{ACTUATOR | SCREEN} ZONE iz1 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX | U surface} \ [SUBSET I range J range K range] ZONE iz2 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX | U surface} \ [SUBSET I range J range K range] TURNING {CONSERVE {ANGLE | PARALLELU} | \ ZERO PARALLELU | \ {SOLIDBODY | VORTEX} val xc yc zc | \ SPECIFY ANGLE α [ROTATE β]} TIP-EFFECT r1 r2 r3 r4 POWER {{DPS | DPT | DPOWER} val | \ TURNING | \ {SOLIDBODY | VORTEX} val xc yc zc} EFFICIENCY {ETA val | \ CLOSS val | \ VORTEX val | \ SCREEN {NORMAL | TOTAL} SOLIDITY sol} {ENDACTUATOR | ENDSCREEN} |
This keyword enables the user to model an actuator disk or screen by specifying a discontinuous change in properties across a zone boundary or portion of a zone boundary. The following restrictions apply:
The various elements of the ACTUATOR | SCREEN input block are defined
as follows:
{ACTUATOR | SCREEN} |
Defines the beginning of the actuator or screen block.
ZONE iz1 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX | U surface} \ [SUBSET I range J range K range] ZONE iz2 BOUNDARY {I1 | IMAX | J1 | JMAX | K1 | KMAX | U surface} \ [SUBSET I range J range K range] |
These two lines define the location of the actuator disk or screen.
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 | Zone to which increments will be added when passing information to iz2 | ||
---|---|---|---|
iz2 | Zone receiving positive increments, increments will be subtracted when passing information back to zone iz1 |
BOUNDARY specification for structured zones is done via the I, J, or K parameters. For unstructured zones, U surface is used to specify the surface ID number.
The SUBSET parameter may be used to specify that the change in
properties occurs only over a part of the structured zone boundary.
Otherwise (and for unstructured zones), 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.
In addition, for two-dimensional cases, the K parameter must
be specified as either K 1 1 or K ALL.
TURNING {CONSERVE {ANGLE | PARALLELU} | \ ZERO PARALLELU | \ {SOLIDBODY | VORTEX} val xc yc zc | \ SPECIFY ANGLE α [ROTATE β]} |
Defines the net change in parallel velocity across the zone boundary.
CONSERVE | Conserves the net flow angle (ANGLE) or the parallel velocity components (PARALLELU) across the zone boundary. (The ANGLE option is currently not implemented.) | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
ZERO PARALLELU | Sets the parallel components of velocity across the zone boundary to zero | ||||||||||
SOLIDBODY | Defines a solidbody rotation increment to the parallel velocity,
where:
| ||||||||||
VORTEX | Defines free vortex flow increment to parallel velocity, where:
| ||||||||||
SPECIFY ANGLE | Allows the user to specify the flow turning angle.
|
TIP-EFFECT r1 r2 r3 r4 |
Forces increments to go to zero at hub and/or tip to avoid solution discontinuities at the boundaries. A scalar, (0-1) multiplies the turning and power when this option is on. This is required for engine face models (where the wall velocity at the tip must be zero in the diffuser frame of reference). r1-r4 define linear regions ranging from 0 to 1 between r1 and r2, and from 1 to 0 between r3 and r4. r1, r2, r3, and r4 define the distance from the center of rotation (inches).
This keyword requires that TURNING SOLIDBODY,
TURNING VORTEX, or POWER SOLIDBODY be specified.
POWER {{DPS | DPT | DPOWER} val | \ TURNING | \ {SOLIDBODY | VORTEX} val xc yc zc} |
Defines the power increment across the zone boundary.
Screens require setting the power to zero. i.e., POWER DPOWER 0.
DPS | val specifies the static pressure increment across the actuator boundary (psi). Requires that the efficiency be specified, using EFFICIENCY ETA. | ||
---|---|---|---|
DPT | val specifies the total pressure increment across the actuator boundary (psi). Requires that the efficiency be specified, using EFFICIENCY ETA. | ||
DPOWER | val specifies a (constant) power per unit area increment
(ft-lb/sec-ft2).
