|
|
▶ E-mail Subscription
Follow the
announcement blog
to receive announcements and
reminders via e-mail.
|
▶ Contacts
Boris Diskin [ E-mail ]
Hiroaki Nishikawa [ E-mail
]
|
▶ Past Seminars
Seminars 2011-2012
|
▶ NIA Researcher/Faculty
|
Boris Diskin, Ph.D.
Associate Research Fellow, NIA
Research Associate Professor,
Mechanical and Aerospace Engineering,
University of Virginia
Adjoint-based optimization methods, Finite-volume discretizations, Multigrid methods on structured/unstructured grids
Web
|
E-mail
|
Lian Duan, Ph.D.
Research Scientist, NIA
E-mail
|
Elbert Jeyapaul, Ph.D.
Postdoctoral Fellow, NASA
Flow separation, Single-point turbulence modeling and LES.
E-mail
|
Wei Liao, Ph.D.
Research Scientist, NIA
Aerodynamic optimization, Flow instability, laminar flow control,
turbulence simulation, Kinetic methods, Non-equilibrium flows, Flapping wings
E-mail
|
Li-Shi Luo, Ph.D.
The Richard F. Barry Jr. Distinguished Endowed Professor (in Residence, NIA)
Mathematics and Statistics,
Old Dominion University
Kinetic methods for CFD, Nonequilibrium flows, Complex fluids
Web
|
E-mail
|
Bill Moore, Ph.D.
Professor in Residence, NIA
Atmospheric & Planetary Sciences,
Hampton University
Thermal Evolution of Planet and Satellite Inteiors, Dynamical Evolution of Planets and Satellites, Coupled Atmosphere-Interior Modeling of Planets, What Makes a Planetary Body Habitable?
Web
|
E-mail
|
Yi Liu, Ph.D.
Sr. Research Engineer, NIA
Micro Air Vehicle - Flapping Wing, Rotorcraft Aeromechanics and Aeroacoustics, Circulation Control and Flow Control
Web
|
E-mail
|
Hiroaki Nishikawa, Ph.D.
Sr. Research Scientist, NIA
Viscous/inviscid discretization and convergence acceleration methods for unstructured grids
Web
|
E-mail
|
CFD Notes
|
Matteo Parsani, Ph.D.
Research , NIA
high-order accurate methods for large-eddy simulation and aeroacoustics, efficient explicit and implicit time integrators and acceleration techniques for compressible flows
|
E-mail
|
Sriram Rallabhandi, Ph.D.
Sr. Research Engineer, NIA
Aircraft Design, Sonic Boom Modeling, Multi-Disciplinary Design
Optimization, Aerodynamic Analysis, Computational Fluid Dynamics, Reduced Order Modeling and Model Order Reduction
Web
|
E-mail
|
Jinwei Shen, Ph.D.
Sr. Research Engineer, NIA
Rotorcraft Aeromechanics, Multibody Dynamics, Vibration Control, Numerical Analysis
Web
|
E-mail
|
Balaji Shankar Venkatachari, Ph.D.
Postdoctoral Fellow, University of Alabama at Birmingham
Resident at the NASA Langley Research Center in the Computational AeroSciences Branch,
working on numerical algorithm development, Hypersonics, TPS modeling (continuum and multi-scale modeling), and CAA.
E-mail
|
|
|
|
NIA CFD Seminar Schedule
Click here to view the full list of videos.
