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Neal T. Frink - One of the best experts on this subject based on the ideXlab platform.

  • enhancement of usm3d unstructured Flow Solver for high speed high temperature shear Flows
    47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, 2009
    Co-Authors: Mohagna J. Pandya, Khaled S Abdolhamid, Neal T. Frink
    Abstract:

    Large temperature and pressure fluctuations have a profound effect on turbulence development in transonic and supersonic jets. For high-speed, high-temperature jet Flows, standard turbulence models lack the ability to predict the observed mixing rate of a shear layer. Several proposals to address this deficiency have been advanced in the literature to modify the turbulence transport equations in a variety of ways. In the present study, some of the most proven and simple modifications to two-equation turbulence models have been selected and implemented in NASA's USM3D tetrahedral Navier-Stokes Flow Solver. The modifications include the addition of compressibility correction and pressure dilatation terms in the turbulence transport equations for high-speed Flows, and the addition of a simple modification to the Boussinesq's closure model coefficient for high-temperature jets. The efficacy of the extended models is demonstrated by comparison with experimental data for two supersonic axisymmetric jet test cases at design pressure ratio.

  • Implementation of Flow Tripping Capability in the USM3D Unstructured Flow Solver
    44th AIAA Aerospace Sciences Meeting and Exhibit, 2006
    Co-Authors: Mohagna J. Pandya, Khaled S. Abdol-hamid, Richard L. Campbell, Neal T. Frink
    Abstract:

    A Flow tripping capability is added to an established NASA tetrahedral unstructured parallel Navier-Stokes Flow Solver, USM3D. The capability is based on prescribing an appropriate profile of turbulence model variables to energize the boundary layer in a plane normal to a specified trip region on the body surface. We demonstrate this approach using the k-e two-equation turbulence model of USM3D. Modification to the solution procedure primarily consists of developing a data structure to identify all unstructured tetrahedral grid cells located in the plane normal to a specified surface trip region and computing a function based on the mean Flow solution to specify the modified profile of the turbulence model variables. We leverage this data structure and also show an adjunct approach that is based on enforcing a laminar Flow condition on the otherwise fully turbulent Flow solution in userspecified region. The latter approach is applied for the solutions obtained using other oneand two-equation turbulence models of USM3D. A key ingredient of the present capability is the use of a graphical user-interface tool PREDISC to define a trip region on the body surface in an existing grid. Verification of the present modifications is demonstrated on three cases, namely, a flat plate, the RAE2822 airfoil, and the DLR F6 wing-fuselage configuration.

  • progress toward overset grid moving body capability for usm3d unstructured Flow Solver
    17th AIAA Computational Fluid Dynamics Conference, 2005
    Co-Authors: Mohagna J Pandyna, Neal T. Frink, Ralph Noack
    Abstract:

    A static and dynamic Chimera overset-grid capability is added to an established NASA tetrahedral unstructured parallel Navier-Stokes Flow Solver, USM3D. Modifications to the Solver primarily consist of a few strategic calls to the Donor interpolation Receptor Transaction library (DiRTlib) to facilitate communication of solution information between various grids. The assembly of multiple overlapping grids into a single-zone composite grid is performed by the Structured, Unstructured and Generalized Grid AssembleR (SUGGAR) code. Several test cases are presented to verify the implementation, assess overset-grid solution accuracy and convergence relative to single-grid solutions, and demonstrate the prescribed relative grid motion capability.

  • Agglomeration Multigrid for an Unstructured-Grid Flow Solver
    42nd AIAA Aerospace Sciences Meeting and Exhibit, 2004
    Co-Authors: Mohagna J. Pandya, Neal T. Frink
    Abstract:

    An agglomeration multigrid scheme has been implemented into the sequential version of the NASA code USM3Dns, tetrahedral cell-centered finite volume Euler/Navier-Stokes Flow Solver. Efficiency and robustness of the multigrid-enhanced Flow Solver have been assessed for three configurations assuming an inviscid Flow and one configuration assuming a viscous fully turbulent Flow. The inviscid studies include a transonic Flow over the ONERA M6 wing and a generic business jet with Flow-through nacelles and a low subsonic Flow over a high-lift trapezoidal wing. The viscous case includes a fully turbulent Flow over the RAE 2822 rectangular wing. The multigrid solutions converged with 12%-33% of the Central Processing Unit (CPU) time required by the solutions obtained without multigrid. For all of the inviscid cases, multigrid in conjunction with an explicit time-stepping scheme performed the best with regard to the run time memory and CPU time requirements. However, for the viscous case multigrid had to be used with an implicit backward Euler time-stepping scheme that increased the run time memory requirement by 22% as compared to the run made without multigrid.

