WIND User's Guide - Keyword Reference, ARBITRARY INFLOW

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ARBITRARY INFLOW - Arbitrary inflow (block)

{ARBITRARY INFLOW | DIFFUSER INFLOW}
   [STATIC | TOTAL]
   [HOLD_TOTALS | HOLD_CHARACTERISTICS]
   [DIRECTION {SPECIFIED | NORMAL [TO INFLOW PLANE] | ALONG [GRID LINES]}]
   ZONE n
   [UNIFORM [M P T alpha beta] [val_k [val_om]]
      [sp₁ sp₂ ... sp_n]]
   [IJK_RANGE [FROZEN] imin imax jmin jmax kmin kmax M P T alpha beta \
                       [val_k [val_om]]
      [sp₁ sp₂ ... sp_n]]
   [UNSTEADY var_name freq ampl phase]
   [{VORTEX | SOLIDBODY | ROTATESOLID} M_n P T alpha beta xc yc zc \
      {dw1 | dw1 dw2 dw3}]
   [USERSPEC fs bl1 bl2 npts
      y1 M P T alpha beta
      y2 M P T alpha beta
      ...
      yn M P T alpha beta]
   [USERCHEM fs bl1 bl2 npts
      y1 M P T alpha beta sp₁ sp₂ ... sp_n
      y2 M P T alpha beta sp₁ sp₂ ... sp_n
      ...
      yn M P T alpha beta sp₁ sp₂ ... sp_n]
   [USERKE fs bl1 bl2 npts
      y1 M P T alpha beta val_k [val_om]
      y2 M P T alpha beta val_k [val_om]
      ...
      yn M P T alpha beta val_k [val_om]]
   [USERCHEMKE fs bl1 bl2 npts
      y1 M P T alpha beta sp₁ sp₂ ... sp_n val_k [val_om]
      y2 M P T alpha beta sp₁ sp₂ ... sp_n val_k [val_om]
      ...
      yn M P T alpha beta sp₁ sp₂ ... sp_n val_k [val_om]]
[ENDINFLOW]

Several options are available to set conditions at arbitrary inflow boundaries. The default is uniform inflow (i.e., no boundary layer) at the conditions that are set using the FREESTREAM keyword. Other options are selected by using either of the equivalent keywords ARBITRARY INFLOW or DIFFUSER INFLOW.

The remaining lines select the specific type of nonuniform entrance data to be provided. Discussion of the input data for each of these options is presented in the remainder of this subsection, grouped by "Control Functions", "Condition Specification", and "Special Capabilities". These keywords can start in any column. Generally, they should be indented from the ARBITRARY INFLOW keyword to set them apart.

This keyword may also be used to initialize (or reinitialize) the flow conditions within the specified zone, as described in the section Flowfield Initialization.

Note: The GAS keyword and the CHEMISTRY keyword block, if used, must come before the ARBITRARY INFLOW keyword block in the input data (.dat) file.

Control Functions

ENDINFLOW

This optional keyword may be used to end the arbitrary inflow definition.

STATIC | TOTAL

Arbitrary inflow conditions specified after this keyword will be considered as static or total, depending which of these is set. By default, the flag is set to the value from the FREESTREAM keyword.

Note: TOTAL is only valid for an ideal gas.

HOLD_TOTALS | HOLD_CHARACTERISTICS

Specifying HOLD_TOTALS indicates that total temperature and local flow angles are to be held at their specified values, and is only valid for a perfect gas. Specifying HOLD_CHARACTERISTICS indicates that characteristic values are to be held constant. The option specified will be applied at all the arbitrary inflow regions in the zone, and will remain in effect for all following ZONE keywords.

In WIND 5.201 and later the default is HOLD_CHARACTERISTICS. In earlier versions the default is HOLD_TOTALS.

HOLD_TOTALS only works in conjunction with the UNIFORM, IJK_RANGE, VORTEX, SOLIDBODY, and ROTATESOLID keywords.

The total pressure is always held fixed, whether HOLD_TOTALS is specified or not. Although the Mach number is specified with the UNIFORM and IJK_RANGE keyword parameters, it may be adjusted during the boundary condition treatment.

Note that the HOLD_TOTALS keyword in the ARBITRARY INFLOW keyword block applies to arbitrary inflow boundaries only. See the HOLD keyword for information on holding conditions at freestream boundaries with inflow.

