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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Computation of Supersonic Jet Mixing Noise Using PARC Code With a kappa-epsilon Turbulence Model

A number of modifications have been proposed in order to improve the jet noise prediction capabilities of the MGB code. This code which was developed at General Electric, employees the concept of acoustic analogy for the prediction of turbulent mixing noise. The source convection and also refraction of sound due to the shrouding effect of the mean flow are accounted for by incorporating the high frequency solution to Lilley's equation for cylindrical jets (Balsa and Mani). The broadband shock-associated noise is estimated using Harper-Bourne and Fisher's shock noise theory. The proposed modifications are aimed at improving the aerodynamic predictions (source/spectrum computations) and allowing for the non- axisymmetric effects in the jet plume and nozzle geometry (sound/flow interaction). In addition, recent advances in shock noise prediction as proposed by Tam can be employed to predict the shock-associated noise as an addition to the jet mixing noise when the flow is not perfectly expanded. Here we concentrate on the aerodynamic predictions using the PARC code with a k-E turbulence model and the ensuing turbulent mixing noise. The geometry under consideration is an axisymmetric convergent-divergent nozzle at its design operating conditions. Aerodynamic and acoustic computations are compared with data as well as predictions due to the original MGB model using Reichardt's aerodynamic theory.

Khavaran, A.↗
NASA NTRS1981

Overview of advanced wing design

Examples of experiment theory correlation are presented to give an indication of the capabilities and limitations of wing design and analysis for transonic applications by potential flow theory. The examples include correlations of experimental pressure distributions with theoretical results from isolated wing codes and wing-body codes. Both conservative and non conservative differencing as well as body and boundary layer corrections are considered. A full potential isolated wing code correlates well with data from an isolated wing test but may give poor prediction of the aerodynamic characteristics of some wing-body configurations. Potential flow wing body codes were found to improve the correlation for the wing-body configurations considered.

Hicks, R. M.↗
NASA NTRS1991

Structural reliability methods: Code development status

The Probabilistic Structures Analysis Method (PSAM) program integrates state of the art probabilistic algorithms with structural analysis methods in order to quantify the behavior of Space Shuttle Main Engine structures subject to uncertain loadings, boundary conditions, material parameters, and geometric conditions. An advanced, efficient probabilistic structural analysis software program, NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) was developed as a deliverable. NESSUS contains a number of integrated software components to perform probabilistic analysis of complex structures. A nonlinear finite element module NESSUS/FEM is used to model the structure and obtain structural sensitivities. Some of the capabilities of NESSUS/FEM are shown. A Fast Probability Integration module NESSUS/FPI estimates the probability given the structural sensitivities. A driver module, PFEM, couples the FEM and FPI. NESSUS, version 5.0, addresses component reliability, resistance, and risk.

Millwater, Harry R.↗
NASA NTRS1988

Autonomous star identification for spacecraft attitude control

Research is being conducted to enhance the Advanced Star and Target Reference Optical Scanner (ASTROS I) so that it will be able to automatically track a star and recognize the star's pointing position. Previously developed field identification algorithms, coded on a flight-scale computer, are linked to a breadboard ASTROS star tracker to calculate pointing vectors in real time. A simple graph-searching algorithm was used in an initial study to find stellar positions based on pattern recognition. Results from this study and plans for further development are presented.

Rappaport, Barry↗
NASA NTRS1992

Numerical simulation of a low-emission gas turbine combustor using KIVA-II

A modified version of the KIVA-II code was used to obtain a multidimensional numerical solution for the turbulent two-phase chemically reacting flows inside a staged turbine combustor (STC). The STC under consideration is equipped with an advanced airblast fuel nozzle and encompasses a fuel nozzle (FN), a rich-burn (RB) zone, a converging connecting pipe, a quick-quench (QQ) zone, a diverging connecting pipe, and a lean-combustion (LC) zone. The STC was divided into two subsystems, namely, FN/RB zone and QQ/LC zones, and the numerical solutions were obtained separately for each subsystem. Preliminary data characterize the major features of the flow and temperature fields inside the STC. Information on velocity, temperature, and some critical species in the FN/RB zone is presented. In the QQ/LC zones, formation of the co- and counter-rotating bulk flow and the sandwiched-ring-shaped temperature field can be clearly seen. The calculations of the mass-weighted standard deviation and the pattern factor of temperature indicated that the mixing performance of the STC is very promising.