Click the camera icon below to go directly to the video for each seminar.
|
05-28-2013
12:30pm - 1:30pm (EST)
NIA Room 101
 video
A Reconstructed Discontinuous Galerkin Method Based on a Hierarchical WENO Reconstruction for Compressible Flows on Hybrid Grids
Recently, reconstructed discontinuous Galerkin (DG) methods have been developed to solve compressible flow problems. The idea behind RDG methods is to combine the efficiency of the reconstruction methods in finite volume methods and the accuracy of the DG methods to obtain a better numerical algorithm in computational fluid dynamics. The beauty of the resulting reconstructed discontinuous Galerkin (RDG) methods is that they provide a unified formulation for both finite volume and DG methods, and contain both classical finite volume and standard DG methods as two special cases of the RDG methods, and thus allow for a direct efficiency comparison. In this presentation, a reconstructed discontinuous Galerkin (RDG) method based on a Hierarchical WENO reconstruction, termed HWENO(P1P2), designed not only to enhance the accuracy of discontinuous Galerkin methods but also to ensure the nonlinear stability of the RDG method, is presented for solving the compressible Navier-Stokes equations on hybrid grids. In this HWENO(P1P2) method, a quadratic polynomial solution (P2) is first reconstructed using a Hermite WENO reconstruction from the underlying linear polynomial (P1) discontinuous Galerkin solution to ensure the linear stability of the RDG method and to improve the efficiency of the underlying DG method. By taking advantage of handily available and yet invaluable information, namely the derivatives in the DG formulation, the stencils used in the reconstruction involve only von Neumann neighborhood (adjacent face-neighboring cells) and thus are compact. The first derivatives of the quadratic polynomial solution are then reconstructed using a WENO reconstruction in order to eliminate spurious oscillations in the vicinity of strong discontinuities, thus ensuring the nonlinear stability of the RDG method. The developed HWENO(P1P2) method is used to compute a variety of flow problems on hybrid meshes to demonstrate its accuracy, robustness, and non-oscillatory property. The numerical experiments indicate that the HWENO(P1P2) method is able to capture shock waves within one cell without any spurious oscillations, and achieve the designed third-order of accuracy: one order accuracy higher than the underlying DG method, indicating the potential of this RDG method to become a viable, competitive, and perhaps superior DG method over existing DG methods for the solution of the compressible Navier-Stokes equations.
| [ presentation file (pdf) ]
|
Hong Luo |
|
Speaker Bio:
|
Dr. Hong Luo is a professor in the Department of Mechanical and Aerospace Engineering at North Carolina State University. He received his Ph.D. in Applied Mathematics from Pierre and Marie Curie University (University of Paris 6) in France in 1989. Prior to joining NC State in 2007, he worked as a post-doctoral research associate at Purdue University from 1989 to 1991 and as a senior research scientist at Science Applications International Corporation from 1991 to 2007. His current research interests include: Computational Fluid Dynamics, Computational Aeroacoustics, and Computational mgnetohydrodynamics; Reconstructed Discontinuous Galerkin Methods on Unstructured Hybrid Grids; High Performance Computing on Hybrid CPU/GPU Architectures; Moving Boundary Problems and Fluid-Structure Interaction; Large Eddy Simulation of Turbulent Flows; Multi-phase Flows and Chemically Reactive Flows; Geometry Modeling, Unstructured Grid Generation, and Grid Adaptation.
|
|
Relevant Publications:
|
Luo, H., Xia Y., Spiegel, S., Nourgaliev, R., Jiang, Z., A Reconstructed Discontinuous Galerkin Method Based on a Hierarchical WENO Reconstruction for Compressible Flows on Tetrahedral Grids, Journal of Computational Physics, Vol. 236, pp. 477-492, 2013.
[ journal ]
Luo, H., Xia Y., Li. S., Nourgaliev, R., and Cai, C., A Hermite WENO Reconstruction-Based Discontinuous Galerkin Method for the Euler Equations on Tetrahedral Grids, Journal of Computational Physics, Vol. 231, pp. 5489-5503, 2012.
[ journal ]
Luo, H., Luo, L., and Nourgaliev, R., A Reconstructed Discontinuous Galerkin Method for the Euler Equations on Arbitrary Grids, Communication in Computational Physics, Vol. 12, No. 5, pp. 1495-1519, 2012.