Note also that the syntax is slightly different for arbitrary inflow and freestream boundaries. For arbitrary inflow boundaries, HOLD_TOTALS and HOLD_CHARACTERISTICS are used in the ARBITRARY INFLOW keyword block, with an underscore. For freestream boundaries, HOLD TOTALS and HOLD CHARACTERISTICS are used, without an underscore.

DIRECTION {SPECIFIED | NORMAL [TO INFLOW PLANE] | ALONG [GRID LINES]}

The DIRECTION keyword indicates how the flow angle is to be set at an inflow plane. The options for setting the flow direction are:

SPECIFIED Set the flow at the angles of attack and yaw specified elsewhere in the ARBITRARY INFLOW block. This is the default.
NORMAL Set the flow normal to the inflow plane.
ALONG Set the flow in the direction of the grid lines intersecting the inflow plane.

Specifying DIRECTION NORMAL or DIRECTION ALONG will override any angles of attack or yaw specified with the UNIFORM, IJK_RANGE, VORTEX, SOLIDBODY, and ROTATESOLID keywords. However, if UNIFORM is used without specifying the flow conditions, the angles specified with the FREESTREAM keyword will be used, and the DIRECTION keyword will have no effect. The DIRECTION keyword also does not affect flow angles in profiles specified with the USERSPEC, USERCHEM, USERKE, or USERCHEMKE keywords.

The DIRECTION keyword will not modify the flow angles that are set when ARBITRARY INFLOW is being used to initialize (or reinitialize) flow conditions within a zone.

The DIRECTION option used will remain in effect for all following ZONE keywords.

ZONE n

This keyword, which must be specified, identifies the zone for which inflow conditions are being set. For example, if zone 2 is an internal jet, conditions other than freestream may be desired at the inflow to zone 2.

Within the ARBITRARY INFLOW keyword block, the ZONE keyword must come before any "Condition Specification" keyword for that zone, but after any HOLD_TOTALS, HOLD_CHARACTERISTICS, or DIRECTION keyword for that zone. In addition, inflow conditions may only be specified for one zone at a time.

Example

The following ARBITRARY INFLOW block specifies that total conditions are to be held constant at arbitrary inflow surfaces in zones 1 and 2, with M = 3.5, P_T = 251.15 psi, and T_T = 1167.9 °R. In zone 3, characteristic values are to be held constant at arbitrary inflow surfaces, consistent with the flow conditions given with the FREESTREAM keyword.

   ARBITRARY INFLOW 
      TOTAL
      HOLD_TOTALS
         ZONE 1
         UNIFORM 2.5 251.15 1167.9 0.0 0.0
         ZONE 2
         UNIFORM 2.5 251.15 1167.9 0.0 0.0
      HOLD_CHARACTERISTICS
         ZONE 3
         UNIFORM
   ENDINFLOW

Condition Specification

UNIFORM [M P T alpha beta] [val_k [val_om]]
   [sp₁ sp₂ ... sp_n]

The entrance flow is uniform, at the conditions specified. If no flow conditions are specified, those specified with the FREESTREAM keyword are used. No other data is provided to select this option. This is the default option, and is selected automatically if no extended input options are selected.

Different conditions can be specified within each zone. This is done by adding the run conditions after the keyword. These data are added in free format, one or more blanks separating values.

M Mach number
P Pressure
T Temperature
alpha, beta Angles of attack and yaw, relative to the Cartesian x direction
sp₁, sp₂, ..., sp_n Species mass fractions

Pressure and temperature are static or total, depending on whether STATIC or TOTAL is specified. As always, pressure is specified in pounds per square inch, temperature in degrees Rankine, and alpha and beta in degrees.

If the SST turbulence model is being used (see the TURBULENCE keyword), val_k and val_om may be used to specify inflow turbulence levels. Note that you may specify either val_k, or val_k and val_om, but not val_om by itself. Note also that if these values are being specified, the TURBULENCE keyword must come before the ARBITRARY INFLOW keyword block in the input data (.dat) file.

