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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Mixer Analysis of Nacelle/Nozzle Flow

Flow over idealized nozzle computed. Analysis and computer program calculate flow over idealized mixer nozzle. Nozzle idealized by unwrapping it so planform lies in z=O plane. Linearized compresible flow used to calculate flow and mixer shape given loading on mixer. End goal to achieve maximum amount of mixing downstream of mixer while retaining reasonable shape for mixer. Because analysis assumes linearized flow, calculation of effects of deep lobe penetration cannot be made using this program.

Barber, T. J.↗
NASA NTRS1952

Buckling of Low Arches or Curved Beams of Small Curvature

A general solution, based on the classical buckling criterion, is given for the problem of buckling of low arches under a lateral loading acting toward the center of curvature. For a sinusoidal arch under sinusoidal loading, the critical load can be expressed exactly as a simple function of the beam dimension parameters. For other arch shapes and load distributions, approximate values of the critical load can be obtained by summing a few terms of a rapidly converging Fourier series. The effects of initial end thrust and axial and lateral elastic support are discussed. The buckling load based on energy criterion of Karman and Tsien is also calculated. Results for both the classical and the energy criteria are compared with experimental results.

Fung, Y C↗
NASA NTRS1986

An experiment for determining the Euler load by direct computation

A direct algorithm is presented for computing the Euler load of a column from experimental data. The method is based on exact inextensional theory for imperfect columns, which predicts two distinct deflected shapes at loads near the Euler load. The bending stiffness of the column appears in the expression for the Euler load along with the column length, therefore the experimental data allows a direct computation of bending stiffness. Experiments on graphite-epoxy columns of rectangular cross-section are reported in the paper. The bending stiffness of each composite column computed from experiment is compared with predictions from laminated plate theory.

Thurston, Gaylen A.↗
NASA NTRS2001

Flow Past a Descending Balloon

In this report, we present our findings related to aerodynamic loading of partially inflated balloon shapes. This report will consider aerodynamic loading of partially inflated inextensible natural shape balloons and some relevant problems in potential flow. For the axisymmetric modeling, we modified our Balloon Design Shape Program (BDSP) to handle axisymmetric inextensible ascent shapes with aerodynamic loading. For a few simple examples of two dimensional potential flows, we used the Matlab PDE Toolbox. In addition, we propose a model for aerodynamic loading of strained energy minimizing balloon shapes with lobes. Numerical solutions are presented for partially inflated strained balloon shapes with lobes and no aerodynamic loading.

Baginski, Frank↗
NASA NTRS2012

An Update on the Mechanical and EM Performance of the Composite Dish Verification Antenna (DVA-1) for the SKA

This paper will give an overview of the unique mechanical and optical design of the DVA-1 telescope. The rim supported carbon fibre reflector surfaces are designed to be both low cost and have high performance under wind, gravity, and thermal loads. The shaped offset Gregorian optics offer low and stable side lobes along with a large area at the secondary focus for multiple feeds with no aperture blockage. Telescope performance under ideal conditions as well as performance under gravity, wind, and thermal loads will be compared directly using calculated radiation patterns for each of these operating conditions.

composite dish↗
NASA NTRS1994

Structural/aerodynamic Blade Analyzer (SAB) User's Guide, Version 1.0

The structural/aerodynamic blade (SAB) analyzer provides an automated tool for the static-deflection analysis of turbomachinery blades with aerodynamic and rotational loads. A structural code calculates a deflected blade shape using aerodynamic loads input. An aerodynamic solver computes aerodynamic loads using deflected blade shape input. The two programs are iterated automatically until deflections converge. Currently, SAB version 1.0 is interfaced with MSC/NASTRAN to perform the structural analysis and PROP3D to perform the aerodynamic analysis. This document serves as a guide for the operation of the SAB system with specific emphasis on its use at NASA Lewis Research Center (LeRC). This guide consists of six chapters: an introduction which gives a summary of SAB; SAB's methodology, component files, links, and interfaces; input/output file structure; setup and execution of the SAB files on the Cray computers; hints and tips to advise the user; and an example problem demonstrating the SAB process. In addition, four appendices are presented to define the different computer programs used within the SAB analyzer and describe the required input decks.