[ journal ]
|
|
|
05-20-2013
11:00am - noon (EST)
NIA Room 101
video
A Consistent Hybrid LES/RANS Framework with High-Order LES Solver on Cartesian Mesh
In this talk we present a hybrid solver coupling a high-order LES solver with
Cartesian mesh and a RANS solver with body-fitting mesh. The hybrid solver is
developed within a dual-mesh, consistent hybrid framework, where LES and RANS
simulations for the same flow are conducted simultaneously on different
computational domains and different meshes. A relaxation approach is used to
enforce the immersed boundary conditions in the LES. The flows over periodic
hills at Reynolds numbers Re = 2800 and 10595 are simulated using the new
solver. The adequacy of the boundary representation and forcing strategy is
shown. The numerical studies also demonstrate the flexibility of the extended
solver and the predictive capability of the new hybrid framework, which consists
of two solvers operating on the same physical domain, but with non-conforming
computational domains (i.e., a Cartesian mesh based LES solver combined with a
body-fitting mesh based RANS solver). With the current framework, the potential
of many existing academic codes for practical flow simulations, where complex
geometries and wall resolution requirements represent major hurdles, can be
explored.
|
Speaker Bio:
|
Dr. Heng Xiao is currently an Assistant Professor in the Department
of Aerospace and Ocean Engineering at Virginia Tech. He received his Ph.D. in
Civil Engineering from Princeton University in 2009. From 2009 to 2012 he worked
as a post-doctoral researcher in ETH Zurich, Switzerland. His current research
focuses on computational mechanics of fluids and particles in ocean engineering.
|
|
Relevant Publications:
|
Heng Xiao and Patrick Jenny,
A Dual-Mesh Hybrid LES/RANS Framework with Implicit Consistency,
Workshop, Direct and Large-Eddy Simulation 9 April 3-5, Dresden, Germany
[ pdf ]
H. Xiao, Y. Sakai, R. Henniger, P. Jenny, Simulating Flow over Periodic Hills Using a Dual-Mesh Hybrid Solver with High-Order LES, Seventh International Conference on Computational Fluid Dynamics (ICCFD7),
Big Island, Hawaii, July 9-13, 2012
[ pdf ]
Heng Xiao and Patrick Jenny, A consistent dual-mesh framework for hybrid LES/RANS modeling, JCP, 231, 2012 (1848-1865)
[ journal ]
|
|
|
05-14-2013
11:00am - noon (EST)
NIA Room 101
video
Numerical Investigations on a Hot Jet in Cross Flow Using Scale-Resolving Simulations
Numerical methods for the simulation of hot jets in cross flow at high Reynolds numbers and small momentum ratios are presented. Different turbulence modeling strategies, i.e. URANS, SAS, DDES and ELES, are validated against experimental data on a generic configuration, highlighting the necessity of scale-resolution for a correct prediction of thermal mixing. The analysis of transient flow simulations allows the identification of inherent flow dynamics as well as mixing phenomena and the application of the Proper Orthogonal Decomposition revealed the lateral wake meandering as being one of them. Due to the multi-scale problem which arises when simulating jets in cross flow on real aircraft configurations, the sequential approach based on the SAS turbulence model is introduced. As results for the exhaust of a nacelle anti-icing system comprising multiple jets in cross flow agree well with flight test data, the approach is applied in a last step to the complex exhaust of a pre-cooling system, emphasizing the capabilities of this methodology in an industrial environment
|
Speaker Bio:
|
Dr. Benjamin Duda started a post-doctoral fellowship at NASA Langley Research Center, working on hybrid RANS/LES turbulence modeling. He received his Ph.D. in fluid dynamics from ISAE Toulouse, where he was working on scale-resolving simulations for jets in cross flow. The work for this industry-sponsored doctoral research study was carried out at Airbus and Ansys and supervised by ONERA.
