NASA Technical Reports Server (NTRS) 20010013824: Advanced Aerodynamic Design of Passive Porosity Control Effectors

32 Pages·1.4 MB·English

by  NASA Technical Reports Server (NTRS)

AIAA 2001-0249
Advanced Aerodynamic Design of
Passive Porosity Control Effectors
C.A. Hunter, S.A. Viken, R.M. Wood, and S.X.S. Bauer
NASA Langley Research Center
Hampton, Virginia
39th AIAA Aerospace Sciences
Meeting & Exhibit
8-11 January 2001 / Reno, NV
For permission to copy or republish, contact the American Institute of Aeronautics and Astronautics
1801 Alexander Bell Drive, Suite 500, Reston, VA 20191
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AIAA 2001-0249
ADVANCED AERODYNAMIC DESIGN OF PASSIVE POROSITY CONTROL EFFECTORS
Craig A. Hunter', Sally A. Viken _, Richard M. W_×)d, and Steven X.S. BaueF t
NASA Langley Research Center
Hampton, Virginia
Abstract control 114-191. Based on the initial control cffector
research reported b3 Bauer [171, passive porosity has
This paper describes aerodynamic design work aimed at evolved into an extensively tested and well proven
developing a passive porosit3 control effector system aercv,Jynamic 1"1o_control technology with a _vidc range
for a generic tailless fighter aircraft. As part of this of capabilities and applications 11,20-231. The passivc
work, a computational design tool was developed and porosity concept consists of a porous outer surface, a
used to layout passive porosity effector systems for plenum, and a solid inner surface, as shown in Figure 1.
longitudinal and lateral-directional control at a low- Pressure differences between high- and low-pressure
speed, high angle of attack condition. Aerodynamic regions on the outer surface "'communicate" through the
analysis was conducted using the NASA Langley plenum, thereby modifying the pressure loading on the
computational fluid dynamics code USM3D, in outer surface. In concert with this pressure
conjunction with a newly formulated surface boundary' communication, there is a small amount of mass
condition for passive porosity,. Results indicate that transfer into and out of the plenum that changes the
passive porosity effectors can provide maneuver control effective aerodynamic shape of the outer surface.
increments that equal and exceed those of con_ entional
aerodynamic effectors for low-speed, high-alpha flight, When regions with a large pressure difference are
with control levels that are a linear function of porous connected by a passive porosity, system, it has the
area. This work demonstrates the tremendous potential potential to act as a control effector. For example,
of passive porosity to yield simple control effector connecting a low-pressure region on the upper surface
systems that have no external moving parts and will of an aircraft with a corresponding high-pressure region
preserve an aircraft's fixed outer moldline. on the lower surface of the aircraft would reduce the
pressure difference between the two regions, decreasing
Introduction the local normal force and translating the center of
pressure. Applied strategically to different areas of an
Since 1990, the aeronautics research community has aircraft, as shown in Figure 2, this can result in an
explored novel concepts for aircraft shaping and extremely powerful control effector system capable of
aerodynamic control 11-9]. These concepts seek to generating a variety of forces and moments. The
increase aerodynamic performance, improve general idea would be to equip an aircraft with a
survivability, and reduce weight and complexity by number of porous cavities and interconnected plenums
eliminating the breaks, gaps, hinges, and mechanical that could be controlled and actuated by valves or other
components found in conventional aircraft control simple devices, as illustrated in Figure 3. Compared to
effector designs and replacing them with a combination a traditional control effector such as a trailing edge flap,
of blended control surfaces, smart materials, and flow passive porosity has no external moving parts, it
control actuators. The result of this design approach is preserves the vehicle outer moldline, and it should
a continuous or even fixed outer moldline aircraft that provide better performance by generating a control
is able to morph its effective aerodynamic shape and force that varies linearly with vehicle lift in a
provide maneuver control in a smooth, continuous, predictable manner [1I.
