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CTR events

CTR Tea : Friday, March 24, 2017 - 4:15pm : Speaker(s): Dr. Patrick Joseph Blonigan, Postdoctoral Fellow, NASA Ames Research Center
Abtract:

Adjoint-based sensitivity methods are powerful design tools for engineers who use computational fluid dynamics. In recent years, these engineers have started to use scale-resolving simulations like large-eddy simulations (LES) and direct numerical simulations (DNS), which resolve more scales in complex flows with unsteady separation and jets than Reynolds-averaged Navier-Stokes (RANS) methods. However, the conventional adjoint method computes large, unusable sensitivities for scale-resolving simulations, which unlike RANS simulations exhibit the chaotic dynamics inherent in turbulent flows.... Read More

Bio:
Dr. Blonigan received his B.S. in Mechanical Engineering from Cornell University in 2011. In June 2011 he started his Ph.D. at Massachusetts Institute of Technology in the Department of Aeronautics... Read More
CTR Tea : Friday, March 17, 2017 - 4:15pm : Speaker(s): Dr. Mahdi Esmaily-Moghadam, CTR Postdoctoral Fellow, Center for Turbulence Research, Stanford University
Abtract:

Clustering of inertial particles plays a key role in the formation of rain to that of the planets in our early solar system. It has been known for decades that heavy tiny particles in a turbulent flow segregate spatially, forming clusters. The degree of clustering highly depends on the particle relaxation time relative to that of the background flow, viz. the Stokes number. While minimal clustering is observed at very large or small Stokes numbers, clustering is maximized when the two time-scales are comparable and St ≈ 1. This nonmonotonic variation, although observed experimentally and re... Read More

Bio:
Dr. Mahdi Esmaily-Moghadam received his B.Sc. and M.Sc. with high distinction from Sharif University and a second M.Sc. and Ph.D. in Mechanical Engineering from UCSD in 2014. During his doctoral... Read More
CTR Tea : Friday, March 10, 2017 - 4:15pm : Speaker(s): Dr. Freddie David Witherden, Postdoctoral Scholar, Department of Aeronautics and Astronautics, Stanford University
Abtract:

High-order numerical methods for unstructured grids combine the superior accuracy of high-order spectral or finite difference methods with the geometrical flexibility of low-order finite volume or finite element schemes. The Flux Reconstruction (FR) approach unifies various high-order schemes for unstructured grids within a single framework. Additionally, the FR approach exhibits a significant degree of element locality, and is thus able to run efficiently on modern many-core hardware platforms, such as graphics processing units (GPUs). The aforementioned properties of FR mean it offers a p... Read More

Bio:
Dr. Witherden studied Physics with Theoretical Physics at Imperial College London between 2008–2012 earning an MSci degree with first class honours. In September of 2012 he started a PhD in... Read More
CTR Tea : Friday, March 3, 2017 - 4:30pm : Speaker(s): Shigan Chu, Johns Hopkins University, Department of Mechanical Engineering
Abtract:

Even a nominally immiscible drop will grow or dissolve in an ambient liquid due to diffusion. The mass flux at the drop surface is dictated by the drop composition. For a pure drop, this composition is essentially constant in time.  The situation is very different for a multicomponent drop in which, due to the mutual interaction of the constituents, their concentrations at the drop surface differ from the respective solubilities and depends on time. The result is a memory term for the mass flux through the interface, which does not exist for a drop of a pure liquid.   

In this talk,... Read More

Bio:
Shigan Chu is currently a Ph.D. candidate in Mechanical Engineering Department of the Johns Hopkins University. He received M.S. in Mechanical Engineering from the Johns Hopkins University and B.S.... Read More
CTR Tea : Friday, February 10, 2017 - 4:15pm : Speaker(s): Thomas Jaravel, CTR Postdoctoral Fellow, Stanford University
Abtract:

Stringent regulations of pollutant emissions now apply to new-generation combustion devices. To achieve low nitrogen oxides (NOx) and carbon monoxide (CO) emissions simultaneously, a complex optimisation process is required in the development of new concepts for engines. Already efficient for the prediction of turbulent combustion, Large Eddy Simulation (LES) is also a promising tool to better understand the processes of pollutant formation in gas turbine conditions and to provide their quantitative prediction at the design stage. In this work, a new methodology for the prediction with LES... Read More

Bio:
Dr. Jaravel graduated from Ecole Polytechnique (Paris-Saclay) in mechanical engineering and applied mathematics and from Supaéro (Toulouse) in aerospace engineering. He received his PhD in 2016 from... Read More
CTR Tea : Friday, January 27, 2017 - 4:30pm
Abtract:

Visualizations of turbulent boundary layers show an abundance of characteristic arcshaped structures whose apparent similarity suggests a common origin in a coherent dynamic process. While the structures have been likened to the hairpin vortices observed in the late stages of transitional flow, a consistent description of the underlying mechanism has remained elusive. Detailed studies of coherent turbulent processes are complicated by the chaotic nature of the flow which modulates each manifestation and renders the isolation of representative samples a challenging task.