|
|
Relevant Publications:
|
Ph.D. Thesis (2012) [
pdf ]
|
|
|
04-30-2013
11:00am - noon (EST)
NIA Room 101
video
Simulation of Stratified Turbulence Over the Coastal Shelf
Turbulent shear flows on shallow continental shelves (here shallow means that the interaction with the solid, no-slip bottom is important) are of great importance because of their role in vertical mixing as well as on the transport of sediment and bioactive material. The presence of a wavefield in these areas can lead to the appearance of longitudinal coherent vortical structures which is known as Langmuir circulation. The purpose of this study is to quantify via Large Eddy Simulation the effect of a stable stratification on the dynamics of Langmuir Circulation. Among the questions addressed are: does LC mix the water column and thus destroy the stratification or does strong stratification substantially modify or eliminate LC?
|
Speaker Bio:
|
Dr. Guillaume Martinat is a postdoctoral researcher at the Center for Coastal Physical Oceanography, Old Dominion University, Norfolk, VA. He graduated a M.Sc in applied physics from Université de Rennes 1, France and a D.Sc in Fluid Dynamics from Université de Toulouse, France. His research interest include turbulence modeling, geophysical fluid dynamics and unsteady separated flows.
|
|
|
04-16-2013
11:00am - noon (EST)
NIA Room 137
video
Adjoint-based optimization of unsteady turbulent flows: Recent advances and current challenges
This presentation is a rehearsal of the talk to be presented at 'Weizmann workshop 2013 on multilevel computational methods and optimization'. This talk reviews a discrete adjoint-based methodology for unsteady turbulent flows on three-dimensional overset unstructured grids. The methodology provides a general framework for performing discretely consistent and highly efficient sensitivity analysis for problems involving arbitrary combinations of overset unstructured grids that can be static, undergoing rigid or deforming motions, or any combination of thereof. The methodology is especially effective for gradient-based optimization with many design parameters. The implementation is verified with a complex-variable approach and illustrated by large-scale optimization examples. It will be shown that in the current high-performance computing environment, the memory is not a limiting factor for practical large-scale applications. Other challenges, such as significant CPU time and possible instabilities in application to chaotic flows, will be discussed.
|
Speaker Bio:
|
Dr. Boris Diskin is an Associate Research Fellow at NIA. He earned Ph.D. in Applied Mathematics at The Weizmann Institute of Science, Israel in 1998. He was a Senior Research Scientist at ICASE and joined NIA from its inception in 2003. His area of expertise is adjoint-based optimization and grid adaptation methods, finite-volume discretizations, and multigrid methods.
|
|
|
04-09-2013
11:00am - noon (EST)
NIA Room 137
&nbs
video
Recent Developments for the Multigrid Scheme in the DLR TAU-Code
The presentation will give a short overview about recent
developments for the multigrid scheme that is used in the hybrid
unstructured RANS solver TAU developed at DLR (German Aerospace Center;
Home Page of DLR TAU code).
Solutions to overcome the possible difficulties concerning the practical
usage of the scheme, which were presented in the talk "Overview of the Multigrid Scheme in the DLR TAU-Code" , are illustrated.
|
Speaker Bio:
|
Dipl.-Ing Axel Schwöppe is a senior engineer in the Institute of Aerodynamics
and Flow Technology at the German Aerospace Center (DLR). He is working as a developer
of the DLR TAU-Code with focus on unstructured and structured discretization schemes.
|
|
|
04-02-2013
11:00am - noon (EST)
NIA Room 137
video
Design of Optimal Explicit Runge-Kutta Schemes for the High-Order Spectral Difference Method
Explicit Runge-Kutta schemes with large stable step sizes are developed for integration of high order spectral difference spatial discretizations on quadrilateral grids. The new schemes permit an effective time step that is substantially larger than the maximum admissible time step of standard explicit Runge--Kutta schemes available in literature.
