VORTEX [GENERATOR]
  ZONE iz1 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX} \
       [SUBSET I range J range K range]
  ZONE iz2 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX} \
       [SUBSET I range J range K range]
  NUMBER ival
    vg_boundary {XLOC xl | YLOC yl | ZLOC zl} chord height alpha \
       [VEL vmax] [DEL delta]
ENDVORTEX

This keyword block is applicable to three-dimensional cases and enables the user to specify a discontinuous change in secondary velocity across a zone boundary in order to simulate the vortices produced by an array of vane-type vortex generators. A vortex generator array consists of one or more vortex generators mounted on viscous wall boundaries. A separate vortex generator keyword block must be used for each array. The model is only applicable to generators placed on viscous wall boundaries. It is the user's responsibility to check this - WIND currently has no mechanism for flagging this input error.

The vortex generator model determines the strength of each vortex based on the generator chord length, height and angle of incidence with the incoming flow, as well as the incoming flow core velocity and boundary layer thickness. Each vortex center is placed at the grid point closest to the location determined by the user-specified generator location on the boundary, and the generator height.

Note that the vortex generator model is derived from experimental data taken at axial stations which were one chord length downstream of the trailing edge of the generators, and therefore the secondary velocities produced by the model simulate vortices at this station, rather than at the generator trailing edges. For most accurate results, the boundary where the vortex generator boundary condition is applied should be at this one chord length station.

The following restriction applies:

• The BOUNDARY TVD FACTOR 0 keyword option should be used at all interface boundaries containing vortex generators.

The various elements of the VORTEX GENERATOR input block are defined as follows:

VORTEX [GENERATOR]

Defines the beginning of the vortex generator keyword input block.

ZONE iz1 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX} \ [SUBSET I range J range K range] ZONE iz2 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX} \ [SUBSET I range J range K range]

These two lines define the location of the vortex generator array. The relevant zones are given by the values of iz1 and iz2, and the relevant boundaries within zones iz1 and iz2 are specified via the BOUNDARY keyword parameter.

	iz1		The "upstream" zone. The secondary velocities will be increased when passing information from this zone to iz2.
	iz2		The "downstream" zone, i.e., the zone receiving increased secondary velocities from zone iz1. Secondary velocities will be decreased when passing information from this zone back to zone iz1.

Note: Currently, the vortex generators must be located at either an i₁ or i_max boundary. Thus, the only valid choices with the BOUNDARY keyword parameter are I1 and IMAX.

Note that the secondary velocity is the flow in a plane normal to the primary velocity. For example, for a vortex generator array at an i-interface boundary, the primary flow is in the i direction, and the secondary velocity is in the j and k directions.

The SUBSET parameter may be used to specify that the change in secondary velocity occurs only over a part of the zone boundary. Otherwise, it is assumed that the change occurs over the entire boundary. The range parameters define the part of the zone boundary over which the change occurs, and take one of the following forms:

	index1 index2		Starting and ending indices in the specified direction. LAST may be used for the last index.
	ALL		Equivalent to 1 LAST.

The starting and ending indices for the appropriate I, J, or K parameter (depending on the boundary specified) must be the same, and correspond to that boundary.

NUMBER ival

This defines the number of vortex generators in the vortex generator array (i.e., on the specified boundary).

vg_boundary {XLOC xl | YLOC yl | ZLOC zl} chord height alpha \ [VEL vmax] [DEL delta]

Defines the location and geometric parameters of each vortex generator. A separate line of input must be included for each generator.

	vg_boundary		The minimum or maximum index, specified as IM, IX, JM, JX, KM, or KX, within the specified boundary surface (as specified by ZONE and SUBSET) where the generator is mounted. This boundary must have been defined as a viscous wall in GMAN. As an example, for a vortex generator array at an i-interface boundary, either JM, JX, KM, or KX should be specified, where JM means the generator is at the j = 1 interface boundary, JX means it's at the j = jmax boundary, etc.
	XLOC, YLOC, ZLOC		xl, yl, or zl is the x, y, or z coordinate location in inches of the base of the vortex generator on the already specified boundary surface and wall boundary. (Currently, only one coordinate direction and location may be specified. This may lead to ambiguity in specifying the locations for generators placed in complex duct geometries. This shortcoming will be addressed in future code updates.)
	chord		The chord length of the vortex generator in inches. Must be greater than zero.
	height		The height of the vortex generator in inches. Must be greater than zero.
	alpha		The angle of incidence of the generator in degrees. Must be non-zero. More specifically, it is defined as the angle the generator chord line makes with the primary flow direction. The sign of alpha is determined using the "right-hand rule" of vector mechanics. For a given generator, use a normal vector pointing into the wall (the thumb), and the primary flow direction (fingers). If the rotation from the primary flow direction towards the generator follows the right-hand rule, then the sign of alpha is positive. Otherwise, it is negative. A positive value of alpha generally results in a vortex with a counterclockwise rotation, and conversely. The recommended range of magnitudes for alpha is between 8 and 20 degrees.
	VEL		vmax is the maximum velocity at the vortex generator station, in ft/sec. The default is for WIND to compute this value from the flow. It is currently recommended that this value be specified by the user. Must be greater than zero.
	DEL		delta is the boundary layer thickness of the incoming flow, in inches. The default is for WIND to compute this value from the flow. It is currently recommended that this value be specified by the user. Must be greater than zero.

In selecting values for the above described parameters, keep in mind that the vortex generator model was derived from conservation of momentum and inviscid theory, correlated with experimental data having height/chord ratios between 0.13 and 2.62, height/delta ratios between 0.12 and 2.60, and for duct flows with core Mach numbers ranging from 0.20 to 0.60. Because of the theory used in its derivation, the model is intended to work well outside of the range of the experiments. However, there is one caveat: past experience indicates that the model does not work when the vortex generators are placed in regions of sonic flow.

ENDVORTEX

Ends the vortex generator input block

Example

The following example illustrates the use of the VORTEX GENERATOR input block for one vortex generator array located between zones 2 and 3. The interface between zones 2 and 3 corresponds to the i_max boundary of zone 2 and the i₁ boundary of zone 3. The array contains two vortex generators, both mounted on the j_max viscous wall boundary of the zone interface with z coordinate values of -0.52 inches and 0.52 inches. The generators have the same geometric parameters: the chord length is 1.6 inches, the height is 0.4 inches, and the angle of incidence is 16 degrees.

   VORTEX GENERATOR
     ZONE 2 BOUNDARY IMAX
     ZONE 3 BOUNDARY I1
     NUMBER 2
       JX ZLOC -0.52 1.6 0.4 16.0
       JX ZLOC  0.52 1.6 0.4 16.0
   ENDVORTEX