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CTR events

CTR Tea : Friday, July 21, 2017 - 4:15pm : Speaker(s): Dr. Marco Giometto, Postdoctoral Fellow, Center for Turbulence Research, Stanford University
Abtract:

Buoyancy driven turbulent flows over inclines will be considered within the conceptual framework of the Prandtl slope-flow model. Such flows are ubiquitous in engineering and the environment, but despite decades of active research, they remain a poorly understood problem. The sensitivity of the system to the model parameters is first characterized via direct numerical simulations, with a focus on variations in mean flow, second order statistics, and budget equations for the mean- and turbulent-kinetic energy. Turbulent flows resulting from upward moving warm fluid and downward moving cold f... Read More

Bio:
Dr. Marco Giometto is a Postdoctoral Fellow in the Center for Turbulence Research at Stanford University. He received his B.Sc. and M.Sc. degrees from the University of Padua, a Ph.D. in Civil and... Read More
CTR Tea : Friday, July 7, 2017 - 4:15pm : Speaker(s): Professor Shuisheng He, Department of Mechanical Engineering, University of Sheffield, United Kingdom
Abtract:

Professor He will present a new perspective of transient turbulent flow and show that in such flows, turbulence does not progressively evolve from one state to another. Instead, the flow is characterised by the development of a laminar boundary layer followed by transition to turbulence. The talk will begin with a review of DNS results, followed by discussing recent laboratory experiments of a flow accelerating from an initially turbulent state following the opening of a valve, together with LES of the experiments and extended Stokes first problem solutions for the early stages of the flow.... Read More

Bio:
Professor Shuisheng He is the Chair in Thermofluids in Department of Mechanical Engineering at the University of Sheffield in the United Kingdom (UK). He received his BSc and MSc from Huazhong... Read More
CTR Tea : Friday, June 9, 2017 - 4:15pm : Speaker(s): Mohamed Houssem Kasbaoui, PhD Candidate, Aerospace Engineering, Sibley School of Mechanical and Aerospace Engineering, Cornell University
Abtract:

Particle-laden flows of sedimenting small heavy solid particles or droplets in a carrier gas have strong inter-phase coupling even at low volume fractions. The slip velocity between phases leads to sustained clustering that strongly modulates the overall flow. The analysis of inertial aerosols in homogeneous shear reveals three fundamental mechanisms contributing to the formation of clusters: (1) the preferential concentration of inertial particles in the stretching regions of the flow (2) particle-trajectory crossing (PTC) and (3) a Rayleigh-Taylor instability due to the vertical stacking... Read More

Bio:
Mohamed Houssem Kasbaoui holds a Diplome d’Ingenieur from Ecole Centrale Paris with an Applied Mathematics Major, and a Master of Science in Physics from University Paris-Sud. He joined Cornell... Read More
CTR Tea : Friday, June 2, 2017 - 4:15pm : Speaker(s): Michael S. Dodd, Department of Aeronautics and Astronautics, University of Washington
Abtract:

Understanding how droplets and turbulence interact is important in numerous applications ranging from rain formation to oil spills to spray combustion, yet most of our knowledge of two-phase turbulence is limited to solid particles. In contrast to solid particles, droplets introduce new phenomena and parameters into the flow, e.g., droplets can deform, break up, coalesce, develop internal circulation, and change phase. In this talk, Dodd will review efforts towards improved understanding of droplet-turbulence interaction. Dodd uses direct numerical simulation (DNS) to capture the exchange o... Read More

Bio:
Michael S. Dodd is a Ph.D. Candidate in the Department of Aeronautics and Astronautics at the University of Washington. He earned his B.S. in Aerospace Engineering from the University of Michigan.... Read More
CTR Tea : Friday, May 26, 2017 - 4:15pm : Speaker(s): Professor Kenneth M. Kamrin, Department of Mechanical Engineering, Massachusetts Institute of Technology
Abtract:

Fluids and solids tend to be addressed using distinct computational approaches.  Solid deformation is most commonly simulated with Lagrangian finite-element methods, whereas fluid flow is amenable to Eulerian-frame approaches such as finite difference and finite volume methods.  Problems that mix fluid and solid behaviors simultaneously present interesting numerical challenges.   This is true when fluids and solids occupy different regions of space --- i.e. fluid-structure interaction (FSI) --- or in cases where materials behave like a solid but can undergo enormous levels of plastic flow m... Read More

Bio:
Professor Ken Kamrin received a BS in Engineering Physics and a minor in Mathematics at UC Berkeley in 2003, and a PhD in Applied Mathematics at MIT in 2008.  He was an NSF Postdoctoral Research... Read More
CTR Tea : Friday, May 19, 2017 - 4:15pm : Speaker(s): Shabnam Raayai-Ardakani, PhD Candidate, Department of Mechanical Engineering, Massachusetts Institute of Technology
Abtract:

