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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

An approximate method for calculating three-dimensional inviscid hypersonic flow fields

An approximate solution technique was developed for 3-D inviscid, hypersonic flows. The method employs Maslen's explicit pressure equation in addition to the assumption of approximate stream surfaces in the shock layer. This approximation represents a simplification to Maslen's asymmetric method. The present method presents a tractable procedure for computing the inviscid flow over 3-D surfaces at angle of attack. The solution procedure involves iteratively changing the shock shape in the subsonic-transonic region until the correct body shape is obtained. Beyond this region, the shock surface is determined using a marching procedure. Results are presented for a spherically blunted cone, paraboloid, and elliptic cone at angle of attack. The calculated surface pressures are compared with experimental data and finite difference solutions of the Euler equations. Shock shapes and profiles of pressure are also examined. Comparisons indicate the method adequately predicts shock layer properties on blunt bodies in hypersonic flow. The speed of the calculations makes the procedure attractive for engineering design applications.

Riley, Christopher J.↗
NASA NTRS1943

A method for calculating heat transfer in the laminar flow region of bodies

This report has been prepared to provide a practical method for determining the chordwise distribution of the rate of heat transfer from the surface of a wing or body of revolution to air. The method is limited in use to the determination of heat transfer from the forward section of such bodies when the flow is laminar. A comparison of the calculated average heat-transfer coefficient for the nose section of the wing of a Lockheed 12-A airplane with that experimentally determined shows a satisfactory agreement. A sample calculation is appended.

Allen, H Julian↗
NASA NTRS1956

The Compressible Laminar Boundary Layer with Heat Transfer and Arbitrary Pressure Gradient

An approximate method for the calculation of the compressible laminar boundary layer with heat transfer and arbitrary pressure gradient, based on Thwaites' correlation concept, is presented. With the definition of dimensionless shear and heat-transfer parameters and an assumed correlation of these parameters in terms of a momentum parameter, a complete system of relations for calculating skin friction and heat transfer results. Knowledge of velocity or temperature profiles is not necessary in using this calculation method. When the method is applied to a convergent-divergent, axially symmetric rocket nozzle, it shows that high rates of heat transfer are obtained at the initial stagnation point and at the throat of the nozzle. Also indicated are negative displacement thicknesses in the convergent portion of the nozzle; these occur because of the high density within the lower portions of the cooled boundary layer. (author)

Cohen, Clarence B↗
NASA NTRS1979

An improved Woodward's panel method for calculating leading-edge and side-edge suction forces at subsonic and supersonic speeds

Woodward's panel method for subsonic and supersonic flow was improved by employing control points determined by exactly matching two-dimensional pressure at a finite number of points. The results show great improvement in the predicted pressure distribution of a flapped airfoil. With the paneling scheme of cosine law in both chordwise and spanwise directions, the method is shown to accurately predict leading edge and side edge suction forces of various configurations in subsonic and supersonic flow.

Lan, C. E.↗
NASA NTRS1975

SINDA/SINFLO computer routine, volume 1, revision A

The SINFLO package was developed to modify the SINDA preprocessor to accept and store the input data for fluid flow systems analysis and adding the FLOSOL user subroutine to perform the flow solution. This reduced and simplified the user input required for analysis of flow problems. A temperature calculation method, the flow-hybrid method which was developed in previous VSD thermal simulator routines, was incorporated for calculating fluid temperatures. The calculation method accuracy was improved by using fluid enthalpy rather than specific heat for the convective term of the fluid temperature equation. Subroutines and data input requirements are described along with user subroutines, flow data storage, and usage of the plot program.

Oren, J. A.↗
NASA NTRS1974

A direct method for calculating flutter speeds

The basic objective of this work is to provide a direct and simple means for calculating classical flutter. The analysis makes no use of free vibration modes, although the method is readily adaptable to a modal type approach. Only subsonic aerodynamics are considered; however, the method applies to any speed regime. The problems of following modes and modal coupling are completely avoided. The simplicity and accuracy of the direct solution is stressed. The analysis is applicable to both straight and swept wings although only straight wings, uniform as well as nonuniform, are presented.

