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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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At least 1,009 records · Page 56

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NASA NTRS1991

A multi-passage three-dimensional Navier-Stokes simulation of turbine rotor-stator interaction

This paper deals with the development and validation of a 3D multipassage Navier-Stokes code for predicting the unsteady effects due to rotor-stator interaction in turbomachines. Prior work in two dimensions has demonstrated the necessity of including multiple rotor and stator passages in order to closely approximate the stator-to-rotor airfoil count ratio and thus accurately predict the unsteady flowfield resulting from rotor-stator interaction. In the present paper, this multipassage capability is extended to three dimensions. Numerical results obtained from a multipassage (three stator and four rotor passage) calculation of an axial turbine stage are presented. The stator-to-rotor airfoil count ratio (3:4) used in the present calculations is a close approximation to that in the actual turbine configuration (22:28). The present multipassage calculation results in a more accurate prediction of the unsteady flowfield than that possible from a single-passage calculation.

Madavan, N. K.↗

NASA NTRS1993

A determination of the external forces required to move the benchmark active controls testing model in pure plunge and pure pitch

In view of the strong need for a well-documented set of experimental data which is suitable for the validation and/or calibration of modern Computational Fluid Dynamics codes, the Benchmark Models Program was initiated by the Structural Dynamics Division of the NASA Langley Research Center. One of the models in the program, the Benchmark Active Controls Testing Model, consists of a rigid wing of rectangular planform with a NACA 0012 profile and three control surfaces (a trailing-edge control surface, a lower-surface spoiler, and an upper-surface spoiler). The model is affixed to a flexible mount system which allows only plunging and/or pitching motion. An approximate analytical determination of the forces required to move this model, with its control surfaces fixed, in pure plunge and pure pitch at a number of test conditions is included. This provides a good indication of the type of actuator system required to generate the aerodynamic data resulting from pure plunging and pure pitching motion, in which much interest was expressed. The analysis makes use of previously obtained numerical results.

Dcruz, Jonathan↗

NASA NTRS1993

The annual pressure cycle on Mars: Results from the LMD Martian atmospheric general circulation model

We have been developing a General Circulation Model (GCM) of the martian atmosphere since 1989. The model has been described rather extensively elsewhere and only the main characteristics are given here. The dynamical part of the model, adapted from the LMD terrestrial climate model, is based on a finite-difference formulation of the classical 'primitive equations of meteorology.' The radiative transfer code includes absorption and emission by CO2 (carefully validated by comparison to line-by-line calculations) and dust in the thermal range and absorption and scattering by dust in the visible range. Other physical parameterizations are included: modeling of vertical turbulent mixing, dry convective adjustment (in order to prevent vertical unstable temperature profiles), and a multilayer model of the thermal conduction in the soil. Finally, the condensation-sublimation of CO2 is introduced through specification of a pressure-dependent condensation temperature. The atmospheric and surface temperatures are prevented from falling below this critical temperature by condensation and direct precipitation onto the surface of atmospheric CO2. The only prespecified spatial fields are the surface thermal inertia, albedo, and topography.

Hourdin, Frederic↗

NASA NTRS1995

Investigation of infra-red and nonequilibrium air radiation

This report describes progress on the first year of a research program on the infrared radiation of air plasmas conducted in the High Temperature Gasdynamics Laboratory at Stanford University. This program is intended to investigate the masking of infrared signatures by the air plasma formed behind the bow shock of high velocity missiles. To this date, the radiative emission of air plasmas in the infrared has been the object of few experimental investigations, and although several infrared systems are already modeled in radiation codes such as NEQAIR, measurements are required to validate numerical predictions and indicate whether all transitions of importance are accounted for. The present program is motivated by the fact that 9 excited states (A, B, C, D, B', F, H, and H') of NO radiate in the infrared, especially between 1 and 1.5 microns where at least 9 transitions involving can be observed. Because these IR transitions are relatively well separated from each other, excited NO states concentrations can be easily measured, thus providing essential information on excited-state chemistry for use in optical diagnostics or in electronic excitation model validation. Developing accurate collisional-radiative models for these excited NO states is of importance as the UV-VUV transitions of NO (beta, gamma, epsilon, beta prime, gamma prime) produce a major, if not dominant, fraction of the radiation emitted by air plasmas. During the first year of the program, research has focused on the spectral range 1.0 to 1.5 microns, as detailed in Section 2 of this report. The measurements, conducted in a 50 kW radio-frequency inductively coupled plasma torch operating on air at atmospheric pressure, extend previous shock tube investigations by Wray to a wider spectral range (1.0 to 1.5 microns vs 0.9 to 1.2 microns) and higher temperatures (7600 K in the plasma torch versus 6700 K in the shock-tube). These higher temperatures in the present experiment have made it possible to observe high-lying excited NO states that were previously undetectable. These measurements are currently being extended up to 5 microns, with particular attention paid to the rovibronic bands of ground state NO, molecular continua, CO transitions, and other systems of importance. Publications and presentations resulting from or related to this work are cited in Section 3, and Section 4 lists the personnel who contributed to this report.