The present s... Read More

Bio:
Dr. Philipp Hack received his Ph.D. from Imperial College London in 2014. His theoretical and computational work on the stability of boundary layers was awarded in 2013 with the EPSRC Doctoral Prize... Read More
CTR Tea : Friday, January 13, 2017 - 4:15pm : Speaker(s): Aaron Towne, CTR Postdoctoral Fellow, Stanford University
Abtract:

Reduced-order models that capture the essential features of turbulent flows can be used to gain insight into the flow physics, predict quantities of interest, and provide a handle for flow-control efforts.  This talk will compare and contrast a selection of empirical (data-based) and non-empirical (equation-based) model-reduction methods, including several variants of proper orthogonal decomposition, dynamic mode decomposition, resolvent analysis, and balanced truncation.  The hope is that this introduction will help listeners interpret the work of others and select appropriate approaches f... Read More

Bio:
Aaron Towne is a postdoctoral fellow in the Center for Turbulence Research.  He received his B.S. in Engineering Mechanics from the University of Wisconsin-Madison and his M.S. and Ph.D. in... Read More
CTR Tea : Friday, November 11, 2016 - 4:15pm : Speaker(s): Mohsen Zayernouri, Assistant Professor of Computational Mathematics, Science, & Engineering (CMSE) and Mechanical Engineering (ME) at Michigan State University (MSU)
Abtract:

Fractional PDE models generalize the standard (integer-order) calculus and PDEs to any differential form of fractional orders. Fractional PDEs open up new possibilities for robust mathematical modeling of physical processes that exhibit anomalous (sub- or super-) diffusion, nonlocal interactions, self-similar structures, long memory dependence, and power-law effects. Fractional PDEs are emerging as the right tool for exploring fractal operators and for modeling sharp interfaces in multi-phase problems, wave propagation in disordered media, and multi-scale materials. Such phenomena occur in... Read More

Bio:
Mohsen Zayernouri is an assistant professor of Computational Mathematics, Science, & Engineering (CMSE) and Mechanical Engineering (ME) at Michigan State University (MSU). Although he started as... Read More
CTR Tea : Friday, November 4, 2016 - 4:15pm : Speaker(s): Professor Kai Schneider, Centre de Mathematiques et d'Informatique, Aix-Marseille Universite
Abtract:

Insects fly even under heavy turbulent air flow conditions. To understand the impact of turbulent fluctuations on the aerodynamics of flapping wings, we model a bumblebee with fixed body and prescribed wing motion, flying in a numerical wind tunnel. The inflow condition of the tunnel varies from unperturbed laminar to strongly turbulent. Massively parallel simulations show that turbulence does not significantly alter the wing's leading edge vortex that is required for elevated lift production. Mean flight forces, moments and aerodynamic power expenditures are thus unaffected, suggesting lit... Read More

Bio:
Kai Schneider is a Professor of Mechanics and Applied Mathematics at I2M (Institute of Mathematics of Marseille), Aix-Marseille University, France. He obtained his Master degree in 1993 and his Ph.D... Read More
CTR Tea : Friday, October 28, 2016 - 4:15pm : Speaker(s): Dr. Yu Lv, Post-doctoral Fellow, Department of Mechanical Engineering, Stanford University
Abtract:

In recent years, variational-formulation based high-order schemes, such as discontinuous Galerkin (DG) scheme, have demonstrated promising capabilities for CFD applications. Compared to commonly used numerical methods, these high-order schemes are particularly attractive for (i) providing high-order accurate solutions with less sensitivity to mesh topology; (ii) enforcing physical realizability on solutions to guarantee numerical nonlinear stability; and (iii) better balancing computational robustness and resolution requirement for multi-physics simulations. This talk will start by illustra... Read More

Bio:
Dr. Yu Lv is Postdoc Fellow working in the ME Department, Stanford University, under Professor Matthias Ihme. He joined Stanford in 2013 after finishing his Master’s degree in Aerospace Engineering (... Read More

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