# 4. Boundary Conditions

## 4.1. Boundary Condition List

You will probably want the
table of boundary conditions below available.
When processing your grid, use either the indices in the first column
or the second column.
When you get your results back, the forces that are summarized in the
`[project].forces`

file will be labeled using the notation in the second
column.
This is done so that existing boundary condition flags may be used,
while still allowing for 4-digit boundary conditions in the solver,
which enable room for future growth. _Note that if you want to change
a boundary condition, you must pre-process the grid over again. The
BC indices are hardwired into the partition files._ This is on our
to-do list to change.

Grid Index | FUN3D Index | Description | Notes |
---|---|---|---|

6661 | 6661 | Symmetry Plane | x plane only: enforces zero crossflow velocity |

6662 | 6662 | Symmetry Plane | y plane only: enforces zero crossflow velocity |

6663 | 6663 | Symmetry Plane | z plane only: enforces zero crossflow velocity |

3 | 5000 | Farfield | Riemann invariant node based |

4 | 4000 | Viscous | strong enforcement of no-slip condition |

5 | 3000 | Tangency | weak enforcement of zero normal velocity through fluxes |

6100 | 6100 | Periodicity | Discrete periodicity, limited to nominally 2D grids extruded across n planes in a third dimension |

Element Based Boundary Conditions ( Version 10.5 )—Values ( where required ) set up
in `&boundary_conditions`

namelist in `namelist.input`

(`fun3d.nml`

for
versions 10.9.0 and later)

Grid Index | FUN3D Index | Description | Notes |
---|---|---|---|

5025 | 5025 | Farfield | Riemann invariants |

5026 | 5026 | Extrapolate | Supersonic outflow |

5050 | 5050 | Farfield | Freestream |

5051 | 5051 | Back pressure | Specified static pressure (allows supersonic flow) |

5052 | 5052 | Back pressure2 | Static pressure set by specified Mach number ( M < 1 ) |

7011 | 7011 | Subsonic inflow | Subsonic inflow (pt,Tt) for nozzle plenum |

7012 | 7012 | Subsonic outflow | Subsonic outflow (p0) for inlet duct |

7031 | 7031 | Mass flow out | Specification of massflow out of the control volume |

7036 | 7036 | Mass flow in | Specification of massflow in to the control volume |

7100 | 7100 | Fixed inflow | Fixed primitive variables in to control volume |

## 4.2. Value Input Format (Version 11.0)

For code released at 10.8.0 or later,
a change in the boundary condition
input format has been made. The patch number associated with
a boundary condition now used to directly index the physical
conditions. `bc_count`

and `bc_patch(n)`

are no longer used.

Please report any problems, inconsistencies, issues, etc. with the new
`boundary_conditions`

input to FUN3D Support.

! This file contains namelists used for specifying inputs to ! FUN3D. For versions 10.8 and later, the following namelists ! apply (if a namelist is not present, its variables take on ! their default values): ! boundary_conditions ! &boundary_conditions grid_units = 'meters' ! options: meters, inches, millimeters ! DEFAULT=meters | Used in dimensional unit conversion massflow_dimensions = 'nondim' ! options: metric (kg/s), nondim (mesh units squared) ! DEFAULT=metric | Used in dimensional unit conversion total_pressure_ratio(n) = 1 ! Input for BC 7011 associated with bc patch number -n- ! DEFAULT=1 total_temperature_ratio(n) = 1 ! Input for BC 7011 associated with bc patch number -n- ! DEFAULT=1 subsonic_inflow_velocity(n) = 'normal' ! Direction of inflow velocities for BC 7011 ! associated with bc patch number -n- ! options: 'normal', 'alpha,beta' ! DEFAULT='normal' alpha_bc(n) = 0.0 ! Input for BC 7011 associated with bc patch number -n- ! DEFAULT=0.0 beta_bc(n) = 0.0 ! Input for BC 7011 associated with bc patch number -n- ! DEFAULT=0.0 static_pressure_ratio(n) = 1 ! Input for BC 7012, 5051 associated with bc patch number -n- ! DEFAULT=1 mach_bc(n) = 0 ! Input for BC 5025 patch number associated with bc patch number -n- ! DEFAULT=0 q_set(n,5) = 0 ! Input for BC 7100, 7105 associated with bc patch number -n- ! DEFAULT=(0.,0.,0.,0.,0.) massflow(n) = 0 ! Input for BC 7031, 7036 associated with bc patch number -n- ! DEFAULT=0 wall_temperature(n) = 1 ! Input for BC associated with patch number -n- ! Sets Twall/Tref value. (Note that corresponding ! wall_temp_flag(n) must be set to .true.) ! DEFAULT=1 wall_temp_flag(n) = .false. ! Input for BC associated with patch number -n- to activate ! use of wall temperature input ! DEFAULT=.false. ! !------------------------------------------------------------- !------------------------------------------------------------- /