Previous investigations have suggested that surfaces textured with riblets can reduce the frictional drag force in high Reynolds number laminar and turbulent flow regimes. Shark skin and synthetic manufactured “shark tape” are widely known as examples of such passive drag reduction mechanisms. Inspired by the ribs on the denticles of fast swimming shark species, riblets of different shapes have been studied under laminar and turbulent flow conditions to understand their drag reduction mechanism and to offer guides for designing optimized low-friction bio-inspired surfaces, often with confou... Read More

Bio:
Shabnam Raayai-Ardakani is a PhD candidate at the Department of Mechanical Engineering at MIT, working at the Hatsopoulos Microfluidics Laboratory (HML) with Professor Gareth McKinley and is... Read More
CTR Tea : Friday, April 21, 2017 - 4:15pm : Speaker(s): Professor Fletcher J. Miller, Department of Mechanical Engineering, San Diego State University and also in attendance, Dr. Miller’s Ph.D. Advisor, Dr. Arlon Hunt, former Senior Scientist at Lawrence Berkeley Laboratory
Abtract:

The concept of absorbing concentrated solar radiation volumetrically, rather than on a surface, is being researched by several groups with differing designs for high temperature solar receivers.  The Small Particle Heat Exchange Receiver (SPHER), one such design, is a gas-cooled central receiver capable of producing pressurized air in excess of 1000 C designed to be directly integrated into a Brayton-cycle power block to generate electricity from solar thermal power.  The unique heat transfer fluid used in the SPHER is a low-density suspension of carbon nanoparticles (diameter ~ 25... Read More

Bio:
Fletcher Miller earned a Ph.D. in Mechanical Engineering from UC Berkeley in 1988 in the area of radiation heat transfer in participating media with applications to solar energy.  After two years at... Read More
CTR Tea : Friday, April 14, 2017 - 4:15pm : Speaker(s): Qian Yang, PhD Candidate, Institute for Computational and Mathematical Engineering, and Professor Evan Reed, Materials Science and Engineering, Stanford University
Abtract:

Complex chemical processes, such as the decomposition of energetic materials and the chemistry of planetary interiors, are typically studied using large-scale molecular dynamics simulations that run for weeks on high performance parallel machines. These computations may involve thousands of atoms forming hundreds of molecular species and undergoing thousands of reactions. It is natural to wonder whether this wealth of data can be utilized to build more efficient, interpretable, and predictive models. In this talk, we will use techniques from statistical learning to develop a framework for c... Read More

Bio:
Qian Yang is a Ph.D. candidate in the Institute for Computational and Mathematical Engineering at Stanford University. She received her B.A. in Applied Mathematics from Harvard College in 2009,... Read More
CTR Tea : Friday, April 7, 2017 - 4:15pm : Speaker(s): Dr. Hadi Pouransari, Mechanical Engineering and Computer Science, Stanford University
Abtract:

In the realm of scientific computing, solving a linear system of equations is often the main bottleneck of the calculations. We extend ideas from the fast multipole method and propose a novel fast linear solver for sparse and dense matrices. The proposed algorithm is fully algebraic and has numerically proved linear complexity with the problem size. Our method relies on the low-rank compression of the new fill-in blocks generated during the elimination process. The compressed fill-ins are computed and stored in a hierarchical tree structure. The proposed solver can be used as a stand-alone... Read More

Bio:
Dr. Hadi Pouransari received his B.S. in Computer Science and Mechanical Engineering from Sharif University of Technology in 2011. He joined Stanford University at the same year and received his M.S... Read More
CTR Tea : Friday, March 31, 2017 - 4:15pm : Speaker(s): Professor Andy Bragg, Department of Civil and Environmental Engineering, Duke University
Abtract:

The question of how particles suspended in turbulence move relative to each other may be addressed from the point of view of forward-in-time (FIT) and backward-in-time (BIT) dispersion. FIT dispersion is physically related to how groups of particles spread out in turbulence, whereas BIT dispersion is physically related to how particles mix together, and is also important for understanding particle collisions in turbulence. When FIT and BIT dispersion are different it signifies irreversibility, and since FIT and BIT dispersion are related to different problems, understanding the irreversibil... Read More

Bio:
Dr. Bragg joined Duke University as an Assistant Professor of Civil and Environmental Engineering in Fall 2016. Prior to this, he was a Postdoctoral Associate in the Applied Mathematics and Plasma... Read More

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