Papers & Reports 2005

This paper examines the behavior of flux and slope limiters on non-uniform grids in multiple dimensions. Many slope limiters in standard use do not preserve linear solutions on irregular grids impacting both accuracy and convergence.
Analysis of Slope Limiters on Irregular Grids,43rd AIAA Aerospace Sciences Meeting, Reno, NV, January 10-13, 2005.

A discrete-adjoint formulation is presented for the three-dimensional Euler equations discretized on a Cartesian mesh with embedded boundaries. The solution algorithm for the adjoint and flow-sensitivity equations leverages the Runge–Kutta time-marching scheme in conjunction with the parallel multigrid method of the flow solver.
Adjoint Formulation for an Embedded-Boundary Cartesian Method,43rd AIAA Aerospace Sciences Meeting, Reno, NV, January 10-13, 2005.

Inlets and exhaust nozzles are often omitted in aerodynamic simulations of aircraft due to the complexities involved in the modeling of engine details and flow physics. However, the omission is often improper since inlet or plume flows may have a substantial effect on vehicle aerodynamics. A method for modeling the effect of inlets and exhaust plumes using boundary conditions within an inviscid Cartesian flow solver is presented.
Validation of Inlet and Exhaust Boundary Conditions for a Cartesian Method,NAS Technical Report, NAS-05-001, January 2005.

The role of plasma in plasma enhanced chemical vapor deposition of carbon nanotubes and nanofibers is investigated with both experimental and computational diagnostic techniques.
An Investigation of Plasma Chemistry for dc Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes and Nanofibers,NAS Technical Report, NAS-05-002, March 2005.

A 3-D full Navier-Stokes simulation of a large scale computing facility at NASA Ames Research center was carried out to assess the adequacy of the existing air handling and conditioning system. The flow simulation of this modern facility was modeled with a viscous, compressible flow solver code OVERFLOW-2 with low Mach number pre-conditioning.
Navier-Stokes Simulation of Air-Conditioning Facility of a Large Modern Computer Room,NAS Technical Report, NAS-05-003, May 2005.

An implementation of both finite rate and equilibrium chemistry have been completed for the OVERFLOW code, a chimera capable, complex geometry flow code widely used to predict transonic flowfields. The implementation builds on the computational efficiency and geometric generality of the solver.
Implementation of Finite Rate Chemistry Capability in OVERFLOW,NAS Technical Report, NAS-05-004, May 2005.

The Lag model has shown great promise in prediction of low speed and transonic separations. The predictions of the model, along with other models (Spalart-Allmaras and Menter SST) are assessed for various high speed flowfields. In addition to skin friction and separation predictions, the prediction of heat transfer are compared among these models, and some fundamental building block flowfields, are investigated.
The Lag Model Applied to High Speed Flows,NAS Technical Report, NAS-05-005, May 2005.

The objective of this work is the development of grid-based approaches through which NASA data centers can become active participants in serving data users by transforming archived data into the specific form needed by the user. This approach involves generating custom data products from data stored in multiple NASA data centers.
Distributed Generation of NASA Earth Science Data Products,NAS Technical Report, NAS-05-006, May 2005.

A new, high-order, conservative, and efficient method for conservation laws on unstructured grids has been developed. It combines the best features of structured and unstructured grid methods to attain computational efficiency and geometric flexibility; it utilizes the concept of discontinuous and high-order local representations to achieve conservation and high accuracy; and it is based on the finite-difference formulation for simplicity.
Multi-Dimensional Spectral Difference Method for Unstructured Grids,NAS Technical Report, NAS-05-009, May 2005.

Methods using OpenMP directives have been studied to parallelize an inherently sequential GaussSeidel algorithm on shared memory computers. Both hyperplane and pipeline parallelization schemes have been implemented to a non-equilibrium real-gas flow simulation code. The effects of different parallelization strategies and grid sizes on the parallel efficiency have been investigated on SGI Origin and Altix systems.
Parallelization of Gauss-Seidel Relaxation for Real Gas Flow,NAS Technical Report, NAS-05-011, June 2005.

We focus on the computation of objective function gradients using a discrete adjoint method for embedded-boundary Cartesian meshes. This is a significant step in our research toward using computer-aided design (CAD) directly for adjoint-based gradient computations.
Adjoint Algorithm for CAD-Based Shape Optimization Using a Cartesian Method,17th Computational Fluid Dynamics Conference, Toronto, ON, June 6-9, 2005.

The effect of resistive, Hall, and viscous terms on the flow structure compared with compressible ideal MHD is studied numerically for a one-fluid non-ideal MHD model. The goal of the present study is to shed some light on the emerging area of non-ideal MHD modeling and simulation.
A Numerical Study of Resistivity and Hall Effects for a Compressible MHD Model,36th AIAA Plasmadynamics and Lasers Conference, Toronto, ON, June 6-8, 2005.

Recent developments in three pieces of software for performing pre-processing and post-processing work on numerical computations using overset grids are presented. The first is the OVERGRID graphical interface which provides a unified environment for the visualization, manipulation, generation and diagnostics of geometry and grids.
Advances in Software Tools for Pre-processing and Post-processing of Overset Grid Computations,9th International Conference on Numerical Grid Generation in Computational Field Simulations, San Jose, CA, June 11-18, 2005.

The Cosmic Microwave Background (CMB) is an exquisitely sensitive probe of the fundamental parameters of cosmology. In this work we present MADbench, a lightweight version of the MADCAP CMB power spectrum estimation code that retains the operational complexity and integrated system requirements.
Integrated Performance Monitoring of a Cosmology Application on Leading HEC Platforms,NAS Technical Report, NAS-05-012, September 2005.

A Cray X1 computer system was installed at the NASA Advanced Supercomputing (NAS) facility at NASA Ames Research Center in 2004. An evaluation study of this unique high performance computing (HPC) architecture, from the standpoints of processor and system performance, ease of use, and production computing readiness tailored to the needs of the NAS scientific community, was recently completed.
NAS Experience with the Cray X1,NAS Technical Report, NAS-05-013, September 2005.

In this paper, we describe two application development experiences that exposed problems with expressivity and performance as a result of limitations in the current OpenMP specification. We then propose mechanisms to overcome these limitations, including the notation of thread subteams and thread topology.
Support for Flexibility and User Control of Worksharing in OpenMP,NAS Technical Report, NAS-05-015, October 2005.

Multilevel parallel versions of CFL3D have been created and their performance has been evaluated for a complete aircraft problem on NAS platforms. CFL3D is a three-dimensional multi-block Navier-Stokes flow solver for structured grids and the official version of the code employs MPI to execute calculations in parallel over the discrete geometrical regions
Creation of a Multilevel Parallel Version of CFL3D,NAS Technical Report, NAS-05-016, December 2005.

Columbia is a 10,240-processor supercluster consisting of 20 Altix nodes with 512 processors each, and currently ranked as one of the fastest computers in the world. In this paper, we present the performance characteristics of Columbia obtained on up to four computing nodes interconnected via the InfiniBand and/or NUMAlink4 communication fabrics.
An Application-Based Performance Characterization of the Columbia Supercluster,NAS Technical Report, NAS-05-017, December 2005.

This paper focuses on the parallel performance of two high-performance aerodynamic simulation packages on the newly installed NASA Columbia supercomputer. These packages include both a high-fidelity, unstructured, Reynolds-averaged Navier-Stokes solver, and a fully-automated inviscid flow package for cut-cell Cartesian grids.
High Resolution Aerospace Applications using the NASA Columbia Supercomputer,NAS Technical Report, NAS-05-018, December 2005.