Conferences, Lectures, & Seminars
Events for September
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AME Seminar
Wed, Sep 04, 2019 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Basile Radisson, USC
Talk Title: Insights into the Nonlinear Evolution of Flame Fronts through Experiments and Models
Abstract: Due to the exothermicity of combustion reaction, premixed flames are intrinsically unstable. Consequently, cellular patterns are formed on the flame front resulting in rich and complex dynamics. Combustion involves several hundreds of elementary chemical reactions occurring at a submillimetric interface, rendering a detailed description computationally intractable. Simplified models offer much insight into these complex dynamics. Through asymptotic analysis, the shape of the flame front can be described by a set of poles and their dynamic evolution in the complex plane. Here, we demonstrate for the first time the validity of such model in comparison to experimental flame evolution. A premixed flame propagates in a reactive mixture held between two vertically oriented ceramic glass plates separated by a 5mm gap. By extracting a flame front from this experiment, we demonstrate the feasibility of describing the shape of the front by a set of pole solutions. The flame front dynamics are well described for approximately ten times the characteristic time of the instability. Beyond this time, the comparison is limited by the sensitivity to initial condition. However, by studying statistical properties of the flame front, here statistics of cell sizes, we demonstrate that the pole description is still valid at long time. Moreover, these statistics satisfy a gamma distribution, characteristic of phenomena for which the elementary interaction rule is of additive nature and which results here from the pole to pole attraction. This analytical prediction of the cell-size distribution could be of great interest for the understanding of turbulent flame dynamics.
Biography: Basile Radisson is a postdoctoral scholar in the Aerospace and Mechanical Engineering department at the University of Southern California since June 2019. Prior to joining USC, Basile received his PhD from IRPHE, AixMarseille Universite, France, working on flame front dynamics under the supervision of C. Almarcha and B. Denet. His research interests lie in instability phenomena driven by geometric nonlinearities. He is currently working on snap instabilities in fast elastic filaments under the supervision of E. Kanso.
Host: Kanso
Location: SLH 102
Audiences: Everyone Is Invited
Contact: Tessa Yao
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
AME Seminar
Wed, Sep 11, 2019 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Eckart Meiburg, UC Santa Barbara
Talk Title: Settling of Cohesive Sediment: Particle-resolved Simulations
Abstract: We develop a physical and computational model for performing fully coupled, grain resolving Direct Numerical Simulations of cohesive sediment, based on the Immersed Boundary Method. The model distributes the cohesive forces over a thin shell surrounding each particle, thereby allowing for the spatial and temporal resolution of the cohesive forces during particle particle interactions.
We test and validate the cohesive force model for binary particle interactions in the Drafting Kissing Tumbling (DKT) configuration. Cohesive sediment grains can remain attached to each other during the tumbling phase following the initial collision, thereby giving rise to the formation of flocs. The DKT simulations demonstrate that cohesive particle pairs settle in a preferred orientation, with particles of very different sizes preferentially aligning themselves in the vertical direction, so that the smaller particle is drafted in the wake of the larger one. This preferred orientation of cohesive particle pairs is found to remain influential for much larger simulations of 1,261 polydisperse particles released from rest. These simulations reproduce several earlier experimental observations by other authors, such as the accelerated settling of sand and silt particles due to particle bonding, the stratification of cohesive sediment deposits, and the consolidation process of the deposit. This final phase also shows the build-up of cohesive and direct contact intergranular stresses. The simulations demonstrate that cohesive forces accelerate the overall settling process primarily because smaller grains attach to larger ones and settle in their wakes. An investigation of the energy budget shows that the work of the collision forces substantially modifies the relevant energy conversion processes.
Bio
Eckart Meiburg received his Ph.D. from the University of Karlsruhe. After a postdoc at Stanford, he became an assistant professor in applied mathematics at Brown. He then moved to USC as associate then full professor. He later moved to UC Santa Barbara.
His research interests are fluid dynamics and transport phenomena, primarily computational fluid dynamics. He uses highly resolved direct numerical simulations to investigate physical mechanisms governing the spatio temporal evolution of a wide variety of geophysical, porous media, and multiphase flow fields. Some of his current interests are gravity and turbidity currents, Hele Shaw displacements, double diffusive phenomena in particle laden flows, and internal bores.
Meiburg has received a Presidential Young Investigator Award, a Humboldt Senior Research Award, and a Senior Gledden Fellowship (Institute of Advanced Studies, University of Western Australia). He is fellow of the American Physical Society and the ASME, was the 2012 Lorenz G. Straub Award Keynote Speaker (Univ. Minn.), gave the Ronald F. Probstein Lecture at MIT in 2018, and was Shimizu Visiting Professor at Stanford University.
Host: AME Department
More Info: https://ame.usc.edu/seminars/
Location: John Stauffer Science Lecture Hall (SLH) - 102
Audiences: Everyone Is Invited
Contact: Tessa Yao
Event Link: https://ame.usc.edu/seminars/
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
Ph.D. Dissertation Defense
Fri, Sep 13, 2019 @ 01:00 PM - 02:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Pradeep Rajendran, AME Ph.D. candidate
Talk Title: Speeding Up Trajectory Planning for Autonomous Robots Operating in Complex Environments
Abstract: Advances in sensing and computing hardware have physically equipped robots to operate in complex environments. In many real-world settings, we desire robots to operate at a high-level of autonomy to reduce operating costs and manpower requirements. A high-level of autonomy can be achieved only when robots are able to plan missions and tasks themselves. Trajectory planning is a fundamental building block required to support high-level decision making in robots.