Yang, S. L.↗
NASA NTRS1994

Advanced End-to-end Simulation for On-board Processing (AESOP)

Developers of data compression algorithms typically use their own software together with commercial packages to implement, evaluate and demonstrate their work. While convenient for an individual developer, this approach makes it difficult to build on or use another's work without intimate knowledge of each component. When several people or groups work on different parts of the same problem, the larger view can be lost. What's needed is a simple piece of software to stand in the gap and link together the efforts of different people, enabling them to build on each other's work, and providing a base for engineers and scientists to evaluate the parts as a cohesive whole and make design decisions. AESOP (Advanced End-to-end Simulation for On-board Processing) attempts to meet this need by providing a graphical interface to a developer-selected set of algorithms, interfacing with compiled code and standalone programs, as well as procedures written in the IDL and PV-Wave command languages. As a proof of concept, AESOP is outfitted with several data compression algorithms integrating previous work on different processors (AT&T DSP32C, TI TMS320C30, SPARC). The user can specify at run-time the processor on which individual parts of the compression should run. Compressed data is then fed through simulated transmission and uncompression to evaluate the effects of compression parameters, noise and error correction algorithms. The following sections describe AESOP in detail. Section 2 describes fundamental goals for usability. Section 3 describes the implementation. Sections 4 through 5 describe how to add new functionality to the system and present the existing data compression algorithms. Sections 6 and 7 discuss portability and future work.

Mazer, Alan S.↗
NASA NTRS2011

Kinetic Simulation and Energetic Neutral Atom Imaging of the Magnetosphere

Advanced simulation tools and measurement techniques have been developed to study the dynamic magnetosphere and its response to drivers in the solar wind. The Comprehensive Ring Current Model (CRCM) is a kinetic code that solves the 3D distribution in space, energy and pitch-angle information of energetic ions and electrons. Energetic Neutral Atom (ENA) imagers have been carried in past and current satellite missions. Global morphology of energetic ions were revealed by the observed ENA images. We have combined simulation and ENA analysis techniques to study the development of ring current ions during magnetic storms and substorms. We identify the timing and location of particle injection and loss. We examine the evolution of ion energy and pitch-angle distribution during different phases of a storm. In this talk we will discuss the findings from our ring current studies and how our simulation and ENA analysis tools can be applied to the upcoming TRIO-CINAMA mission.

Fok, Mei-Ching H.↗
NASA NTRS2017

CFD Study of NACA 0018 Airfoil with Flow Control

The abilities of two different Reynolds-Averaged Navier-Stokes codes to predict the effects of an active flow control device are evaluated. The flow control device consists of a blowing slot located on the upper surface of an NACA 0018 airfoil, near the leading edge. A second blowing slot present on the airfoil near mid-chord is not evaluated here. Experimental results from a wind tunnel test show that a slot blowing with high momentum coefficient will increase the lift of the airfoil (compared to no blowing) and delay flow separation. A slot with low momentum coefficient will decrease the lift and induce separation even at low angles of attack. Two codes, CFL3D and FUN3D, are used in two-dimensional computations along with several different turbulence models. Two of these produced reasonable results for this flow, when run fully turbulent. A more advanced transition model failed to predict reasonable results, but warrants further study using different inputs. Including inviscid upper and lower tunnel walls in the simulations was found to be important in obtaining pressure distributions and lift coefficients that best matched experimental data. A limited number of three-dimensional computations were also performed.

Eggert, Christopher A.↗
NASA NTRS2017

Programmable Logic Device (PLD) Design Description for the Integrated Power, Avionics, and Software (iPAS) Space Telecommunications Radio System (STRS) Radio

