Papers & Reports 2011

As a collaborative effort among government aerospace research laboratories, an advanced version of a widely used computational fluid dynamics code, OVERFLOW2.1z, was recently released. This latest version includes additions to model multiple flexible, rotating blades.
CFD-based Computations of Flexible Helicopter Blades for Stability Analysis,AIAA /AHS Structural Dynamics Conference, Denver, CO, April, 2011.

A modular capability to compute dynamic aeroelastic characteristics of rotor blades using the Euler/Navier- Stokes flow equations and finite element structural equations is presented. The approach is based on a time-accurate analysis procedure that is suitable for nonlinear fluid-structure interaction problems.
Computational-Fluid-Dynamics- and Computational-Structural-Dynamics-Based Time-Accurate Aeroelasticity of Helicopter Rotor Blades,Journal of Aircraft, Vol. 47, No. 3, May-June 2011.

One of the current challenges in tropical cyclone (TC) research is how to improve our understanding of TC inter-annual variability and the impact of climate change on TCs. Paired with the substantial computing power of the NASA Columbia and Pleiades supercomputers, the newly-developed Coupled Global Multiscale Modeling and Concurrent Visualization System (CAMVis; Shen et al., 2011) shows potential for such studies.
Recent Development of the NASA CAMVis for Tropical Cyclone Studies,2011 NASA Earth Science Technology Forum, Pasadena, CA, June 21-23, 2011.

This paper conducts a numerical study of four sets of aerodynamic control surfaces, called grid fins, mounted on a full Launch Abort Vehicle geometry using a Cartesian Euler Solver with embedded boundaries and adjoint-driven adaptive meshing. Since Cartesian methods are insensitive to complex geometry, this makes them suitable for the highly complex resulting configuration.
Analysis of Grid Fins for Launch Abort Vehicle Using a Cartesian Euler Solver,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Two unsteady Reynolds-averaged Navier-Stokes solvers are used to compute the rotor airloads on the UH-60A rotorcraft at several flight conditions across the flight envelope. One code, OVERFLOW, solves the flow equations using either structured grids, or a combination of structured and Cartesian grids.
Code-to-Code Comparison of CFD/CSD Simulation for a Helicopter Rotor in Forward Flight,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Time-dependent Reynolds-averaged Navier-Stokes simulations for a highly flexible aeroelastic UH-60A rotor have been carried out for forward flight. The fluid structure interaction is accomplished by loosely coupling the OVERFLOW Computational Fluid Dynamics (CFD) code with the helicopter comprehensive code CAMRAD II.
High-Order Accurate CFD/CSD Simulation of the UH-60 Rotor in Forward Flight,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

We consider analysis and design of low sonic-boom aircraft through the use of an inviscid, embedded-boundary Cartesian mesh method. Adjoint error estimation and adaptive meshing are used in the analysis portion of this study to determine resolution requirements of the computational domain, while adjoint-based gradients in conjunction with a parallel optimization framework are used for design.
Adjoint-Based Low-Boom Design with Cart3D,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Overset grids resolve complicated geometries by creating high quality structured grids that are independently built for each component. This simplifies the process of grid generation, but domain connectivity must be performed so that adjacent grids share information.
Automation of Hole-Cutting for Overset Grids Using the X-rays Approach,20th AIAA Computational Fluid Dynamics Conference, Honolulu, Hawaii, June 2011.

Supersonic retropropulsion (SRP) has been proposed as a candidate enabling technology for future high-mass Mars missions. Fast, automated, and robust computations are useful for investigating the preliminary design space and are necessary for eventual optimization of such a system.
Analysis of Inviscid Simulations for the Study of Supersonic Retropropulsion,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Traditionally, span-wise load distribution on a wing or the axial load distribution on a rocket is computed using approximations that utilize a combination of theory and empirical observations. The present effort describes a method with which sectional loads can be efficiently computed along an arbitrary direction from a computational fluid dynamics simulation.
Computation of Sectional Loads from Surface Triangulation and Flow Data,20th AIAA Computational Fluid Dynamics Conference, Honolulu, Hawaii, June 2011.

Some of the simulation work performed by the computational aerosciences project under the NASA Constellation program is presented. The challenges of simulating the powered flight of the Orion launch abort vehicle for the purposes of building an aerodynamics database are discussed.
Computational Challenges in Simulating Powered Flight of the Orion Launch Abort Vehicle,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Developing a Near-Field Cylindrically-Shaped, Mesh Projecting a Layered Cylindrically-Shaped Prism Mesh, Shearing & Stretching of the Prismatic Grid, Circumferential Refinement of Outer Prismatic Grid
Evaluation of Refined Tetrahedral Meshes with Projected, Stretched, and Sheared Prism Layers for Sonic Boom Analysis,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Recent developments in strategies and software tools for overset structured grid generation and domain connectivity are described. A scripting approach based on a library of grid generation script macros is adopted to speed up the grid generation process.
Developments in Strategies and Software Tools for Overset Structured Grid Generation and Connectivity,20th AIAA Computational Fluid Dynamics Conference, Honolulu, Hawaii, June 2011.

An engineering approach is presented for database generation of aerodynamic force and moment coefficients on Solid Rocket Boosters (SRBs) during separation from a Heavy Lift Launch Vehicle. The approach balances accuracy and affordability by generating a steady- state database of solutions using the inviscid flow solver Cart3D with adjoint based adaptive mesh refinement.
Aerodynamic Database Generation for SRB Separation from a Heavy Lift Launch Vehicle,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Time-accurate high-fidelity Computational Fluid Dynamics (CFD) simulations of the launch environment are an important part of the successful launch of new and existing space vehicles. The capability to accurately predict certain aspects of the launch environment, such as ignition overpressure (IOP) waves and launch acoustics, is paramount to mission success.
Space-Time Accuracy Assessment of CFD Simulations for the Launch Environment,29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

A procedure is developed to generate a large aerodynamic database suitable for the static stability analysis of launch vehicles in the transonic regime by using the Navier-Stokes equations. Effects of structural deformations are also included using modal representation.
Large-Scale Computations for Stability Analysis of Launch Vehicles Using Cluster Computers,Journal of Spacecraft and Rockets, Vol. 48, No. 4, July-August 2011.

Intel provides Hyper-Threading (HT) in processors based on its Pentium and Nehalem micro-architecture such as the Westmere-EP. HT enables two threads to execute on each core in order to hide latencies related to data access. These two threads can execute simultaneously, filling unused stages in the functional unit pipelines.
The Impact of Hyper-Threading on Processor Resource Utilization in Production Applications,IEEE HIPC Conference, Bangalore, India, December 2011.