Chapter 3. INPUT DESCRIPTION FOR BOUNDARY CONDITIONS


TABLE OF CONTENTS CLOSE MANUAL


The number of boundary conditions is specified in the "general input" section (BOUNDARY AND CUT CONTROL) by the parameter FLOWBCS. Previous versions of VULCAN required the specification of a boundary condition type (and possibly supplemental information) for each boundary condition line. This proved to be a tedious methodology when large numbers of grid blocks were present and changes to boundary condition descriptions were required (e.g. a change in the wall temperature). This prompted the adoption of a new approach that allows boundary condition types to be combined into groups (see BCGROUPS). An added benefit to this approach is that it allows fine-grained control over how the VULCAN loads are computed and output when post-processing (further details of this feature will be shown later). The new approach requires a boundary condition grouping section to precede the boundary condition specifications. This section of the input deck defines how the boundary conditions are to be grouped based on the BC NAME (1st column of the boundary condition specification) given to the boundary condition. The first line of input for this section is a comment line (the $ delineator is not required). The succeeding input lines define the boundary condition groupings (which may also require supplemental information). This section is followed by the detailed boundary condition specifications. The first line of the boundary condition specification section is a comment line (the $ delineator is not required). The succeeding input lines define boundary conditions. These lines may be specified in any order, and the number of boundary condition lines must match that specified by FLOWBCS.

Example:

BC GROUPS: NAME      TYPE      OPTION
AIR-IN    SUBIN     NORMAL
Air   Tot. Dens.   U-vel   V-vel   W-vel   Tot. Pres.   Turb. Int.   Vis. Ratio
1.0   7.1975e+00   380.0   0.0     0.0     9.1550e+05   0.01         0.1
OUTFLOW   EXTRAP    PHYSICAL
ISO-WALL  IWALLM     PHYSICAL
T-WALL   TEMP-RLX
300.0    1.0
ADB-WALL  AWALLM     PHYSICAL
BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER
AIR-IN   1  I   MIN    J   MIN   MAX    K   MIN   MAX      1
OUTFLOW  1  I   MAX    J   MIN   MAX    K   MIN   MAX      0
ISO-WALL  1  J   MIN    K   MIN   MAX    I   MIN   MAX      0
ISO-WALL  1  J   MAX    K   MIN   MAX    I   MIN   MAX      0
ADB-WALL  1  K   MIN    I   MIN   MAX    J   MIN   MAX      0
ADB-WALL  1  K   MAX    I   MIN   MAX    J   MIN   MAX      0

Each boundary condition grouping line consists of three character strings:

'NAME' - a character string (up to 10 characters) that matches the BC NAME (1st column of the boundary condition specification) of one or more boundary condition lines.

'TYPE' - a character string (up to 10 characters) that determines the type of boundary condition to be applied (as specified in Table III). Additional lines of supplemental information are required for some boundary condition types.