Furthermore, they have a small principal error norm and admit a low-storage implementation. The advantages of the new schemes are demonstrated through application to the Euler equations, and both laminar and turbulent Navier-Stokes equations at moderate Reynolds numbers.
|
Speaker Bio:
|
Dr. Matteo Parsani is currently a Post-doctoral Fellow at NASA Langley Research Center, working with Dr. Mark H. Carpenter. Prior to this he was a Post-doctoral Researcher at KAUST, working in the group of Professor David Ketcheson. He received his Ph.D. in Mechanical and Aerospace Engineering from Free University of Brussels in December 2010. His research interests include high-order accurate methods for large-eddy simulation and aeroacoustics, efficient explicit and implicit time integrators and acceleration techniques for compressible flows. In 2011 his PhD thesis was selected among the best National Ph.D. theses to be presented at the ECCOMAS Olympiad workshop in Athens.
|
|
|
03-19-2013
11:00am - noon (EST)
NIA Room 137 (Video not available)
Direct Numerical Simulation for Laminar-to-Turbulent Transition Prediction
Laminar-to-turbulent transition prediction and control is one of the key enabling technologies for quiet and efficient aircraft. Accurate prediction of transition requires a holistic approach, which accounts for all major stages within transition (namely, receptivity, linear growth, nonlin- ear interactions and secondary instability) in an integrated manner. In this talk, we will focus on direct numerical simulation (DNS) studies of laminar-to-turbulent transition in two aspects. One is to characterize the acoustic freestream fluctuations radiating from supersonic/hypersonic turbulent boundary layers (under supersonic/hypersonic conditions, with adiabatic/cold walls), which is an important step to enable meaningful application of receptivity theory in the con- text of actual wind-tunnel experiments. The other is to investigate the secondary instability and breakdown mechanisms of crossflow vortices in three-dimensional swept-wing boundary layers, which is critical for the development of engineering methodologies for the design and optimization of roughness-based laminar flow control.
| [ presentation file not available ]
|
Lian Duan |
|
Speaker Bio:
|
Dr. Lian Duan is currently a research scientist at the National Institute of Aerospace resident in NASA Langley Research Center. He received his Ph.D. in Mechanical and Aerospace Engineering from Princeton University in 2011. His research interests include direct and large-eddy simulations, chemically reacting flow modeling, high-speed transitional and turbulent flow simulation, and laminar and turbulent flow control. He is a winner of AIAA Laurence J. Bement Award for Young Professional Paper Competition (2012) and a recipient of Princeton University Crocco Award for Teaching Excellence (2008).
|
|
|
03-05-2013
11:00am - noon (EST)
NIA Room 141
video
Study of Bioparticle Transport Using Lattice Boltzmann Method and Immersed Boundary Method
This talk will present a computational framework to simulate bioparticle transport involving complex fluid-structure interactions. Several important numerical issues have to be addressed: (1) Numerical stiffness and convergence challenges due to the strong fluid-structure interactions; (2) Resolution of unsteady phenomena such as wakes, separation and vortices induced by interactions of flows with deformable moving boundaries. To overcome these challenges, the lattice Boltzmann equation (LBE) is used to model the fluid motion because of its accuracy (low dissipation/low dispersion and better isotropy) and computational advantages including its excellent parallel scalability, absence of the need to solve a time consuming elliptic Poisson-type equation for the pressure field, and ease of representa- tion of complex boundaries on Cartesian grids. The immersed boundary method (IBM) is chosen to track the deformable moving boundaries for its ease of implementation without re-meshing to generate the body-fitted mesh. One of the main motivations for this study comes from the Lab-on-a-chip (LoC) application, important for
biomedical, pharmaceutical, and environmental industries. Some numerical results of flow-induced deformation of a red blood cell and its shape recovery from shear flow induced deformation are presented.
|
Speaker Bio:
|
Dr. Yan Peng is an Assistant Professor in Department of Mathematics and Statistics in Old Dominion University. Her research has been concentrated on the mathematical analysis, numerical modeling and simulations by using kinetic methods, such as the lattice Boltzmann equation (LBE) and gas kinetic scheme. Currently she is working on numerical study of complex bio-fluids in microfluidic lab-on-a-chip for bio-medical applications.
|
|
|
02-19-2013
11:00am - noon (EST)
NIA Room 137 (Video not available)
More Innovation Using SC/Tetra, the Innovative CFD Software
CAE software, including CFD, has been extensively used in R&D in many industries and becoming indispensable tools. However, each simulation is merely one of many aspects an engineer needs to consider about. Therefore, ideally, each tool utilized for R&D is easy, fast, robust, accurate, reliable and being able to interact with other tools to aid the innovation in one's design.