Beres, D. P.↗
NASA NTRS1991

Aerodynamics and heat transfer investigations on a high Reynolds number turbine cascade

The results of aerodynamic and heat transfer experimental investigations performed in a high Reynolds number turbine cascade test facility are analyzed. The experimental facility simulates the high Reynolds number flow conditions similar to those encountered in the Space Shuttle Main Engine. In order to determine the influence of Reynolds number on aerodynamic and thermal behavior of the blades, heat transfer coefficients were measured at various Reynolds numbers using liquid crystal temperature measurement technique. Potential flow calculation methods were used to predict the cascade pressure distributions. Boundary layer and heat transfer calculation methods were used with these pressure distributions to verify the experimental results.

Schobeiri, Taher↗
NASA NTRS1991

Aerodynamics and heat transfer investigations on a high Reynolds number turbine cascade

The results of aerodynamic and heat transfer experimental investigations performed in a high Reynolds number turbine cascade test facility are analyzed. The experimental facility simulates the high Reynolds number flow conditions similar to those encountered in the Space Shuttle Main Engine. In order to determine the influence of Reynolds number on aerodynamic and thermal behavior of the blades, heat transfer coefficients were measured at various Reynolds numbers using liquid crystal temperature measurement technique. Potential flow calculation methods were used to predict the cascade pressure distributions. Boundary layer and heat transfer calculation methods were used with these pressure distributions to verify the experimental results.

Schobeiri, Taher↗
NASA NTRS1979

A simplified method for calculating the atmospheric heating rate by absorption of solar radiation in the stratosphere and mesosphere

Calculations of the atmospheric heating rate by absorption of solar radiation by O3, H2O, and CO2 are reported. The method needs only seven parameters for each molecule and is particularly useful for heating calculations in three-dimensional global circulation models below 80 km. Applying the formula to the observed distributions of O3, H2O, and CO2 produces reasonable latitudinal and seasonal variations in the heating rate. The calculated heating rate, however, is sensitive to the global distributions of the absorbing gases, and uncertainties in the O3 distribution above approximately 50 km and the H2O distribution below approximately 20 km may seriously affect the global distributions of the heating rate in these regions.

Shimazaki, T.↗
NASA NTRS1997

A Modified Linear-Mixing Method for Calculating Atmospheric Path Radiances of Aerosol Mixtures

The top-of-atmosphere (TOA) path radiance generated by an aerosol mixture can be synthesized by linearly adding the contributions of the individual aerosol components, weighted by their fractional optical depths. The method, known as linear mixing, is exact in the single-scattering limit. When multiple scattering is significant, the method reproduces the atmospheric path radiance of the mixture with less than 3% errors for weakly absorbing aerosols up to optical thickness of 0.5. However, when strongly absorbing aerosols are included in the mixture, the errors are much larger. This is due to neglecting the effect of multiple interactions between the aerosol components, especially when the values of the single-scattering albedos of these components are so different that the parameter epsilon = (Sigma)f(sub i) absolute value of bar omega(sub i) - bar omega(sub mix)/bar omega(sub i), is larger than approx. 0.1, where bar omega(sub i) and f(sub i) are the single-scattering albedo and the fractional abundance of the i th component, and bar omega(sub i) is the effective single-scattering albedo of the mixture. We describe an empirical, modified linear-mixing method which effectively accounts for the multiple interactions between aerosol components. The modified and standard methods are identical when epsilon = 0.0 and give similar results when epsilon less than or equal to 0.05. For optical depths larger than approx. 0.5, or when epsilon greater than 0.05, only the modified method can reproduce the radiances within 5% error for common aerosol types up to optical thickness of 2.0. Because this method facilitates efficient and accurate atmospheric path radiance calculations for mixtures of a wide variety of aerosol types, it will be used as part of the aerosol retrieval methodology for the Earth Observing System (EOS) multiangle imaging spectroradiometer (MISR), scheduled for launch into polar orbit in 1998.