organic manner, similar to the methods birds and fish
use in nature. While promising, much of the recent In the past, passive porosity has been applied to existing
research in this area has focused on fundamental flow aircraft configurations, working within the limitations
physics and material/actuator development, and many and constraints of aircraft designed to use conventional
control effector concepts remain unproven at realistic control effectors. While much of this work has been
full scale flight conditions at this time II0-131. successful, the full potential of passive porosity control
effectors can best be explored with a clean-sheet
One exception in this area is the passive porosity approach - one using an aircraft design that is suitable
concept, which was originally developed in the early for advanced aerodynamic control effectors and can be
1980s as a means of shock - boundary layer interaction configured to exploit the working principles of passive
* Configuration Aerodynamics Branch Copyright c'_2001 by the American Institute of Aeronautics and
** Flow Physics and Control Branch Astronautics. Inc. No copyright isasserted in the tlnited States under
5" Associate Fellow AIAA Title 17. US Code. The US Government has a royalty-free license to
exercise all rights under the copyright claimed herein for government
purposes. All other rights are reserved b_ the copyright ov,,ner.
American Institute of Aeronautics and Astronautics
AIAA 2001-0249
porosity. This paper describes aerodynamic design thick bi-convex airfoil. The resulting S!204
work aimed at developing a passive porosity control configuration is shown in Figure 5. As developed, the
effector system for such an aircraft, based on a simple S1204 configuration preserves the relevant
tailless fighter concept. In the current investigation, the characteristics of the ACWFT 1204 and is a good
focus has been narrowed to address longitudinal and generic testbed for advanced aerodynamic control
lateral-directional maneuver control at low-speed, high effector concepts, making it well suited for the present
angle of attack conditions. Future studies will extend investigation. Prior to the work discussed in this report,
this design work to more general maneuvering in other preliminary CFD analysis was conducted on the S1204
regimes. configuration at a variety of flow conditions to verify
that its aerodynamic performance was consistent with
Nomenclature the original ACWFI' 1204.
_t,AOA Angle of Attack, degrees Computational Fluid Dynamics Simulation
BL, 2_ Butt Line (spanwise) Coordinate, inches
c Aerodynamic Chord (local), inches The NASA Langley unstructured computational fluid
Ct, Lift Coefficient dynamics code "'USM3D" 1251 was used for Navier-
CD Drag Coefficient Stokes analysis in this study. Within the tetrahedral
Cy Sideforce Coefficient cell-centered, finite volume flow solver, inviscid flux
Ci Rolling Moment Coefficient quantities are computed across each cell face using
Cm Pitching Moment Coefficient Roe's flux-difference splitting scheme. A novel
C, Yawing Moment Coefficient reconstruction process is used for spatial discretization.
CG Center of Gravity based on an analytical formulation for computing
Cp Pressure Coefficient gradients within tetrahedral cells. Solutions arc
FS, x Fuselage Station (axial) Coordinate, inches advanced to a steady state condition using an implicit
Forebody Polar Angle, degrees backward-Euler time-stepping scheme.
m Porous Surface Net Mass Flux, slug/sec
M Mach Number Within USM3D, turbulence closure is given by the
R Computation Residual Spalart-AIImaras one-equation model I261. This model
Ro Initial Computation Residual solves a single local transport equation for the turbulent
WL, z Water Line (vertical) Coordinate, inches viscosity. The turbulence model can be integrated
down to the wall, or can be coupled with a turbulent
boundary layer wall function to reduce the number of
Aircraft Configuration cells in the sublayer region of the boundary layer. The
latter approach was used here.
The aircraft used in this investigation is based on
fighter configurations developed under the Air Force Computational Model
Wright Lab "Aero Configuration/Weapons Fighter
Technology" (ACWFF) program 1241. The goal of this The VGRID/GridTool software system 127,281 was
program was to develop multi-mission fighter aircraft used to generate the unstructured grids for this studt.
configurations with advanced technologies and VGRID uses an advancing-front method for generating
performance characteristics capable of addressing post- Euler tetrahedral grids, and an advancing-layer method
year-2000 needs and threats. Special emphasis was for thin-layer tetrahedral viscous grids required for
placed on the design and performance of advanced Navier-Stokes analysis. In defining the computational
aerodynamic control effectors for tailless or reduced- domain, boundaries are represented by bi-linear surface
tail concepts. Through a combination of wind-tunnel patches that are constructed in GridTool based on user-
testing, performance analyses, and trade studies, a specified geometries. Grid characteristics like cell
concept was selected for design refinement, resulting in spacing and stretching are also specified in GridTool bx
the ACWFr 1204 configuration shown in Figure 4. the placement of cell "'sources".