Cradle has been providing CFD solutions to aid the innovation of the product design in many industries through unique features, capabilities, and vast amount of our expertise. In this presentation, you will learn the secrets of why and how SC/Tetra has been able to contribute
to the innovation, especially in Japanese market.
[ Software Cradle HP |
Software Cradle History ]
|
Speaker Bio:
|
Yuya Ando is the General Manager at Cradle North America Inc., the subsidiary of Software Cradle Co., Ltd. He has been with Cradle for since 2002 and has worked as a sales engineer and global marketing manager. He has been directing Cradle North America and its business since 2008 and is also responsible for business developments and strategic partnerships.
|
|
|
02-05-2013
11:00am - noon (EST)
NIA Room 101
video
Improvements to Second-Order CFD Methods, New Third-Order Schemes, and Extensions to Higher-Order
For decades, second-order methods have dominated CFD codes in industry and government. While enormous progress has been made for certain applications, the shortcomings of these methods for many vortex-dominated and turbulent flows are now widely recognized. High-order unstructured grid methods may overcome many of these shortcomings. This talk addresses three main topics: (1) Improvements to conventional second-order methods, (2) New third-order schemes, and (3) Extensions of these ideas to fourth and higher orders. Specific topics include mesh quality studies, non-planar face treatment, multigrid techniques, and truncation error-cancelling schemes. A goal of this research is to reduce the upfront costs and complexity required to transition from second-order to high-order unstructured grid methods.
|
Speaker Bio:
|
Dr. Katz is currently an assistant professor of Mechanical and Aerospace Engineering at Utah State University in Logan, UT. His research interests include aspects of Computational Fluid Dynamics algorithms, including mesh quality effects, discretization error, high-order methods, meshless methods, and multigrid techniques. Applications of interest include rotorcraft aerodynamics and nuclear energy. Before his current position, Dr. Katz was a post-doctoral researcher with the Department of Defense CREATE program at Ames Research Center in Moffett Field, CA, investigating strand grid methods for rotorcraft CFD applications. Prior to this, Dr. Katz received his PhD from Stanford University under the direction of Professor Antony Jameson developing meshless CFD algorithms. He was supported in his graduate studies by a National Defense Science and Engineering Graduate (NDSEG) Fellowship administered through the Department of Defense High Performance Computing Modernization Program.
|
|
|
01-22-2013
11:00am - noon (EST)
NIA Room 101
video
The Level Set Method applied to Structural Topology Optimization
This presentation will review how the level set method can be applied to solve problems in structural topology optimization. Traditional topology optimization methods rely on finding the optimal distribution of material within a discretized domain. This approach often leads to solutions with fuzzy, unclear boundaries and areas of partial material. This ambiguity can make solutions difficult to interpret. The benefit of the level set approach is that the position of the structural boundary can be extracted from the implicit level set function, avoiding any ambiguity. The presentation will provide an overview of the level set topology optimization approach and discuss the challenges it presents.
|
Speaker Bio:
|
Dr. Peter Dunning is a recently appointed Research Scholar at NIA. He received his Ph.D in Aerospace Engineering from The University of Bath, UK in 2011. His research focussed on robust structural topology optimization using the level set method. He then worked at an engineering consultancy, specialising in FEA, before joining NIA at the start of 2013. He is currently working at extending the capability of the level set optimization approach for application to wing internal structure design.
|
|
Relevant Publications:
|
Introducing Loading Uncertainty in Level Set-Based Structural Topology Optimisation, 2011
[ PhD Thesis (pdf) ]
|
|
|
12-18-2012
11:00am - noon (EST)
NIA Room 101
video
First, Second, and Third Order Finite-Volume Schemes for Diffusion
This talk will show how straightforward it is to construct diffusion schemes;
first, second and third order finite-volume schemes will be constructed quite easily for diffusion.
