple inlets in a single domain, inserting if desired multiple different fluid phases. Starting with v2019, nanoFluidX also has an option to specify circular inlets and starting with 2020, the user can define arbitrary shape and orientation inlets using the INLET REGION feature.

By specifying an inlet boundary, we define a rectangle at one of the min/max domain boundaries through which a fluid enters at a specified velocity. As already mentioned, it is now possible to define an arbitrary number of inlets on any of the BC_min/BC_max planes. We define multiple inlets by creating multiple “inlet” sub-sections in the main “inlets” parameter section. Each inlet is geometrically defined by two points which belong to one of the BC_min/BC_max planes: min_inlet_domain and max_inlet_domain.



Figure 1. . Definition of an inlet area in the Xmin plane. RECTANGULAR: The two red dots are points which bound the inlet area on the Xmin plane. CIRCULAR: Defining location of the inlet center and its radius unambiguously defines a circular inlet in the Xmin plane. Please note that specifying the X-coordinate of the points is meaningless for this plane, as the plane has already been defined.
inlet_type
Inlet type.
Options: RECTANGULAR, CIRCULAR
min_inlet_domain
Specifies the starting (minimum) point of the inlet rectangle.
If the inlet is specified as minimum X domain boundary (which is a Y-Z plane), the definition of the position vector “X Y Z” will ignore the X coordinate, as only Y and Z coordinates make sense in a Y-Z plane. This applies accordingly to all possible boundaries.
max_inlet_domain
Specifies the ending (maximum) point of the inlet rectangle.
If the inlet is specified as minimum X domain boundary (which is a Y-Z plane) the definition of the position vector “X Y Z” will ignore the X coordinate, as only Y and Z coordinates make sense in a Y-Z plane. This applies accordingly to all possible boundaries.
inlet_center
Specifies the center of the circular inlet.
Only applicable to the CIRCULAR inlet.
If the inlet is specified as minimum X domain boundary (which is a Y-Z plane) the definition of the position vector “X Y Z” will ignore the X coordinate, as only Y and Z coordinates make sense in a Y-Z plane. This applies accordingly to all possible boundaries.
inlet_radius
Scalar value defining the radius of the circular inlet.
Only applicable to the CIRCULAR inlet.
inlet_phase
Specify the number of the phase that comes through the inlet.
inlet_vel
Prescribed inlet velocity.
Note: Inlet velocities can be only perpendicular to the specified boundary plane.
t_damp_inletvel_start
Begin time for the inlet velocity damping.
Using this command can delay the inlet if necessary.
t_damp_inletvel_end
End time of the damping for the inlet velocity.
After this time the velocity will have its full magnitude which is specified by inlet_vel.
surrounding_ghost_cells
Creates a layer of ghost particles surrounding the inlet. This is to help potential leaks around the inlet zone, as the additional layer of ghost particles will equalize the pressure of the particles trying to escape through the corners between the geometry and the inlet boundary plane.
Options: true / false
Default: false
Now we have reached the confusing point. In order to actually define to which BC_min/BC_max plane does the inlet belong, we need to again specify the BC_min/BC_max variables. The key difference is that the only important thing in this “second” definition of BC_min/BC_max is the keyword “INLET”, everything else will be ignored.
BC_min (Inlet parameters)
This definition of BC_min serves the sole purpose of defining to which boundary plane does the inlet belong to. All the other possible boundary condition keywords (OPEN / PERIODIC / OUTLET / SIMPLEOUTLET) will be ignored.
BC_max (Inlet parameters)
This definition of BC_min serves the sole purpose of defining to which boundary plane does the inlet belong to. All the other possible boundary condition keywords (OPEN / PERIODIC / OUTLET / SIMPLEOUTLET) will be ignored.

We understand that this can introduce some confusion into the process, but for practical reasons, and due to the current text-based input, the definition of multiple inlets could not be carried out in a different manner. This implementation of inlets is still active for historical reasons, but is subject to deprecation if the user community adopts the INLET_REGIONS.