Table III. Boundary Condition Types

B.C. TYPE DEFINITION
EXTRAP Supersonic outflow boundary with zeroth order extrapolation of all variables.
EXTRAP2 Supersonic outflow boundary with first order extrapolation of all variables.
REGOUT Supersonic outflow boundary with zeroth order extrapolation of all variables. Use REGOUT or REGOUT2 only as an outflow B.C. when the block-boundary is also connected (using either a CUT or PATCH) to a block in a different region.
REGOUT2 Supersonic outflow boundary with first order extrapolation of all variables. Use REGOUT or REGOUT2 only as an outflow B.C. when the block-boundary is also connected (using either a CUT or PATCH) to a block in a different region.
SYMM Symmetry boundary (generic).
REFLCU Symmetry boundary that reflects the x-component of velocity only.
REFLCV Symmetry boundary that reflects the y-component of velocity only.
REFLCW Symmetry boundary that reflects the z-component of velocity only.
REFFIX Supersonic inflow boundary with all variables specified under REFERENCE CONDITIONS in the General Control Data section of the Input Description.
AREFFIX Supersonic inflow boundary with all variables specified under REFERENCE CONDITIONS in the General Control Data section of the Input Description. Velocity vector is aligned to be tangent with the grid in the streamwise direction.
SWALL Slip wall (standard EULER wall boundary with pressure extrapolated in the wall normal direction).
AWALL No slip adiabatic wall.
AWALLM No slip adiabatic wall using wall functions. Only available with K-OMEGA and MENTER turbulence models. Should be used if y+ of fine grid is expected to be greater than 2.0 or 3.0.
CHARACTER Characteristic inflow boundary with Mach number specified based on the value entered in the REFERENCE CONDITIONS section of the input deck. Use only with calorically perfect gas model.
PROFILE Input profile to be read in from a profile file containing the conserved variables. See Chapter 15. PROFILE FILE OUTPUT FORMAT for the profile file format.
PPROFILE Input profile to be read in from a profile file containing primitive variables. See Chapter 15. PROFILE FILE OUTPUT FORMAT for the profile file format.
STWALL Specified temperature distribution on a no slip wall where the distribution is specified in a profile file. See Chapter 15. PROFILE FILE OUTPUT FORMAT for the profile file format.
STWALLM No slip wall using wall functions where the wall temperature distribution is to be read in from a profile file. Only available with K-OMEGA and MENTER turbulence models. See Chapter 15. PROFILE FILE OUTPUT FORMAT for the profile file format.
CPWALLM No slip wall using wall functions coupled with a 1-D solid wall heat transfer analysis. The wall external surface temperature, wall thickness and wall thermal conductivity are variable to be read in from a profile file. Only available with K-OMEGA and MENTER turbulence models. See Chapter 15. PROFILE FILE OUTPUT FORMAT for the profile file format.
AXICL Axisymmetric center-line (singular boundary aligned with the X axis). NOTE: This not generalized for Y and Z axis.
SINGULAR

or

NOSLPSNG

Singularity exists on boundary condition face. The averaging direction must also be specified (see OPTION). Valid choices are IDIR, JDIR, KDIR or ALL. For example, use KDIR if a polar singularity exists on a J face and the grid is collapsed in the K direction. ALL applies to spherical singularities and implies that the grid is collapsed in all three grid coordinate directions. NOSLPSNG should be used when the B.C. is along a no slip wall.
PERSYM Periodic symmetry. The velocity components to be reflected and the coordinate direction of the periodicity must also be specified (see OPTION). Valid choices are: UVI, UVJ, UVK, UWI, UWJ, UWK, VWI, VWJ, VWK, where VW indicates a reflection of V and W as -V and -W, and K indicates periodicity in the K direction.
The following BC TYPEs require that additional information be provided:
FIXED Supersonic inflow boundary with mass fractions (thermally perfect flows only), density, velocity, temperature/pressure (a positive value implies temperature, a negative value implies pressure), turbulence intensity (if applicable), and turbulent to molecular viscosity ratio (if applicable) specified on the next 2 lines of input, e.g.
 Rho    Uvel  Vvel Wvel   Temp
0.3515  1200.0  0.0  0.0  1000.0

AFIXED Supersonic inflow boundary. This B.C. is the same as FIXED, with the velocity vector realigned to be tangent to the streamwise grid lines, e.g.
        Air    Rho    Uvel  Vvel Wvel   Temp  Turb Int  Vis Ratio
     1.0  0.3515  1200.0  0.0  0.0  1000.0   0.01       0.1

IWALL No slip isothermal wall. Wall temperature and an under-relaxation parameter to follow on the next 2 lines of input, e.g.
Wall Temp  Relax
350.0     0.9

IWALLM No slip isothermal wall using wall functions. Wall temperature and an under-relaxation parameter to follow on the next 2 lines of input. Only available with K-OMEGA and MENTER turbulence models. Should be used if y+ of fine grid is expected to be greater than 2.0 or 3.0, e.g.
Wall Temp  Relax
750.0     1.0

TCWALLM No slip wall using wall functions coupled with a 1-D solid wall heat transfer model. The wall thickness to wall thermal conductivity ratio, external surface temperature, and an under-relaxation parameter are to follow on the next 2 lines of input. Only available with K-OMEGA and MENTER turbulence models:
Thickness/Conductivity  Ext. Temp  Relax
       2.2e-05           750.0     1.0