Kruger, Charles H.↗

NASA NTRS1994

Investigation of Infra-red and Nonequilibrium Air Radiation

This report summarizes the results obtained during a research program on the infrared radiation of air plasmas conducted in the High Temperature Gasdynamics Laboratory at Stanford University. This program was intended to investigate the masking of infrared signatures by the air plasma formed behind the bow shock of high velocity missiles. Prior to this work, the radiative emission of air plasmas in the infrared had been the object of few experimental investigations, and although several infrared systems were already modeled in radiation codes such as NEQAIR, measurements were required to validate numerical predictions and indicate whether all transitions of importance were accounted for in the model. The program was further motivated by the fact that 9 excited states (A, B, C, D, B', F, H, and H') of NO radiate in the infrared, especially between 1 and 1.5 microns where at least 9 transitions involving can be observed. Because these IR transitions are relatively well separated from each other, excited NO states concentrations can be easily measured, thus providing essential information on excited-state chemistry for use in optical diagnostics or in electronic excitation model validation. Detailed comparisons between measured and simulated spectra are presented.

Kruger, Charles H.↗

NASA NTRS1998

MODIS Science Team Member Semi-annual Report

This paper presents a semi-annual report of the MODerate resolution imaging Spectroradiometer (MODIS) Science Team Members. The most important activities undertaken during this reporting period are the following: 1) Versions 2.1 and 2.2 surface reflectance L2/L3 DAAC/SDST delivery; 2) Version 2.0 1km and 250m VI product delivery (assist Arizona); 3) Version 2.1 surface reflectance L2 testing; 4) Land Synthetic data set generator improvements; 5) QA; 6) Surface reflectance error budget generation (SWAMP request); 7) SCF Hardware; 8) Aerosol transport modeling; 9) Aerosol optical depth retrieval from AVHRR data; 10) Aerosol characteristics retrieval from SeaWIFS/AVHRR fusioned data; 11) Validation activities; 12) Aerosol climatology; and 13) 6S code. The report includes summaries of the topics above.

Vermote, Eric↗

NASA NTRS2001

Rotor Broadband Noise Prediction with Comparison to Model Data

This paper reports an analysis and prediction development of rotor broadband noise. The two primary components of this noise are Blade-Wake Interaction (BWI) noise, due to the blades' interaction with the turbulent wakes of the preceding blades, and "Self" noise, due to the development and shedding of turbulence within the blades' boundary layers. Emphasized in this report is the new code development for Self noise. The analysis and validation employs data from the HART program, a model BO-105 rotor wind tunnel test conducted in the German-Dutch Wind Tunnel (DNW). The BWI noise predictions are based on measured pressure response coherence functions using cross-spectral methods. The Self noise predictions are based on previously reported semiempirical modeling of Self noise obtained from isolated airfoil sections and the use of CAMRAD.Modl to define rotor performance and local blade segment flow conditions. Both BWI and Self noise from individual blade segments are Doppler shifted and summed at the observer positions. Prediction comparisons with measurements show good agreement for a range of rotor operating conditions from climb to steep descent. The broadband noise predictions, along with those of harmonic and impulsive Blade-Vortex Interaction (BVI) noise predictions, demonstrate a significant advance in predictive capability for main rotor noise.

Brooks, Thomas F.↗

NASA NTRS2001

Photochemical Phenomenology Model for the New Millennium

The "Photochemical Phenomenology Model for the New Millennium" project tackles the issue of reengineering and extension of validated physics-based modeling capabilities ("legacy" computer codes) to application-oriented software for use in science and science-support activities. While the design and architecture layouts are in terms of general particle distributions involved in scattering, impact, and reactive interactions, initial Photochemical Phenomenology Modeling Tool (PPMT) implementations are aimed at construction and evaluation of photochemical transport models with rapid execution for use in remote sensing data analysis activities in distributed systems. Current focus is on the Composite Infrared Spectrometer (CIRS) data acquired during the CASSINI flyby of Jupiter. Overall, the project has stayed on the development track outlined in the Year 1 annual report and most Year 2 goals have been met. The issues that have required the most attention are: implementation of the core photochemistry algorithms; implementation of a functional Java Graphical User Interface; completion of a functional CORBA Component Model framework; and assessment of performance issues. Specific accomplishments and the difficulties encountered are summarized in this report. Work to be carried out in the next year center on: completion of testing of the initial operational implementation; its application to analysis of the CASSINI/CIRS Jovian flyby data; extension of the PPMT to incorporate additional phenomenology algorithms; and delivery of a mature operational implementation.