For the current study, a simplified aircraft A surface mesh is generated in VGRID by triangulating
configuration, dubbed "S1204"', was developed by each surface patch with a two-dimensional (2D) version
extracting salient features of the basic 1204 planform of the advancing-front method. Triangulated surface
and outer mold line to form an analytically defined patches then form the initial "'front" for the generation
geometry (required for future studies involving of three-dimensional (3D) tetrahedral volume cells by
reshaping). To reduce complexity, the 1204's cockpit the advancing-layer and advancing-front methods.
and engine inlets were removed, and the exhaust nozzle Smooth variation of grid spacing is achieved by solving
was faired over. In addition, the 1204"s NACA a Poisson equation on a cartesian background grid,
6-1--series airfoil shape was replaced with a simpler 4% using the GridTool-defined cell sources as inputs.
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American Institute of Aeronautics and Astronautics
AIAA 2001-0249
T_vo grids were developed for this study: a semi-span holes of 0.020-0.050 inch diameter are typicall_ used in
grid suitable for longitudinal control analysis, and a wind tunnel and flight applications of passive porosity).
full-span grid intended for lateral-directional control Based on previous aerodynamic testing [1,17,22], a
analysis. The semi-span grid with symmetry plane is porosit 5 level of 22c_ openness was used in this study.
shown in Figure 6, and the full-span surface mesh is
shown in Figure 7. In both cases, the computational The porous boundary condition has been validated b_
domain extended roughly 10-14 mean aerodynamic comparing computational results to experimental data
chord lengths from the aircraft CG in all directions. obtained for a GA(W)-I wing _vith leading-edge
The semi-span grid contained a total of 961481 porosit3 111 and a 5 caliber, tangent-ogive forebody
tetrahedral cells and 168390 nodes, and the full span with circumferential porosit3 1221. In both cases,
grid contained twice that amount. computational results sho_ved remarkable agreement
with experimental force and pressure data 1291.
Boundary Conditions
Solution Procedure
Outer boundaries of the computational domain were
treated as characteristic inflo_v/outflo_v surfaces with All solutions presented in this paper were obtained by
freestream conditions specified by Mach number, running USM3D on the "'Von Neumann'" Cra\ (7-90 at
Reynolds Number, flow angle, and static temperature NASA Ames, using 10 processors in multi-task mode.
(the semi-span case used a reflection boundary Typical cases needed 6000-8000 c3cles for full
condition at the symmetry plane). For comparison with convergence. Semi-span computations required about
the ACWFT database, Io_v-speed high angle of attack 175 megawords of memory and 60-85 hours of
conditions of M = 0.14 and et = 28° were selected for computer time. Full span cases required double those
analysis. Reynolds number was chosen to match the amounts. During the computation, global CFL number
Ix10'Tft - 2x 10"/ft conditions of the various ACWFI" ranged from 5 to approximatel_ 30.
wind tunnel tests.
Convergence was judged by several methods. The first
Aircraft surfaces were treated as no-slip viscous involved tracking the solution residual until it dropped
boundaries. In cases involving the application of several orders of magnitude and leveled out, as shown
passive porosity control effectors, selected patches on in Figure 8(a). Integrated aerodynamic performance
the aircraft surface were treated as porous surfaces coefficients shown in Figure 8(b) were also used to
using the newly implemented porosity boundary verify convergence. Finall 3. in cases using the passive
condition in USM3D. The boundary condition is porosity boundary condition, average porous surface
structured to allow any number of surface patches to pressure, plenum pressure, and porous surface net mass
communicate through a common plenum, with flow were tracked. Typical histories of these
provisions for up to eight independent plenums. parameters are shown in Figures 8(c) and 8(d).
Specific details of this boundary condition will be given
in a forthcoming paper [291, so onl5 a basic overview Baseline Results
will be given here.