REWALL No slip wall in radiative equilibrium with its ambient environment. Wall emissivity, an under-relaxation parameter and the ambient temperature to follow on the next two lines of input. NOTE: This boundary condition typically requires low under-relaxation coefficients (typically 0.1 or less):
Wall Emissivity  Amb. Temp  Relax
      0.5         250.0     0.1

SUBMDOTI Subsonic inflow boundary with mass fractions (thermally perfect flows only), static density, velocity, total temperature, and (when solving turbulent flow) the turbulence intensity and turbulent to molecular viscosity ratio to follow on the next 2 lines of input. The product of the input velocity and the static density is used to compute the mass flux, and the mass flux is held constant. The inflow static pressure is determined from the flow inside the computational domain. A method used to compute the inflow velocity vector must be specified as either NORMAL, TANGENT, or VECTOR (see OPTION):
 Rho     Uvel  Vvel Wvel   Temp
0.3515   100.0  0.0  0.0   300.0

SUBIN Subsonic inflow boundary with mass fractions (thermally perfect flows only), total density, velocity, total pressure, and (when solving turbulent flow) the turbulence intensity and turbulent to molecular viscosity ratio to follow on the next 2 lines of input. The method used to compute the velocity vector must be specified as either NORMAL, TANGENT, or VECTOR (see OPTION):
             Air  Total Rho  Uvel  Vvel Wvel  Total Pres  Turb Int  Vis Ratio
          1.0   -1.8525   50.0  0.0  0.0     1.0e06      0.01       0.1
A negative value specified for the total density enforces a quasi 1-D initialization that yields a subsonic inflow condition and a supersonic outflow condition in the grid coordinate direction normal to the boundary condition face.
SUBSONIC Subsonic inflow or outflow boundary with mass fractions (for thermally perfect flows), density, velocity, pressure, and (when solving turbulent flow) the turbulence intensity and turbulent to molecular viscosity ratio to follow on the next 2 lines of input. The method used to compute the velocity vector must be specified as either NORMAL, TANGENT, or VECTOR (see OPTION):
             Air  Total Rho  Uvel  Vvel Wvel  Total Pres  Turb Int  Vis Ratio
          1.0   -1.8525   50.0  0.0  0.0     1.0e06      0.01       0.1
If the flow is detected to be into the computational domain the pressure and density are interpreted as being stagnation (total) conditions.
If the flow is detected to be out of the domain the pressure is interpreted to be a static condition.
A negative value specified for the total density enforces a quasi 1-D initialization that yields a subsonic inflow condition and a supersonic outflow condition in the grid coordinate direction normal to the boundary condition face.
SUBOUT Subsonic outflow boundary with static pressure and an under-relaxation parameter specified on the following 2 lines of input:
 Back Pres  Relax
 101325.0   1.0
A negative value specified for the static pressure uses the reference pressure (provided in the REFERENCE CONDITIONS section of the input deck) as the back pressure.
SUBMDOTO Subsonic outflow boundary with mass flow rate specified. The mass flow rate, an under-relaxation parameter, and an initial guess for the back pressure are required on the next 2 lines of input, e.g.
Mass Flow Rate  Relax  Back Pres
  12.076       0.5     -1.0
A negative value specified for the static pressure uses the reference pressure (provided by the REFERENCE CONDITIONS section of the input deck) as the back pressure.
NOTE: The pressure is checked (and possibly limited) to ensure that the contravariant Mach no. at the outflow plane remains subsonic.

Figure 3 illustrates where most of these boundary condition types may be used.


Figure 3. Boundary condition types.