  • recent enhancements to usm3d unstructured Flow Solver for unsteady Flows
    22nd Applied Aerodynamics Conference and Exhibit, 2004
    Co-Authors: Mohagna J. Pandya, Neal T. Frink, Khaled S Abdolhamid, James J Chung
    Abstract:

    NAVAIR, Patuxent River, Maryland 20670 The NASA USM3D unstructured Flow Solver is undergoing extensions to address dynamic Flow problems in support of NASA and NAVAIR efforts to study the applicability of Computational Fluid Dynamics tools for the prediction of aircraft stability and control characteristics. The initial extensions reported herein include two second-order time stepping schemes, Detached-Eddy Simulation, and grid motion. This paper reports the initial code verification and validation assessment of the dynamic Flow capabilities of USM3D. The cases considered are the classic inviscid shock-tube problem, low Reynolds number wake shedding from a NACA 0012 airfoil, high Reynolds number DES-based wake shedding from a 4-to-1 length-to-diameter cylinder, and forced pitch oscillation of a NACA 0012 airfoil with inviscid and turbulent Flow.

Cuong P Nguyen - One of the best experts on this subject based on the ideXlab platform.

  • agent based distributed volt var control with distributed power Flow Solver in smart grid
    IEEE Transactions on Smart Grid, 2016
    Co-Authors: Xu Zhang, Alexander J Flueck, Cuong P Nguyen
    Abstract:

    In this paper, a new and completely distributed algorithm for integrated volt/var control is presented. The algorithm is based on a multiagent system, which provides distributed intelligence to smart grid. The voltage regulator and shunt capacitor controlled by intelligent agents collaborate to determine the optimal setting for the entire system. The optimization objectives include maintaining the system voltage profile within a specified range, minimizing system loss, and reducing the switching of shunt capacitors. To achieve these objectives, an updated agent-based distributed power Flow Solver is used. The proposed algorithm is validated through the modified IEEE 34 node test feeder.

  • a novel agent based distributed power Flow Solver for smart grids
    IEEE Transactions on Smart Grid, 2015
    Co-Authors: Cuong P Nguyen, Alexander J Flueck
    Abstract:

    The goal of this paper is to present a novel agent based distributed power Flow Solver for general unbalanced radial distribution systems utilizing multiagent system communication. The distributed Solver makes use of intelligent agents, which possess three key characteristics, namely autonomy, local view, and decentralization. Comprehensive models of distribution systems will be considered, including lines, switching devices, voltage regulators, transformers, shunt capacitors, distributed energy storage systems, and different load types. The distributed intelligent agents will use the backward/forward sweep technique to iteratively solve the power Flow. A distinguishing feature of the new Solver is that it deals with the problem from a completely distributed perspective. The proposed solution algorithm is evaluated on three standard IEEE distribution test systems with very promising results.

Cy Chan - One of the best experts on this subject based on the ideXlab platform.

  • ISGT - ExaGridPF: A parallel power Flow Solver for transmission and unbalanced distribution systems
    2018 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT), 2018
    Co-Authors: Bin Wang, John Bachan, Cy Chan
    Abstract:

    This paper investigates parallelization strategies for solving power Flow problems in both transmission and unbalanced, three-phase distribution systems by developing a scalable power Flow Solver, ExaGridPF, which is compatible with existing high performance computing platforms. Newton-Raphson (NR) and Newton-Krylov (NK) algorithms have been implemented to verify the performance improvement over both standard IEEE test cases and synthesized grid topologies. For three-phase, unbalanced system, we adapt the current injection method (CIM) to model the power Flow and utilize SuperLU to parallelize the computing load across multiple threads. The experimental results indicate that more than 5 times speedup ratio can be achieved for synthesized large-scale transmission topologies, and significant efficiency improvements are observed over existing methods for the distribution networks.