Results for the baseline S1204 configuration at
The USM3D porous boundaD' condition is an extension M = 0.14 and a = 28° are given in Figures 9 and 10.
of the theory developed by Bush 130] to model flow Figure 9 shows pressure coefficient (Cp) contours over
through a screen. Bush's original model was derived to the upper and lower surface of the aircraft, and Figure
pass information across a coterminous boundary 10 uses particle traces to illustrate the vortical flow
separating an external flow and an internal plenum. In field about the upper surface of the aircraft. These
the revised approach used in USM3D, the Bush model results are typical for a chined body at high angle of
was re-formulated as a surface boundary condition for attack, and are in excellent agreement with the ACWFq"
the external flow, thus eliminating the need to grid and flow visualization results obtained b_ McGrath, et al
compute flow within a plenum. Conservation laws [31 ]. Two large vortices track along the upper surface
from steady, one-dimensional (ID), isentropic, and of the forebody (red and green traces), and wing flow is
adiabatic gas dynamics are used to model flow through characterized by a spanwise vortex originating from
the porous surface, in conjunction with the assumption each leading-edge wing-body junction (blue traces).
of a constant plenum pressure and the requirement of These vortical flows create significant low-pressure
zero net mass flow through the porous surface. Part of regions along the aircraft's upper surface, with a typical
the solution procedure involves a feedback iteration to (Tp level of about -2. As expected, the lower surface of
update the plenum pressure and drive net mass flow to the aircraft is dominated by high-pressure, with Cp
zero. Because of the 1D equations used in the ranging from approximately 0 to 1. This combination
boundar) condition, only the surface porosity level is of Io_- and high-pressure regions is ideal for the
specified, not the actual porous hole geometry (circular application of passive porosity.
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AIAA 2001-0249
Control Effector Design Results in Figure 1I(a) indicate that target areas for
nose-down pitch control are the forebody and leading-
As discussed in the introduction, the basic premise of a edge wing-body junction regions (forward of the
passive porosity control effector system involves aircraft CG). Low-pressure in these regions is due to
connecting low- and high-pressure regions of an aircraft vortical flows, and control of these flows is key to
to alter surface loading and generate maneuver control. obtaining nose-down pitch. Potential yaw control
This can be accomplished by allowing pressure to alter increments in Figure ll(b) show a similar result, and
the surface loading directly, or by controlling a indicate that "asymmetric" control of the vortical flows
secondary flow (such as a vortex) which in turn alters is required for yaw generation. At the et =28 °
surface loading. In general, connecting low-pressure condition, stability-axes yaw depends heavily on both
upper surface regions with high-pressure lower surface yaw and roll about the body axes. Raising pressure on
regions tends to have the largest effect on flow in the one side of the forebody will effect bods-axes yaw.
low-pressure (upper surface) region. The high-pressure while raising pressure on the upper surface of one wing
(lower surface) region typically shows little or no will effect body-axes roll. Combined, these moments
change, and basically acts as an unlimited high-pressure will contribute to yaw in the stability-axes.
source 11,17,20,221. Thus, the design of a passive
porosity control effector system involves two basic Control Effector Cot_gurations
steps: (1) identifying _'target'" regions on the aircraft's
upper surface where the application of high-pressure Based on the design analysis, ten passive porosit)
will generate a desired force or moment, and configurations were developed to effect pitch and ya_
(2) identifying corresponding high-pressure "'source" control. Target regions on the aircraft upper surface
regions on the aircraft's lower surface. In the case of were mated with corresponding source regions on the
the S1204, where the entire lower surface contains lower surface (i.e., lower surface porosity was a direct
high-pressure at high angle of attack, source regions projection of upper surface porosity). From a systems
can be chosen to simplify overall systems integration. standpoint, this approach would minimize the amount
of complexity involved in connecting upper and lower
Design Tool surface regions by a common plenum, making it a good
starting point for design.
For a particular target region on an aircraft's upper
surface, the effect of applying passive porosity will Five proposed pitch control configurations are shown in
depend on several factors: the pressure distribution, the the top row of Figure 12. Configurations PI and P2
local surface geometry, and the location and moment apply porosity to the forebody region, starting at the
arm relative to the aircraft CG. While the effect of nose and going back to FS = 147 (covering 33% of the
these factors is easy to visualize in simple cases, it can forebody area) and FS = 298 (covering 100%),
pose a significant design challenge for complex respectively. Configuration P3 applies porosity to the
geometries and arbitrary surface shapes. In order to leading-edge wing-body junction region, forward of the
streamline the design process, a simple computational aircraft CG at FS = 365. Configurations P4 and P5 are
tool was developed to help identify target areas for the combinations of the PI, t_2,and P3 designs.