'OPTION' - a character string (up to 10 characters) that either defines how the boundary condition is used (PHYSICAL, INITIAL, or BLEND) or declares some option for the specified boundary condition type. The character string entered must match one of the following strings:
'PHYSICAL' Used to denote that this B.C. is the actual boundary condition to be imposed
'INITIAL' Used to denote that this B.C is meant to be used for initialization purposes only
'BLEND' Used to denote that this B.C. should be blended with the current initialized conditions
'NORMAL' Forces inflow velocity normal to the boundary
'TANGENT' Forces inflow velocity tangent to grid lines that intersect the boundary
'VECTOR' Forces inflow velocity tangent to a user-defined vector
'JDIR' Averaging direction for SINGULAR or NOSLPSNG B.C. in J-direction
'KDIR' Averaging direction for SINGULAR or NOSLPSNG B.C. in K-direction
'IDIR' Averaging direction for SINGULAR or NOSLPSNG B.C. in I-direction
'ALL' Averaging direction for SINGULAR or NOSLPSNG B.C. in I, J, & K directions
'UVI' Reflection of U and V as -U and -V, and periodicity in the I direction for PERSYM B.C.
'UVJ' Reflection of U and V as -U and -V, and periodicity in the J direction for PERSYM B.C.
'UVK' Reflection of U and V as -U and -V, and periodicity in the K direction for PERSYM B.C.
'UWI' Reflection of U and W as -U and -W, and periodicity in the I direction for PERSYM B.C.
'UWJ' Reflection of U and W as -U and -W, and periodicity in the J direction for PERSYM B.C.
'UWK' Reflection of U and W as -U and -W, and periodicity in the K direction for PERSYM B.C.
'VWI' Reflection of V and W as -V and -W, and periodicity in the I direction for PERSYM B.C.
'VWJ' Reflection of V and W as -V and -W, and periodicity in the J direction for PERSYM B.C.
'VWK' Reflection of V and W as -V and -W, and periodicity in the K direction for PERSYM B.C.
'PROFILE' Causes a profile file to be written at the boundary
'BLEED' Enforces a bleed condition (in or out of the domain) at the boundary

NOTE: INITIAL sets a temporary B.C. to define the desired information to be propagated into the block, thereby resetting the initialization to the specified B.C. conditions. This B.C. data is only used during the initialization process and is ignored thereafter. This option can only be used in conjunction with FIXED, REFFIX, and SUBIN boundary conditions. The SUBIN option, if used soley for initialization, must utilize the quasi 1-D initialization feature.

NOTE: BLEND is designed to be propagate the given B.C. into the block while being linearly blended with the interior cell conditions for a distance equal to 25% of the total number of cells in the FACE type direction. More (or less) blending can be controlled by the general input parameter INIT. BLENDING COEF. This blending is only done during the initialization process. The B.C. is treated as a physical B.C. thereafter.

NOTE: B.C. lines utilizing INITIAL & BLEND require an IN-ORDER number > 0

NOTE: NORMAL, TANGENT, & VECTOR apply only to SUBIN, SUBMDOTI, & SUBSONIC

The bleed specification information must follow the boundary condition group that requested the bleed model. The information that is required are the mass fractions (for thermally perfect flows), mass flux, total temperature, percentage of the surface area that are bleed passages, bleed model type, and the number of cells normal to the boundary for applying the bleed source. Currently, the only available bleed model is model "1", which directly specifies the mass flux in or out of the domain. If the mass flux is positive, this implies that a fluid is to be bled into the domain (with the given composition and total temperature). If the mass flux is negative, this implies that fluid is being bled out of the domain, and the values entered for the composition and total temperature will have no influence on the simulation. In either scenario, the pressure in the bleed cells is not altered. The number of cells normal to the bleed surface should initially be set to 1. If stability problems are encountered, which might occur if the bleed rates are very large, this number can be increased as necessary to stabilize the solution.

An example of bleed specification is given below for bleeding air into a surface modeled as an adiabatic wall:

WALL   AWALLM   BLEED
Air   Mass Flux   Tot. Temp   Area %   Model   # Cells
1.0      5.0       300.0      0.08      1         1  

The following example illustrates the use of bleed for a calorically perfect gas being bled out of a surface modeled as an isothermal wall:

WALL   IWALL   BLEED
Wall Temp.  RELAX
300.0    1.0
Mass Flux   Tot. Temp   Area %   Model   # Cells
  -3.0       300.0      0.06      1         1  

The bleed option (in or out of the domain) is available for use in conjunction with any of the wall boundary conditions.

Each boundary condition specification line consists of the following information:

BC NAME: CHARACTER STRING; up to 10 characters indicating a name for the boundary condition. This name must match a B.C. grouping name defined in the preceding section.

BLK: INTEGER; Block number that the boundary condition applies to.

