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MAE Colloquium - Spring 2015

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. However, all members of the UW community are welcome to attend and participate.

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. Dana Dabiri

March 30

Army Research & Development for Aerospace & Extreme Environments

The U.S. Army Laboratory is engaged in an intensive, multidisciplinary program to actively investigate disruptive technologies that are potentially capable of providing game-changing enhancements in capabilities for U.S. Soldiers and the equipment they use. Many of these research efforts occur at the fundamental research level -- largely in collaboration with academia partners -- where new discoveries and new theories are made. Other, more transitional efforts -- largely in collaboration with industry partners -- are focused on applying mature technologies into developmental systems and components. This presentation will provide a brief overview of the Army’s research and development organizations executing these programs and of the major areas of technical endeavor being pursued at the Army Research Laboratory, with specific emphasis on the Weapons and Materials Research Directorate. Also included will be a summary of the various mechanisms of engaging with Army laboratories and centers through leveraging and partnerships – with specific emphasis on the new ARL Open Campus Concept, facilitating enhanced collaboration with faculty and students at major U.S. research universities. Finally, the topic of human capital investment will be discussed, including educational outreach programs (e.g., student internships), fellowships, and hiring opportunities.

Presentation Slides (pdf)

Suggested Readings:
(1) TBD
(2) TBD


April 6

Opportunities and Research Directions for Tracking of Resident Space Objects

Space Situational Awareness (SSA) is defined as the knowledge, present and predicted, of the environment on which space operations depend, including physical, virtual, and human domains. Challenges to SSA directly stem from accurate modeling of the space environment and resident space object (RSO) dynamics as well as appropriate processing of available measurement information. A further complication is the simple fact that sensing resources are finite and the RSO population is growing, the current catalog is on the order of tens of thousands, due to launches, break-ups, and collisions. To make up for the lack of information available through measurements, accurate and efficient modeling of space object dynamics across multiple orbit regimes with Earth as the dominant force source, known as astrodynamics, is required. When measurements are available, appropriate filtering techniques are required to extract the most information possible for detection, tracking, identification, and classification of RSOs in a multi-object, multi-sensor environment. Highlighted challenges include state vector representations, dynamical system modeling, and sensor measurement exploitation. Recent research results with respect to initial orbit determination and uncertainty propagation will be presented.

Presentation Slides (pdf)

Suggested Readings:
(1) National Research Council, "Continuing Kepler's Quest: Assessing Air Force Space Command's Astrodynamic Standards", 2012. Chapter 2.


April 13

Optimization for Energy-Efficient Autonomous Systems

Energy efficiency is a critical performance consideration in evaluating operational capability of many autonomous systems. The advances in technology development of autonomous systems have expanded the scope of energy efficiency from energy savings per required mission/device to including energy harvesting and management capabilities. Improving these performance goals for systems with complex dynamics and mission constraints is challenging, especially when onboard computation is required to realize real-time optimization.

This talk will present our work on developing sophisticated modeling and optimization tools and experimental facilities for the verification of these tools. Advanced optimization schemes are generated by formulating optimization problems with significantly reduced design variables, compact mathematical representations, simplified dynamics, and/or relaxed constraints. The relative optimization schemes, including modified particle swarm optimization, quadratically constrained quadratic programs, and iterative semidefinite programming algorithms, are aiming at overcoming the computational bottleneck of optimization problems classified as NP-hard using the new modeling paradigms. Application examples include integrated energy harvesting and power management of solar-powered ground vehicles and its verification in experimental testbed, path planning of solar-powered unmanned aerial vehicles, and minimum energy formation maintenance and intrusion reaction of fractionated satellites. The overall objective is to realize high level autonomy in energy harvesting and utilization under operational and mission constraints by novel modeling and optimization strategies. Some results obtained in virtual simulation are verified in real-world experimental test, leading to synthesized theoretical and experimental framework for analyzing energy-efficient autonomous systems.

Presentation Slides (pdf)

Suggested Readings:
(1) Camacho, Eduardo F., et al. Control of solar energy systems. Springer Science & Business Media, 2012.
(2) Boyd, Stephen, and Lieven Vandenberghe. Convex optimization. Cambridge university press, 2004.
(3) Wie, Bong. Space vehicle dynamics and control. AIAA, 1998.


