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CTR events

Phase-­field modeling of multiphase flows using the lattice Boltzmann method with adaptive mesh refinement

: Tea Seminar
Friday, June 5, 2015 - 4:00pm
Speaker(s):
Dr. Abbas Fakhari, CTR Postdoctoral Fellowship Candidate, Mechanical Engineering, City College of New York
Abtract:

Numerical modeling of multiphase flows at high Reynolds numbers is a challenging task. Traditional methods based on sharp-­interface models might encounter numerical difficulty in handling rapid topological changes such as breakup and coalescence. Therefore, diffuse-­interface models are widely used for numerical simulation of multiphase flows. As a diffuse-­interface model, the lattice Boltzmann method (LBM) is a well-­established mesoscopic scheme for numerical study of complex fluids. The most interesting feature of the LBM is that all nonlinearity is local and all nonlocality is linear,... Read More

Bio:
Abbas Fakhari graduated with a Bachelor of Science in Physics from Zanjan University in 2006, and received his Master of Science in Mechanical Engineering from the University of Tehran in 2008. In... Read More

Phase-field modeling of multiphase flows using the lattice Boltzmann method with adaptive mesh refinement

: Tea Seminar
Monday, June 1, 2015 - 4:00pm
Speaker(s):
Dr. Abbas Fakhari, CTR Postdoctoral Fellowship Candidate, Mechanical Engineering, City College of New York
Abtract:

Numerical modeling of multiphase flows at high Reynolds numbers is a challenging task. Traditional methods based on sharp-interface models might encounter numerical difficulty in handling rapid topological changes such as breakup and coalescence. Therefore, diffuse-interface models are widely used for numerical simulation of multiphase flows. As a diffuse-interface model, the lattice Boltzmann method (LBM) is a well-established mesoscopic scheme for numerical study of complex fluids. The most interesting feature of the LBM is that all nonlinearity is local and all nonlocality is linear, whi... Read More

Bio:
Abbas Fakhari graduated with a Bachelor of Science in Physics from Zanjan University in 2006, and received his Master of Science in Mechanical Engineering from the University of Tehran in 2008. In... Read More

Identifying coherent structures in fluid flow

: Tea Seminar
Friday, May 29, 2015 - 4:00pm
Speaker(s):
Prof. Gary Froyland, School of Mathematics and Statistics, University of South Wales, Sydney, Australia
Abtract:

The future behavior and transport mechanisms of complicated (chaotic or "turbulent") fluid flow is hard to predict.  However, in many situations there are regions of predictability embedded in the flow that exhibit approximately regular behavior. These regions of predictability are often bounded by strong transport barriers and evolve as coherent, slightly leaky parcels of fluid. Geophysical examples include polar vortices in the stratosphere and ocean gyres and eddies.  I will describe probabilistic (ergodic-theoretic) techniques based on spectral properties of transfer operators to identi... Read More

Bio:
Gary Froyland is currently an Australian Research Council Future Fellow and Professor in the School of Mathematics and Statistics at UNSW Australia. He received his PhD in mathematics from the... Read More

Assessment of a fluidic oscillator utilized for active flow control

: Tea Seminar
Friday, May 15, 2015 - 4:00pm
Speaker(s):
Dr. Eran Arad, Head of CFD Group, RAFAEL, Advanced Defense System, Israel Institute of Technology
Abtract:

Active flow control devices and applications received a lot of attention in the recent three decades. While synthetic jets were the preferred technique during the early stages of this practice, fluidic oscillators, also called sweeping jets actuators, were recently in the focus of several research and engineering projects. These actuators bring in the advantages of no-moving-parts and high amplitude signal. However, their control is not straight forward and many times the exact nature of their output is not fully comprehended.

A combined experimental and numerical-simula... Read More

Bio:
Dr Arad received his PhD from Aero-Space Engineering, Technion, Israel Institute of Technology on 1994. His thesis focused on turbulence modeling. Dr Arad spent 1994 to 1997 as a Research Fellow at... Read More

Particulate flow across multi-scales: numerical strategies for momentum, heat and mass transfer

: Tea Seminar
Friday, April 24, 2015 - 4:00pm
Speaker(s):
Dr. Anthony Wachs, Fluid Mechanics Department,IFP Energies nouvelles, Solaize, France
Abtract:

Particulate flows are ubiquitous in environmental, geophysical and engineering processes. The intricate dynamics of these two-phase flows is governed by the momentum transfer between the continuous fluid phase and the dispersed particulate phase. When significant temperature differences exist between the fluid and particles and/or chemical reactions take place at the fluid/particle interfaces, the phases also exchange heat and/or mass, respectively. While some multi-phase processes may be successfully modelled at the continuum scale through closure approximations, an increasing number of ap... Read More

