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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 289 records · Page 16

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NASA NTRS1974

Fretting in aircraft turbine engines

Fretting usually produces both polished and pitted areas. Fretting occurs in connection with the relative motion between contacting surface elements. Particular attention is given to fretting in seals, splines, fans, compressors, and turbine blades. Recommended approaches to mitigate fretting problems include a reduction of the adhesion between two surfaces. Approaches for doing this may include the development of alloys which spontaneously generate a self-healing surface film, different in composition from the bulk alloy. Other fundamental adhesion studies have shown that surface crystal structure and crystallographic orientation significantly affect the adhesion properties of alloys.

Johnson, R. L.↗

NASA NTRS1975

Computational procedure for three-dimensional boundary layers on aircraft and aerospace vehicles

An implicit numerical procedure is developed to solve the full three-dimensional laminar, boundary layer equations over realistic aircraft and spacecraft configurations. This procedure utilizes splined functions in the direction normal to the surface and finite differences in the cross flow direction. Calculation of off-pitch plane attachment and detachment lines can be calculated. The solution procedure permits the incorporation of a wide variety of turbulent models and boundary conditions including; entropy layer procedures, specified surface temperatures or heat flux distributions, surface catalysis, mass addition, and the coupling to both three-dimensional inviscid codes and surface ablation codes. In addition, reasonable computing times are obtained.

Kendall, R. M.↗

NASA NTRS1977

Dynamic load attenuator

Instrument consists of special bolt head that cuts material from splined washer. Required shear and tensile forces absorb kinetic energy. Cut-away material is retained by shearing action, making device useful where production of loose metal particles is not acceptable.

Crum, P. N.↗

NASA NTRS1975

An investigation of several numerical procedures for time-asymptotic compressible Navier-Stokes solutions

The status of an investigation of four numerical techniques for the time-dependent compressible Navier-Stokes equations is presented. Results for free shear layer calculations in the Reynolds number range from 1000 to 81000 indicate that a sequential alternating-direction implicit (ADI) finite-difference procedure requires longer computing times to reach steady state than a low-storage hopscotch finite-difference procedure. A finite-element method with cubic approximating functions was found to require excessive computer storage and computation times. A fourth method, an alternating-direction cubic spline technique which is still being tested, is also described.

Rudy, D. H.↗

NASA NTRS1975

Numerical methods for the calculation of three-dimensional nozzle exhaust flow fields

Numerical codes developed for the calculation of three-dimensional nozzle exhaust flow fields associated with hypersonic airbreathing aircraft are described. Both codes employ reference plane grid networks with respect to three coordinate systems. Program CHAR3D is a characteristic code utilizing a new wave preserving network within the reference planes, while program BIGMAC is a finite difference code utilizing conservation variables and a one-sided difference algorithm. Secondary waves are numerically captured by both codes, while the underexpansion shock and plume boundary are treated discretely. The exhaust gas properties consist of hydrogen-air combustion product mixtures in local chemical equilibrium. Nozzle contours are treated by a newly developed geometry package based on dual cubic splines. Results are presented for simple configurations demonstrating two- and three-dimensional multiple wave interactions.

Dash, S. M.↗

NASA NTRS1975

Numerical studies of incompressible viscous flow in a driven cavity

A series of project papers is presented in computational fluid dynamics. The work was performed during the 1973-74 academic year at Old Dominion University. Each paper briefly examines a numerical method(s) that can be applied to the Navier-Stokes equations governing incompressible flow in a driven cavity. Solutions obtained with a cubic spline procedure are also included.

Source record↗

NASA NTRS1975

An interactive graphics program to retrieve, display, compare, manipulate, curve fit, difference and cross plot wind tunnel data

The Aerodynamic Data Analysis and Integration System (ADAIS), developed as a highly interactive computer graphics program capable of manipulating large quantities of data such that addressable elements of a data base can be called up for graphic display, compared, curve fit, stored, retrieved, differenced, etc., was described. The general nature of the system is evidenced by the fact that limited usage has already occurred with data bases consisting of thermodynamic, basic loads, and flight dynamics data. Productivity using ADAIS of five times that for conventional manual methods of wind tunnel data analysis is routinely achieved. In wind tunnel data analysis, data from one or more runs of a particular test may be called up and displayed along with data from one or more runs of a different test. Curves may be faired through the data points by any of four methods, including cubic spline and least squares polynomial fit up to seventh order.

Elliott, R. D.↗

NASA NTRS1975

Compression of contour data through exploiting curve-to-curve dependence

An approach to exploiting curve-to-curve dependencies in order to achieve high data compression is presented. One of the approaches to date of along curve compression through use of cubic spline approximation is taken and extended by investigating the additional compressibility achievable through curve-to-curve structure exploitation. One of the models under investigation is reported on.

Yalabik, N.↗

NASA NTRS1976

An analytical study of reduced-gravity flow dynamics

Addition of surface tension forces to a marker-and-cell code and the performance of four incompressible fluid simulations in reduced gravity, were studied. This marker-and-cell code has a variable grid capability with arbitrary curved boundaries and time dependent acceleration fields. The surface tension logic includes a spline fit of surface marker particles as well as contact angle logic for straight and curved wall boundaries. Three types of flow motion were simulated with the improved code: impulsive settling in a model Centaur LH2 tank, continuous settling in a model and full scale Centaur LO2 tank and mixing in a Centaur LH2 tank. The impulsive settling case confirmed a drop tower analysis which indicated more orderly fluid collection flow patterns with this method providing a potential savings in settling propellants. In the LO2 tank, fluid collection and flow simulation into the thrust barrel were achieved. The mixing simulation produced good results indicating both the development of the flow field and fluid interface behavior.