April 20

Development of Advanced Flow Diagnostic Techniques to Study Complex Thermal/Fluids Phenomena

The talk will start with the description of the recent progress made by the speaker in developing a novel molecule-based flow diagnostic technique, named as Molecular Tagging Velocimetry and Thermometry (MTV&T), for simultaneous measurements of flow velocity and temperature distributions in fluid flows. Unlike most commonly-used particle-based flow diagnostic techniques such as Particle Image Velocimetry (PIV), MTV&T utilizes specially-designed phosphorescent molecules, which can be turned into long-lasting glowing marks upon excitation by photons of appropriate wavelength, as the tracers for both flow velocity and temperature measurements. The unique glamour of the MTV&T technique will be demonstrated from the application examples to study the thermal effects on the wake instabilities behind a heated cylinder, to investigate the unsteady heat transfer and phase changing process within micro-sized icing water droplets, and to quantify the transient behavior of the surface water transport process over airfoil surfaces pertinent to aircraft icing and de-/anti-icing applications. The recent research of the speaker’s group on wind turbine aeromechanics and wake interferences among multiple wind turbines sited in onshore and offshore wind farms will also be introduced briefly for higher total power yield and better durability of wind turbines operating in turbulent atmospheric boundary layer (ABL) winds.

Presentation Slides (pdf)

Suggested Readings:
(1) Hu H, Koochesfahani MM, “Thermal Effects on the Wake of a Heated Circular Cylinder Operating in Mixed Convection Regime”, Journal of Fluid Mechanics, Vol.685, pp235-270, 2011. DOI:10.1017/jfm.2011.313.
(2) Hu H, Jin Z, “An Icing Physics Study by using Lifetime-based Molecular Tagging Thermometry Technique", International Journal of Multiphase Flow, Vol. 36, No.8, pp672–681, 2010. DOI:10.1016/j.ijmultiphaseflow.2010.04.001.
(3) Hu H, Yang Z, Sarkar PP, “Dynamic Wind Loads and Wake Characteristics of a Wind Turbine Model in an Atmospheric Boundary Layer Wind", Experiments in Fluids, Vol. 52, No. 5, pp1277-1294, 2012. DOI: 10.1007/s00348-011-1253-5.
(4) W. Tian and A. Ozbay and H. Hu, “Effects of Incoming Surface Wind Conditions on the Wake Characteristics and Dynamic Wind Loads Acting on a Wind Turbine Model”. Physics of Fluids, Vol. 26, No. 12, 125108 (2014).


April 27

Low Reynolds Number Unsteady Airfoils in Pure Pitch Oscillation

Characteristics of the wake vorticity field and conditions for generation of thrust in a pitching airfoil are examined based on results from experiments with molecular tagging velocimetry (MTV) and computations. In particular, the influence of Reynolds number and oscillation amplitude is discussed. Comparison with existing data in the literature points to inconsistencies in the prediction of drag-thrust crossover frequency. Results are also shown to illustrate how asymmetry in the pitch motion trajectory alters the flow structure and forces on the airfoil. Finally, recent advances in MTV diagnostics are briefly described, including the capability to measure surface pressure and shear stress distributions – a unique diagnostics tool for understanding the development of forces on unsteady airfoils.

Suggested Readings:
(1) Turbulent Mixing & Unsteady Aerodynamics Laboratory (TMUAL): Publications


May 4

Micro 3D Printing of Soft Active Materials

Active materials that can adapt to dynamic environment hold great potential in development of autonomous and multifunctional devices. Although various stimuli- responsive soft materials have been extensively studied for the past decades, unique properties and advantages of these materials have not been fully utilized because of limitations of manufacturing methods. In this talk, a novel three-dimensional (3D) microfabrication technique, projection micro-stereolithography (PμSL), will be presented. PμSL is flexible, scalable, and multi-material manufacturing tool, capable of creating structural and functional complexity in 3D micro-architectures. PμSL was used to implement in hydrogel devices design principles inspired by exquisite motions and morphologies of moving plants in nature such as Venus Flytrap. Swelling-induced elastic instability has been studied to enhance actuation speed of soft devices and to create spontaneous structural pattern transformation. In the second part of the talk, ultra-light cellular material with unprecedented specific stiffness will be presented. PμSL and various post-processing techniques were used to build highly ordered meso scale stretching-dominated octet truss materials with micro-scale architecture and nano- scale features, resulting in orders of magnitude greater mechanical efficiency than existing cellular structures and natural materials.

Presentation Slides (pdf)

Suggested Readings:
(1) Howon Lee, C. Xia, and N. X. Fang, "First Jump of Microgel: Actuation Speed Enhancement using Elastic Instability", Soft Matter 6 (2010) 4342-4345.
(2) Howon Lee, J. Zhang, H. Jiang, and N. X. Fang, "Prescribed Pattern Transformation in Swelling Gel Tube by Elastic Instability", Physical Review Letters 108 (2012) 214304.
(3) X. Zheng, Howon Lee, T. Weisgraber, M. Shusteff, J. Deotte, E. Duoss, J. Kuntz, M. Biener, Q. Ge, J. Jackson, S. O. Kucheyev, N. X. Fang, and C. Spadaccini, "Ultralight and Ultra-Stiff Mechanical Metamaterials", Science 344, 1373 (2014).

