National Institute of Aerospace
Computational Fluid Dynamics Seminar

A place to share ideas and problems for barrier-breaking developments




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▶ Contacts

Boris Diskin   [ E-mail ]
Hiroaki Nishikawa   [ E-mail ]
▶ Past Seminars

    Season 6 (2016-2017)
    Season 5 (2015-2016)
    Season 4 (2014-2015)
    Season 3 (2013-2014)
    Season 2 (2012-2013)
    Season 1 (2011-2012)

    List of Speakers
▶ NIA Researchers
Boris Diskin, Ph.D.  
Research Fellow, NIA

Adjoint-based optimization methods, Finite-volume discretizations, Multigrid methods on structured/unstructured grids
Web | E-mail
David Del Rey Fernández, Ph.D.  
Postdoctoral Fellow, NIA

Robust high-order numerical methods for the solution of partial differential equations.
E-mail
Prahladh S. Iyer Ph.D.  
Postdoctoral Fellow, NIA

DNS/ LES of complex flows, transition to turbulence and turbulence modeling.
E-mail
Heather Kline Ph.D.  
Research Engieer, NIA

Adjoint-based design, transition to turbulence, and hypersonic air-breathing propulsion
E-mail
Yi Liu, Ph.D.  
Senior Research Scientist, NIA

high-order accurate methods, turbomachinery and rotorcraft applicaitons.
E-mail
Hiroaki Nishikawa, Ph.D.  
Associate Research Fellow, NIA

Discretization and convergence acceleration methods for unstructured grids
Web | E-mail | CFD Notes                 View Hiroaki Nishikawa's LinkedIn profile Follow HiroNishikawa on Twitter
Juliette Pardue  
PhD Student, ODU/NIA

Mesh generation, parallel algorithms, and computational geometry.
E-mail
Balaji S. Venkatachari, Ph.D.  
Sr. Research Engineer, NIA

Numerical algorithm development, Hypersonics, TPS modeling (continuum and multi-scale modeling), and CAA.
E-mail
Ali Uzun, Ph.D.  
Sr. Research Scientist, NIA

Computational fluid dynamics using high-order numerical methods, turbulence simulations, computational aeroacoustics and parallel computing.
E-mail
Li Wang, Ph.D.  
Sr. Research Engineer, NIA

Turbulent flow simulation and modeling, high-order finite element CFD methods, adjoint-based sensitivity analysis and design optimization, adaptive meshing, multigrid acceleration strategies, and highperformance computing.
E-mail
▶ Faculties in Residence
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
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NIA CFD Seminar Schedule

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96th NIA CFD Seminar:

11-28-2017   11am-noon (EST)   NIA Room 101      video

Hamiltonian-Strand (HAMSTR) Approach Using Hybrid Meshes for Aerodynamic Flow Analysis

A solution framework using Hamiltonian paths and strand grids (HAMSTR) is presented for two and three-dimensional flows. The methodology can create a volume mesh starting from either an unstructured surface mesh comprised of mixed triangular-quadrilateral elements or a fully unstructured volume mesh. "Line structure" through the meshes are found in a robust manner and the flow solver uses line-implicit schemes and stencil-based discretization along these lines, similar to a structured grid flow solver. The framework has been developed mostly for rotorcraft CFD simulations, which requires robust mesh generation around complex geometry and efficient numerical method for large scale problems. HAMSTR is a 3D compressible finite volume solver that can operate across multiple processors using MPI. Hybrid RANS/LES turbulence modeling based on the Spalart-Allmaras turbulence model and Y-[Re]θ-SA laminar/turbulent transition model of Medida-Baeder are integrated into the solver for better predictions of the boundary layer and resulting flowfield as compared with a fully turbulent RANS simulation. Furthermore, deformable meshes can also be handled for elastic body simulations such as rotor blades. An overset technique (using TIOGA) allows for a hybrid mesh system, which consists of a near-body Hamiltonian/Strand grid and off-body Cartesian nested meshes. The integration framework between the various components of the code is performed using Python to allow for ease of integration to other codes in the research group. The current infrastructure is used to explore various cases ranging from simple representative geometries, such as 2D airfoil, to complex geometries such as rotating rotor hub and a full wind turbine. Some, CFD/CSD predictions for a slowed rotor are also studied.