First-order diffusion scheme is energy-stable on arbitrary grids, the second-order diffusion schemes
yield second-order accurate solution and gradients, and the third-order diffusion
schemes yield third-order accurate solution and gradients on triangular grids nearly at the cost of
a second-order scheme.
|
Speaker Bio:
|
Dr. Hiro Nishikawa is Sr. Research Scientist, NIA. He earned Ph.D. in Aerospace Engineering and Scientific
Computing at the University of Michigan in 2001. He then worked as a postdoctoral fellow at the University
of Michigan on adaptive grid methods, local preconditioning methods, multigrid methods,
rotated-hybrid Riemann solvers, high-order upwind and viscous schemes, etc., and joined NIA in 2007.
His area of expertise is the algorithm development for CFD, currently focusing on multigrid methods (
multigrid story )
and hyperbolic methods for robust, efficient, highly accurate viscous discretization schemes (
seminar 1 |
seminar 2 ) .
[ Homepage |
CFD book |
Free CFD codes |
CFD Notes
]
|
|
Relevant Publications:
|
First, Second, and Third-Order Finite-Volume Schemes for Diffusion, AIAA Paper, 2013.
[ AIAA Paper 2013 (pdf) ]
|
|
|
12-04-2012
11:00am - noon
NIA Room 101
video
Divergence Formulation of Source Term
This talk will discuss a simple idea of writing a source term in the divergence form.
A conservation law with a source term can then be written in a single divergence form, and
consequently it can be discretized virtually without any source term discretization.
This talk will focus on its application to the construction of a third-order finite-volume scheme,
which requires a special source term discretization but it can be totally avoided by the divergence formulation.
Other potential applications and future directions will be discussed.
|
Speaker Bio:
|
Dr. Hiro Nishikawa is Sr. Research Scientist, NIA. He earned Ph.D. in Aerospace Engineering and Scientific
Computing at the University of Michigan in 2001. He then worked as a postdoctoral fellow at the University
of Michigan on adaptive grid methods, local preconditioning methods, multigrid methods,
rotated-hybrid Riemann solvers, high-order upwind and viscous schemes, etc., and joined NIA in 2007.
His area of expertise is the algorithm development for CFD, currently focusing on multigrid methods (
multigrid story )
and hyperbolic methods for robust, efficient, highly accurate viscous discretization schemes (
seminar 1 |
seminar 2 ) .
[ Homepage |
CFD book |
Free CFD codes |
CFD Notes
]
|
|
|
11-20-2012
11:00am - noon
NIA Room 137
video
Overview of the Multigrid Scheme in the DLR TAU-Code
The presentation will give a short overview of the multigrid scheme that
is used in the hybrid unstructured RANS solver TAU developed at DLR
(German Aerospace Center; Home Page of DLR TAU code ). The applied multigrid components, i.e. fine
and coarse grid discretization, relaxation scheme, agglomeration,
multigrid-cycles and multigrid-operators, are presented. Possible
difficulties concerning the practical usage of the scheme are
illustrated and an alternative to solve these difficulties is put up for
discussion.
|
Speaker Bio:
|
Dipl.-Ing. Axel Schwöppe is a senior engineer in the Institute of Aerodynamics and
Flow Technology at the German Aerospace Center (DLR). He is working as a
developer of the DLR TAU-Code with focus on unstructured and structured
discretization schemes.