Trajectory planning for autonomous robots operating in complex environments is a challenging problem. The complexity of trajectory planning problems stems from the dimensionality of robot's state space, the complexity of the robot kinematic and dynamic model, the nature of environmental constraints (e.g., obstacles), task constraints (e.g., rules), the optimization objective function, and the planning-time requirements needed for deployment in the real world. Depending on the complexity, these problems can be solved by existing methods to produce feasible trajectories. But, in many practical applications (e.g., automated package delivery), computing a feasible trajectory alone is not enough. The quality of the computed trajectory is also important. However, in many cases, computing truly optimal trajectories is computationally intensive and thus, very time-consuming. As a result, existing methods do not satisfy planning-time constraints required by the application while maintaining optimality. We need a method that produces high-quality trajectories and at the same time produce those trajectories quickly. Anytime methods handle exactly this problem. However, these methods produce high-quality trajectories quickly only when good heuristics are used.
This work focuses on techniques for anytime algorithms that speed up trajectory planning for autonomous robots in complex environments. It is anticipated that the methodology presented in this work will be applicable to mobile robots operating in an outdoor setting such as uneven terrain, water bodies. In such settings, the speed-up techniques will allow the robot to quickly react to the environment and perform tasks safely. Depending on the application domain, this will also serve as an enabling technology for more advanced services. Many industrial processes are currently use high degree-of-freedom manipulators that are manually programmed by a human operator. Methods presented in this work can greatly simplify workflows related to manipulators and improve manufacturing throughput.
Host: SK Gupta
Location: Robert Glen Rapp Engineering Research Building (RRB) - Laufer Library
Audiences: Everyone Is Invited
Contact: SK Gupta
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
AME Seminar
Wed, Sep 18, 2019 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Kunihiko (Sam) Taira, UCLA
Talk Title: Network-Based Characterization, Modeling, and Control of Fluid Flows
Abstract: The network of interactions among fluid elements and coherent structures gives rise to the amazingly rich dynamics of vortical flows. To describe these interactions, we consider the use of mathematical tools from the emerging field of network science that is comprised of graph theory, dynamical systems, data science, and control theory. In this presentation, we discuss ways to describe unsteady fluid flows with vortical interaction, modal-interaction, and probability transition networks. The insights gained from these formulations can be used to characterize, model, and control laminar and turbulent flows. We will also discuss some of the challenges of applying network based techniques to fluid flows and the prospects of addressing them through data-inspired techniques.
Biography: Kunihiko (Sam) Taira is an Associate Professor of Mechanical and Aerospace Engineering at UCLA. His research focuses on computational fluid dynamics, flow control, and network science. He received his B.S. degree from the University of Tennessee, and his M.S. and Ph.D. degrees from the California Institute of Technology. He is a recipient of the 2013 U.S. Air Force Office of Scientific Research and 2016 Office of Naval Research Young Investigator Awards.
Host: AME Department
More Info: https://ame.usc.edu/seminars/
Location: John Stauffer Science Lecture Hall (SLH) - 102
Audiences: Everyone Is Invited
Contact: Tessa Yao
Event Link: https://ame.usc.edu/seminars/
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
Ph.D. Dissertation Defense
Fri, Sep 20, 2019 @ 11:00 AM - 01:00 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Longlong Chang, AME Ph.D. candidate
Talk Title: Dynamic Modeling and Simulation of Flapping-Wing Micro Air Vehicles
Host: Nestor Perez-Arancibia
More Information: DissertationAbastract_LonglongChang.pdf
Location: Robert Glen Rapp Engineering Research Building (RRB) - Laufer Library
Audiences: Everyone Is Invited
Contact: Nestor Perez-Arancibia
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
AME Seminar
Wed, Sep 25, 2019 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Dana Dabiri, University of Washington
Talk Title: Design & Implementation of a 3D-PTV System
Abstract: The dream of experimental fluid dynamicists is to be able to measure complex, three-dimensional turbulent flow fields globally with very high spatial and temporal resolution. While we are still far from fully realizing this dream, significant progress has been made towards this goal during the last three decades. Early quantitative measurement methods using Pitot tubes, Venturi tubes and later measurement methods, such as Hot Wire Anemometry (HWA) and Laser-Doppler Anemometry (LDA), by their nature, were measurement methods that provided instantaneous velocity signals at single-points through time. Early emphasis in turbulence research and its theoretical advancement therefore necessitated a statistical description of turbulent flow fields, which relied heavily upon measurements provided by these single-point measurement techniques. Since the early seventies, the discovery of the existence of three-dimensional coherent structures within turbulent flows using qualitative flow visualization methods (i.e. shadowgraphs, Schlieren systems, dye injection, etc.) has been of significant interest for turbulence researchers. While flow visualization techniques have been around since the days of Prandtl, it is only due to the advent of modern imaging, laser, and data acquisition technology has allowed for qualitative flow visualization to become quantitative. These advents have allowed for the development and advancement of are relatively new measurement technique, Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) in two dimensions, and more recently in 3 dimensions. Because of its ability to provide global two/three-dimensional kinematic information as well as its ability to map the evolution of coherent structures through time, PIV/PTV has become a powerful tool in studying, understanding, and modeling fluid flow behavior. In this talk, I will describe the particulars of the 3D Particle Tracking Velocimetry method we have developed and touch on some applications in microflows and LES studies.
Host: AME Department
More Info: https://ame.usc.edu/seminars/
Location: John Stauffer Science Lecture Hall (SLH) - 102
Audiences: Everyone Is Invited
Contact: Tessa Yao
Event Link: https://ame.usc.edu/seminars/
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor.