(Corresponds to unsteady (rotor) free vortex turning)
| ||
TURNING | Specifies work corresponding to the net turn across the
zone boundary (specified in the TURNING element).
Assumes all turning is done in an unsteady process (by the rotor),
i.e., no stator.
where ω is the rotation rate of the rotor, r is the local radius from the center of the rotor, and w is the local circumferential velocity. This option requires that TURNING SOLIDBODY be specified. | ||
SOLIDBODY | VORTEX | Defined as in the TURNING element.
This defines the turning accomplished by the rotor.
The net turning may be altered by another process (e.g.,
by a stator).
Note: Currently vortex turning (i.e., POWER VORTEX) is not allowed. This would correspond to constant work across the rotor. However, currently, the procedure used to eliminate the vacuum at the core (setting Pmin = 0.1 P∞) makes the work input independent of the strength of the vortex, so the user could not vary the work input by changing κ. |
EFFICIENCY {ETA val | \ CLOSS val | \ VORTEX val | \ SCREEN {NORMAL | TOTAL} SOLIDITY sol} |
Defines the efficiency of the actuator disk or screen.
ETA | Compressor efficiency, val = [(Pt2 / Pt1)(γ − 1)/γ − 1] / [(Tt2 / Tt1) − 1] | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
CLOSS | Loss coefficient, val = (Pt1 - Pt2) / q, where q = ρU2/2 (U based on normal Mach number) | ||||||||||||||
VORTEX | Free vortex total pressure loss.
val is the maximum value of
(Pt2 − Pt1) / (Pt)∞
(i.e., the loss at the center of the vortex).
A linear distribution is assumed from the vortex center to the
radius a, where a is determined by the strength
value specified using TURNING VORTEX, or directly using
TEST 180.
This option requires that TURNING VORTEX be specified. | ||||||||||||||
SCREEN | Use screen loss relations to define total pressure loss, where
If solidity is specified, the screen loss coefficient associated with the screen model is defined by the solidity correlation of Cornell [Cornell, W. G. (1958) "Losses in Flow Normal to Plane Screens," Transactions of the ASME, May 1958, pp. 791-799.], unless the optional CLOSS value is specified. The screen model is not intended for use with choked screens, where the screen is significantly limiting the mass flow rate. During the solution start-up phase, it may be necessary to specify a low solidity, then increase it to the desired value to avoid strong choking in transients. This option requires that the power be zero. i.e., POWER DPOWER 0. |
{ENDACTUATOR | ENDSCREEN} |
Ends actuator or screen input block
Examples
The following examples illustrate the use of the ACTUATOR | SCREEN
input block for an engine face and for a screen.
Engine face model
ACTUATOR ZONE 1 BOUNDARY IMAX ZONE 2 BOUNDARY I1 TURNING SOLIDBODY 240000. 312. 54. 0. TIP-EFFECT 5. 5.1 39.8 40.0 POWER TURNING EFFICIENCY ETA 0.85 ENDACTUATOR BOUNDARY TVD FACTOR 0 ZONE 1 BOUNDARY IMAX BOUNDARY TVD FACTOR 0 ZONE 2 BOUNDARY I1Screen
SCREEN ZONE 3 BOUNDARY K1 ZONE 2 BOUNDARY IMAX TURNING ZERO PARALLELU POWER DPOWER 0.0 EFFICIENCY SCREEN NORMAL SOLIDITY 0.1 ENDSCREEN BOUNDARY TVD FACTOR 0 ZONE 3 BOUNDARY K1 BOUNDARY TVD FACTOR 0 ZONE 2 BOUNDARY IMAX
See Also: BOUNDARY TVD, TEST 180
Last updated 1 Apr 2016