application of passive porosity on an aircraft upper
surface. Using USM3D solution and grid files as Five proposed yaw control configurations are shown in
inputs, the tool surveys the surface geometry and the bottom row of Figure 12. Configurations Y1 and
configuration layout of low-pressure, upper-surface Y2 are asymmetric counterparts of the P! and P2
regions and calculates the potential forces and moments configurations, covering 17% and 50% of the total
that would be generated if the local surface pressure forebody area, respectively. The Y3 configuration is
coefficient were raised to a specified target level. For similar to the P3 configuration, except that porosit)
the present investigation, Cp = 0 ffreestream pressure) extends further back to 50% chord, and is applied to the
was deemed a suitable target _,alue. left wing only. Finally, the Y4 and Y5 configurations
are combinations of the Y 1,Y2, and Y3 designs.
Results from the design tool are shown in Figure 1l(a)
and 11(b), for nose-down pitch and yaw, respectively A single plenum was used to connect upper and lower
(moments referenced to the stability axes). In each surface porosity in the P1, P2, Y l, Y2, and Y3
plot, potential increments in moment are plotted per configurations. Two separate plenums were used for
unit area over the aircraft upper surface. It is important the P3 case, one for each wing-body junction region.
to note that results from the design tool do not indicate Three separate plenums were used in the P4 and P5
the direct effects of applying passive porosity; rather, cases, one for the forebody region, and one for each
they indicate the effect of raising local pressure on the wing-body junction region. Similarly, two separate
upper surface. Passive porosity is simply one method plenums were used in the asymmetric Y4 and Y5 cases.
of accomplishing this, either by direct loading or one for the forebody, and one for the left wing.
through the control of secondaD _flows.
American Institute of Aeronautics and Astronautics
AIAA 2001-0249
Longitudinal Control passive porosity completely eliminated the wing-body
.junction vortices seen in the previous configurations.
Results for the PI configuration are shown in Figures Here. blue particle traces originating from the wing-
13-16. Comparing the (,p contours in Figure 13 with bod3 ,junction region roll into the forebod5 vortices,
those of the baseline configuration (Figure 9), it is which are better defined and more coherent than the
obvious that the application of passive porosity resulted baseline case.
in a large overall increase in local pressure on the
forward upper surface of the forebody, but pressure on Results for the P4 and P5 configurations are shown in
the lower surface was _irtually unchanged (as Figures 24-27. As expected, these configurations
expected). Figure 14 gives a plot of surface Cp versus incorporate flow features and characteristics from the
polar angle around the forebody at FS = 100, for the basic PI-P3 porosit_ layouts. The P5 configuration
baseline and PI configurations. At this location, the shows the most striking results: by combining full
upper surface pressure in the PI configuration is nearly forebody porosity from P2 with wing porosity from P3,
constant at Cp ,--0.65, leveling out the suction peaks of major pressure gradients on the upper surface of the P5
the baseline configuration. configuration appear to be complete 5 blended out.
Accordingly, particle traces for the P5 configuration in
l)ownstream of the porous region, the upper surface Figure 27 show a lack of the strong vortical flows
pressure distribution is very similar to the baseline case. present in earlier cases, with only minor rollup over the
Looking at the particle traces depicted in Figure 15, it aft portion of the aircraft.
appears that passive porosity delayed onset of the
forebody vortices: instead of rolling up at the nose, the Pitch Increments
vortices formed downstream of the porous region, as
indicated by the red particle traces. Crossflow Nose-down pitch control effectiveness for the five
streamlines at FS = 100 are shown in Figure 16(a) and passive porosity configurations is summarized in Figure
16(b), for the baseline and Pl configurations, 28, along with data for selected ACWFF pitch control
respectively. Based on the information shown here, it effectors [24I. The passive porosity control effectors
would seem that passive porosity prevented windward provided nose-down pitch increments ranging from
flow from rolling into vortices as itseparated across the AC_ = -0.089 for the P1 configuration to AC,,,= -0.3 I
chine. This is likely a direct result of mass transfer out for the P5 configuration, comparing favorabb to the
of the upper porous surface, which blunted the effect of range of ACWFI" devices and conventional controls.
