Experimental Investigation of the Aerodynamic Ground Effect of a Tailless Lambda-Shaped UCAV

209 Pages·2006·1.62 MB·English

EXPERIMENTAL INVESTIGATION OF THE AERODYNAMIC GROUND
EFFECT OF A TAILLESS LAMBDA-SHAPED UCAV WITH WING FLAPS

THESIS

Jason T. Mostaccio, Ensign, USN

AFIT/GAE/ENY/06-J11

DEPARTMENT OF THE AIR FORCE
AIR UNIVERSITY
AIR FORCE INSTITUTE OF TECHNOLOGY
Wright-Patterson Air Force Base, Ohio

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED
The views expressed in this thesis are those of the author and do not reflect the official
policy or position of the United States Air Force, Department of Defense, or the U.S.
Government.
AFIT/GAE/ENY/06-J11

EXPERIMENTAL INVESTIGATION OF THE AERODYNAMIC GROUND
EFFECT OF A TAILLESS LAMBDA-SHAPED UCAV WITH WING FLAPS

THESIS

Presented to the Faculty
Department of Aeronautics and Astronautics
Graduate School of Engineering and Management
Air Force Institute of Technology
Air University
Air Education and Training Command
In Partial Fulfillment of the Requirements for the
Degree of Master of Science in Aeronautical Engineering

Jason T. Mostaccio, BS
Ensign, USN

June 2006

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED
AFIT/GAE/ENY/06-J11

EXPERIMENTAL INVESTIGATION OF THE AERODYNAMIC GROUND
EFFECT OF A TAILLESS LAMBDA-SHAPED UCAV WITH WING FLAPS

Jason T. Mostaccio, BS
Ensign, USN

Approved:

____________________________________ ________
Dr. Milton E. Franke (Chairman) Date
____________________________________ ________
Dr. Mark F. Reeder (Member) Date

____________________________________ ________
Lt Col Eric J. Stephen (Member) Date
AFIT/GAE/ENY/06-J11
Abstract
This experimental study adequately identified the ground effect region of a
lambda-shaped unmanned combat air vehicle (UCAV). The lambda planform used in this
study was originally tested in a previous experiment to determine the stability and control
characteristics generated out-of-ground-effect. The following study extends the existing
database by analyzing the inherent aerodynamic behavior that is produced by employing
trailing edge flap deflections while flying in-ground-effect (IGE). To accomplish this
objective, static ground effect tests were performed in the AFIT 3’ x 3’ subsonic wind
tunnel where a ground plane was used to simulate the forces and moments on the UCAV
IGE. Removable aluminum flap pieces were attached to the model, in a split flap
configuration, along the midboard and outboard trailing edges of the UCAV, and the
corresponding IGE data was collected for symmetric and asymmetric deflections of +10o
and +20o.
Based on the results of this study, the ground effect region for the lambda UCAV,
with flaps deployed was characterized by an increase in the lift, a reduction in the
induced drag but an increase in the overall drag, and an increase in the lift-to-drag ratio.
These trends were noted in previous ground effect studies for aircraft with trailing edge
flaps, and similar aspect ratios and wing sweep. Additionally, a flow visualization
analysis revealed that a vortical flow pattern, that is characteristic of delta wing
configurations, developed over the upper surface of the wing at high angles of attack.

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To my parents and sister who have always supported me in all of my endeavors and to my
grandfather; may he have the courage and strength to face every day with a newfound
hope.

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Acknowledgments
I would first and foremost like to thank and express my sincerest gratitude to my
Lord God from whom I have received all the blessings in my life and who has given me
the strength and motivation to complete this thesis, and to my loving family who
continually support me in every endeavor of my life. Also, I would like to thank my
thesis advisor, Dr. Franke for his insightfulness and experience and for allowing me to
spearhead this entire project, from start to finish. I would also like to thank Mr. Ryan
Plumley of the Air Vehicles Directorate of the Air Force Research Lab for his numerous
suggestions and support for this project. Lastly, I would like to express my sincere
gratitude to Dwight Gehring and John Hixenbaugh, AFIT/ENY, for their patience and
hard work that without would have made this project impossible to finish. They helped
immensely with the set-up and operation of the wind tunnel, from installing the ground
planes to calibrating the equipment.