Bradshaw, R. D.↗

NASA NTRS1976

Higher-order numerical methods derived from three-point polynomial interpolation

Higher-order collocation procedures resulting in tridiagonal matrix systems are derived from polynomial spline interpolation and Hermitian finite-difference discretization. The equations generally apply for both uniform and variable meshes. Hybrid schemes resulting from different polynomial approximations for first and second derivatives lead to the nonuniform mesh extension of the so-called compact or Pade difference techniques. A variety of fourth-order methods are described and this concept is extended to sixth-order. Solutions with these procedures are presented for the similar and non-similar boundary layer equations with and without mass transfer, the Burgers equation, and the incompressible viscous flow in a driven cavity. Finally, the interpolation procedure is used to derive higher-order temporal integration schemes and results are shown for the diffusion equation.

Rubin, S. G.↗

NASA NTRS1976

A spectral reflectance estimation technique using multispectral data from the Viking lander camera

A technique is formulated for constructing spectral reflectance curve estimates from multispectral data obtained with the Viking lander camera. The multispectral data are limited to six spectral channels in the wavelength range from 0.4 to 1.1 micrometers and most of these channels exhibit appreciable out-of-band response. The output of each channel is expressed as a linear (integral) function of the (known) solar irradiance, atmospheric transmittance, and camera spectral responsivity and the (unknown) spectral responsivity and the (unknown) spectral reflectance. This produces six equations which are used to determine the coefficients in a representation of the spectral reflectance as a linear combination of known basis functions. Natural cubic spline reflectance estimates are produced for a variety of materials that can be reasonably expected to occur on Mars. In each case the dominant reflectance features are accurately reproduced, but small period features are lost due to the limited number of channels. This technique may be a valuable aid in selecting the number of spectral channels and their responsivity shapes when designing a multispectral imaging system.

Park, S. K.↗

NASA NTRS1976

Concepts for improving turbine disk integrity

Advanced disk structural concepts are used to improve the cyclic lives and reliability of turbine disks. Analytical studies were conducted to evaluate bore-entry disks as potential replacements for the existing first-stage turbine disks in the CF6-50 and JT8D-17 engines. Results of low-cycle fatigue, burst, fracture mechanics, and fragment energy analyses are summarized for the advanced disk designs and the existing disk designs with both conventional and advanced disk materials. Other disk concepts such as composite, laminated, link, multibore, multidisk, and spline disks were also evaluated for the CF6-50 engine.

Kaufman, A.↗

NASA NTRS1977

Separating and turbulent boundary layer calculations using polynomial interpretation

Higher order numerical methods derived from polynomial spline interpolation or Hermitian differencing are applied to a separating laminar boundary layer, i.e., the Howarth problem, and the turbulent flat plate boundary layer flow. Preliminary results are presented. It is found that accuracy equal to that of conventional second order accurate finite difference methods is achieved with many fewer mesh points and with reduced computer storage and time requirements.

Rubin, S. G.↗

NASA NTRS1977

A critical study of higher-order numerical methods for solving the boundary-layer equations

A fourth-order box method is presented for calculating numerical solutions to parabolic, partial differential equations in two variables or ordinary differential equations. The method is the natural extension of the second-order Keller Box Scheme to fourth order and is demonstrated with application to the incompressible, laminar and turbulent boundary-layer equations. The efficiency of the present method is compared with other two-point and three-point higher-order methods; namely, the Keller Box Scheme with Richardson extrapolation, the method of deferred corrections, and the three-point spline methods. For equivalent accuracy, numerical results show the present method to be more efficient than the other higher-order methods for both laminar and turbulent flows.

Wornom, S. F.↗

NASA NTRS1977

Comment of fitting ab initio intermolecular potentials for scattering calculations

The angular dependence of the interaction between two rigid linear rotors is considered, and one of the two expansions in current use is shown to be inappropriate. Interpolation of tabulated radial interactions is also discussed, and numerical tests are presented which demonstrate the accuracy of Lagrange and spline algorithms as a function of the spacing between points.

Green, S.↗

NASA NTRS1978

"Nonfloating" universal joint

Modified crowned-spline joint is lightweight, durable, and requires minimum of parts. It does not use rubber cushions to limit play and is useful over wide temperature range. It has inner ball and socket to provide rigid connection with no axial play. Joint can be adapted to form pinned connection between segmented torque tubes.

Appleberry, W. T.↗

NASA NTRS1978

Edge geometry of turbomachine blades

Computer program calculates leading- and trailing-edge circle radii, tangency angles on leading- and trailing-edge circles, and stagger angle of turbomachinery blade sections, using only spline points defining blade surfaces.

Schumann, L. F.↗

NASA NTRS1977

Turbine disks for improved reliability

Advanced disk structural concepts were employed to improve the cyclic lives and reliability of turbine disks. Analytical studies were conducted to evaluate bore-entry disks as potential replacements for the existing first-stage turbine disks in the CF6-50 and JT8D-17 engines. Results of low cycle fatigue, burst, fracture mechanics, and fragment energy analyses are summarized for the advanced disk designs and the existing disk designs, with both conventional and advanced disk materials. Other disk concepts such as composite, laminated, link, multibore, multidisk, and spline disks were also evaluated for the CF6-50 engine.

Kaufman, A.↗