The following options are possible:

val_k > 0 The turbulent kinetic energy k and the specific dissipation rate omega are specified directly, with
k = val_k (ft²/sec²)
omega = val_om (1/sec)

The turbulent viscosity nu_t is then equal to k/omega.

val_k < 0 The turbulent kinetic energy k is set equal to val_k percent of the "reference" kinetic energy U²/2, where U is computed from the specified values of M and T. Thus
k = 0.01 abs(val_k) (U²/2)

The turbulent viscosity nu_t is automatically set equal to 0.001 nu_l, where nu_l is the laminar viscosity, and the specific dissipation rate is computed as omega = k / nu_t.

val_om < 0 The specific dissipation rate omega is set equal to val_om percent of U/L_ref, where U is computed from the specified values of M and T, and L_ref is the reference length from the grid (.cgd) file. Thus
omega = 0.01 abs(val_om) (U/L_ref)

The turbulent viscosity nu_t is set to the same percentage of the laminar viscosity.
nu_t = 0.01 abs(val_om) (nu_l)

The turbulent kinetic energy is then computed as k = omega nu_t.

If inflow turbulence levels are not specified using one of the above options, or if val_k = 0, default values are computed from

omega = 10 U / L_ref
nu_t = 0.001 nu_l
k = omega nu_t

Note that

If val_k > 0, a positive value must be specified for val_om.
If val_k <= 0, val_om should not be specified.
If val_om < 0, a value must also be specified for val_k, but it is ignored.

Example

   ARBITRARY INFLOW 
      UNIFORM 1.1 100. 900. 10. 0.
   ENDINFLOW

IJK_RANGE [FROZEN] imin imax jmin jmax kmin kmax M P T alpha beta \
                   [val_k [val_om]]
   [sp₁ sp₂ ... sp_n]]

This keyword allows specification of inflow conditions over an arbitrary range of i, j, and k indices on any computational boundary plane. The user specifies the minimum and maximum i, j, and k indices which describe the region, followed by the flow conditions to be applied, as follows:

imin, imax Minimum and maximum i indices bounding the region
jmin, jmax Minimum and maximum j indices bounding the region
kmin, kmax Minimum and maximum k indices bounding the region
M Mach number
P Pressure
T Temperature
alpha, beta Angles of attack and yaw, relative to the Cartesian x direction
sp₁, sp₂, ..., sp_n Species mass fractions

The FROZEN option may be specified to freeze the inflow conditions over the indicated index range at their current values. Note that for a restart case (i.e., when a .cfl file already exists), the "current values" are those in the .cfl file, not those specified with the IJK_RANGE parameter. For an initial run (i.e., when a .cfl file does not exist), the flow conditions will be frozen at the conditions specified with the IJK_RANGE parameter.

If the SST turbulence model is being used (see the TURBULENCE keyword), val_k and val_om may be used to specify inflow turbulence levels. The various options are described above under the UNIFORM keyword.

Up to 500 IJK_RANGE keywords may be specified. This is useful when specifying a boundary layer profile at an inflow boundary, or along solid walls during the flowfield initialization process.

UNSTEADY var_name freq ampl phase

This keyword allows the user to specify unsteady arbitrary inflow conditions, and it must be used with (and follow) the IJK_RANGE keyword. Up to three different perturbations to the inflow conditions may be specified and will be superimposed to create unsteadiness centered about the conditions given with the IJK_RANGE keyword.

var_name One of the keywords MACH, PRESSURE, TEMPERATURE, ALPHA, BETA, or VELOCITY
freq Frequency of the perturbation in Hertz
ampl Amplitude of the perturbation in appropriate variable units
phase Phase angle of the perturbation in degrees

Note that you may specify multiple, independent pairs of IJK_RANGE and UNSTEADY keywords.

{VORTEX | SOLIDBODY | ROTATESOLID} M_n P T alpha beta xc yc zc \ {dw1 | dw1 dw2 dw3}

Specifies uniform inflow conditions with free-vortex or solid-body rotation superimposed. Solid-body rotation may be specified on any arbitrary inflow boundary. For free-vortex rotation, however, the arbitrary inflow boundary must be a constant x, y, or z plane, and the center of rotation must lie on that plane.

M_n Normal component of Mach number
P Pressure (psia)
T Temperature (°R)
alpha, beta Average angles of attack and yaw, relative to the Cartesian x direction
xc, yc, zc Center of rotation in physical coordinates

For VORTEX,

dw1 Vortex strength. (See the ACTUATOR keyword.)