May 11

Compositional Control Synthesis and Verification for Networks

Control synthesis and performance verification techniques are severely limited in their scalability to large networks of interconnected components. We address this problem with a compositional approach that derives network-level guarantees from structural properties of the components and their interconnection. In the first part of the talk we will present a large-scale optimization technique that verifies a network performance criterion from dissipativity properties of the components. In the second part we will pursue control synthesis and verification using formal methods from computer science, which rely on finite state abstractions of dynamical models. We will show that the abstraction task is greatly simplified by exploiting an interconnection property called “mixed monotonicity.” We will illustrate the results with examples from multi-agent systems and traffic networks. In doing so, we will exhibit useful structural properties inherent in these networks.

Presentation Slides (pdf)


May 18

Hybrid unsteady-flow simulation combining PIV/PTV and DNS: Family of data-assimilation algorithms and their capabilities

Applications of state-of-the-art techniques integrating time-resolved particle image velocimetry (PIV) with unsteady computational fluid dynamics (CFD) are recently expanding. Techniques of this type can serve for purposes of data assimilation, filtering of measurement noise, extraction of reduced-order models, unsteady pressure estimation, compensation of missing/sparse data, and combination of some of these. We have developed a series of hybrid-unsteady-simulation techniques combining particle tracking velocimetry (PTV) and direct numerical simulation (DNS), and demonstrated their capability by solving unsteady laminar flows past an airfoil and planar-jet flows. Unsteady velocity fields on a laser sheet in a water tunnel are acquired with time-resolved PTV; subsequently, PTV velocity fields are rectified in a least-squared sense to satisfy the continuity, and they are transplanted to a two-dimensional incompressible Navier—Stokes solver by setting a multiple of the computational time-step equal to the frame rate of the PTV system. The hybrid velocity field is then assimilated into that of the measured one over time with the resolution equivalent to DNS and the noise level much lower than the original PTV data. Unsteady pressure fields can be simultaneously computed, and the set of the computed flow quantities essentially satisfies the governing equations. This presentation introduces hierarchy of hybrid simulations from a reduced-order approach consisting of proper orthogonal decomposition (POD) and the Galerkin projection to a high-fidelity approach adopting the extended Kalman filter, and compares the data-assimilation capabilities of these algorithms. (Work done at the University for Fukui, Japan)

Suggested Readings:
(1) Suzuki, T., Ji, H. & Yamamoto, F., "Unsteady PTV velocity field past an airfoil solved with DNS: Part 1. Algorithm of hybrid simulation and hybrid velocity field at Re≈ 103", Exp. Fluids, 47(6), 957-976 (2009).
(2) Suzuki, T., Ji, H. & Yamamoto, F., "Instability waves in a low-Reynolds-number planar jet investigated with hybrid simulation combining particle tracking velocimetry and direct numerical simulation", J. Fluid. Mech., 655, 344-379 (2010).
(3) Suzuki, T., "Reduced-order Kalman-filtered hybrid simulation combining particle tracking velocimetry and direct numerical simulation", J. Fluid. Mech., 709, 249-288 (2012).

May 25

Campus Holiday - No Class Meeting


June 1

Unusual Flammability Characteristics of Fluorinated Hydrocarbons

The combustion characteristics reported for hydrofluorocarbons (HFCs), which are widely used as fire suppressants, refrigerants and blowing agents, are quite unique and unusual. Past studies have demonstrated that HFC addition can either enhance or inhibit combustion of hydrocarbons depending on the specific conditions such as the added agent concentration. These unusual characteristics partly arise from the competing processes of H-atom removal (active radical loss) to form tightly bound HF and the heat generated from HF formation. In this work, the laminar flame speeds were determined for stoichiometric difluoromethane-air as well as binary mixtures of difluoromethane/tetrafluoropropene and propane/tetrafluoropropene with air using the vertical tube method. To elucidate important reaction pathways, a detailed chemical mechanism was compiled for modeling these systems as well as other fluorinated methanes and ethanes with air. The mechanism was constructed from published sub-mechanisms for C3 hydrocarbons and hydrofluorocarbons with additional oxidation chemistry developed for 2,3,3,3-tetrafluoropropene. The latter sub-mechanism contains an additional 10 species and 41 reactions, whereas the entire compiled mechanism contains 132 species and 1088 reactions. Comparisons between experimental data and numerical predictions point to the need for further work; in particular under fuel-lean conditions.

Presentation Slides (pdf)

Suggested Readings:
(1) TBD
(2) TBD