[ presentation file (pdf) ] Yong Su Jung

Speaker Bio: Yong Su Jung is a Ph.D candidate student in Aerospace Engineering department at the University of Maryland. He holds B.S (2012). and M.S (2014) in Aerospace Engineering from Korea Advanced Institute of Science and Technology. His research interests are in developing and applying Computational Fluid Dynamics methods for external flow simulations, such as rotary wing. His research has been funded by Department of Defense (DoD) HPCMP CREATE-AV program and Korea Aerospace Research Institute. He was a member of the University Maryland team received first place in the graduate category for 2016 AHS Design Competition.


95th NIA CFD Seminar:

10-16-2017   1pm-2pm (EST)   NIA Room 101      video

A Personal Journey Towards High Fidelity Rotorcraft CFD

In the 1980's it was sufficient for CFD to look at very simplified model rotorcraft problems, for example: a 2-D airfoil encountering an isolated prescribed vortex or a non-lifting isolated rotor blade in forward flight generating unsteady shock waves. In most instances the inviscid Euler equations were used or else the flow was assumed to be fully turbulent and an algebraic turbulence model was used for closure. While relatively unsophisticated by today's standards, they were able to provide some key physical insights into such phenomena as blade-vortex interactions and high-speed impulsive noise. It also served to pique interest in the rotorcraft community as to how CFD could be applied to practical problems. High fidelity rotorcraft aerodynamic simulations are inherently multi-disciplinary and require hybrid methods to resolve all relevant fluid scales. Thus, applications of computational fluid dynamics to rotorcraft over the past 25 years have required an increase in the level of sophistication not only of the included physics but also of more complicated configurations with more complex geometries. As a result this has necessitated not only increased computer hardware, but also the development of more sophisticated algorithms. The first part of this seminar will discuss the wide range of improvements made to rotorcraft CFD simulations at the Alfred Gessow Rotorcraft Center over the past 20+ years. In regards to multi-disciplinary physics this includes such areas as: aeroacoustics, structural coupling and trim, low Reynolds number and low Mach number flows, laminar/turbulent transition, two-phase flow (particles in fluids), and the capturing of tip vortices and other large eddies. These have been accompanied by algorithmic improvements that have included: hybrid Eulerian/Lagrangian methods for wake coupling, vortex tracking grids, compact reconstruction of inviscid fluxes, hybrid RANS/LES turbulence modeling, and GPGPU programming. More complicated geometries have been enabled through: implicit hole-cutting for overset meshes, simplified models for flaps and other actuators, and the use of unstructured meshes. The second part of the seminar will focus on the application of uncertainty quantification to look at the effect of uncertainty in free-stream turbulence intensity levels on 2-D airfoil integrated forces and moments as well as flow physics.