|
|
Relevant Publications:
|
Digital-X: DLR's Way Towards the Virtual Aircraft, Norbert Kroll, NIA CFD Conference,
Future Directions in CFD Research, A Modeling and Simulation Conference, August 6-8, 2012, Hampton, Virginia
[ Presentation file ]
|
|
|
11-06-2012
11:00am - noon
NIA Room 137
video
Numerical Simulations of Passive and Active Nematic Polymer Suspensions using Kinetic Model
We first review the kinetic model for passive rigid, rod-like nematic polymers which are elements of many
high-performance nano-composite materials and are peocessed in liquid state to engineer for a varity of
desired material properties. Some interesting stable states, along with their transitions, will be examined in
the space of concentration and shear rate. Then we study a few numerical simulations on the structure
formation of nematic polymers in the plane Couette cell by including flow feedback, boundary effects and
long-range distortional elasticity. Rheological properties will be briefly shown for some complex structures,
such as the defect core. Finally we move on to active nematic polymer suspensions, in which active particles
can push or pull themselves in the liquid. We present the numerical method and show the extensive
computational cost for the simulation of nematic polymers using kinetic model, which is coupled with
Navier-Stokes equations. Several excitable patterns emerging from longwave instabilities of active,
polar nano-rod pusher suspensions at dilute concentrations will be discussed.
|
Speaker Bio:
|
Dr. Zhou is Associate Professor in Department of Mathematics and Statistics at Old Dominion University.
He is currently working on the scientific computations, numerical analysis, and numerical simulations of complex fluids.
[ Home Page ]
|
|
|
10-23-2012
11:00am - noon
NIA Room 137
video
Computing Fluid Flow with Moving Interfaces - Two Examples
Fluid flows with moving interfaces occur in a wide range of natural and technological
phenomena, yet our understanding of the fundamental mechanism involved remains limited
at present due to the strong nonlinearity and the multiphysics inherent in these processes.
In this talk, we will present two examples related to such applications: one
for the study of viscous effects on the interfacial motion between two slightly viscous fluids
(a two-phase flow problem), and the other for the simulation of
a large number of solid fibers sedimenting in Navier-Stokes flow
(a fluid-structure interaction problem). We will focus on the computational
aspects in studying these problems, with some mathematical analysis to augment
the computation when applicable. We will discuss both numerics and some interesting
physics revealed from simulation.
|
Speaker Bio:
|
Dr. Jin Wang is Associate Professor of Mathematics at Old Dominion University.
His research interests include numerical analysis, computational fluid dynamics, and
mathematical biology. More details of his research can be found at his home page:
[ Home Page ]
|
|
|
10-19-2012
11:00am - noon
NIA Room 101
video
Positivity-Preserving High Order Schemes
for Convection Dominated Equations
We give a survey of our recent work with collaborators
on the construction of uniformly high order accurate discontinuous
Galerkin (DG) and weighted essentially non-oscillatory (WENO) finite
volume (FV) and finite difference (FD) schemes which satisfy strict
maximum principle for nonlinear scalar conservation laws, passive
convection in incompressible flows, and nonlinear scalar convection-
diffusion equations, and preserve positivity for density and pressure
for compressible Euler systems. A general framework (for arbitrary
order of accuracy) is established to construct a simple scaling limiter
for the DG or FV method involving only evaluations of the polynomial
solution at certain quadrature points. The bound preserving property is
guaranteed for the first order Euler forward time discretization or
strong stability preserving (SSP) high order time discretizations under
suitable CFL condition. One remarkable property of this approach is
that it is straightforward to extend the method to two and higher
dimensions on arbitrary triangulations. We will emphasize recent
developments including arbitrary equations of state, source terms,
integral terms, shallow water equations, high order accurate finite
difference positivity preserving schemes for Euler equations, and
positivity-preserving high order finite volume scheme and piecewise
linear DG scheme for convection-diffusion equations. Numerical tests
demonstrating the good performance of the scheme will be reported.
|
Speaker Bio:
|
Professor Chi-Wang Shu is Theodore B. Stowell University Professor of
Applied Mathematics at Brown University. His area of expertise is the development of high-order numerical
methods, including TVD, ENO and WENO methodologies, discontinuous Galerkin methods, and spectral methods.
[ Home Page ]
|
|
|
|
