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CTR events

Tea Seminar : Tuesday, September 3, 2019 - 10:00am : Speaker(s): Dr. Andrew Trettel
Abtract:

A recent mean velocity transformation (Trettel and Larsson 2016) converts compressible mean velocities into equivalent incompressible mean velocities.  This transformation works properly for channel flows but does not work properly for boundary layers.  A two-dimensional extension of this transformation reveals the inherent limitations in the transformation as an extension of the incompressible law-of-the-wall.  The transformation cannot properly transform the outer layer coordinate in boundary layers, and the error associated with this correlates highly with the error in the transformation... Read More

Bio:
Dr. Andrew Trettel received his PhD in mechanical engineering from the University of California, Los Angeles in 2019. Trettel’s recent research has been in developing and improving scaling laws for... Read More
Tea Seminar : Friday, August 23, 2019 - 4:30pm : Speaker(s): Professor Jan Nordström
Abtract:

The study of so called transmission problems in  [2] revealed that successful numerical filtering may include a delicate balance between the need to remove high frequency oscillations (filter often for accuracy) and the need to avoid possible growth  (filter seldom for stability).  In this talk we investigate this contradiction, and propose different avenues for improved functionality.

The filter operators derived in [1] are the basic building  blocks.  We demonstrate that explicit use of the basic filter operators guarantee accuracy but lead to instabilities, while an implicit imple... Read More

Bio:
Since 2010 Dr. Jan Nordström is a Professor in Scientific Computing and since 2012 he is the Head of Division of Computational Mathematics, in the Department of Mathematics, at Linköping University (... Read More
Tea Seminar : Thursday, August 22, 2019 - 10:00am : Speaker(s): Dr. Zhao Wu
Abtract:

An unsupervised machine-learning algorithm, the self-organizing map (SOM), is used to identify the turbulent boundary layer (TBL) and non-TBL regions in bypass transition. The data employed for the analysis are from an archived direct simulation publicly available in the Johns Hopkins Turbulence Databases (JHTDB, http://turbulence.pha.jhu.edu). The data points in the entire flow domain are automatically classified into TBL and non-TBL regions by the SOM, based on their standardized velocity, velocity fluctuations, velocity gradients and their spatial locations. Thus the SOM identifies the t... Read More

Bio:
Dr. Zhao Wu received his doctoral degree in Mechanical Engineering from The University of Manchester, UK in 2017. During his PhD, his research was focused on direct numerical simulations of fluid... Read More
Tea Seminar : Wednesday, August 21, 2019 - 10:00am : Speaker(s): Mr. Xiaoyi Lu, Ph.D. Candidate
Abtract:

Lu presents findings on the hydrodynamic stability of a premixed flame subjected to transverse shear. The problem configuration is a situation of interest for laminar and turbulent flames when they travel into a region of shear.

The linear stability problem is first analytically solved, and the dispersion relation is determined. The effects of the transverse shear and thermal expansion are examined. Lu’s research then carried out a weakly nonlinear analysis in the weak thermal expansion limit and derived the modified Michelson-Sivashinsky (MS) equation, which describes the evolution... Read More

Bio:
Mr. Xiaoyi Lu is a Ph.D. Candidate in Theoretical and Applied Mechanics at the University of Illinois at Urbana-Champaign. He received his B.S. degree in Mechanical Engineering from the University of... Read More
Tea Seminar : Friday, August 16, 2019 - 4:30pm : Speaker(s): Dr. Mohammad Amin Khodkar
Abtract:

One-Dimensional (1D) Reduced-Order Models (ROMs) are developed for a 3D highly turbulent Rayleigh Bènard convection (RBC) system with Rayleigh number Ra=106, which is nearly 600 times larger than its critical value, while three general objectives are pursued: 1) Predicting the time-mean response to external forcings, 2) Identification of underlying dynamics, and 3) Short-term prediction of spatiotemporal evolution of the flow. Towards the first aim, Linear Response Function (LRF) of the system is obtained via Green’s Function (GRF) method, which is an equation-dependent method for... Read More

Bio:
Dr. Amin Khodkar is a Postdoctoral Research Associate at the Environmental Fluid Dynamics Group of Mechanical Engineering Department of Rice University. He received his B.Sc. and Ph.D. in Mechanical... Read More
Tea Seminar : Tuesday, August 6, 2019 - 4:30pm : Speaker(s): Professor Sivaramakrishnan Balachandar
Abtract:

No Abstract.