For SOLIDBODY and ROTATESOLID,

dw1, dw2, dw3 x, y, and z components of the rotation rate vector (radians/sec)

The rotational velocity components are added in such a way that total pressure and total temperature are held constant at the inflow boundary. Thus, the TOTAL option should always be used for this mode, since with the STATIC option the computed static pressure and temperature at the inflow boundary may differ from the specified values.

For calculations in a rotating reference frame (see the ROTATE keyword):

If the SOLIDBODY option is used, the total conditions specified are those in the rotating frame, and are held fixed in that frame. The total conditions in the inertial frame will vary.
If the ROTATESOLID option is used, the total conditions specified are those in the inertial frame, and are held fixed in that frame. The total conditions in the rotating frame will vary. Note that the ROTATESOLID option is only valid for calculations in a rotating reference frame.

For both free-vortex and solid-body rotation, the flowfield must already be initialized. (See the Flowfield Initialization section.) I.e., there must be a pre-existing .cfl file. The VORTEX, SOLIDBODY, and ROTATESOLID options cannot be used during a "cold" start.

Special Capabilities

The following arbitrary inflow keywords effect changes only to the i = 1 computational plane.

USERSPEC fs bl1 bl2 npts y1 M P T alpha beta y2 M P T alpha beta ... yn M P T alpha beta

This option allows the user to specify a 1-D profile normal to the surface, translated through some buttline range, below the vehicle. These conditions will be set last and thus the data will overwrite UNIFORM conditions over the range of interest.

fs Fuselage station of the profile (to be checked against the grid i = 1 fuselage station)
bl1, bl2 Minimum and maximum buttline over which to translate the profile
npts Number of points defining the profile
y1 - yn Normal distance from the wall
M Mach number
P Pressure (psia)
T Temperature (°R)
alpha, beta Angles of attack and yaw, relative to the Cartesian x direction

The pressure and temperature may be the total or static conditions, depending upon the current setting of the TOTAL/STATIC keyword. If neither STATIC nor TOTAL have been specified under ARBITRARY INFLOW, then the existing switch from the global input parameters is used (default: TOTAL).

One profile can be specified for each zone. There can be 100 points in each profile. The normal distance is always assumed to be from j = 1 (the reference wall is assumed to be at j = 1). bl1 is the minimum buttline and bl2 is the maximum buttline.

See Also: TEST 157
By default, USERSPEC only specifies conditions below a vehicle. That is, the wall (j = 1) must be above (higher y) the interior grid points. TEST 157 specifies that all points within the specified buttline range will be affected, above and below the vehicle. This should be the default, but isn't.

USERCHEM fs bl1 bl2 npts y1 M P T alpha beta sp₁ sp₂ ... sp_n y2 M P T alpha beta sp₁ sp₂ ... sp_n ... yn M P T alpha beta sp₁ sp₂ ... sp_n

The USERCHEM option is identical to the USERSPEC option, except that chemistry species mass fractions sp₁, sp₂, ..., sp_n are added to the end of each specified profile. Test options can then be set to model the mixing of gas streams which have different chemical compositions. At this time, only mixing can be modeled. The gas streams cannot chemically react.

Note: Only the STATIC input mode is available for chemistry.

Note: For TEST 75 1, the sp input parameters specify the mass fractions of O₂, CO₂, H₂O, NO₂, and N₂, in that order. For TEST 75 2, they specify the mass fractions of O₂, H, H₂, H₂O, and N₂. The user must be careful to enter the mass fractions in the order shown, entering zeroes to leave out particular species.

Part of an example USERCHEM input block follows. The file sets up a rectangular jet where the jet composition is a mixture of O₂, CO₂, H₂O, NO₂, and N₂. The last five columns hold the species mass fractions for the profiles. Note that the second-to-last column consists of zeroes; this is the unused position in the chemistry array which was described above for a four-species chemistry model.

