Aeronautics, Dynamics, and Control Laboratory

Henry Samueli School of Engineering, University of California, Irvine

Vision

(1) interdisciplinary (multi-physics) modeling and analysis, (2) mathematical rigor, and (3) inspiration from Nature are our enabling factors to shape the future of aeronautical engineering.

Lab History

The ADCL was inaugurated in Sep 2014. Since then, it has produced about 120 publications (50 journal articles and 70 conference papers); raised about $4 million; and supported three postdocs, 12 PhDs, and 18 Masters.

Major Contributions

2022: A New Theory of Lift (video)
The Euler equation does not possess a unique solution for the flow over a two-dimensional object. This problem has serious repercussions in aerodynamics; it implies that the inviscid aero-hydrodynamic lift force over a two-dimensional object cannot be determined from first principles; a closure condition must be provided. The Kutta condition has been ubiquitously considered for such a closure in the literature, even in cases where it is not applicable (e.g. unsteady). Our team has revived a special variational principle from the history of analytical mechanics: Hertz’ principle of least curvature. Using this principle, we developed a novel variational formulation of Euler’s dynamics of ideal fluids that is fundamentally different from the previously developed variational formulations based on Hamilton’s principle of least action. Applying this new variational formulation to the century-old problem of the ideal flow over an airfoil, we developed a general (dynamical) closure condition that is, unlike the Kutta condition, derived from first principles. In contrast to the classical theory, the proposed variational theory is not confined to sharp edged airfoils; i.e., it allows, for the first time, theoretical computation of lift over arbitrarily smooth shapes, thereby generalizing the century-old lift theory of Kutta and Zhukovsky. Moreover, the new variational condition reduces to the Kutta condition in the special case of a sharp-edged airfoil, which challenges the widely accepted wisdom about the viscous nature of the Kutta condition. In fact, it suggests the conjecture that Navier-Stokes' solution in the limit of infinite-Reynolds number is the one that minimizes curvature from Euler's family of solutions. This work is published in the Journal of Fluid Mechanics. We made this 6-mins video to explain the idea to a broad audience.

2020: Exquisite Stability of Insect Flight (video)
Over the past two decades, the flapping flight dynamics community has assumed, almost with consensus, that insects are unstable in hovering. Our research group performed a more detailed flight dynamic modeling in combination with a more rigorous mathematical analysis (based on geometric control theory) and discovered an unconventional stabilization mechanism that insects may unconsciuosly exploit during flight. We found that the natural vibration of the insect’s wing and body stabilizes their flight dynamics via a vibrational stabilization phenomenon: similar to an inverted pendulum with a vibratory pivot. This finding is quite intriguing in the sense that it employs state-of-the-art mathematical tools to discover a beautiful, non-intuitive phenomenon in life sciences that is contrary to the community’s belief. We also supported it with a series of experiments and deep physical explanations. Our most complete work in this line is published in a Science Robotics Paper, creating some splash and attracting some media attention. The Science magazine made two posts (1, 2) about it on their social media, Science Robotics published a commentary on it (Karasek 2020). the Journal of Experimental Biology (JEB) featured it in their outside JEB (Putney 2020), the online news media outlet Tech Xplore made an article about it (Yirka 2020), the famous popular science magazine Scientific American (its Arabic version) featured it (Mansour 2020), and the BBC (Arabic) made a report about it. Prof. Taha has received several interviews to discuss this finding, including an interview by one of the most popular shows in the middle east with Mona Elshazly. Finally, the reader is invited to watch the interesting short video made by our group to explain the idea to the public.

2019: Viscous Extension of the Classical Inviscid Theory of Unsteady Aerodynamics
we developed a viscous extension of the classical inviscid theory of unsteady aerodynamics by relaxing the Kutta condition and using a special boundary layer theory to determine the lift over the maneuvering wing. The need for an auxiliary condition alternative to Kutta’s has been persistent for almost a century. The fact that this problem persisted for this long time, almost without a single convincing solution, despite its impact and the community’s continuous dissatisfaction, is already a proof of its elusive nature. It is expected that this JFM Paper will be one of the classical efforts of unsteady aerodynamics.

Research Interests

1. Unsteady Aerodynamics
Unsteady aerodynamics emerges in various subjects such as the flapping wing, flutter analysis, and rotary blades. One of the most famous approaches in this field coming from the potential flow theory is the Theodorsen solution for the harmonically pitching-plunging flat plate which has been mainly devised for the flutter problem. Since lift generation and vorticity production inside are essentially viscous processes, we attempt to study the viscous unsteady aerodynamics rather than utilizing the conventional potential-flow-based solutions. To do so, we labor wind tunnel experimentation, computational fluid dynamics and analytical approaches to account for the viscous phenomenon. Recently, for the first time, we developed a theoretical viscous extension of the Theodorsen lift frequency response based on the triple deck boundary layer theory and validated it with high fidelity CFD simulations of a harmonically pitching airfoil. More phase lag at high reduced frequencies and low Reynolds numbers is the main outcome of the aforementioned study.