The Space Telecommunications Radio System (STRS) provides a common, consistent framework for software defined radios (SDRs) to abstract the application software from the radio platform hardware. The STRS standard aims to reduce the cost and risk of using complex, configurable and reprogrammable radio systems across NASA missions. To promote the use of the STRS architecture for future NASA advanced exploration missions, NASA Glenn Research Center (GRC) developed an STRS compliant SDR on a radio platform used by the Advance Exploration System program at the Johnson Space Center (JSC) in their Integrated Power, Avionics, and Software (iPAS) laboratory. At the conclusion of the development, the software and hardware description language (HDL) code was delivered to JSC for their use in their iPAS test bed to get hands-on experience with the STRS standard, and for development of their own STRS Waveforms on the now STRS compliant platform.The iPAS STRS Radio was implemented on the Reconfigurable, Intelligently-Adaptive Communication System (RIACS) platform, currently being used for radio development at JSC. The platform consists of a Xilinx ML605 Virtex-6 FPGA board, an Analog Devices FMCOMMS1-EBZ RF transceiver board, and an Embedded PC (Axiomtek eBox 620-110-FL) running the Ubuntu 12.4 operating system. Figure 1 shows the RIACS platform hardware. The result of this development is a very low cost STRS compliant platform that can be used for waveform developments for multiple applications.The purpose of this document is to describe the design of the HDL code for the FPGA portion of the iPAS STRS Radio particularly the design of the FPGA wrapper and the test waveform.

VHDL↗
NASA NTRS1987

3-D inelastic analysis methods for hot section components. Volume 2: Advanced special functions models

This Annual Status Report presents the results of work performed during the third year of the 3-D Inelastic Analysis Methods for Hot Sections Components program (NASA Contract NAS3-23697). The objective of the program is to produce a series of computer codes that permit more accurate and efficient three-dimensional analyses of selected hot section components, i.e., combustor liners, turbine blades, and turbine vanes. The computer codes embody a progression of mathematical models and are streamlined to take advantage of geometrical features, loading conditions, and forms of material response that distinguish each group of selected components.

Wilson, R. B.↗
NASA NTRS1991

Composite load spectra for select space propulsion structural components

The objective of this program is to develop generic load models with multiple levels of progressive sophistication to simulate the composite load spectra that are induced in space propulsion system components, representative of Space Shuttle Main Engines (SSME), such as transfer ducts, turbine blades, and liquid oxygen (LOX) posts and system ducting. These models will be developed using two independent approaches. The first approach consists of using state-of-the-art probabilistic methods to describe the individual loading conditions and combinations of these loading conditions to synthesize the composite load spectra simulation. The methodology required to combine the various individual load simulation models (hot-gas dynamic, vibrations, instantaneous position, centrifugal field, etc.) into composite load spectra simulation models will be developed under this program. A computer code incorporating the various individual and composite load spectra models will be developed to construct the specific load model desired. The second approach, which is covered under the options portion of the contract, will consist of developing coupled models for composite load spectra simulation which combine the (deterministic) models for composite load dynamic, acoustic, high-pressure and high rotational speed, etc., load simulation using statistically varying coefficients. These coefficients will then be determined using advanced probabilistic simulation methods with and without strategically selected experimental data. This report covers the efforts of the third year of the contract. The overall program status is that the turbine blade loads have been completed and implemented. The transfer duct loads are defined and are being implemented. The thermal loads for all components are defined and coding is being developed. A dynamic pressure load model is under development. The parallel work on the probabilistic methodology is essentially completed. The overall effort is being integrated in an expert system code specifically developed for this project.

Newell, J. F.↗
NASA NTRS1988

NASA Advanced Propeller Research

Acoustic and aerodynamic research at NASA Lewis Research Center on advanced propellers is reviewed including analytical and experimental results on both single and counterrotation. Computational tools used to calculate the detailed flow and acoustic i e l d s a r e described along with wind tunnel tests to obtain data for code verification . Results from two kinds of experiments are reviewed: ( 1 ) performance and near field noise at cruise conditions as measured in the NASA Lewis 8-by 6-Foot Wind Tunnel and ( 2 ) farfield noise and performance for takeoff/approach conditions as measured in the NASA Lewis 9-by 15-Font Anechoic Wind Tunnel. Detailed measurements of steady blade surface pressures are described along with vortex flow phenomena at off design conditions . Near field noise at cruise is shown to level out or decrease as tip relative Mach number is increased beyond 1.15. Counterrotation interaction noise is shown to be a dominant source at take off but a secondary source at cruise. Effects of unequal rotor diameters and rotor-to-rotor spacing on interaction noise a real so illustrated. Comparisons of wind tunnel acoustic measurements to flight results are made. Finally, some future directions in advanced propeller research such as swirl recovery vanes, higher sweep, forward sweep, and ducted propellers are discussed.

