CTR Seminars Archive 2005
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
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.
Date: December 9, 2005
Time: 4:00pm
Location: CTR Conference Room
Speaker: Qiqi Wang
Title: Monte Carlo Method of Solving the Adjoint Equation
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.
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
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.
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
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.
Date: November 17, 2005 (Thursday)
Time: 4:00pm
Location: CTR Conference Room
Speaker: Professor Jan Nordstrom
Title: A Stable Hybrid Method for Hyperbolic Problems
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.
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
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.
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
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.
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
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
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
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
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
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
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
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
Date: April 22, 2005
Time: 4:00pm
Location: CTR Conference Room
Speaker: Dr. Snezhana Abarzhi
Title: TBD
Date: April 8, 2005
Time: 4:00pm
Location: CTR Conference Room
Speaker: Dr. Irene Moroz
Title: A simplified model of the Martian Atmosphere
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
Date: March 4, 2005
Time: 4:00pm
Location: CTR Conference Room
Speaker: Dr. Daniel Bodony
Title: On the Acoustic Prediction of Turbulent Flows
Date: February 25, 2005
Time: 4:00pm
Location: CTR Conference Room
Speaker: Dr. Benoit Fiorina
Title: Turbulent Combustion Modeling Using a Tabulated Chemistry Method
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
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