FACE:CHARACTER STRING; Face that the boundary condition is to be applied on.
I = I constant boundary
J = J constant boundary
K = K constant boundary

PLACE:CHARACTER STRING; Boundary condition location.
MIN = Boundary condition at minimum face
MAX = Boundary condition at maximum face

DIR1:CHARACTER STRING; Direction "1" for defining the B.C. window (e.g. for FACE 'I', DIR1 would be either 'J' or 'K').
I = I direction
J = J direction
K = K direction

BEG:CHARACTER STRING; Grid point at which to begin boundary condition which runs in the direction specified by DIR1.
MIN = Start at minimum index of DIR1
10  = Start at index 10 of DIR1

END:CHARACTER STRING; Grid point at which to end boundary condition which runs in the direction specified by DIR1.
MAX = End at maximum index of DIR1
22  = End at index 22 of DIR1

NOTE 1: BEG must be less than END by at least 1.

NOTE 2: The sequence (DIR1, BEG, END) must be repeated for DIR2.

IN-ORDER:INTEGER; Indicates whether the B.C. is to be propagated into the interior of the block as a part of the initialization process, and the order it is to be used in the initialization process.
0 = Do not use for initialization
1,2,3, ... = Propagate the B.C. into the block interior as a part of the initialization process, where the number indicates the order in which to use the B.C. in that process.

NOTE: All B.C.s must have an IN-ORDER number assigned to them. If the B.C. is applied to an IMIN face it will be propagated in the positive I direction from the IMIN boundary to the IMAX boundary.

SPECIAL CASES:

1) Writing a solution profile: PROFILE

The name of the profile file to be written must follow the boundary condition input line.

Example:

BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER
PROFILE   1  I   MIN   J   MIN   MAX   K   MIN   MAX      0
outflow.prf

2) Reading a solution profile: PROFILE, PPROFILE, STWALL, STWALLM and CPWALLM

The name of the profile file to be read must follow the boundary condition input line. The manner in which the profile is to interface with the block boundary must also be specified as shown below. The BEG and END character strings can be given as MIN MAX or MAX MIN. The order determines how the profile is read in, i.e.

DIR1  BEG  END
 J    MIN  MAX : profile is read in ascending J order
 J    MAX  MIN : profile is read in descending J order

Example:

BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER
AIR-IN   1  I   MIN    J   MIN   MAX    K   MIN   MAX      1
outflow.prf                    J   MAX   MIN    K   MIN   MAX 

The grouping of boundary conditions provides the additional benefit of providing a mechanism for tracking integrated loads for various components. For instance, a wing and flap combination could conveniently be broken up in the following manner:

BC GROUPS: NAME      TYPE      OPTION
FREESTREAM  REFFIX    PHYSICAL
OUTFLOW   EXTRAP    PHYSICAL
WING      IWALLM     PHYSICAL
T-WALL   TEMP-RLX
300.0    1.0
FLAP      IWALLM     PHYSICAL
T-WALL   TEMP-RLX
300.0    1.0
BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER
OUTFLOW  1  I   MIN    J   MIN   MAX    K   MIN   MAX      0
OUTFLOW  1  I   MAX    J   MIN   MAX    K   MIN   MAX      0
FREESTREAM  1  J   MIN    K   MIN   MAX    I   MIN   MAX      0
FLAP      1  J   MAX    K   MIN   MAX    I    21    51      0
WING      1  J   MAX    K   MIN   MAX    I    51   151      0
FLAP      1  J   MAX    K   MIN   MAX    I   151   181      0

Based on this grouping of boundary conditions, the VULCAN post-processor would output the integrated surface loads for the boundary condition group WING and the boundary condition group FLAP; providing a useful accounting system for the aerodynamic loads.

Further control governing how the VULCAN post-processor outputs integrated loads is provided through the use of boundary condition objects (BCOBJECTS). Boundary condition objects represent "groupings" of boundary condition groups. This allows the integrated loads of two or more boundary condition groups to be summed together. In the example above, one could have defined a boundary condition object that contained the WING and FLAP groupings, resulting in the output of integrated loads for the entire wing/flap combination (in addition to the loads on the wing and flap separately). Each boundary condition object consists of two lines of information. The 1st line contains the boundary condition object name (an arbitrary choice), and the number of boundary condition groupings that the object contains. The 2nd line lists the boundary condition groupings contained within the object. The boundary condition object input section must lie between the boundary condition grouping input description and the boundary condition specification input section. The first line of input for this section is a comment line (the $ delineator is not required).