Note that the above namelist file contains many input variables, but in general it is
not necessary to list them all. One can instead rely on the fact that most of the
defaults are often desired, and only those variables that are **different** from
the defaults need to be given. The following might be an example of a typical
namelist file for a calorically-perfect FUN3D run:

### Sample Boundary Condition Namelists

#### Subsonic inflow / nozzle bc – BC 7011

This is an example of a mesh in inches, one total pressure-total temperature boundary condition associated with patch 3, with the inflow velocity set normal to the patch (default setting) for a pressure ratio of 1.6 ( inflow total pressure normalized by reference static pressure ) and a temperature ratio of 1.0 ( inflow total temperature normalized by reference static temperature).

The non-dimensional freestream static pressure in FUN3D is 1/

&boundary_conditions total_pressure_ratio(3) = 1.6, total_temperature_ratio(3) = 1.0, /

#### Inlet bc Example 1 – BC 7031

This is a sample for an inlet with one mass flow out of
the control volume boundary associated with patch 1, with a mass flow rate
of 0.25 in units of mesh units squared. The desired massflow in this
example is
ramped from 0 to the set condition of 0.25
over 500 iterations as set by `flow_mflux_ramp`

.

&boundary_conditions massflow(1) = 0.25, inlet_solution_method = 'massflux', / &component_parameters flow_mflux_ramp=500, /

#### Inlet bc Example 2 – BC 7012

This is a sample for an inlet mesh with a specified static pressure ratio of 0.9 associated with patch 5. This is the static pressure required at the outflow boundary normalized by the reference static pressure.

&boundary_conditions static_pressure_ratio(5) = 0.9, /

#### Fixed Inflow/Outflow – BC 7100/7105

Patch 8 is a fixed inflow or outflow boundary setting the normalized density to 1, the normalized velocities of u, v, and w to 0.5, 0.0, and 0.0 respectively and the pressure to 0.714.

&boundary_conditions q_set(8,:) = 1.0, 0.5, 0.0, 0.0, 0.714, /

#### Total Pressure Inflow/Static Pressure Outflow – BC 7011-7012

Patch 5 is a total pressure—total temperature boundary condition
associated assuming `alpha=0`

and `beta=0`

with the total pressure
ratio of 1.984 and a total temperature ratio of 1.201. The total
pressure ratio is ramped from 1.0 to 1.984 over 100 iterations via
the parameter `inflow_pt_ramp`

. The second boundary condition
patch is 6 and is a static pressure ratio and static temperature
ratio boundary set to the conditions of 1.364 and 1.0 respectively.

&boundary_conditions total_pressure_ratio(5) = 1.984 total_temperature_ratio(5) = 1.201 static_pressure_ratio(6) = 1.364 / &component_parameters inflow_pt_ramp=100 /

#### Specified Mach Number – BC 5052

The Mach number of 0.5 is specified for patch 5.

&boundary_conditions mach_bc(5) = 0.5 /

#### Static Pressure for Flow Out of Control Volume – BC 5051

The static pressure ratio of 0.25 is specified for patch 2.

&boundary_conditions static_pressure_ratio(2) = 0.25 /

Today's NASA Official:
Eric Nielsen, a member of
The FUN3D Development Team

Contact: FUN3D-support@lists.nasa.gov

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