2. Geometric Control Theory
Linear Control has reached a mature stage of development and qualitative questions such as Controllability and Observability has been answered satisfactorily. For nonlinear systems, however, questions about fundamental structural properties such as Controllability are yet to be answered with the hope of reaching analogous results to linear systems. We aim at formalizing feedback-invariant necessary and sufficient conditions for Controllability of nonlinear systems and also we aim to develop a meaningful measure of degree of Controllability of nonlinear systems. If successful, the results of this project will hopefully revive interest in Geometric Control, a branch of control theory that is concerned with studying nonlinear systems using mathematical tools from Differential Geometry.

3. Engineering Applications
Geometric nonlinear controllability analysis sometimes leads to very interesting and non-intuitive results. A car with two controls (forward/backward and steering) is obviously not linearly controllable because of the inability to generate pure side motions. However, the nonlinear geometric analysis shows that the system is nonlinearly controllable and through some manipulation of the available two controls, one can generate side motions. This idea has been generalized to many nonlinear dynamical control systems, where the question is “Will the system still be controllable, if one or more actuators are missed?” One example is the attitude dynamics of a spacecraft (rigid body) where it has been shown that the system is still controllable even if one or two pairs of gas jets are removed, in spite of the system being linearly uncontrollable. In this research, we perform a geometric nonlinear controllability analysis for airplane flight dynamics to study whether the airplane will remain controllable if one or more of the control surfaces fail. Recently, we showed that a twin-engined airplane might still be controllable if it lost all control surfaces (thrust-only flight control system), despite the fact that it is linearly noncontrollable. From another perspective, if that control surface is not needed for control, then how can we use to improve efficiency or to execute unconventional maneuvers? One example is that we found that realizing the Lie bracket between the elevator and aileron deflections leads to a novel rolling mechanism that has a higher authority near stall than the conventional rolling mechanism (using aileron only). The reason is that the traditional mechanism depends on the value of the aileron sensistivity which vanishes near stall, whereas the novel mechanism depends on the rate of change of that sensistivity, which has a significant value near stall as shown in the figure. As such, this novel mechanism might be effective for near-stall or post-stall maneuvers.