   ARBITRARY INFLOW
      ZONE 1
      USERCHEM 0.0 -10.0 10.0 6
        0.0   0.3  5.70   433.1  0.0  0.0  0.234  0.0    0.0    0.0  0.766
      123.05  0.3  5.70   433.1  0.0  0.0  0.234  0.0    0.0    0.0  0.766
      123.05  1.8  5.66  1940.0  0.0  0.0  0.096  0.120  0.048  0.0  0.736
      133.75  1.8  5.66  1940.0  0.0  0.0  0.096  0.120  0.048  0.0  0.736
      133.75  0.3  5.70   433.1  0.0  0.0  0.234  0.0    0.0    0.0  0.766
      257.0   0.3  5.70   433.1  0.0  0.0  0.234  0.0    0.0    0.0  0.766
   ENDINFLOW
   TEST 157 1     USERSPEC ABOVE AND BELOW VEHICLE

USERKE fs bl1 bl2 npts
   y1 M P T alpha beta val_k [val_om]
   y2 M P T alpha beta val_k [val_om]
   ...
   yn M P T alpha beta val_k [val_om]

The USERKE option is identical to the USERSPEC option, except that the values val_k and val_om are added to specify inflow turbulence levels when the SST turbulence model is being used. The various options are described above under the UNIFORM keyword.

USERCHEMKE fs bl1 bl2 npts y1 M P T alpha beta sp₁ sp₂ ... sp_n val_k [val_om] y2 M P T alpha beta sp₁ sp₂ ... sp_n val_k [val_om] ... yn M P T alpha beta sp₁ sp₂ ... sp_n val_k [val_om]

The USERCHEMKE option is identical to the USERCHEM option, except that the values val_k and val_om are added to specify inflow turbulence levels when the SST turbulence model is being used. The various options are described above under the UNIFORM keyword.

See Also: TURBULENCE, REINITIALIZE, ROTATE

	`SPECIFIED`		Set the flow at the angles of attack and yaw specified elsewhere in the `ARBITRARY INFLOW` block. This is the default.
	`NORMAL`		Set the flow normal to the inflow plane.
	`ALONG`		Set the flow in the direction of the grid lines intersecting the inflow plane.

	M		Mach number
	P		Pressure
	T		Temperature
	alpha, beta		Angles of attack and yaw, relative to the Cartesian x direction
	sp₁, sp₂, ..., sp_n		Species mass fractions

	val_k > 0		The turbulent kinetic energy k and the specific dissipation rate omega are specified directly, with k = val_k (ft²/sec²) omega = val_om (1/sec) The turbulent viscosity nu_t is then equal to k/omega.
	val_k < 0		The turbulent kinetic energy k is set equal to val_k percent of the "reference" kinetic energy U²/2, where U is computed from the specified values of M and T. Thus k = 0.01 abs(val_k) (U²/2) The turbulent viscosity nu_t is automatically set equal to 0.001 nu_l, where nu_l is the laminar viscosity, and the specific dissipation rate is computed as omega = k / nu_t.
	val_om < 0		The specific dissipation rate omega is set equal to val_om percent of U/L_ref, where U is computed from the specified values of M and T, and L_ref is the reference length from the grid (.cgd) file. Thus omega = 0.01 abs(val_om) (U/L_ref) The turbulent viscosity nu_t is set to the same percentage of the laminar viscosity. nu_t = 0.01 abs(val_om) (nu_l) The turbulent kinetic energy is then computed as k = omega nu_t.

	imin, imax		Minimum and maximum i indices bounding the region
	jmin, jmax		Minimum and maximum j indices bounding the region
	kmin, kmax		Minimum and maximum k indices bounding the region
	M		Mach number
	P		Pressure
	T		Temperature
	alpha, beta		Angles of attack and yaw, relative to the Cartesian x direction
	sp₁, sp₂, ..., sp_n		Species mass fractions

	var_name		One of the keywords `MACH`, `PRESSURE`, `TEMPERATURE`, `ALPHA`, `BETA`, or `VELOCITY`
	freq		Frequency of the perturbation in Hertz
	ampl		Amplitude of the perturbation in appropriate variable units
	phase		Phase angle of the perturbation in degrees

	M_n		Normal component of Mach number
	P		Pressure (psia)
	T		Temperature (°R)
	alpha, beta		Average angles of attack and yaw, relative to the Cartesian x direction
	xc, yc, zc		Center of rotation in physical coordinates

	fs		Fuselage station of the profile (to be checked against the grid i = 1 fuselage station)
	bl1, bl2		Minimum and maximum buttline over which to translate the profile
	npts		Number of points defining the profile
	y1 - yn		Normal distance from the wall
	M		Mach number
	P		Pressure (psia)
	T		Temperature (°R)
	alpha, beta		Angles of attack and yaw, relative to the Cartesian x direction