Example: Simple 2-D scramjet combustor

BC GROUPS: NAME      TYPE      OPTION
AIR-IN    SUBIN     NORMAL
Air   Tot. Dens.   U-vel   V-vel   W-vel   Tot. Pres.   Turb. Int.   Vis. Ratio
1.0   7.1975e+00   380.0   0.0     0.0     9.1550e+05   0.01         0.1
OUTFLOW   EXTRAP    PHYSICAL
COMB-WALL  IWALLM     PHYSICAL
T-WALL   TEMP-RLX
500.0    1.0
RAMP1  IWALLM     PHYSICAL
T-WALL   TEMP-RLX
650.0    1.0
RAMP2  IWALLM     PHYSICAL
T-WALL   TEMP-RLX
650.0    1.0
CAVITY  IWALLM     PHYSICAL
T-WALL   TEMP-RLX
800.0    1.0
BC OBJECTS: NAME      # OF GROUP MEMBERS
RAMPS             2
RAMP1   RAMP2
PILOT             3
RAMP1   RAMP2   CAVITY
COMBUSTOR           4
RAMP1   RAMP2   CAVITY   COMB-WALL
BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER
AIR-IN   1  I   MIN    J   MIN   MAX    K   MIN   MAX      0
COMB-WALL  1  J   MIN    K   MIN   MAX    I   MIN   MAX      0
COMB-WALL  1  J   MAX    K   MIN   MAX    I   MIN   MAX      0
RAMP1  2  J   MIN    K   MIN   MAX    I   MIN   MAX      0
RAMP2  2  J   MAX    K   MIN   MAX    I   MIN   MAX      0
CAVITY  3  I   MIN    J   MIN    61    K   MIN   MAX      0
CAVITY  3  I   MIN    J   101   MAX    K   MIN   MAX      0
CAVITY  3  I   MAX    J   MIN    61    K   MIN   MAX      0
CAVITY  3  I   MAX    J   101   MAX    K   MIN   MAX      0
CAVITY  3  J   MIN    K   MIN   MAX    I   MIN   MAX      0
CAVITY  3  J   MAX    K   MIN   MAX    I   MIN   MAX      0
OUTFLOW  4  I   MAX    J   MIN   MAX    K   MIN   MAX      0
COMB-WALL  4  J   MIN    K   MIN   MAX    I   MIN   MAX      0
COMB-WALL  4  J   MAX    K   MIN   MAX    I   MIN   MAX      0

In the example above, three boundary condition objects have been defined (RAMPS, PILOT, and COMBUSTOR). When the VULCAN post-processor is executed, integrated loads will be output for each of the boundary condition groups, followed by the integrated loads for each of the boundary condition objects. The RAMPS object will contain the sum of the integrated loads for each ramp injector, the PILOT object will contain the sum of the integrated loads for each ramp injector plus the cavity flameholder, and the object COMBUSTOR will contain the sum of the integrated loads for each ramp injector plus the cavity flameholder plus all of the combustor walls.

It is still possible to enter in the boundary conditions using the older VULCAN format (although BLEED and some boundary condition types require the use of the boundary condition groups format). The old format does not utilize boundary condition groupings, so the boundary condition type (and any supplemental information) must be given for each boundary condition specification. VULCAN defaults to this format if the BCGROUPS line is missing, or if a value of zero is entered for this parameter. The format of each boundary condition specification line is identical to the current format, except an extra column is required to specify the boundary condition type:

BC TYPE:CHARACTER STRING; Type of boundary condition to be used (see Table III for legitimate BC TYPEs). BC TYPE depends to some extent on, and must be consistent with, the gas model specified in the "gas and thermodynamic data" section, above (either calorically perfect (CP) or thermally perfect (TP)).