[ presentation file (pdf) ] James D. Baeder

Speaker Bio: Dr. James D. Baeder is a member of the Alfred Gessow Rotorcraft Center as Professor in Aerospace Engineering at the University of Maryland; he is currently the Associate Langley Professor Chair at the National Institute for Aerospace. He holds a B.S. in Mechanical Engineering from Rice University and M.S. and Ph.D. in Aeronautics and Astronautics from Stanford University. He joined the AGRC in 1993 after nine years at AFDD. His research interests are in developing and applying Computational Fluid Dynamic methods to better understand and predict rotary and flapping wing aerodynamics, acoustics and dynamics. One of his key research thrusts is the development of multi-fidelity coupled CFD/ free-wake/ structural dynamics/ acoustic methods. His pioneering efforts in predicting high-speed vibration and noise of helicopters, together with Dr. Chopra, are leading to a better understanding of the physical mechanisms responsible for the large increase in vibrations at such conditions. Additional applications include simulating: the use of active elements; helicopter "brownout"; interactional aerodynamics; aerodynamic performance and flow-field of small-scale rotary and flapping UAV; vertical axis wind turbines (VAWT); and offshore wind turbines. Currently he is pioneering the development of improved CFD algorithms, with a focus on GPGPU technology, to: capture the details of laminar/turbulent transition; dynamic stall; as well as tip vortex formation, convection and interaction with other surfaces including fuselages, towers or the ground and including adjoint capabilities. Dr. Baeder's research has been funded by Excelon, NASA Ames and Langley, the Army Aeroflightdynamics Directorate, the Army Research Office, the National Rotorcraft Technology Center, NAVAIR and DARPA, with support from the various helicopter companies. He has authored more than 45 archival journal articles. He received the 1993 Schroers Award for Outstanding Rotorcraft Research from the San Francisco Bay Area Chapter of the AHS and the 2010 AIAA National Capital Section Engineer of the Year Award. He advised the University of Maryland team to receive First Place in the Undergraduate Category of the 2017 American Helicopter Design Competition. Dr. Baeder is an Associate Fellow of AIAA and a member of AHS. He currently chairs the Innovation and Commercialization Committee of the Business Network for Offshore Wind as well as the National Offshore Wind Innovation Center.


94th NIA CFD Seminar:

09-28-2017   12 pm-1pm (EST)   NIA Room 137      video

Flexible Multibody Dynamics Tools For Rotorcraft Comprehensive Analysis

Flexible multibody dynamics techniques provide a framework for the dynamic analysis of aerospace vehicles in general and of rotorcraft, in particular. Dymore is a flexible multibody dynamics code that includes geometrically-exact beam elements, rigid bodies, kinematic joints, and modal elements. Through an integrated set of interface routines, Dymore enables the use of simple aerodynamic models but also allows the coupling of structural dynamics models with advanced CFD tools such as FUN3D or OVERFLOW. SectionBuilder is a finite element based tool that evaluates exact solutions of three-dimensional elasticity for beams of general cross-sectional shape made of anisotropic materials; the three-dimensional stress field at any point of the blade is a byproduct of these exact solutions. Rotor blade detailed design, structural integrity, fatigue life, and optimization all depend on the accurate knowledge of three-dimensional stress distributions.

Recently, a parallel version of Dymore has been developed by integrating three key techniques: (1) the motion formalism, which removes most kinematic nonlinearities from the governing equations of motion, (2) domain decomposition techniques that partition the system to exploit the reduced nonlinearities and (3) parallel computation is then a natural consequence of the independence of the sub- domains. Ongoing and future developments of Dymore and SectionBuilder will be presented; they include (1) the development of spectral solvers for the evaluation of periodic solutions for flexible multibody systems, (2) the development of discretely consistent adjoint-based sensitivity analysis, and (3) the development of nonlinear three-dimensional finite element modeling of rotorcraft structures based on the motion formalism.

[ presentation file (pdf) ] Olivier A. Bauchau

Speaker Bio: Dr. Bauchau earned his B.S. degree in engineering at the Université de Ličge, Belgium, and M.S. and Ph.D. degrees from the Massachusetts Institute of Technology. He has been a faculty member of the Department of Mechanical Engineering, Aeronautical Engineering, and Mechanics at the Rensselaer Polytechnic Institute in Troy, New York (1983-1995), a faculty member of the Daniel Guggenheim School of Aerospace Engineering of the Georgia Institute of Technology in Atlanta, Georgia (1995-2010), a faculty member of the University of Michigan Shanghai Jiao Tong University Joint institute in Shanghai, China (2010-2015). He is now Igor Sikorsky Professor of Rotorcraft in the Department of Aerospace Engineering at the University of Maryland.

His fields of expertise include finite element methods for structural and multibody dynamics, rotorcraft and wind turbine comprehensive analysis, and flexible multibody dynamics. He is a Fellow of the American Society of Mechanical Engineers, a Technical Fellow of the American Helicopter Society, and a senior member of the American Institute of Aeronautics and Astronautics. His book entitled "Flexible Multibody Dynamics" has won the 2012 Textbook Excellence Award from the Text and Academic Authors Association. He is the 2015 recipient of the ASME d'Alembert award for lifelong contributions to the field of multibody system dynamics.