Groeneweg, John F.↗
NASA NTRS1988

Accomplishments at NASA Langley Research Center in rotorcraft aerodynamics technology

In recent years, the development of aerodynamic technology for rotorcraft has continued successfully at NASA LaRC. Though the NASA Langley Research Center is not the lead NASA center in this area, the activity was continued due to facilities and individual capabilities which are recognized as contributing to helicopter research needs of industry and government. Noteworthy accomplishments which contribute to advancing the state of rotorcraft technology in the areas of rotor design, airfoil research, rotor aerodynamics, and rotor/fuselage interaction aerodynamics are described. Rotor designs were defined for current helicopters and evaluated in wind tunnel testing. These designs have incorporated advanced airfoils defined analytically and also proven in wind tunnel tests. A laser velocimetry system has become a productive tool for experimental definition of rotor inflow/wake and is providing data for rotorcraft aerodynamic code validation.

Wilson, John C.↗
NASA NTRS1990

Recent advances in hypersonic technology

This paper will focus on recent advances in hypersonic aerodynamic prediction techniques. Current capabilities of existing numerical methods for predicting high Mach number flows will be discussed and shortcomings will be identified. Physical models available for inclusion into modern codes for predicting the effects of transition and turbulence will also be outlined and their limitations identified. Chemical reaction models appropriate to high-speed flows will be addressed, and the impact of their inclusion in computational fluid dynamics codes will be discussed. Finally, the problem of validating predictive techniques for high Mach number flows will be addressed.

Dwoyer, Douglas L.↗
NASA NTRS2002

The International Intercomparison of 3-Dimensional Radiation Codes

I3RC (International Intercomparison of 3-dimensional Radiation Codes) has as its primary goal to compare a wide variety of three-dimensional (3D) radiative transfer methods applied to Earth's atmosphere, with a few selected cloud fields as input, and a few selected radiative quantities as output. Phases 1 and 2 are now complete, and participants represented institutions in Canada, France, Germany, Russia, the United Kingdom, and the USA, who met for two workshops in Tucson, Arizona USA, and compared results from 5 cloud fields of varying complexity, beginning with simplified atmosphere and surface, and proceeding to more realistic cases. Phase 3 is now underway, focusing on improvement and sharing of 3D radiation code, aided by working groups on "Approximations" and "Open Source". The "Approximations" group has so far focused on diffusive approximate methods in an attempt to gain advantages in execution time, and also to advance the understanding of 3D radiation processes. The "Open Source" subgroup is developing a Monte Carlo radiative transfer toolkit that makes state-of-the-art techniques available to a wide range of users. Activities of both subgroups are further explained at the I3RC website http://i3rc.gsfc.nasa.gov. Participants in 13RC are forming a 3D Working Group under the auspices of the International Radiation Commission, and will meet for this and related activities at a workshop in Tucson in November 2002.

Cahalan, R. F.↗
NASA NTRS1997

Detection of Ocean Reflected GPS Signals: Theory and Experiment

A number of advanced applications of the Global Positioning System (GPS) have been proposed which use the signal reflected from a smooth ocean surface. The viability of these concepts hinges upon the ability to acquire and code track the reflected signal for an extended period of time over a variety of sea states. The analytical theory of specularly and diffusely reflected radio frequency radiation from a rough surface is reviewed. Experiments to demonstrate tracking of a reflected signal were performed on three aircraft flights over the Chesapeake Bay and the Eastern Shore of Virginia. The experimental hardware consisted of two of-the-shelf receivers configured so that one received the GPS signal in the conventional manner using a right hand circularly polarized (RHCP) antenna on top of the fuselage and the other could receive the reflected signal using a left hand circularly polarized (LHCP) antenna on the bottom of the fuselage. Three tests were performed on the data to verify that the signals received in the bottom antenna were viewed as sea surface reflections; Pseudorange double differences were compared against predicted geometric range double differences; Characteristics of a signal reflected from a random surface were observed in the carrier to noise ratio; Predicted specular points were plotted which demonstrate reflection only from wet areas. These tests indicated tracking of reflected signals for extended periods of time at altitudes of up to 5500 m and sporadic signal acquisition at higher altitudes. The duration of the continuous signal tracking was limited by the receiver's need to maintain carrier tracking.

Garrison, James L.↗
NASA NTRS1993

NASA MMIC Reliability Assurance Program

Over the past few years considerable advancements have been made in the design and manufacture of Millimeter-Wave/Microwave Monolithic Integrated Circuits (MMIC).

MMIC Guide Code QE screening standard high reliabi↗