This B.C. specification format allows for any boundary condition name in the BC NAME column, except for the reserved strings that are used to define how a boundary condition is used (i.e. the strings used in the OPTION column of the boundary condition grouping section described above):

'INITIAL' Used to denote that this B.C is meant to be used for initialization purposes only
'BLEND' Used to denote that this B.C. should be blended with the current initialized conditions
'NORMAL' Forces inflow velocity normal to the boundary
'TANGENT' Forces inflow velocity tangent to grid lines that intersect the boundary
'VECTOR' Forces inflow velocity tangent to a user-defined vector
'JDIR' Averaging direction for SINGULAR or NOSLPSNG B.C. in J-direction
'KDIR' Averaging direction for SINGULAR or NOSLPSNG B.C. in K-direction
'IDIR' Averaging direction for SINGULAR or NOSLPSNG B.C. in I-direction
'ALL' Averaging direction for SINGULAR or NOSLPSNG B.C. in I, J, & K directions
'UVI' Reflection of U and V as -U and -V, and periodicity in the I direction for PERSYM B.C.
'UVJ' Reflection of U and V as -U and -V, and periodicity in the J direction for PERSYM B.C.
'UVK' Reflection of U and V as -U and -V, and periodicity in the K direction for PERSYM B.C.
'UWI' Reflection of U and W as -U and -W, and periodicity in the I direction for PERSYM B.C.
'UWJ' Reflection of U and W as -U and -W, and periodicity in the J direction for PERSYM B.C.
'UWK' Reflection of U and W as -U and -W, and periodicity in the K direction for PERSYM B.C.
'VWI' Reflection of V and W as -V and -W, and periodicity in the I direction for PERSYM B.C.
'VWJ' Reflection of V and W as -V and -W, and periodicity in the J direction for PERSYM B.C.
'VWK' Reflection of V and W as -V and -W, and periodicity in the K direction for PERSYM B.C.
'PROFILE' Causes a profile file to be written at the boundary

The BC TYPEs that require additional input must be specified for each specific boundary condition line. The boundary condition types that require additional input, as indicated in Table III, all have the same read format. This format requires that the user supply a group of real numbers equal to the number of governing equations being solved. Two additional lines of input are required. The first is a comment line for naming the variables to be specified in the next line. The second consists of numerical values separated by commas and/or spaces. The information required for each equation slot is described in Table IV for each of the BC TYPEs. Examples are given following the table.


Table IV. Required Additional Information for Relevant Boundary Condition Types
BC TYPE Continuity Eqs. Momentum Eqs. Energy Eqs. Turbulence Eqs.
FIXED mass frac. &/or rho u, v, w -Ps or Ts int., v.r.
AFIXED mass frac. &/or rho u, v, w -Ps or Ts int., v.r.
IWALL n.e. relax (u position)  Ts n.e.
IWALLM n.e. relax (u position)  Ts n.e.
TCWALLM wall thickness /
wall conductivity 		relax (u position)  Text n.e.
REWALL emissivity relax (u position)  Tamb n.e.
SUBMDOTI mass frac. &/or rho u, v, w  Tt int., v.r.
SUBIN mass frac. &/or rhot or -rhot u, v, w
(used for t.k.e.) 		 Pt int., v.r.
SUBSONIC mass frac. &/or rhot or -rhot u, v, w
(used for t.k.e.) 		 Pt or Ps int., v.r.
SUBOUT n.e. relax (u position) -Pr or Ps n.e.