Morel, M. R.↗
NASA NTRS1993

Parametric binary dissection

Binary dissection is widely used to partition non-uniform domains over parallel computers. This algorithm does not consider the perimeter, surface area, or aspect ratio of the regions being generated and can yield decompositions that have poor communication to computation ratio. Parametric Binary Dissection (PBD) is a new algorithm in which each cut is chosen to minimize load + lambda x(shape). In a 2 (or 3) dimensional problem, load is the amount of computation to be performed in a subregion and shape could refer to the perimeter (respectively surface) of that subregion. Shape is a measure of communication overhead and the parameter permits us to trade off load imbalance against communication overhead. When A is zero, the algorithm reduces to plain binary dissection. This algorithm can be used to partition graphs embedded in 2 or 3-d. Load is the number of nodes in a subregion, shape the number of edges that leave that subregion, and lambda the ratio of time to communicate over an edge to the time to compute at a node. An algorithm is presented that finds the depth d parametric dissection of an embedded graph with n vertices and e edges in O(max(n log n, de)) time, which is an improvement over the O(dn log n) time of plain binary dissection. Parallel versions of this algorithm are also presented; the best of these requires O((n/p) log(sup 3)p) time on a p processor hypercube, assuming graphs of bounded degree. How PBD is applied to 3-d unstructured meshes and yields partitions that are better than those obtained by plain dissection is described. Its application to the color image quantization problem is also discussed, in which samples in a high-resolution color space are mapped onto a lower resolution space in a way that minimizes the color error.

Bokhari, Shahid H.↗
NASA NTRS1972

High altitude flight test of a disk gap band parachute deployed behind a bluff body at a Mach number of 2.69

A flight test was conducted with a 55-foot diameter disk-gap-band parachute located at a trailing distance of 4.4 forebody diameters behind a 15-foot diameter bluff-body planetary entry aeroshell and attached instrumented payload. At the time of parachute deployment the aeroshell-payload combination was oscillating through an angle-of-attack range of plus or minus 40 deg. Continued oscillatory motion of the aeroshell-payload combination and similar motion of the parachute caused rapid changes in parachute shape and loading which resulted in extensive cloth damage in the band and outer disk-edge areas of the parachute canopy. During steady-state descent the damage parachute provided an effective-drag coefficient of about 0.33 which was about 60 percent of that expected.

Eckstrom, C.↗
NASA NTRS1972

Finite element displacement analysis of a lung.

A method is given based on the technique of finite elements which determines theoretically the mechanical behavior of a lung-shaped body loaded by its own weight. The results of this theoretical analysis have been compared with actual measurements of alveolar size and pleural pressures in animal lungs.

Matthews, F. L.↗
NASA NTRS1974

Specialists Meeting on Rotorcraft Dynamics, Moffett Field, Calif., February 13-15, 1974, Proceedings

Analysis of specific problems in rotorcraft dynamics. Topics include hingeless rotor theory, dynamic stall modelling, periodic systems identification, analysis of complex systems with phasing matrices, flapping stability, flap-lag dynamics at high advance ratios, finite element analysis and fuselage free-vibration characteristics, coupled rotor/frame vibration methods, gust response characteristics with unsteady stall effects, antiresonance theory, cyclic feathering motions and dynamic loads, control load envelope shaping, rotor aeroelasticity, use of Floquet theory, theory of proprotors and tilt-rotors, two-bladed teetering rotors, stability of air and ground resonance, vertical-plane pendulum absorbers, multicyclic jet-flap control, engine/frame interface dynamics, and others. The minutes of the question and answer periods following the presentations are presented in the supplement. Individual items are announced in this issue.