the chine, filled in the wake on the leeward side of the Both the P2 and P5 configurations provided enough
forebody, and deterred the formation of secondary nose-down pitch increment to reach "'absolute" nose-
flows. down control, countering the configuration's inherent
nose-up pitching moment at the M = 0.14, _ = 28 °
Results for the P2 configuration are shown in Figures condition. With increments of A('n, =-0.243 and
17-20. In this case, the application of passive porosity AC,,, = -0.3 I, respectively, the I'2 and P5 configurations
provided a notable increase in upper surface pressure on roughb equaled or exceeded the AC,, =-0.25 provided
the entire forebods, and also increased pressure in the by the con_ entional ACWFF elevons deflected to 60°.
leading-edge wing-body junction region. As a result,
formation of the forebody and wing body junction Associated Lift Increments
vortices was greatly inhibited. Instead of the distinct
vortex families seen in the baseline and Pl cases, Lift increments for the PI-P5 configurations are shown
particle traces for the P2 configuration roll up into a in Figure 29, along with estimates made from the
larger, less organized vortex system on each side of the ACWFT data 124]. Like the ACWFI" forebody devices,
aircraft (see Figure 18). the porous configurations generate nose down pitch b)
reducing local lift on the aircraft forebods, which
An upper surface Cp plot for the P3 configuration, with reduces overall lift in each case. This is in contrast to
passive porosit 3 applied to the leading-edge wing conventional aft-mounted pitch effectors, which
region forward of the CG, is given in Figure 21. These increase overall lift. Relative to the baseline
results show that the application of passive porosity configuration's CL= 1.748, the PI, P3, and P4
increased pressure and smoothed out pressure gradients configurations reduced lift by 6-13c_. These levels
in the leading-edge wing-body junction region. This is compare favorably to the ACWFT forebody devices,
confirmed by the Cp plot in Figure 22 (taken at the which reduced lift by 4-17c_ for similar nose-down
spanwise location BL =-100), which shows that the pitch levels. The P2 and P5 configurations reduced lift
wing's suction peak was leveled off to a near constant by larger amounts - 17% and 26%, respectivel 5 - but
value over much of the upper surface, while the lower these reductions are commensurate with the larger pitch
surface pressure was largely unaffected. Based on the increments provided by these configurations.
vortical flow field depicted in Figure 23, it appears that
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Pitch Control Trends Yaw Increments
Using the baseline and porous results obtained here as Yaw control effectiveness for the Y I-Y5 configurations
guidance, one can construct the trends given in is summarized in Figure 44, along with ACWFI"
Figure 30, which show that the passive porosity pitch control effector and historical data 124]. The passive
system provides control effect that varies linearly with porosity control effectors provided yaw increments
porous forebody area. These results indicate that a ranging from ACn= 0,012 to 0,051, compared with the
simple means of controlling the open porous area on the levels of 0.018 to 0.020 for conventional rudder
forebody (such as the sliding plates or louvers shown in controls on the F-15 and F/A-18, and 0.011 to 0.025 for
Figure 3) would yield a passive porosity effector system the various ACWFT devices. While the YI and Y3
with linear, variable pitch control. configurations provided yaw increments in line with the
ACWFT devices and conventional rudders, the Y2, Y4,
Lateral-Directional Control and Y5 configurations performed significantly better,
generating 2-5 times more yaw than the other effectors.
Results for the Y I and Y2 yaw control configurations
are presented in Figures 31-36. As asymmetric Associated Forces and Moments
counterparts of the P1 and P2 configurations, the
pressure and flow field results seen here are consistent Adverse roll increments are presented in Figure 45,
with earlier discussion. The partial porosity of the Y 1 which shows that roll levels generated by the Y I-Y5
configuration is seen to raise pressure on the porous yaw control effectors are in line with other
ACWFT devices [24[, and well within the ACk= 0.06
for_vard-left upper surface region of the forebody and
delay the onset of the vortex on that side, while the full level of corrective roll authority available from the
ACWFI" aileron system. The porous yaw control
porosity of the Y2 configuration raised pressure on the
effectors also induced nose-down pitch and lift
entire left side of the forebody upper surface and nearly
increments, summarized in the table below.
eliminated the vortex on that side. Cp plots for the Y2
configuration at FS = 100 and 220 (Figures 35 and 36)
Table I:Assoc. PRch &Lifthwrements. YI-Y5Configs.
