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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1998

Development of an Aeroelastic Analysis Including a Viscous Flow Model

Under this grant, the flutter versions of the three-dimensional Navier-Stokes aeroelastic code (TURBO-AE) have been developed. The TURBO-AE aeroelastic code allows flutter calculations for a fan, compressor, or turbine blade row. This code models a vibrating three-dimensional bladed disk geometry and the associated unsteady flow (including shocks, and viscous effects) to calculate the aeroelastic instability using a work-per-cycle or eigenvalue approach. Steady and unsteady calculations have been performed with the 3D Navier-Stokes (TURBO) code to gain familiarity with the code. Calculations were done with the NASA Rotor-67 configuration which has been used as a standard test case by turbomachinery researchers. Additional calculations have been performed for the NASA/GE EEE fan and a proprietary configuration.

Keith, Theo G., Jr.↗

NASA NTRSDate not supplied

Development of Physics-Based Transition Models for Unstructured-Mesh CFD Codes Using Deep Learning Models

Predicting transition locations over a vehicle surface is of fundamental importance for many engineering applications. With the transition information, the Reynolds-averaged Navier-Stokes (RANS) computations can turn on the turbulence model at the right locations so that drag, lift and other aerodynamic quantities can be accurately predicted. In contrast to the popularity of RANS-based transition modeling in which transition onset is governed by the turbulence equations, physics-based transition models that account for instability waves within the boundary layer, thus more compliant to flow physics, only gained more attention in recent years. This paper describes the development of a new physics-based transition model based on either the linear stability theory (LST) or parabolized stability equations (PSE). The model is designed to communicate with a structured or unstructured-mesh RANS solver back and forth in order to more accurately compute transition fronts over a three-dimensional body. In the developed model, the Python suite of interface codes in conjunction with the LASTRAC software can be executed autonomously to produce transition onset locations for a given laminar or RANS-computed transitional state. In addition, as a proof of concept, the tool set consists of a deep learning neural network model that has been designed and trained to predict instability wave evolutions inside the boundary layer for various instability wave mechanisms across a selected speed range. A machine-learned intelligent profile interpolation model has also been devised to enable reliable instability-wave spectra predictions with just a few points in the mean flow profiles.

Transition Modeling↗

NASA NTRS1992

Finite difference time domain grid generation from AMC helicopter models

A simple technique is presented which forms a cubic grid model of a helicopter from an Aircraft Modeling Code (AMC) input file. The AMC input file defines the helicopter fuselage as a series of polygonal cross sections. The cubic grid model is used as an input to a Finite Difference Time Domain (FDTD) code to obtain predictions of antenna performance on a generic helicopter model. The predictions compare reasonably well with measured data.

Cravey, Robin L.↗

NASA NTRS1979

Development of a Model and Computer Code to Describe Solar Grade Silicon Production Processes

The program aims at developing mathematical models and computer codes based on these models, which allow prediction of the product distribution in chemical reactors for converting gaseous silicon compounds to condensed-phase silicon. The major interest is in collecting silicon as a liquid on the reactor walls and other collection surfaces. Two reactor systems are of major interest, a SiCl4/Na reactor in which Si(l) is collected on the flow tube reactor walls and a reactor in which Si(l) droplets formed by the SiCl4/Na reaction are collected by a jet impingement method. During this quarter the following tasks were accomplished: (1) particle deposition routines were added to the boundary layer code; and (2) Si droplet sizes in SiCl4/Na reactors at temperatures below the dew point of Si are being calculated.

Srivastava, R.↗

NASA NTRS1990

Radial diffusion models of energetic electrons and Jupiter's synchrotron radiation. I - Steady state solution

The results of a computer code modeling of the radial diffusion of equatorially confined energetic electrons in Jupiter's inner magnetosphere are compared with spacecraft as well as ground-based radio (synchrotron radiation) data. It is found that the synchrotron radiation spectrum cannot be reproduced without a significant hardening of the electron spectrum between L = 3 and L = 1.5. This hardening may be due to energy degradation by Jupiter's ring particles. The calculations also suggest that there may be larger-sized material outside Jupiter's ring up to L of about 4 or Io's orbit.