News

May 2022		Cody and Taha have their paper paublished in the Journal of Fluid Mechanics on their remarkable Variational Theory of Lift. New chapters will be written in aerodynamic books!
May 2022		Mahmoud, Dipan, Moatasem and Laura have successfully passed their PhD Qualifying Exam. Congratulations!
Apr 2022		Professor Taha is giving a seminar at University of Cincinnati on the Exquisite Stability of Insect Flight and A New Theory of Lift.
Apr 2019		Nabil is presenting at the Socal Fluid Physics Workshop at UCLA on his variational theory of vortex dynamics.
Mar 2022		Professor Taha is giving a seminar at MIT, Physical Mathematics Group on our groundbreaking new variational theory of aero-hydrodynamics.
Mar 2022		Professor Taha is giving a seminar at Stevens Institute on the Exquisite Stability of Insect Flight and A New Theory of Lift.
Mar 2022		Professor Taha is giving an invited talk at the Aerospace Control and Guidance Systems Committee (ACGSC) on the Lie Bracket Rolling Mechanism.
Jan 2022		Moatasem Fouda is awarded the Melucci Fellowship for Winter 2021-2022.
Jan 2022		Our team is presenting 10 papers at the AIAA Scitech conference.
Nov 2021		Cody and Taha are presenting their new theory of lift at the APS DFD conference.
Sep 2017		Mahmoud Abdelgalil is awarded the Holmes Fellowship for the academic year 2021-2022.
Sep 2021		Colin Sledge has successfully defended his PhD. Congratulations Dr. Sledge!
Sep 2021		Our team has published a paper in Nonlinear Dynamics on the interesting nonlinear flight physics of the LIBRA mechanism.
Sep 2021		Our team has published a paper in the Journal of Fluid Mechanics, developing a geometric control formulation of unsteady aerodynamics.
Sep 2021		Dr. dos Santos and Dr. Rezaei have published a paper in Physics of Fluids, developing a viscous extension of vortex methods in unsteady aerodynamics.
Sep 2021		Miquel and Dipan have published a paper in Bioinspiration & Biomemetics on the aerodynamic characteristics of the clapping effect in bioinspired flight.
Sep 2021		Taha and Rezaei have published a paper in the AIAA Journal, developing a state space model for viscous unsteady aerodynamics.
Jul 2021		Professor Taha is giving a seminar at Alexandria University, Egypt on the interesting Stability characteristics of Insect Flight and our New Theory of Lift.
Jun 2021		Professor Taha is giving a seminar at Nile University, Egypt on the Exquisite Stability of Insect Flight and A New Theory of Lift.
Jun 2021		Professor Taha is giving an invited talk at the 3rd World Congress on Robotics in Russia on Vibrational Control in Insect Flight.
Feb 2019		Professor Taha is awarded the School of Engineering Excellence in Research Mid-Career Award. Congratulations!
Apr 2021		Mahmoud Abdelgalil has an accepted paper in Automatica on a novel extremum seeking approach that ensures asymptotic stability.
Mar 2021		Professor Taha is giving 2 plenary talks at the 14th International Conference of Fluid Dynamics in Egypt.
Jan 2021		Dr. Eisa joined the aerospace and University of Cincinnati as a tenure track assistant professor. Congratulations, Prof. Eisa!
Jan 2021		Our team is presenting 6 papers at the AIAA Scitech conference.
Dec 2020		Professor Taha is giving a seminar at the Australian College in Kuwait on Mathematical Control Theory in Aeronautics.
Nov 2020		Our team is presenting 4 talks at the APS DFD conference.
Oct 2020		Dr. Rezaei has an accepted paper in the Journal of Fluids and Structures on the relation between the Kutta condition and circulation nonlinear dynamics during laminar-to-turbulent transition.
Oct 2020		The Science magazine has made two posts (1, 2) highlighting our recent paper Vibrational Vibrational control: A hidden stabilization mechanism in insect flight on their Facebook page. Yaay! What a great discovery!
Sep 2020		Our team has an accepted paper in Composite Structures on nonlinear electro-aeroelastic dynamics of composite beams.
Aug 2020		Dr. Hassan has an accepted paper in the IEEE Transactions on Aerospace and Electronic Systems on a novel roll mechanisms for airplanes at high angles of attack.
May 2020		The ADCL receives $300,000 grant from the NSF to develop viscous extension of potential-flow unsteady aerodynamics. Congratulations!
Mar 2020		Professor Taha receives the amazing news about his tenure. Congratulations!
Mar 2020		Colin has successfully passed his PhD Qualifying Exam. Congratulations Colin!
Jan 2020		Mahmoud is presenting at the Socal Control Workshop.
Jan 2020		The ADCL welcomes Laura Pla Olea as a PhD student.
Jan 2020		Professor Taha is giving 3 talks (2 papers) at the AIAA SciTech 2020.
Jan 2020		Taha and Rezaei have a published a paper in the Journal of Fluids and Structures, On the high-frequency response of unsteady lift andcirculation. Congratulations!
Dec 2020		Laura Pla Olea has successfully defended her MS. Congratulations Laura!
Dec 2020		Amir Rezaei has successfully defended his PhD. Congratulations Dr. Rezaei!
Nov 2019		Professor Taha is giving a seminar at UCLA MAE Department on Exploitation of Unsteady Aerodynamics & Nonlinear Flight Mechanics in Aeronautical Engineering.
Oct 2019		Professor Taha is giving a talk at UCI MAE Departmental Seminar on Geometric Control, Flapping Flight, and Unsteady Aerodynamics.
Sep 2019		The ADCL welcomes two new PhD students: Asmaa Eldesouky and Cody Gonzalez.
