CTR Tea Seminars - Archives 2005
The Center of Turbulence Research organizes tea seminars approximately every other week at 4:00 PM on Friday at CTR conference room, underground floor of CTR building near Building 500, Stanford University. The seminar series presents various speakers with the research areas related to turbulence or flow physics. Light refreshment will be served.
See most recent seminars
| Date: | December 16, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Srinivas Ramakrishnan, Ph.D. |
| Title: | Towards Multi-Scale Modeling of Turbulent Flows in Complex Geometries |
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| Abstract: | Accurate and efficient turbulence simulation in complex geometries is a formidable challenge. Traditional methods are often limited by low accuracy and/or restrictions to simple geometries. We explore the merger of Discontinuous Galerkin (DG) with Variational Multi-Scale (VMS), termed Local VMS (LVMS), to overcome these limitations. DG spatial discretizations support arbitrarily high-order accuracy on unstructured grids amenable for complex geometries. Furthermore, high-order hierarchical representation within DG provides a natural framework for a priori scale separation crucial for VMS implementation, a promising approach to LES. Moreover, the locality of DG provides the flexibility to specify model parameters individually on each element. This unique feature of LVMS can be exploited for surgical modeling in a wide range of turbulent flows. As a first step, we explore the capabilities of LVMS for turbulence simulation using a fully-developed turbulent channel flow. |
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| Date: | December 9, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Qiqi Wang |
| Title: | Monte Carlo Method of Solving the Adjoint Equation |
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| Abstract: | Solution to the adjoint equation of steady state PDEs has been proved to be very useful in many aspects, including aerodynamic optimization, fluid control, posteriori error estimation and automatic mesh refinement. Because of the amount of storage required by traditional approach of solving time dependent adjoint equations, however, application of adjoint equation of unsteady PDEs has been very limited. This work introduces a Monte Carlo approach of solving adjoint equation, which overcomes the difficulty of traditional approach. In contrast to the traditional approach, the Monte Carlo method in this work is a forward-time procedure, that solves the adjoint equation which is a backward-time equation. Several variance reduction technique, including importance sampling is used in order to achieve faster convergence of the solution. |
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| Date: | November 28, 2005 (Monday) |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Professor Jan Nordstrom |
| Title: | Conservative Finite Difference Formulations, Variable Coefficients and Artificial Dissipation |
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| Abstract: | Artificial dissipation terms for finite difference approximations of linear hyperbolic problems with variable coefficients are determined such that an energy estimate and strict stability is obtained. Both conservative and non-conservative approximations are considered. The dissipation terms are computed such that there is no loss of accuracy. |
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| Date: | November 18, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Andrew Ooi, University of Melbourne |
| Title: | Flow and Acoustic Field Generated by Bubble Oscillations |
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| Abstract: | In this seminar, three different data sets from experimental visualization of the flow and acoustic fields around oscillating bubbles will be presented. Firstly, the microstreaming flow around an oscillating gas bubble resting on a solid boundary is investigated for several different modes of oscillation. Each mode shows distinct streaming flow patterns, which are visualized using streak photography. The streaming flow patterns are shown to be dependent on the frequency of excitation and, in principle permitting chaotic mixing at microscopic scales. Secondly, experimental flow visualization of the jet generated by an oscillating bubble placed on a rigid boundary with an orifice is presented. It is observed that the jet forms only at certain frequencies and that the spreading rate of the jet is dependant on the frequency of excitation. Lastly, an experimental and theoretical study of the acoustic field in the vicinity of a vertical chain of rising bubbles is presented. It will be shown that the propagation of sound is much slower, though more efficient, along the bubble chain than normal to it. A simple mathematical model using a linear, coupled-oscillator approximation can be used to explain this result. |
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| Date: | November 17, 2005 (Thursday) |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Professor Jan Nordstrom |
| Title: | A Stable Hybrid Method for Hyperbolic Problems |
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| Abstract: | A stable hybrid method for hyperbolic problems occurring in fluid dynamics that combines the unstructured finite volume method with high-order finite difference methods has been developed. The coupling procedure is based on energy estimates and stability can be guaranteed. Numerical calculations verify that the hybrid method is efficient and accurate |
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| Date: | November 4, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Xiaohau Wu, Research Associate |