De Pater, Imke↗

NASA NTRS2004

Space Applications of the FLUKA Monte-Carlo Code: Lunar and Planetary Exploration

NASA has recognized the need for making additional heavy-ion collision measurements at the U.S. Brookhaven National Laboratory in order to support further improvement of several particle physics transport-code models for space exploration applications. FLUKA has been identified as one of these codes and we will review the nature and status of this investigation as it relates to high-energy heavy-ion physics.

Anderson, V.↗

NASA NTRS1992

Three-dimensional numerical modeling of indium phosphide Point-Contact Solar Cells

The Point-Contact Solar Cell (PCSC) geometry has proven very effective for silicon cells. To date, it has not been implemented in III-V materials. In addition, modeling such a geometry is very difficult because of its three-dimensional nature. We have developed a three-dimensional finite element modeling code (FIESTA ROC). In this paper, we present results from a three-dimensional modeling study of InP point-contact solar cells.

Clark, Ralph O.↗

NASA NTRS1994

Lidar performance analysis

Section 1 details the theory used to build the lidar model, provides results of using the model to evaluate AEOLUS design instrument designs, and provides snapshots of the visual appearance of the coded model. Appendix A contains a Fortran program to calculate various forms of the refractive index structure function. This program was used to determine the refractive index structure function used in the main lidar simulation code. Appendix B contains a memo on the optimization of the lidar telescope geometry for a line-scan geometry. Appendix C contains the code for the main lidar simulation and brief instruction on running the code. Appendix D contains a Fortran code to calculate the maximum permissible exposure for the eye from the ANSI Z136.1-1992 eye safety standards. Appendix E contains a paper on the eye safety analysis of a space-based coherent lidar presented at the 7th Coherent Laser Radar Applications and Technology Conference, Paris, France, 19-23 July 1993.

Spiers, Gary D.↗

NASA NTRS1992

LDEF's map experiment foil perforations yield hypervelocity impact penetration parameters

The space exposure of LDEF for 5.75 years, forming a host target in low earth orbit (LEO) orbit to a wide distribution of hypervelocity particulates of varying dimensions and different impact velocities, has yielded a multiplicity of impact features. Although the projectile parameters are generally unknown and, in fact not identical for any two impacts on a target, the great number of impacts provides statistically meaningful basis for the valid comparison of the response of different targets. Given sufficient impacts for example, a comparison of impact features (even without knowledge of the project parameters) is possible between: (1) differing material types (for the same incident projectile distribution); (2) differing target configurations (e.g., thick and thin targets for the same material projectiles; and (3) different velocities (using LDEF's different faces). A comparison between different materials is presented for infinite targets of aluminum, Teflon, and brass in the same pointing direction; the maximum finite-target penetration (ballistic limit) is also compared to that of the penetration of similar materials comprising of a semi-infinite target. For comparison of impacts on similar materials at different velocities, use is made of the pointing direction relative to LDEF's orbital motion. First, however, care must be exercised to separate the effect of spatial flux anisotropies from those resulting from the spacecraft velocity through a geocentrically referenced dust distribution. Data comprising thick and thin target impacts, impacts on different materials, and in different pointing directions is presented; hypervelocity impact parameters are derived. Results are also shown for flux modeling codes developed to decode the relative fluxes of Earth orbital and unbound interplanetary components intercepting LDEF. Modeling shows the west and space pointing faces are dominated by interplanetary particles and yields a mean velocity of 23.5 km/s at LDEF, corresponding to a V(infinity) Earth approach velocity = 20.9 km/s. Normally resolved average impact velocities on LDEF's cardinal point faces are shown. As 'excess' flux on the east, north, and south faces is observed, compatible with an Earth orbital component below some 5 microns in particle diameter.