Bishop, James↗

NASA NTRS2004

Numerical Modeling of Active Flow Control in a Boundary Layer Ingesting Offset Inlet

This investigation evaluates the numerical prediction of flow distortion and pressure recovery for a boundary layer ingesting offset inlet with active flow control devices. The numerical simulations are computed using a Reynolds averaged Navier-Stokes code developed at NASA. The numerical results are validated by comparison to experimental wind tunnel tests conducted at NASA Langley Research Center at both low and high Mach numbers. Baseline comparisons showed good agreement between numerical and experimental results. Numerical simulations for the inlet with passive and active flow control also showed good agreement at low Mach numbers where experimental data has already been acquired. Numerical simulations of the inlet at high Mach numbers with flow control jets showed an improvement of the flow distortion. Studies on the location of the jet actuators, for the high Mach number case, were conducted to provide guidance for the design of a future experimental wind tunnel test.

Allan, Brian G.↗

NASA NTRS1997

Viscous Effects in the Elastodynamics of Thick Beams

A viscoelastic higher-order thick beam finite element formulation is extended to include elastodynamic deformations. The material constitutive law is a special differential form of the Maxwell solid. In the constitutive model, the elastic strains and the conjugate viscous strains are coupled through a system of first- order ordinary differential equations. The total time-dependent stress is the superposition of its elastic and viscous components. The elastodynamic equations of motion are derived from the virtual work principle. Computational examples are carried out for a thick orthotropic cantilevered beam. A quasi-static relaxation problem is employed as a validation test for the elastodynamic algorithm. The elastodynamic code is demonstrated by analyzing the damped vibrations of the beam which is deformed and then released to freely vibrate.

Johnson, A. R.↗

NASA NTRS2006

Meteoroid Risk Assessment of Lunar Habitat Concepts

Preliminary analyses have been performed of meteoroid impacts on lunar surface structures built with elements made from in situ materials. The SPHC hydrodynamic code was used to simulate impacts, and was validated against hypervelocity impact test results. Impact risk will affect necessary wall thicknesses, depth of burial, and placement of lunar base structures.

Evans, Steven W.↗

NASA NTRS2006

A Dynamic/Anisotropic Low Earth Orbit (LEO) Ionizing Radiation Model

The International Space Station (ISS) provides the proving ground for future long duration human activities in space. Ionizing radiation measurements in ISS form the ideal tool for the experimental validation of ionizing radiation environmental models, nuclear transport code algorithms, and nuclear reaction cross sections. Indeed, prior measurements on the Space Transportation System (STS; Shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the Low Earth Orbit (LEO) environment. Previous studies using Computer Aided Design (CAD) models of the evolving ISS configurations with Thermo Luminescent Detector (TLD) area monitors, demonstrated that computational dosimetry requires environmental models with accurate non-isotropic as well as dynamic behavior, detailed information on rack loading, and an accurate 6 degree of freedom (DOF) description of ISS trajectory and orientation.

Badavi, Francis F.↗

NASA NTRS2006

Adapting Analysis Tools to Engine Externals Analysis

Market forces are driving industry to reproduce product cycle time (the time required to conceive, design, build, test, validate and deliver a product). Application of existing tools in new areas can reduce the time required to design a new product and increase the confidence of acceptable test results later in the expensive testing and validation phase. Finite element methods, computational fluid dynamics codes and sharing of CAD datasets when applied to the design of engine externals can provide methods for product improvement and expedited delivery to the customer.

Dunkelberg, Ken↗

NASA NTRS2012

As-Flown Shuttle Micro-Meteoroid Orbital Debris (MMOD) Assessment History

The final flight of the Space Shuttle program was completed on July 21st of 2011. The reusable nature of the Orbiter vehicles has provided NASA with a unique opportunity to inspect and sample spacecraft surfaces exposed to the MMOD environment in low Earth orbit. This paper will provide details of MMOD damages found on Orbiter surfaces after recent flights, as well as putting these damages in context by providing historical comparisons of recent damage to previous flights. The Bumper threat assessment computer code is used by NASA to determine spacecraft MMOD penetration risk. The tool was used before each mission to estimate pre-flight MMOD risk for the Shuttle Program Office using planned vehicles attitudes and exposure times. This paper summarizes the efforts of the authors to assess the expected number MMOD impacts of selected particles sizes of 52 shuttle missions ranging from STS-50 (1992) through STS-133 (2011) using as-flown attitude data. The missions encompass the Shuttle/Mir precursors to the International Space Station (ISS) as well as the ISS assembly flights. The paper includes a comparison of observed MMOD impact damage to the predicted number of impacts from Bumper code assessments. This data can be used to validate engineering models of the orbital debris and micrometeoroid environment, such NASA s ORDEM debris model and MEM meteoroid model.