Abdou, W. A.↗
NASA NTRS1997

A Modified Linear-Mixing Method for Calculating Atmospheric Path Radiances of Aerosol Mixtures

The top-of-atmosphere (TOA) path radiance generated by an aerosol mixture can be synthesized by linearly adding the contributions of the individual aerosol components, weighted by their fractional optical depths. The method, known as linear mixing, is exact in the single-scattering limit. When multiple scattering is significant, the method reproduces the atmospheric path radiance of the mixture with less than 3% errors for weakly absorbing aerosols up to optical thickness of 0.5. However, when strongly absorbing aerosols are included in the mixture, the errors are much larger. This is due to neglecting the effect of multiple interactions between the aerosol components, especially when the values of the single-scattering albedos of these components are so different that the parameter e = the sum of f(sub i)[(bar)omega(sub i) - (bar)omega(sub mix)]/(bar)omega(sub i) is larger than approximately 0.1, where (bar)omega(sub i)and f(sub i) are the single-scattering albedo and the fractional abundance of the ith component, and (bar)omega(sub mix) is the effective single-scattering albedo of the Mixture. We describe an empirical, modified linear-mixing method which effectively accounts for the multiple interactions between aerosol components. The modified and standard methods are identical when epsilon = 0.0 and give similar results when epsilon is less than or equal to 0.05. For optical depths larger than approximately 0.5, or when epsilon is greater than 0.05, only the modified method can reproduce the radiances within 5% error for common aerosol types up to optical thickness of 2.0. Because this method facilitates efficient and accurate atmospheric path radiance calculations for mixtures of a wide variety of aerosol types, it will be used as part of the aerosol retrieval methodology for the Earth Observing System (EOS) multiangle imaging spectroradiometer (MISR), scheduled for launch into polar orbit in 1998.

Abdou, W. A.↗
NASA NTRS1995

A study of various methods for calculating locations of lightning events

This article reports on the results of numerical experiments on finding the location of lightning events using different numerical methods. The methods include linear least squares, nonlinear least squares, statistical estimations, cluster analysis and angular filters and combinations of such techniques. The experiments involved investigations of methods for excluding fake solutions which are solutions that appear to be reasonable but are in fact several kilometers distant from the actual location. Some of the conclusions derived from the study are that bad data produces fakes, that no fool-proof method of excluding fakes was found, that a short base-line interferometer under development at Kennedy Space Center to measure the direction cosines of an event shows promise as a filter for excluding fakes. The experiments generated a number of open questions, some of which are discussed at the end of the report.

Cannon, John R.↗
NASA NTRS1990

Systematic methods for calculation of the dielectric properties of arbitrary plasmas

In the novel approach presented for calculating the dispersion integrals needed for determining plasma dielectric properties, the dispersion integrals for an arbitrary distortion function with a continuous derivative are systematically expanded in terms of a set of orthogonal functions whose corresponding dispersion functions are already known. This general approach is, on the one hand, implemented for unmagnetized plasmas, and on the other generalized to treat relativistic and magnetized plasmas. The method allows the systematic and efficient calculation of dispersion integrals, for the cases of either real or complex arguments.

Robinson, P. A.↗
NASA NTRS1991

Recent advances in Euler and Navier-Stokes methods for calculating helicopter rotor aerodynamics and acoustics

This paper outlines some recent advances in the application of the Euler and Navier-Stokes computational fluid dynamics methods to analyze nonlinear problems of helicopter aerodynamics and acoustics. A complete flowfield simulation of helicopters is currently not feasible with these methods. However, the use of the state-of-the-art numerical algorithms in conjunction with powerful supercomputers, like the Cray-2, have enabled notable progress to be made in modeling several individual components of this complex flow in hover and forward flight.

Srinivasan, G. R.↗
NASA NTRS1924

A Short Method of Calculating Torsional Stresses in an Airplane Fuselage

This report deals with an investigation carried out in the Civil Engineering Laboratory of the University of California, to determine the accuracy of existing methods of computing the stresses in an airplane fuselage when subjected to torsion, and to derive a simple approximate formula for the rapid calculation of these stresses.

Younger, John E↗