MAE Colloquium - Spring 2014
The Aerospace Engineering Colloquium (AE 598) is a required course that satisfies the professional development component of the Master of Aerospace Engineering (MAE).MAE students are required to complete nine (9) credits of colloquium participation to satisfy the degree requirements. Only students admitted into the MAE degree program are eligible to enroll in this course for credit. However, all students and faculty are welcome to attend.
Topics may include current research and advances in aerospace technology as well as other themes relevant to the professional development of aerospace engineers. To earn credit for this course, students must complete a required set of writing assignments.
Faculty Coordinator: Prof. Kristi Morgansen
Reduced-Order Phenomenological Modeling of Unsteady Aerodynamics
- Jeff Eldredge, Associate Professor
Department of Mechanical & Aerospace Engineering, University of California - Los Angeles
Aquatic and airborne creatures are capable of agile maneuvers and adaptation to environmental disturbances in manners not achieved by human-engineered systems. In spite of revelatory advances in the experimental and computational investigations of these creatures' fluid dynamics, we still lack the tools to reduce these mechanics into their simplest and most essential contributions to locomotion or energy extraction. This severely limits the ability of robotic systems to exploit phenomena that occur on fast time scales, e.g. on the order of a wing beat. Much of the reason for this can be attributed to the intrinsically unsteady and non-linear phenomena that underlie such mechanics.
In this talk, Prof. Eldgredge will discuss his team's recent efforts to develop a modeling framework that enables the mechanics of agile bio-inspired locomotion to be distilled into a low-order model. This framework is based on a physics-based template model that retains the essential non-linear dynamics of the full problem, but in a small number of degrees of freedom. The template model is informed from empirical data by applying a variational principle to minimize the difference in a target metric, such as a fluid dynamic force. He will illustrate the modeling approach with examples involving unsteady maneuvers of a flat plate. He will also discuss our ongoing efforts to develop a generic and open-source computational library for high-fidelity simulations of bio-inspired flows.
Presentation Slides (pdf)
(1) M. S. Hemati, J. D. Eldredge and J. L. Speyer, “Improving vortex models via optimal control theory,” Accepted for publication in J. Fluids Struct., March 2014.
(2) Chengjie Wang and Jeff D. Eldredge, "Low-order phenomenological modeling of leading-edge vortex formation," Theor. Comput. Fluid Dyn. 27(5) : 577--598, August 2013.
Evaluation and Feedback: If it’s important, why not do it well?
- Jim Borgford-Parnell, Associate Director & Instructional Consultant
Center for Engineering Learning & Teaching, University of Washington
Assessment and evaluation practices are so much a part of our academic and professional lives, isn’t it important that they be done efficiently and meaningfully? This presentation will focus on some of the common ways that we find ourselves on the giving or receiving end of assessments and what we should know that can make them more effective.
Presentation Slides (pdf)
Spacecraft Guidance and Control for Relative Motion
- Morgan Baldwin, Research Aerospace Engineer - Guidance, Navigation, & Control Section
Space Vehicles Directorate, U.S. Air Force Research Laboratory (Kirtland AFB)
Since the beginning of manned space flight, the United States has chosen a manual course of action concerning rendezvous and relative motion. This approach enables flexibility for a given mission and eliminates the need for redundancy and complexity. With the increasing number of space objects, autonomous operations are needed to effectively, both in terms of cost and efficiency, complete certain space operations, including capture, servicing, monitoring, and inspection. An autonomous system is expensive during development, but the system can be standardized and cost benefits are achieved through the system's lifecycle. Currently, guidance solutions are determined by ground operators employing impulsive models for spacecraft propulsion capability; only after lengthy analysis are these solutions uploaded to the spacecraft and implemented using closed-loop trajectory control.
This talk will present three approaches to improving onboard robustness of spacecraft relative motion guidance and control. The first approach is based on Model Predictive Control (MPC), and its capability for robust trajectory execution by changing the environment with a sudden obstacle appearing along its path. The second approach uses an Extended Command Governor (ECG) that augments a nominal LQ controller. The ECG modifies commanded set-points to the inner loop LQ controller when it becomes necessary to avoid constraint violation. The third approach makes use of safe positively invariant sets. In this approach, a connectivity graph is constructed between a set of forced equilibria, forming a virtual net that is centered around a nominal orbital position. A graph search algorithm is implemented to find an efficient path around the obstacle(s). Simulations results will be presented.
(1) Peterson, C., Juanzemis, A., Baldwin, M., Holzinger, M., Kolmanovsky, I.V., and Erwin, R., "Model Predictive Control and Extended Command Governor for Improving Robustness of Relative Motion Guidance and Control," Proc. 24th AAS/AIAA Space Flight Mechanics Meeting, Santa Fe, NM, January 2014.
(2) Weiss, A., Baldwin, M., Petersen, C., Erwin, R. S., and Kolmanovsky, I. V. "Spacecraft Constrained Maneuver Planning for Moving Debris Avoidance Using Positively Invariant Constraint Admissible Sets," Proc. Amer. Contr. Conf. pp. 4809 - 4814, Washington, D.C., June 2013.