Source record↗
NASA NTRS1979

Variable-shape solar-energy concentrator

Proposed low cost three dimensional tracking solar concentrator fabricated from lightweight, flexible polymeric film membrane is controlled in shape by differential pressure loading. Fine adjustments to shape could be made by mounting electrets or magnets on membrane or applying electric or magnetic field.

Miller, C. G.↗
NASA NTRS1985

Development of non-linear finite element computer code

Recent work has shown that the use of separable symmetric functions of the principal stretches can adequately describe the response of certain propellant materials and, further, that a data reduction scheme gives a convenient way of obtaining the values of the functions from experimental data. Based on representation of the energy, a computational scheme was developed that allows finite element analysis of boundary value problems of arbitrary shape and loading. The computational procedure was implemental in a three-dimensional finite element code, TEXLESP-S, which is documented herein.

Becker, E. B.↗
NASA NTRS1987

Static aeroelastic effects on the flutter of a supercritical wing

It is well known that wings with supercritical airfoils generally have lower transonic flutter speeds than similar wings with conventional airfoils and that small increases in angle of attack from zero and the accompanying static aeroelastic deformations have further detrimental effects on transonic flutter. The results of an effort to calculate the effects of angle of attack and the associated aeroelastic deformation on the flutter of a highly swept supercritical wing (TF 8A) by use of the modified strip analysis employed in previous studies of this wing are presented. The spanwise distributions of steady-state section lift-curve slope and aerodynamic center required as input for these calculations were obtained from static aeroelastic calculations for the wing by use of the FL022 transonic code and an assumed dynamic pressure as that used to calculate the statically deformed shape and loading about which the flutter oscillation occurs. The results show that the unconventional backward turn of the transonic dip in the experimental flutter boundary for angles of attack greater than zero is caused by variations in mass ratio and not by static aeroelastic deformation, although inclusion of the latter appears to be required for quantitative accuracy in the calculations.

Yates, E. Carson, Jr.↗
NASA NTRS1987

Static aeroelastic effects on the flutter of a supercritical wing

The results of an effort to calculate the effects of angle of attack and the associated aeroelastic deformation on the flutter of a highly swept supercritical wing by use of the modified strip analysis employed in previous studies of this wing are discussed. The spanwise distributions of steady state section lift-curve slope and aerodynamic center required as input for these calculations were obtained from static aeroelastic calculations for the wing by use of the FLO22 transonic code and an assumed dynamic pressure. The process is iterative so that flutter can be obtained at the same dynamic pressure as that used to calculate the statistically deformed shape and loading about which the flutter oscillation occurs (matched conditions). The results of this investigation show that the unconventional backward turn of the transonic dip in the experimental flutter boundary for angles of attack greater than zero is caused by variations in mass ratio and not by static aeroelastic deformation, although inclusion of the latter appears to be required for quantitative accuracy in the calculations.

Yates, E. Carson, Jr.↗
NASA NTRS1990

Computing Deformations Of Rubbery Materials

Better use made of experimental data in finite-element computations. New formulation of constitutive equations of rubbery, nonlinearly elastic material enables finite-element analysis of boundary-value stress-and-strain problems involving arbitrary shapes and loads. In development of formulation, principal stretches used as arguments of strain-energy-density function.

Peng, Steven T. J.↗
NASA NTRS1991

Extrinsic factors in the mechanics of bridged cracks

The far-reaching effects of such extrinsic factors as specimen shape and load distribution on bridged crack propagation, in cases where bridging-zone length is comparable to any of the crack and/or specimen dimensions, are presently demonstrated in view of calculation results for single-edge-notch specimens under uniform remote tension. The inherent risk of nonconservative predictions or reliability and strength may be reduced by considering the relationship between the bridging tractions and the crack-opening displacement as a fundamental material property. The fundamentality of the 'bridging length scale', or initial crack extension over which the bridging zone matures, is demonstrated.

Cox, B. N.↗