93rd NIA CFD Seminar:

09-19-2017   11:00am-noon (EST)   NIA Room 101      video

Third-Order Edge-Based Hyperbolic Navier-Stokes Scheme for Three-Dimensional Viscous Flows

We present a third-order edge-based scheme for the three-dimensional Navier-Stokes equations. The node-centered edge-based scheme achieves third-order accuracy on tetrahedral grids with quadratic least-squares gradients and linear flux reconstruction for the Euler equations. It is extended to the viscous terms by the hyperbolic Navier-Stokes method, in which the viscous terms are written as a first-order hyperbolic system with source terms. The source terms introduced by the hyperbolic formulation are discretized by a new quadrature formula recently discovered, which does not require second derivatives. Third-order accuracy is demonstrated not only for the solution variables but also for their gradients on fully irregular grids. The developed scheme is implemented in NASA's FUN3D code, and tested for three-dimensional laminar flow problems. The seminar concludes with a brief discussion on future work towards third-order turbulent-flow computations on unstructured grids.

[ presentation file (pdf) ] Yi Liu

Speaker Bio: Dr. Yi Liu graduated from Georgia Institute of Technology with a Ph.D degree in aerospace engineering in 2003. He also holds a M.E. from Beijing University of Aeronautics and Astronautics in Beijing, China. In 2004, he joined the National Institute of Aerospace after a one-year postdoctoral fellowship at Georgia Tech. He has previously served as a senior research engineer at NIA in the area of computational fluid dynamics (CFD) and multi-disciplinary analysis of rotorcraft configurations. He has conducted various research projects, including work in the areas of rotorcraft aerodynamic analysis and acoustic prediction; micro-air vehicle and flapping wing aerodynamics sponsored by ARL and NASA. Currently, he is conducting the research project of implementation of third-order edge-based scheme in NASA CFD solver FUN3D with collaboration of researchers at NASA LaRC-Computational AeroSciences Branch.


92nd NIA CFD Seminar:

08-18-2017   11:00am-noon (EST)   NIA Room 137      video

SLAU2 and Post Limiter for (Unlimited) Second-Order Flow Simulations on Unstructured Grids

This talk will present two methods: SLAU2 flux function and "Post Limiter." SLAU2 is robust against shockwave-induced anomalous solutions at hypersonic speeds ("carbuncle" phenomena), while it can be used at low speeds e.g., Mach 0.001 - thus, designated as an all-speed scheme. SLAU2, with its predecessor SLAU, has been incorporated into JAXA's CFD code "FaSTAR", and widely used by many researchers and practitioners in- and outside Japan. The present talk will focus on its very recent extension to supercritical fluids, in which an energy equation to be solved was replaced by its mathematically-equivalent, pressure-evolution equation, to suppress numerical oscillations.

"Post Limiter (simple a posteriori slope limiter)" is a means to deactivate a conventional slope limiter as much as possible (even at shocks), unless it is truly needed. In other words, "unlimited" slopes are favored rather than the limited ones by the slope limiter at all the cell-interfaces. As a result, dramatic improvements of both flow resolution (four times in each dimension) and convergence have been observed. This approach is powerful especially when a spatially second-order reconstruction is performed and grid points are clustered to physics-rich regions on unstructured grids, such as in FaSTAR.

[ presentation file (pdf) ] Keiichi Kitamura

Speaker Bio: Dr. Keiichi Kitamura was an exchange student at University of Michigan, Ann Arbor (2007), and received Dr. of Engineering from Nagoya University, Japan (2008). Then he experienced Postdoctoral Researcher at JAXA (2008-2011) and NASA Glenn (2011-2012), Assistant Prof. at Nagoya University (2012-2014), and became Associate Prof. at Yokohama National University, Japan (2014). He has proposed several numerical flux functions such as SLAU2 (2013), and also a new limiting strategy called "Post Limiter" (2017) to turn off a slope limiter at unnecessary places.



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