    KEY:
    1. mass frac.: Species mass fractions in gas (1 per species).
    2. rho: Static density of gas (kilograms/meter**3).
    3. rhot: Total density of gas (kilograms/meter**3). If -rhot is used, a quasi 1-D initialization for subsonic inflow and supersonic outflow will be made in the grid coordinate direction normal to the boundary condition face.
    4. u,v,w: Cartesian velocity components (meter/second).
      All are required, except when using the SUBIN or SUBSONIC BC TYPEs (required to initialize the turbulent kinetic energy).
    5. -Ps,Ts: Static pressure or temperature.
      6. > 0 = use as static temperature (Kelvin).
      < 0 = use as static pressure (Pascal).
    6. Pt: Total pressure (Pascal).
    7. Tt: Total temperature (Kelvin).
    8. Pt,Ps: Total or static pressure (Pascal). (When SUBSONIC is the boundary condition type, the specified pressure is used as a static pressure or total pressure depending on the contravariant Mach number).
    9. -Pr,Ps: Static pressure for back pressure.
      10. > 0 = use as static pressure (Pascal).
      < 0 = use reference pressure instead.
    10. wall thickness / wall conductivity: The wall thickness (meters) divided by the wall material thermal conductivity (Watts/meter-Kelvin).
    11. Text: Wall external surface temperature (Kelvin).
    12. emissivity: Wall emissivity (a coefficient that is less than 1.0)
    13. Tamb: Ambient temperature to which wall radiates (Kelvin).
    14. relax: Under-relaxation coefficient. A less-than-unity number to "soften" the specification of the temperature (or pressure). Values that are negative or greater than unity will be reset to unity (in effect, turning the under-relaxation off). Must be in the 1st velocity position.
    15. int.: Intensity of velocity fluctuations (2-equation turbulence models only) (generally 0.05 or less).
    16. v.r.: Eddy viscosity / molecular viscosity (1-equation and 2-equation turbulence models).
    17. n.e.: input is required but not used (null entry).

Example 1 (FIXED): Calorically perfect gas; Laminar flow. 5 equations must be solved, so that 5 variables must be entered in the variable line. It will be the 5th condition propagated during initialization.

BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER  BC-TYPE
AIR-IN   1  I   MIN    J   MIN   MAX    K   MIN   MAX      5  FIXED 
   Rho    Uvel  Vvel Wvel    Ts
 0.3515  1200.0  0.0  0.0  1000.0

Example 2 (SUBIN): Gas made up of 7 species; 2-equation turbulence model. A quasi 1-D nozzle initialization will be performed during the initialization process.

BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER  BC-TYPE
AIR-IN   1  I   MIN  J  MIN   MAX    K   MIN   MAX      0  SUBIN
  H2   O2  H2O  OH  O   H    N2    Rhot  Uvel Vvel Wvel    Pt    Tint Vrat
 0.0 0.233 0.0 0.0 0.0 0.0 0.767 -7.1975 380.0 0.0  0.0 915500.0 0.01  0.1

Example 3 (IWALLM): Gas made up of 8 species; 2-equation turbulence model. An isothermal wall with a specified wall static temperature of 292.0 Kelvin using the wall matching functions for the k-omega or Menter 2-equation turbulence models. It will be the 3rd BLENDed B.C. during the initialization process.

BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER  BC-TYPE
BLEND   1  I   MIN    J   MIN   MAX    K   MIN   MAX      3  IWALLM 
 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A T_wall N/A N/A
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 292.00 0.0 0.0

Example 4: PROFILE (specified as the BC NAME): Writes a profile file. The name of the profile file to be written must follow the boundary condition input line.

BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER  BC-TYPE
PROFILE   1  I   MIN   J   MIN   MAX   K   MIN   MAX      1  EXTRAP 
outflow.prf

Example 5: PROFILE, PPROFILE, STWALL, STWALLM and CPWALLM (specified as the BC TYPE): Reads a profile file. The name of the profile file to be read must be given on the following line. The manner in which the profile is to interface with the block boundary must be specified as shown below. The BEG and END character strings must be given as MIN MAX or MAX MIN. The order determines how the profile is to be read in, i.e.

DIR1  BEG  END
 J    MIN  MAX : profile is read in ascending J order
 J    MAX  MIN : profile is read in descending J order

BC-NAME  BLK  FACE  PLACE  DIR1   BEG   END  DIR2   BEG   END  IN-ORDER  BC-TYPE
AIR-IN   1  I   MIN    J   MIN   MAX    K   MIN   MAX      1 PROFILE
outflow.prf                    J   MAX   MIN    K   MIN   MAX 

As a final note, if the old boundary condition format is used (i.e. if the BCGROUPS line is missing, or if a value of zero is entered for this parameter) the VULCAN post-processor outputs the integrated loads on an individual boundary condition basis, followed by the integrated loads on a per block basis, and finally the integrated loads for the total computational domain are output.


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