more clearly show the asymmetric effect of passive
porosity. While pressure on the left upper surface
region of the forebody (180-270 °) changed
ACm -0Y.0I35 -0Y.t221-0.060Y3 -0Y.0498 I Y-0"I80_
considerabl} from the baseline case, the remainder of
the foreN_ly surface pressure was unaffected to a large ACL -0.030 -0=11_.! -0.149 -0.179 /-0.226_
extent. This demonstrates the capability of passive
porosity to act as a localized control effector. Ideally, the generation of yaw should be accomplished
with as little net sideforce as possible. Figure 46 shows
Results for the Y3 configuration are shown in Figures sideforce increments generated by the Yi-Y5 porous
37 and 38, and are in line with previous results seen for configurations compared to estimates from ACWFI
the similar P3 configuration. The application of passive data and typical historical levels 1241. Increments of
porosit5 to the forward half of the left wing is seen to ACv = 0.029-0.039 for the Y 1, Y3, and Y4 cases fall
have a notable effect on thc upper surface pressure below the sideforce levels of the ACWFT devices and
distribution shown in Figure 37. Porosity smoothed out conventional rudders for equal or greater ya_
pressure gradients in the wing-body junction area, increments, indicating that the porous configurations
eliminated the wing-body junction vortex, and raised are more effective at producing yaw. The Y2 and Y5
the overall wing upper surface pressure. As shown in configurations produced larger sideforce increments, of
Figure 39, the wing suction peak was reduced and 0.076 and 0.105 respectively, but these levels are
upper surface pressure was leveled off to a near consistent with the larger amounts of yaw produced bx
constant value of Cp- -0.9 at the BL = -100 location. these control effectors. In reality, the Y2 and Y5
configurations produce about the same amount of
Upper surface Cp plots and particle traces for the sideforce for a given yaw as the other porous cases.
composite Y4 and Y5 configurations are given in
Figures 40-43. These results are amalgamations of Yaw Control Trends
earlier results seen for the Y1-Y3 configurations,
As in the previous discussion of pitch control effectors,
combining the various elements from each case. Not
the baseline and Y I-Y5 data were used to construct
surprisingly, the Y5 configuration appears to give the
control trends, shown in Figure 47. Like the pitch case,
best results, by combining full forebody porosity (Y2)
the passive porosity system is seen to provide ya_
with wing porosity (Y3) on the left side of the aircraft.
control increments that vary linearly with porous
Particle traces in Figure 43 show only weak signs of
forebody area.
vortical flow along the left side of the aircraft, with
slow roilup aft of the wing.
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AIAA 2001-0249
Concluding Remarks Acknowledgements
Advanced aerodynamic design and analysis of passive The authors would like to thank Neal Frink, Paresh
porosity control effectors has been conducted in this Parikh, and Shahyar Pirzadeh for their help and support
investigation. Using a generic tailless fighter aircraft with USM3D, VGRID, and ViGPIot, all part of the
concept, Navier-Stokes CFD and aerodynamic design Tetrahedral Unstructured Software System "'TetrUSS'"
tools were applied to develop control effectors capable developed at NASA l_angle5.
of generating longitudinal and lateral-directional
control for low-speed high angle of attack conditions. References
Specific conclusions and comments are as follows:
Wood, R.M. and Bauer, S.X.S. "'Advanced
I.
I. For longitudinal (pitch) control, the P1-P5 passive Aerodynamic Control Effectors". SAE Paper,
porosity effectors provided nose-down pitch increments 1999-01-5619, October 1999.
that were competitive _ith ACWFI' devices and
conventional controls. Two of the porous 2. Scott, M., Montgomery', R., and Weston, R.
configurations actually produced large enough pitch "'Subsonic Maneuvering Efectiveness of High
increments to effect absolute nose-down control at the Performance Aircraft which Emplo 3 Quasi-Static
high-alpha condition, equaling or exceeding the control Shape Change Devices". SPIE 3326-24, 1998.
authority provided b5 conventional elevons. The pitch
control came with reductions in overall lift ranging l)orsett, K.M. and Mehl, D.R. "'Innovative Control
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from 6 to 26c_. Passive porosity pitch control effectors Effectors (ICE)". Wright Laborato_ Report
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