Hyde, James L.↗

NASA NTRS2018

Overview of Recent EAST Testing, Modeling & Analysis

Shock Layer Radiation at NASA Ames - Background: Complex aerothermal and thermochemical phenomena of planetary entry define convective and radiative heating. A spacecraft's TPS (Thermal Protective System) mitigates heat transfer to substructure. Successful TPS design relies on verifiable characterization of these phenomena in the anticipated flight environment. - Approach: EAST (Electric Arc Shock Tube) [facility at Ames] simulates high-enthalpy, real-gas phenomena encountered by hypersonic vehicles entering planetary atmospheres by spectrally imaging the flow behind a moving shock wave. - Goal: Validate aerothermal models (DPLR (Data Parallel Line Relaxation Code) and NEQAIR (Nonequilibrium Radiative Transport and Spectra Program)), inform model improvements, reduce uncertainty and quantify design uncertainties. - Recent Relevant Projects: MSL (Mars Science Laboratory) & Mars 2020, InSight, OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security Regolith Explorer), Orion EFT-1 (Exploration Flight-1) and EM-1 (Exploration Mission-1) and New Frontiers.

Brandis, Aaron↗

NASA NTRS2019

Preliminary Soot Computations Based on a Model Aircraft Combustor With OpenNCC

In a preliminary effort to extend our current capabilities used in the design & testing of aero-engine combustors to particulate emissions, we incorporated several existing 2- equation soot models into the Open National Combustion Code (OpenNCC). The paper presents results from a validation study based on a well-characterized, swirl-stabilized, turbulent sooting flame generated by a model aero-engine combustor developed at DLR, Germany. The calculations are based on a Reynolds-Averaged Navier Stokes (RANS) simulation with standard k-e turbulence model & a finite-rate chemical kinetic mechanism. A separate transport equation is solved for all individual species involved in ethylene/air combustion. The predicted velocity and temperature are mostly in good agreement with the measured data and reasonable agreement was found for soot. While the calculated SVF (Soot Volume Fraction) behavior is similar to some other predicted results reported in literature, the measured soot lasts farther downstream than the calculated soot indicating a need for further improvement in the soot models employed.

Raju, Manthena↗

NASA NTRSDate not supplied

Pretest Simulations of a Supersonic Mixing and Combustion Validation Experiment to Assess Sensitivities

The reliance on CFD simulations to develop, design, and optimize scramjet systems (or components) has become commonplace. This reliance inevitably hinges on the ability of the computational analyst to quantify the level of confidence in their computational results. Unfortunately, nearly all the measured data available for this assessment comes from antiquated experimental datasets, or from tests that focused on the extraction of scramjet system (or component) performance. The objective of a CFD validation experiment is to quantify the predictive accuracy of one or more of the CFD physics submodels, implying that other uncertainties related to replicating the facility flow environment (e.g., knowledge of boundary conditions) must be minimized to the extent possible. This inevitably places stringent requirements on the quality and quantity of measurements taken to accurately specify inflow, outflow, and surface conditions for the CFD simulations; in addition to the measurements taken for the validation of physics submodels. This places additional demands on the experimental process above and beyond those for test article performance assessment. A recent high speed code credibility workshop series sponsored by AFRL identified a gap in existing validation data for fundamental assessments of turbulent mixing and combustion CFD closure models at scramjet engine relevant conditions. To address this gap, engineers at AFRL have designed a coaxial jet flame configuration that will be tested at two facilities (Research Cell 19 at the Air Force Research Lab, and at Purdue University). The effort described here documents pretest simulations of this validation experiment with the goal of fleshing out the extent of the facility flowpath that must be included to adequately reproduce the facility test section flow environment. The findings indicate that the flow around the support structure for the fuel injection centerbody upstream of the facility nozzle generates disturbances that persist throughout the nozzle expansion process; corrupting the azimuthal symmetry that was desired in the fuel/air mixing region of the test section. Simulations without this support structure maintained a high degree of azimuthal symmetry up until the fuel injection plane. However, even in this scenario the azimuthal symmetry was not maintained once the centerbody boundary layer transitioned to a wake flow downstream of the fuel injection plane.

CFD↗

NASA NTRSDate not supplied

Pretest Simulations of a Supersonic Mixing and Combustion Validation Experiment to Assess Sensitivities

CFD↗