Mcdonnell, J. A. M.↗

NASA NTRSDate not supplied

Mechanics of Structure Genome-Based Nonlinear Shell Analysis

In this paper, a mechanics of structure genome (MSG)-based nonlinear shell theory is introduced. The theory uses an implicit algorithm combining the Euler’s and Newton’s method that can be applied for shell modeling as well as 3D homogenization. This theory has been implemented into the general-purpose constitutive modeling code SwiftComp, which was originally developed for linear analyses. For the convenience of implementing different nonlinear material models, the SwiftComp user material (SCUMAT), which has a similar interface to the Abaqus user subroutine UMAT, is developed. The capability of the MSG-based nonlinear shell is validated with numerical examples with different material models. A 2-step nonlinear homogenization, with a micromechanics step and a shell analysis step, is demonstrated.

Yufei Long↗

NASA NTRS1988

A new look at coding for APD-based direct-detection optical channels

Coding for avalanche-photodiode (APD)-based direct-detection optical channels is investigated using a simple channel model that clearly points out the difference between the signal-dependent optical noise channel model and the additive white Gaussian noise channel model. Coding and modulation are viewed as a single entity, and the coding/modulation gain (CMG) is used to analyze and construct good codes for APD-based optical receivers. It is shown that the structure of block codes, when used in conjunction with on-off keying signaling, renders these codes fairly inefficient with respect to obtaining reasonable CMG on the optical channel. In contrast, codes (or modulations) that use fewer channel ones (pulses) than information ones per block can offer substantial CMG on the optical channel. For bandwidth-constrained applications, it is proposed that pulse-position modulation be used with more than one pulse per word to obtain reasonable CMG while consuming small amounts of bandwidth.

Herro, Mark A.↗

NASA NTRS2012

Thermal Analysis of Small Re-Entry Probe

The Small Probe Reentry Investigation for TPS Engineering (SPRITE) concept was developed at NASA Ames Research Center to facilitate arc-jet testing of a fully instrumented prototype probe at flight scale. Besides demonstrating the feasibility of testing a flight-scale model and the capability of an on-board data acquisition system, another objective for this project was to investigate the capability of simulation tools to predict thermal environments of the probe/test article and its interior. This paper focuses on finite-element thermal analyses of the SPRITE probe during the arcjet tests. Several iterations were performed during the early design phase to provide critical design parameters and guidelines for testing. The thermal effects of ablation and pyrolysis were incorporated into the final higher-fidelity modeling approach by coupling the finite-element analyses with a two-dimensional thermal protection materials response code. Model predictions show good agreement with thermocouple data obtained during the arcjet test.

Agrawal, Parul↗

NASA NTRS2004

Infrared Spectroscopy of Star Formation in Galactic and Extragalactic Regions

Last year we submitted and had accepted a paper entitled "The Far-Infrared Emission Line and Continuum Spectrum of the Seyfert Galaxy NGC 1068," by Spinoglio, L., Malkan, M., Smith. HA, Gonzalez-Alfonso, E., and Fischer, J. This analysis was based on the SWAS Monte Carlo code modeling of the OH lines in galaxies observed by ISO. Since that meeting last spring considerable effort has been put into improving the Monte Carlo code. A group of European astronomers, including Prof. Eduardo Gonzalez-Alfonso, had been performing Monte Carlo modeling of other molecules seen in ISO galaxies. We used portions of this grant to bring Prof. Gonzalez-Alfonso to Cambridge for an intensive working visit. A second major paper on the ISO IR spectroscopy of galaxies, "The Far Infrared Spectrum of Arp 220," Gonzalez-Alfonso, E., Smith. H., Fischer, J., and Cernicharo, J., is in press. Spitzer science development was the major component of this past year;s research. This program supported the development of five Early Release Objects for Spitzer observations on which Dr. Smith was Principal Investigator or Co-Investigator, and another five proposals for GO time. The early release program is designed to rapidly present to the public and the scientific community some exciting results from Spitzer in the first months of its operation. The Spitzer instrument and science teams submitted proposals for ERO objects, and a competitive selection process narrowed these down to a small group with exciting science and realistic observational parameters. This grant supported Dr. Smith's participation in the ERO process, including developing science goals, identifying key objects for observation, and developing the detailed AOR (observing formulae) to be use by the instruments for mapping, integrating, etc.). During this year Dr. Smith worked on writing up and publishing these early results. The attached bibliography includes six of Dr. Smith's articles. During this past year Dr. Smith also led or helped to develop proposals for ten Spitzer GO Programs, and three others. Appendix B lists the programs involved.