Bio:
Dr Anthony Wachs received BS & MS degrees from University Louis Pasteur, Strasbourg and his PhD from the Institut National Polytechnique of Grenoble in 2000. He joined Institut Français du... Read More

Gas-solid flow analysis using particle-resolved direct numerical simulation: mechanism, quantification and modeling

: Tea Seminar
Friday, April 17, 2015 - 4:00pm
Speaker(s):
Mohammad Mehrabadi, Mechanical Engineering, Iowa State University, Ames, IA
Abtract:

Gas-solid flows are encountered in many industrial processes such as pneumatic conveying, fluid catalytic cracking, CO2 capturing and fast pyrolysis process. In spite of all experimental and numerical studies performed to understand the physics governing observed phenomena in gas-solid flows, and propose accurate closure models for computational fluid dynamics (CFD) simulations using the averaged conservation equations, there are several challenges in gas-solid flows that yet need to be addressed. In many of the industrial processes, the solid-to-fluid density ratio is of the order of 100 t... Read More

Bio:
Mohammad Mehrabadi is a PhD candidate in Mechanical Engineering at Iowa State University. Before attending the Iowa State, he received his Master’s degree at University of Tehran, Iran in 2006 with... Read More

Numerical simulation of multiphase immiscible flow on unstructured meshes

: Tea Seminar
Friday, February 20, 2015 - 4:00pm
Speaker(s):
Dr. Lluis Jofre-Cruanyes, Postdoctoral Fellow, Center for Turbulence Research
Abtract:

The present talk tries to summarize the work performed by Lluis Jofre-Cruanyes during his PhD.The research aims at developing a basis for the numerical simulation of multiphase flows of immiscible fluids. The formulation is based on a finite-volume approach and is suitable for three-dimensional (3-D) unstructured meshes, as well for Cartesian grids. The software implemented is part of an in-house high performance computing platform able to simulate multiphysics problems. This platform is based on object-oriented programming, using C++ language, and parallelization is accomplished via... Read More

Bio:
Dr. Lluis Jofre-Cruanyes is a new postdoctoral fellow athe Center for Turbulence Research (CTR). He is interested in numerical methods for computational fluid dynamics and multiphysics. His research... Read More

Rethinking tsunami preparedness - What is the role of vegetation?

: Tea Seminar
Friday, February 6, 2015 - 4:00pm
Speaker(s):
Professor Jenny Suckale, Geophysics Department, Stanford University
Abtract:

The role of coastal forests in the mitigation of tsunami disasters has become a hotly debated topic in the aftermath of the devastating tsunami in the Indian Ocean in 2004 and Japan in 2011. Unfortunately, our knowledge of the interactions between tsunamis and vegetation is limited and the associated danger of ineffective or even potentially harmful policies is concerning. Through this project, we hope to contribute to bridging the gap between science and policy and provide new insights on whether and how coastal trees or forests may be promising for protective purposes. Since our res... Read More

Bio:
Dr. Jenny Suckale is an Assistant Professor in the Department of Geophysics at Stanford University. She is also an affiliated faculty member of Stanford’s Institute for Computational and Mathematical... Read More

Streak Instabilities in Pressure Gradient Boundary Layers

: Tea Seminar
Friday, January 23, 2015 - 4:00pm
Speaker(s):
Dr. Philipp Hack, Imperial College, London
Abtract:

Linear stability analysis is applied to pre-transitional boundary layer flow fields extracted from direct numerical simulations (DNS) of bypass transition (Hack & Zaki, J. Fluid Mech., 2014a). The presence of broadband free-stream forcing in the DNS leads to the formation of a spectrum of high-amplitude streaks inside the boundary layer. The streaky base flow becomes susceptible to high-frequency modal instabilities which are localized on single streaks and which eventually induce breakdown to turbulence. It is shown that linear stability theory can capture the attributes of the instabi... Read More

Streak Instabilities in Pressure Gradient Boundary Layers

: Tea Seminar
Friday, January 9, 2015 - 4:00pm
Speaker(s):
Dr. Babak Hejazi, Cascade Technologies
Abtract:

Linear stability analysis is applied to pre-transitional boundary layer flow fields extracted from direct numerical simulations (DNS) of bypass transition (Hack & Zaki, J. Fluid Mech., 2014a). The presence of broadband free-stream forcing in the DNS leads to the formation of a spectrum of high-amplitude streaks inside the boundary layer. The streaky base flow becomes susceptible to high-frequency modal instabilities which are localized on single streaks and which eventually induce breakdown to turbulence. It is shown that linear stability theory can capture the attributes of the instabi... Read More

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