No Class Meeting
Students are encouraged to consider participating in the 2014 JCATI Symposium, "Advancing Public-Private Partnerships in Aerospace."
Creating Optimal Learning in Diverse Teaching Environments
Dr. Saenz will give an overview of select social psychological concepts that inform the experience of women and underrepresented minorities in learning environments/working groups. This work will focus on three key areas that influence outcomes for these individuals: content, process, and structure.
Part interactive workshop and part lecture, the presentation will demonstrate how ‘normative’ social dynamics may serve to disadvantage underrepresented group members. In addition to presenting research from the field and from her own lab, Dr. Saenz will provide recommendations for creating more equitable learning opportunities. Connections will be drawn between the research and application of the concepts and recommendations to engineering settings (classroom and workplace).
No Class Meeting
A Fast Pressure-correction Method for Simulating Two-fluid Flows and DNS of Droplet-laden Isotropic Turbulence
- Antonino Ferrante, Assistant Professor
Wm. E. Boeing Department of Aeronautics & Astronautics, University of Washington
Direct numerical simulation (DNS) studies of droplet-laden turbulent flows have mostly been limited to sub-Kolmogorov size droplets using the point-particle approach. DNS of finite-size droplets, characteristic of the size of fuel droplets during secondary atomization, requires fully- resolving the flow inside and around the droplets while accounting for the effects of surface tension. The main goal of the present study is to investigate via DNS the effects of finite-size deformable droplets on decaying isotropic turbulence.
In order to achieve this objective, first, we have developed a three-dimensional volume of fluid (VoF) method for tracking droplets accurately and efficiently in incompressible velocity fields. The novelty of the developed approach is that besides conserving mass globally, a condition not always satisfied by VoF methods, mass conservation is also ensured locally while requiring half the number of advection and reconstruction steps of conventional methods. Then, we have developed and coupled a new pressure-correction method with the VoF method for simulating incompressible two-fluid flows. The method's main advantage is that the variable coefficient Poisson equation that arises in solving the incompressible Navier-Stokes equations for two-fluid flows is reduced to a constant coefficient equation. This equation can then be solved directly using, e.g., the FFT-based parallel Poisson solver that we have developed for petascale supercomputers. For a 1024^3 mesh, our new pressure-correction method using the FFT-based parallel Poisson solver is ten to forty times faster than the standard pressure-correction method using multigrid. In general, the new pressure-correction method could be coupled with other interface advection methods such as level-set, phase-field, or front-tracking.
Our new pressure-correction/VoF flow solver has been verified up to density and viscosity ratios of 10,000 against theoretical results, validated against experimental results, and shown to conserve mass, momentum, and kinetic energy in the inviscid limit. Finally, I will present results from DNS of non-evaporating droplet-laden isotropic turbulence and the effects of varying the droplet Weber number and the density ratio on the time development of the turbulence kinetic energy budget.
(1) Baraldi, A., M. S. Dodd, and A. Ferrante. "A mass-conserving volume-of-fluid method: volume tracking and droplet surface-tension in incompressible isotropic turbulence." Computers & Fluids (2013).
(2) Lucci, Francesco, Antonino Ferrante, and Said Elghobashi. "Modulation of isotropic turbulence by particles of Taylor length-scale size." Journal of Fluid Mechanics 650 (2010): 5-55.
(3) Ferrante, A., and S. Elghobashi. "On the physical mechanisms of two-way coupling in particle-laden isotropic turbulence." Physics of Fluids (1994-present) 15, no. 2 (2003): 315-329.
Aircraft Structural Safety
- S. Rao Varanasi, Chief Engineer (Ret.) for In-Service Structures & Aging Fleet
Boeing Commercial Aircraft
This talk presents a brief chronological review of the evolution of aircraft structural safety since the advent of the large jet transport category airplanes in the 1950s, including the contributions and limitations of the aircraft structural design standards that contributed to safety efforts over time.
The presentation also discusses the genesis of the Aging Airplane Programs which are implemented under the Aircraft Structures Safety System to assure the airworthiness of airplanes as they age. Each Aging Airplane Program is discussed with examples to show the implementation details and the close participation of the stake holders of the Aircraft Structural Safety System.
(1) Aging Aircraft Program (www.faa.gov)
Campus Holiday - No Class
Designing Figures for Science and Engineering Research
- Marco Rolandi, Assistant Professor
Department of Materials Science & Engineering, University of Washington
In science and engineering fields, figures play an increasingly important role as means of efficiently conveying large amounts of data in a short time frame. Most scientists and engineers do not receive any formal training in visual communication. In this talk, Prof. Rolandi will present collaborative efforts between faculty in the Division of Design, School of Art and the Materials Science and Engineering Department to produce educational materials for scientist and engineers on how to design effective figures to present their research.