| Title: | Flow Visualization and Computation of Helicopter Tip Vortex |
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| Abstract: | Flow gallery images extracted from DNS of transitional boundary layer and LES of jet engine fuel nozzle rig will be presented first. This is followed by a discussion of recent RANS work on capturing helicopter rotor tip vortex in the DARPA hybrid unsteady simulation of helicopters project. |
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| Date: | October 21, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Magnus Svard |
| Title: | A High-Order Finite Difference Code for the Navier-Stokes Equations |
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| Abstract: | The objective is to develop a high-order accurate and stable finite difference code for the Navier-Stokes equations. The first steps were taken when schemes that have a summation-by-parts property were derived. Those yielded energy estimates on Cartesian grids. We use the original summation-by-parts schemes as a starting point in the development of a robust computational scheme. But, there were a number of stumbling blocks on the road towards a stable Navier-Stokes solver. For example, boundary conditions for the entire system, curvilinear grids, multi-block grids, artificial dissipation. These issues have been addressed and solved such that the full discretization of the linearized three-dimensional Navier-Stokes equations can be proven stable. Numerical computations corroborate the theoretical results. |
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| Date: | September 30, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Javier Jimenez, Profess of Fluid Mechanics, Universidad Politecnica de Madrid |
| Title: | The Largest Turbulent Channel Flow Calculation to Date |
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| Date: | August 26, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Mr. Ali Mani, Flow Physics and Computation Group, Department of Mechanical Engineering |
| Title: | Statistical Description of Aero-Optical Distortion |
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| Date: | August 1, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Rajat Mittal
Associate Professor, Department of Mechanical and Aerospace Engineering, The George Washington University |
| Title: | Fluid Dynamics of Swimming in Fish and Humans |
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| Date: | July 15, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Professor Alexei Novikov
Assistant Professor, Department of Mathematics, Penn State University |
| Title: | Transport in Fluid flows with large intensity Abstract |
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| Date: | July 1, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Professor Arnaud Trouvé
Associate Professor, Department of Fire Protection Engineering, University of Maryland
Affiliate Associate Professor, Department of Mechanical Engineering, University of Maryland |
| Title: | Direct Numerical Simulation of Non-Premixed Flame-Wall Interactions |
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| Date: | June 3, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Professor Yeshayahou
Levy, Head, Turbo & Jet Engine Laboratory
Faculty of Aerospace Engineering, Technion, Israel Institute of Technology, Haifa, 32000, Israel |
| Title: | FLOXCOM, a Novel Low NOx Jet Engine combustion Technology |
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| Date: | May 27, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speakers: | Dr. Christophe Bogey, Charge de Recherche CNRS, Centre Acoustique, France
Prof. Christophe Bailly, Centre Acoustique, France |
| Title: | Direct Noise Computations using Large Eddy Simulations based on explicit filtering. Application to subsonic jets |
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| Date: | May 20, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Prof. Hiromichi Kobayashi, Center for Turbulence Research, Senior Visiting Fellow |
| Title: | Very simple and stable local SGS models based on coherent structures |
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| Date: | April 22, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Snezhana Abarzhi |
| Title: | TBD |
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| Date: | April 8, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Irene Moroz |
| Title: | A simplified model of the Martian Atmosphere |
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| Date: | March 18, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Vincent Moureau |
| Title: | Large-Eddy Simulation of in-cylinder flows in piston engines |
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| Date: | March 4, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Daniel Bodony |
| Title: | On the Acoustic Prediction of Turbulent Flows |
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| Date: | February 25, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Benoit Fiorina |
| Title: | Turbulent Combustion Modeling Using a Tabulated Chemistry Method |
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| Date: | January 21, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Francesco Fedele |
| Title: | Freak waves in random seas and streaks in channel flows: possible stochastic similarities |
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| Date: | January 7, 2005 |
| Time: | 4:00pm |
| Location: | CTR Conference Room |
| Speaker: | Dr. Ing. Florian Menter |
| Title: | A Scale-Adaptive Simulation MOdel using Two-Equation Models; Transition Modeling for General CFD Applications in Aeronautics |
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