  • ExaGridPF: A Parallel Power Flow Solver for Transmission and Unbalanced Distribution Systems
    arXiv: Computational Engineering Finance and Science, 2017
    Co-Authors: Bin Wang, John Bachan, Cy Chan
    Abstract:

    This paper investigates parallelization strategies for solving power Flow problems in both transmission and unbalanced, three-phase distribution systems by developing a scalable power Flow Solver, ExaGridPF, which is compatible with existing high-performance computing platforms. Newton-Raphson (NR) and Newton-Krylov (NK) algorithms have been implemented to verify the performance improvement over both standard IEEE test cases and synthesized grid topologies. For three-phase, unbalanced system, we adapt the current injection method (CIM) to model the power Flow and utilize SuperLU to parallelize the computing load across multiple threads. The experimental results indicate that more than 5 times speedup ratio can be achieved for synthesized large-scale transmission topologies, and significant efficiency improvements are observed over existing methods for the distribution networks.

Alexander J Flueck - One of the best experts on this subject based on the ideXlab platform.

  • agent based distributed volt var control with distributed power Flow Solver in smart grid
    IEEE Transactions on Smart Grid, 2016
    Co-Authors: Xu Zhang, Alexander J Flueck, Cuong P Nguyen
    Abstract:

    In this paper, a new and completely distributed algorithm for integrated volt/var control is presented. The algorithm is based on a multiagent system, which provides distributed intelligence to smart grid. The voltage regulator and shunt capacitor controlled by intelligent agents collaborate to determine the optimal setting for the entire system. The optimization objectives include maintaining the system voltage profile within a specified range, minimizing system loss, and reducing the switching of shunt capacitors. To achieve these objectives, an updated agent-based distributed power Flow Solver is used. The proposed algorithm is validated through the modified IEEE 34 node test feeder.

  • a novel agent based distributed power Flow Solver for smart grids
    IEEE Transactions on Smart Grid, 2015
    Co-Authors: Cuong P Nguyen, Alexander J Flueck
    Abstract:

    The goal of this paper is to present a novel agent based distributed power Flow Solver for general unbalanced radial distribution systems utilizing multiagent system communication. The distributed Solver makes use of intelligent agents, which possess three key characteristics, namely autonomy, local view, and decentralization. Comprehensive models of distribution systems will be considered, including lines, switching devices, voltage regulators, transformers, shunt capacitors, distributed energy storage systems, and different load types. The distributed intelligent agents will use the backward/forward sweep technique to iteratively solve the power Flow. A distinguishing feature of the new Solver is that it deals with the problem from a completely distributed perspective. The proposed solution algorithm is evaluated on three standard IEEE distribution test systems with very promising results.

Bin Wang - One of the best experts on this subject based on the ideXlab platform.

  • ISGT - ExaGridPF: A parallel power Flow Solver for transmission and unbalanced distribution systems
    2018 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT), 2018
    Co-Authors: Bin Wang, John Bachan, Cy Chan
    Abstract:

    This paper investigates parallelization strategies for solving power Flow problems in both transmission and unbalanced, three-phase distribution systems by developing a scalable power Flow Solver, ExaGridPF, which is compatible with existing high performance computing platforms. Newton-Raphson (NR) and Newton-Krylov (NK) algorithms have been implemented to verify the performance improvement over both standard IEEE test cases and synthesized grid topologies. For three-phase, unbalanced system, we adapt the current injection method (CIM) to model the power Flow and utilize SuperLU to parallelize the computing load across multiple threads. The experimental results indicate that more than 5 times speedup ratio can be achieved for synthesized large-scale transmission topologies, and significant efficiency improvements are observed over existing methods for the distribution networks.

  • ExaGridPF: A Parallel Power Flow Solver for Transmission and Unbalanced Distribution Systems
    arXiv: Computational Engineering Finance and Science, 2017
    Co-Authors: Bin Wang, John Bachan, Cy Chan
    Abstract:

    This paper investigates parallelization strategies for solving power Flow problems in both transmission and unbalanced, three-phase distribution systems by developing a scalable power Flow Solver, ExaGridPF, which is compatible with existing high-performance computing platforms. Newton-Raphson (NR) and Newton-Krylov (NK) algorithms have been implemented to verify the performance improvement over both standard IEEE test cases and synthesized grid topologies. For three-phase, unbalanced system, we adapt the current injection method (CIM) to model the power Flow and utilize SuperLU to parallelize the computing load across multiple threads. The experimental results indicate that more than 5 times speedup ratio can be achieved for synthesized large-scale transmission topologies, and significant efficiency improvements are observed over existing methods for the distribution networks.