Aug 2019		Professor Taha is giving a talk at Cairo University on a Applications of Differential-Geometric Control and Unsteady Aerodynamics to Unconventional Flying Concepts.
Aug 2019		Mahmoud got married to Asmaa who is joining our group next Fall. Yaay! Congratulations, Mahmoud and Asmaa!
May 2019		The Flapping MAV team won the 3rd place prize ($5,000) of the Cornell Cup competition over 83 national teams. Yaay!
Apr 2019		The ADCL group is presenting four talks at the Socal Fluid Physics Workshop at UC Santa Barbara. Great Effort!
Apr 2019		The ADCL receives $450,000 grant from the AFOSR to study geometric control of unsteady aerodynamics. Congratulations!
Mar 2019		Professor Taha is giving an invited talk at the American Mathematical Society Spring Central and Western Sectional Meeting on a Novel Rolling Mechanism for Airplanes Near Stall.
Feb 2019		Taha and Rezaei have a published a paper in the prestigious Journal of Fluid Mechanics, developing a viscous extension of the classical theory of unsteady aerodynamics. Congratulations!
Feb 2019		Professor Taha is awarded the prestigious NSF CAREER award. Congratulations!
Jan 2019		The ADCL group is presenting eight papers at the AIAA SciTech 2019 in San Diego. Great Effort!
Dec 2018		Amir has successfully passed his PhD Qualifying Exam. Congratulations Amir!
Nov 2018		Miquel Balta has successfully defended his MSc. Congratulations Miquel!
Nov 2018		Professor Taha is presenting at the APS DFD Meeting.
Nov 2018		Ahmed is presenting at the Socal Control Workshop.
Nov 2018		Ahmed Hassan has successfully defended his PhD. Congratulations Dr. Hassan!
Nov 2017		Ahmed Hassan has an accepted paper in the prestigious Journal of Nonlinear Science
Oct 2018		Professor Taha is giving an invited talk at the Aerospace Control and Guidance Systems Committee (ACGSC) on Vibrational Control of Flapping Flight.
Sep 2018		The ADCL welcomes four new PhD students: Moatasem Fouda, Nabil Khalifah, Dipan Deb, and Mahmoud Abdul Galil.
Aug 2018		Professor Taha is giving a talk at the University of Southern California.
Jul 2018		Imran and Sameh have their paper (Controllability Perspective of Dynamic Soaring) accepted at the Journal of Nonlinear Dynamics.
Jan 2018		Professor Taha is presenting papers at the AIAA Aviation and the IEEE ACC conferences.
Jun 2018		The Flapping MAV team won the first prize ($10,000) of the Beall and Butterworth competition. Yaay!
May 2018		The Flapping MAV team is selected to perform at the Ingenuity 2018 Showcase. Congratulations Flappers!
May 2018		Professor Taha is awarded the "AIAA OC 2018 Young Professional of the Year Award", for "high potential for continued professional engineering growth in teaching and for technical contribution to Advanced Flight Dynamics Research".
May 2018		Amir is awarded the "AIAA OC 2018 Student of the Year Award", for "demonstrated capability in his aerospace studies, for continued academic excellence and for developing CFD (Computerized Fluid Dynamics) code for solving unsteady aerodynamics". Congratulations, Amir!
May 2018		Ahmed and Amir are presenting at the AIAA OC ASAT Conference.
May 2018		Sameh and Imran have their paper accepted at the Journal of Aerospace Science and Technology.
May 2018		Sameh is presenting at the Socal Control Workshop.
May 2018		Professor Taha has a paper accepted at the Aerospace Science and Technology with his VT collaborators on the variational dynamics of unsteady vortices .
Apr 2018		Marco got married. Yaay! Congratulations, Marco!
Apr 2018		Ahmed and Amir are presenting at the Socal Fluids Workshop.
Mar 2018		The Flapping MAV team won the Dean's selection in the Winter Design Review. Congratulations Flappers!
Jan 2018		Professor Taha is giving a talk at NYU Abu Dhabi in the memory of the Benjamin Franklin medalist Ali Nayfeh.
Jan 2018		Mohammadali Kiani has an accepted paper in the IEEE American Control Conference (ACC).
Jan 2018		Mohammadali Kiani has an accepted paper in the prestigious International Conference on Robotics and Automation (ICRA).
Jan 2018		Professor Taha is presenting two papers at the AIAA SciTech conference.
Nov 2017		Mohammadali Kiani has an accepted paper in IEEE Robotics and Automation Letters on his demonstration of the vibrational stabilization phenomenon in flapping flight.
Sep 2017		Ahmed Hassan got married. Hooray!
Sep 2017		Professor Taha is giving a talk at the University of Michigan Ann Arbor.
Sep 2017		Ahmed Hassan is awarded Holmes Fellowship for the academic year 2017-2018.
Aug 2017		Professor Taha is giving a talk at NASA AMES Research Center.
Aug 2017		Dr. Sameh Eisa joins our research group as a post-doctoral fellow. Welcome Sameh!
Aug 2017		Mohammadali Kiani and Joel Navarro succeeded to experimentally demonstrate the Vibrational Stabilization phenomenon in flapping flight. Good job, indeed!
Jun 2017		Ahmed Hassan has an accepted paper in the prestigious journal of Guidance, Control and Dynamics.
Mar 2017		Professor Taha is giving a seminar at the University of Maryland College park.
Jan 2017		Ahmed Hassan has an accepted paper in the prestigious journal of Nonlinear Dynamics.
Jan 2017		Ahmed Hassan is among the six finalists for the Student Best Paper Award at the AIAA GNC, by his paper A combined Averaging-Shooting Approach ...
Jan 2017		Our research group is attending the AIAA SciTech 2017 meeting at Dallas Texas, presenting six papers.
Jan 2017		Professor Taha is awarded an NSF EAGER grant to revisit the Vibrational Control Theory.