Jason T. Mostaccio

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Table of Contents
Page
Abstract..............................................................................................................................iv
Acknowledgments.............................................................................................................vi
List of Figures....................................................................................................................ix
List of Tables....................................................................................................................xv
List of Symbols................................................................................................................xix
I. Introduction....................................................................................................................1
Section 1 – Wing-in-Ground Effect................................................................................1
Section 2 - Wing-In-Ground Vehicles............................................................................2
Section 3 – Unmanned Aerial Vehicles (UAVs)............................................................4
Section 4 – Motivation....................................................................................................6
II. Literature Review...........................................................................................................7
Section 1 – Ground Effect Theory..................................................................................7
Section 1.1 – Induced Drag.........................................................................................7
Section 1.2 – Lift.........................................................................................................9
Section 2 – Boundary Layer Interaction with the Ground Plane..................................11
Section 2.1 – Static and Dynamic Ground Effect Tests............................................11
Section 2.1 – Boundary Layer Theory......................................................................11
Section 2.3 – Boundary Layer Removal...................................................................14
Section 3 – Adverse Ground Effect..............................................................................16
Section 4 – Experimental Objectives............................................................................18
III. Experimental Equipment............................................................................................20
Section 1 – UCAV Model.............................................................................................20
Section 2 – Ground Representation..............................................................................23
Section 3 – Wind Tunnel..............................................................................................25
Section 4 – Strain Gage Balance...................................................................................28
Section 5 – Dantec Hot-wire Anemometer...................................................................29
IV. Experimental Procedures............................................................................................31
Section 1 – Hot-wire Anemometer...............................................................................31
Section 1.1 – Hot-wire Calibration...........................................................................31
Section 1.2 – Blockage Corrections..........................................................................32
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Page
Section 2 – Data Acquisition........................................................................................36
Section 3 – Data Reduction..........................................................................................38
V. Results & Analysis.......................................................................................................39
Section 1 – Hot-wire Anemometer & Wind Tunnel Blockage Corrections.................39
Section 2 - Wind Tunnel Ground Effect Tests.............................................................42
Section 2.1 – Longitudinal Stability Characteristics, OGE......................................43
Section 2-1.1 Midboard and Outboard Trailing Edge Flaps.................................48
Section 2.2 – Longitudinal Characteristics, IGE......................................................53
Section 2.2.1 – Lift Coefficient IGE.....................................................................53
Section 2.2.2 – Drag Coefficient IGE...................................................................63
Section 2.2.3 – Lift-to-Drag IGE..........................................................................72
Section 3 – Lambda UCAV Flow Visualization..........................................................75
Section 3.1 – OGE Flow Visualization.....................................................................76
Section 3.2 – IGE Flow Visualization......................................................................78
Section 4 – Height-to-Span Ratio and Angle of Attack................................................80
VI. Conclusions and Recommendations...........................................................................83
Section 1 – Conclusions................................................................................................83
Section 2 – Recommendations......................................................................................85
Appendix A: Additional UCAV Pictures.........................................................................87
Appendix B: Ground Plane Schematics............................................................................89
Appendix C: MATLAB Data Reduction Sample Calculation..........................................92
Appendix D: Ground Plane Boundary Layer Analysis..................................................101
Appendix E: Additional Plots.........................................................................................107
Appendix F: Data Tables................................................................................................130
Appendix G: MATLAB Data Reduction Code..............................................................169
Appendix H: Lambda UCAV Flap Specifications.........................................................182
References.......................................................................................................................184
Vita..................................................................................................................................187
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List of Figures
Figure Page
Figure 1: Percent Lift Increase in Ground Effect for Various Aircraft ............................10
Figure 2: Theoretical Boundary Layer Analysis of the Ground Plane.............................13
Figure 3: Requirements for the Application of an Endless-Belt Moving Ground Plane .16
Figure 4: Adverse Ground Effect for the F-106, AOA = 14o ..........................................17
Figure 5: Adverse Ground Effect for the Lambda UCAV ...............................................18
Figure 6: Original Scale Lambda UCAV..........................................................................20
Figure 7: Four Views of the ½ - Scaled Lambda Model OGE and IGE (h/b = 0.05) with
Mid/Outboard Trailing Edge Split Flap Deflections........................................................22
Figure 8: Top and Separated View of the Removable Ground Plane ..............................25
Figure 9: Dimensions of the Wind Tunnel Intake and Convergent Section ....................26
Figure 10: Hot-wire Probe Access Panels .......................................................................27
Figure 11: AFIT 3’x3’ Wind Tunnel Schematic ..............................................................28
Figure 12: Wind Tunnel Coordinates ..............................................................................30
Figure 13: Hot-wire Location for Blockage Measurements.............................................33
Figure 14: Hot-wire Test Grid for Blockage Measurements............................................34
Figure 15: Hot-wire Test Grid for Boundary Layer Measurements.................................35
Figure 16: Wind Tunnel Velocity Differences Between the Hot-wire and Pressure
Transducer.........................................................................................................................40
Figure 17: Hot-wire Velocity Comparison.......................................................................41
Figure 18: Aerodynamic Comparison of the Lift Coefficient, No Flaps..........................43
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