Smith, Howard A.↗

NASA NTRS2002

Finite Element Modeling of the NASA Langley Aluminum Testbed Cylinder

The NASA Langley Aluminum Testbed Cylinder (ATC) was designed to serve as a universal structure for evaluating structural acoustic codes, modeling techniques and optimization methods used in the prediction of aircraft interior noise. Finite element models were developed for the components of the ATC based on the geometric, structural and material properties of the physical test structure. Numerically predicted modal frequencies for the longitudinal stringer, ring frame and dome component models, and six assembled ATC configurations were compared with experimental modal survey data. The finite element models were updated and refined, using physical parameters, to increase correlation with the measured modal data. Excellent agreement, within an average 1.5% to 2.9%, was obtained between the predicted and measured modal frequencies of the stringer, frame and dome components. The predictions for the modal frequencies of the assembled component Configurations I through V were within an average 2.9% and 9.1%. Finite element modal analyses were performed for comparison with 3 psi and 6 psi internal pressurization conditions in Configuration VI. The modal frequencies were predicted by applying differential stiffness to the elements with pressure loading and creating reduced matrices for beam elements with offsets inside external superelements. The average disagreement between the measured and predicted differences for the 0 psi and 6 psi internal pressure conditions was less than 0.5%. Comparably good agreement was obtained for the differences between the 0 psi and 3 psi measured and predicted internal pressure conditions.

Grosveld, Ferdinand W.↗

NASA NTRS2023

Utilizing Code Generation from Models for Electric Aircraft Motor Controller Flight Software

The processes followed to develop and test safety-critical flight software significantly increase development effort and overhead in comparison to both non-safety-critical and non-flight software. Generating code from models can be used to reduce development effort; however, the processes for using code generation to develop flight software are relatively immature. This work presents an approach for developing safety-critical flight software utilizing code generation from models to reduce development time and effort. The presented use-case is of electric aircraft motor control software developed for NASA's X-57 Maxwell aircraft.

flight software↗

NASA NTRS2006

Finite and Boundary Element Modeling of the NASA Langley Aluminum Testbed Cylinder (ATC)

Grosveld, Ferdinand W.↗

NASA NTRS2002

2-D Magnetohydrodynamic Modeling of A Pulsed Plasma Thruster

Experiments are being performed on the NASA Marshall Space Flight Center (MSFC) MK-1 pulsed plasma thruster. Data produced from the experiments provide an opportunity to further understand the plasma dynamics in these thrusters via detailed computational modeling. The detailed and accurate understanding of the plasma dynamics in these devices holds the key towards extending their capabilities in a number of applications, including their applications as high power (greater than 1 MW) thrusters, and their use for producing high-velocity, uniform plasma jets for experimental purposes. For this study, the 2-D MHD modeling code, MACH2, is used to provide detailed interpretation of the experimental data. At the same time, a 0-D physics model of the plasma initial phase is developed to guide our 2-D modeling studies.

Thio, Y. C. Francis↗

NASA NTRS2002

An Experimental Study of a Pulsed Electromagnetic Plasma Accelerator

Experiments are being performed on the NASA Marshall Space Flight Center (MSFC) pulsed electromagnetic plasma accelerator (PEPA-0). Data produced from the experiments provide an opportunity to further understand the plasma dynamics in these thrusters via detailed computational modeling. The detailed and accurate understanding of the plasma dynamics in these devices holds the key towards extending their capabilities in a number of applications, including their applications as high power (greater than 1 MW) thrusters, and their use for producing high-velocity, uniform plasma jets for experimental purposes. For this study, the 2-D MHD modeling code, MACH2, is used to provide detailed interpretation of the experimental data. At the same time, a 0-D physics model of the plasma initial phase is developed to guide our 2-D modeling studies.

Thio, Y. C. Francis↗