Predicting Aerodynamic Loads on Highly Flexible Membrane Wings

131 Pages·2015·6.06 MB·English

AN ABSTRACT OF THE DISSERTATION OF
Trenton James Carpenter for the degree of Doctor of Philosophy in
Mechanical Engineering presented on June 4, 2015.
Title: Predicting Aerodynamic Loads on Highly Flexible Membrane Wings
Abstract approved:
Roberto Albertani
Throughpassiveadaptationtoincidentalflow, flexibleaerodynamicsurfacesexploit
effects of increased lift, delayed stall and disturbance rejection. Wings of birds, bats, and
insects exhibit these passive effects, and at the same time through the use of structural
state feedback sensed from the loads on the wing, active control is applied to achieve
stable and highly dynamic maneuvers. The goal of this research is to predict aerodynamic
loads on flexible wings, by sensing their structural responses to static and dynamic air-
flow conditions. Three approaches are presented to estimate aerodynamic loads on highly
flexible membrane wings, under static and dynamic conditions, at low Reynolds number.
The first applies a linear membrane formulation to correlate the wing’s structural strain
to lift, through wing-tip vorticity. In the second, the Poisson equation for a 2D linear-
elastic membrane with out-of-plane deformation was used to calculate normal pressure
distribution from virtual strain sensors using proper orthogonal decomposition basis func-
tions and a recursive least squares minimization. Finally, potential flow theory and a first
order state space representation is applied to the transient flow effects around a pitching
membrane airfoil to model the time varying loads due to dynamic pitching.
(cid:13)cCopyright by Trenton James Carpenter
June 4, 2015
All Rights Reserved
Predicting Aerodynamic Loads on Highly Flexible Membrane Wings
by
Trenton James Carpenter
A DISSERTATION
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Doctor of Philosophy
Presented June 4, 2015
Commencement June 2016
Doctor of Philosophy dissertation of Trenton James Carpenter presented on June 4, 2015
APPROVED:
Major Professor, representing Mechanical Engineering
Head of the School of Mechanical, Industrial, and Manufacturing Engineering
Dean of the Graduate School
I understand that my dissertation will become part of the permanent collection of Oregon
State University libraries. My signature below authorizes release of my dissertation to
any reader upon request.
Trenton James Carpenter, Author
ACKNOWLEDGMENTS
IgreatlyappreciatetheconstantsupportofmyadviserRobertoAlbertani, andcommittee
members Robert Paasch and Belinda Batten. Also invaluable, were the contributions of
Cody Ray and Brent Osterberg to the presented work.
CONTRIBUTION OF AUTHORS
Contributions in Chapter 2
Acknowledge; Dr. Albertani for his conceptual direction, Cody Ray for his involvement
in data collection and many a conceptual conversation.
Contributions in Chapter 3
Acknowledge; Dr. Albertani for his conceptual direction, and Dr. Belinda Batten for her
direction in singular value decomposition.
Contributions in Chapter 4
Acknowledge; Dr. Albertani for his conceptual direction, Brent Osterberg for his involve-
ment in data collection, and Dr. Masarati, Dr. Morandini and Mattia Alioli for their
numerical membrane simulations.
TABLE OF CONTENTS
Page
1. INTRODUCTION ........................................................... 1
1.1. A Brief History of MAV’s and Flexible Wings........................... 2
1.2. Preface................................................................. 8
2. CORRELATION OF STRUCTURAL STRAIN TO TIP VORTICITY AND
LIFT FOR A MAV PLIANT MEMBRANE WING .......................... 10
2.1. Abstract ............................................................... 10
2.2. Introduction............................................................ 10
2.3. Experimental Setup.................................................... 12
2.4. Force Estimation from Vorticity........................................ 16
2.4.1 Surface Reconstruction.......................................... 17
2.4.2 Numerical Fluid Model ......................................... 19
2.4.3 Lift from Circulation............................................ 21
2.5. Force Estimation From Poisson Model.................................. 24
2.6. Results and Discussion................................................. 25
2.6.1 Aerodynamic Loads............................................. 25
2.6.2 Surface Reconstruction.......................................... 26
2.6.3 Material Characterization....................................... 30
2.6.4 Lift Calculation................................................. 31
2.7. Conclusion............................................................. 33
2.8. Future Work ........................................................... 34
2.9. Acknowledgments ...................................................... 34
3. AERODYNAMICLOADESTIMATIONFROMVIRTUALSTRAINSENSORS
FOR A PLIANT MEMBRANE WING ....................................... 36
3.1. Abstract ............................................................... 36
3.2. Introduction............................................................ 37
TABLE OF CONTENTS (Continued)
Page
3.3. Methods................................................................ 39
3.3.1 Membrane Wing................................................ 39
3.3.2 Virtual Strain Sensors .......................................... 40
3.3.3 Strain Field Estimation ......................................... 41
3.3.4 Membrane Model ............................................... 43
3.3.5 Surface Deformation Estimation................................. 46
3.4. Experimental Setup.................................................... 48
3.4.1 Digital Image Correlation ....................................... 49
3.4.2 Hydrostatic Pressure Test....................................... 50
3.4.3 Wing Tunnel Experiment ....................................... 51
3.4.4 Numerical Fluid Model ......................................... 52
3.5. Results................................................................. 54
3.5.1 Material Properties ............................................. 54
3.5.2 Strain Fields.................................................... 54
3.5.3 Surface Deformation ............................................ 56
3.5.4 Pressure Distribution ........................................... 58
3.5.5 Aerodynamic Loads............................................. 64
3.6. Conclusion............................................................. 67
4. MODELING EFFECTS OF MEMBRANE TENSION ON DYNAMIC STALL
FOR A THIN MEMBRANE WING .......................................... 70
4.1. Abstract ............................................................... 70
4.2. Nomenclature.......................................................... 70
4.3. Introduction............................................................ 71
4.4. Methods................................................................ 72
4.4.1 Static Lift Model ............................................... 72
Potential Flow.......................................................... 73
Leading Edge Separation ............................................... 73
Membrane Displacement................................................ 74
Membrane Stability .................................................... 76
Attached Flow Model................................................... 78
TABLE OF CONTENTS (Continued)
Page
Separated Flow Model.................................................. 80
4.4.2 Degree of Trailing Edge Separation.............................. 81
4.4.3 Dynamic Stall Model ........................................... 83
4.5. Experimental Setup.................................................... 86
4.5.1 Test Article..................................................... 86
4.5.2 Test Conditions................................................. 87
4.5.3 Membrane Pre-Tension ......................................... 91
4.5.4 Digital Image Correlation ....................................... 92
4.5.5 Wind Tunnel Testing ........................................... 94
4.6. Results................................................................. 95
4.6.1 Static Model.................................................... 95
4.6.2 Dynamic Stall Model ........................................... 101
4.7. Summary & Conclusion ................................................ 104
5. CONCLUSION .............................................................. 105
BIBLIOGRAPHY ............................................................... 108