Bio:
http://www.mae.ufl.edu/people/balachandar
Tea Seminar : Friday, August 2, 2019 - 4:30pm : Speaker(s): Professor William R. Wolf
Abtract:

Unsteady flows over plunging and pitching airfoils with large excursions in effective angle of attack exhibit the phenomenon of dynamic stall. This process is characterized by unsteady separation and formation of a large leading-edge vortex that exerts high amplitude fluctuations in aerodynamic loads. Although several studies have been conducted for pitching airfoils at high Reynolds numbers, research on dynamic stall for plunging airfoils is more scarce, especially at low and moderate Reynolds numbers.

We employ large eddy simulations to study the flow physics of deep dynamic stall... Read More

Bio:
William R. Wolf is the founder and PI of the Laboratory of Aeronautical Sciences in the School of Mechanical Engineering at University of Campinas, Brazil. He received his BSc in Mechanical... Read More
Tea Seminar : Tuesday, June 11, 2019 - 4:30pm : Speaker(s): Dr. Kazuki Maeda
Abtract:

Cavitation and bubble dynamics are of critical importance in various industrial systems. In ultrasound therapy, cloud cavitation that is nucleated in the human body is crucial for treatment outcomes; bubble clouds can coherently collapse to cause injury as well as scatter the wave energy to shield therapy targets. In this talk, I will present a method for multi-scale modeling and simulation of intense cloud cavitation in a compressible liquid, and its application for medical ultrasound. The method employs an Eulerian-Lagrangian approach to solve mixture- averaged equations of motion, in tha... Read More

Bio:
Dr. Kazuki Maeda is an Acting Assistant Professor of Mechanical Engineering at the University of Washington. He received his BS degree in Mechanical Engineering from the University of Tokyo in 2013,... Read More
Tea Seminar : Friday, May 24, 2019 - 4:30pm : Speaker(s): Mr. Angxiu Ni
Abtract:

Turbulence is an important example of chaotic dynamical systems, and sensitivity analysis is a powerful tool for design via computation.  However, traditional sensitivity methods explode for chaotic systems, posing the challenge we will address in this talk.  We first review how to compute meaningful derivatives of long-time-averaged objectives in chaotic systems via the shadowing method, which we then reformulate as a 'non-intrusive' minimization problem on the unstable subspace. Then we show a recent adjoint shadowing theorem, based on which we develop an adjoint sensitivity algorithm, NI... Read More

Bio:
Mr. Angxiu Ni (pronounces as ang-shyou-knee) got his BS in Mechanical Engineering from Tsinghua University. He then got two MS, one at Tsinghua University working with Professor Haixin Chen, one at... Read More
Tea Seminar : Friday, May 3, 2019 - 4:30pm : Speaker(s): Mr. Seyedshahabaddin (Shahab) Mirjalili
Abtract:

From oceanic breaking waves to atomization of liquid fuels for combustion, two-phase flows are omni-present in natural and industrial settings. Despite decades of numerical method development, due to the many challenges involved in simulation of realistic two-phase flows, no gold-standard has yet emerged in the literature. In this study, we present a novel diffuse interface method that addresses various challenges for simulation of incompressible, immiscible two-phase flows. The boundedness of this mass-conserving interface-capturing method is proven analytically. Then, a comparison of the... Read More

Bio:
Shahab Mirjalili defended his PhD in Mechanical Engineering at Stanford University in March 2019. During his PhD under the supervision of Professor Ali Mani, he focused on development of numerical... Read More

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