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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

The solution of radiative transfer problems in molecular bands without the LTE assumption by accelerated lambda iteration methods

An iterative method based on the use of approximate transfer operators, which was designed initially to solve multilevel NLTE line formation problems in stellar atmospheres, is adapted and applied to the solution of the NLTE molecular band radiative transfer in planetary atmospheres. The matrices to be constructed and inverted are much smaller than those used in the traditional Curtis matrix technique, which makes possible the treatment of more realistic problems using relatively small computers. This technique converges much more rapidly than straightforward iteration between the transfer equation and the equations of statistical equilibrium. A test application of this new technique to the solution of NLTE radiative transfer problems for optically thick and thin bands (the 4.3 micron CO2 band in the Venusian atmosphere and the 4.7 and 2.3 micron CO bands in the earth's atmosphere) is described.

Kutepov, A. A.↗
NASA NTRS1999

Dynamically controlled crystallization method and apparatus and crystals obtained thereby

A method and apparatus for dynamically controlling the crystallization of proteins including a crystallization chamber or chambers for holding a protein in a salt solution, one or more salt solution chambers, two communication passages respectively coupling the crystallization chamber with each of the salt solution chambers, and transfer mechanisms configured to respectively transfer salt solution between each of the salt solution chambers and the crystallization chamber. The transfer mechanisms are interlocked to maintain the volume of salt solution in the crystallization chamber substantially constant. Salt solution of different concentrations is transferred into and out of the crystallization chamber to adjust the salt concentration in the crystallization chamber to achieve precise control of the crystallization process.

Arnowitz, Leonard↗
NASA NTRS2003

Dynamically controlled crystallization method and apparatus and crystals obtained thereby

A method and apparatus for dynamically controlling the crystallization of molecules including a crystallization chamber (14) or chambers for holding molecules in a precipitant solution, one or more precipitant solution reservoirs (16, 18), communication passages (17, 19) respectively coupling the crystallization chamber(s) with each of the precipitant solution reservoirs, and transfer mechanisms (20, 21, 22, 24, 26, 28) configured to respectively transfer precipitant solution between each of the precipitant solution reservoirs and the crystallization chamber(s). The transfer mechanisms are interlocked to maintain a constant volume of precipitant solution in the crystallization chamber(s). Precipitant solutions of different concentrations are transferred into and out of the crystallization chamber(s) to adjust the concentration of precipitant in the crystallization chamber(s) to achieve precise control of the crystallization process. The method and apparatus can be used effectively to grow crystals under reduced gravity conditions such as microgravity conditions of space, and under conditions of reduced or enhanced effective gravity as induced by a powerful magnetic field.

Arnowitz, Leonard↗
NASA NTRS1981

Finite-analytic numerical solution of heat transfer in two-dimensional cavity flow

Heat transfer in cavity flow is numerically analyzed by a new numerical method called the finite-analytic method. The basic idea of the finite-analytic method is the incorporation of local analytic solutions in the numerical solutions of linear or nonlinear partial differential equations. In the present investigation, the local analytic solutions for temperature, stream function, and vorticity distributions are derived. When the local analytic solution is evaluated at a given nodal point, it gives an algebraic relationship between a nodal value in a subregion and its neighboring nodal points. A system of algebraic equations is solved to provide the numerical solution of the problem. The finite-analytic method is used to solve heat transfer in the cavity flow at high Reynolds number (1000) for Prandtl numbers of 0.1, 1, and 10.

Chen, C.-J.↗
NASA NTRS1975

Approximate solutions of radiative transfer in dusty nebulae. I - Pure hydrogen nebulae

This is the first of a series of papers dealing with transfer of radiation in dusty nebulae. The formulae for the general problem are presented. This paper discusses nebulae containing dust and hydrogen. Approximate solutions, accurate to within 50 percent, are obtained for spherical nebulae containing purely absorbing dust. Less accurate solutions are presented for the general case of scattering and absorbing dust. The results are presented in a form convenient for calculating the required number of ionizing photons, the fractional ionization of hydrogen, and the fractions of ionizing photons absorbed by dust and gas in terms of size, hydrogen density, dust albedo, and optical depth. Explicit relations between these quantities are obtained for uniform nebulae. Simple integrals are presented for calculating the above quantities for spherically symmetric nebulae with nonuniform gas and dust distribution.

Petrosian, V.↗
NASA NTRS1975

Approximate solutions of radiative transfer in dusty nebulae. 2: Hydrogen and helium

The ionization structure of hydrogen and helium in dusty nebulae is discussed. The general equations for pure hydrogen nebulae are modified to include helium. An approximate analytic solution is presented for Stroemgren radii of hydrogen and helium in the absence of dust. It is shown that these results, with simple modifications, are also applicable to dusty nebulae where the effective absorption cross section of dust grains varies slowly with frequency in the 1000 to 200A range. No analytic solutions are possible if this cross section varies rapidly with frequency. In this case, however, simple coupled differential equations are derived. Approximate analytic expressions are presented for evaluation of the variation of the fraction of ionizing radiation absorbed by dust and the ratio of the volume emission measures of He II to H II regions with the spectrum of the ionizing source, helium abundance, and absorption properties of dust. The effects of dust on the He III zone are discussed. Results are restricted to spherically symmetric nebulae, but nonuniform gas and dust distributions and clumpiness can be taken into account.

Dana, R. A.↗
NASA NTRS1976

Approximate solutions of radiative transfer in dusty nebulae. II - Hydrogen and helium

The ionization structure of hydrogen and helium in dusty nebulae is discussed. General equations for pure hydrogen nebulae have been modified to include helium. An approximate analytical solution is presented for Stroemgren radii of hydrogen and helium in the absence of dust. It is shown that these results, with simple modifications, are also applicable to dusty nebulae where the effective absorption cross section of dust grains varies slowly with frequency in the range from 1000 to 200 A. No analytical solutions are possible if this cross section varies rapidly with frequency. In this case, however, simple coupled differential equations are derived which can easily be solved numerically. Approximate analytical expressions are given for evaluating the variation of the fraction of ionizing radiation absorbed by dust and the ratio of the volume emission measures of He II to H II regions with the spectrum of the ionizing source, helium abundance, and absorption properties of dust. The effects of dust on the He III zone are discussed. The present results are restricted to spherically symmetric nebulae, but nonuniform gas and dust distributions and clumpiness can be taken into account by the general results.

Dana, R. A.↗
NASA NTRS1989

Green's function solution to heat transfer of a transparent gas through a tube

A heat transfer analysis of a transparent gas flowing through a circular tube of finite thickness is presented. This study includes the effects of wall conduction, internal radiative exchange, and convective heat transfer. The natural mathematical formulation produces a nonlinear, integrodifferential equation governing the wall temperature and an ordinary differential equation describing the gas temperature. This investigation proposes to convert the original system of equations into an equivalent system of integral equations. The Green's function method permits the conversion of an integrodifferential equation into a pure integral equation. The proposed integral formulation and subsequent computational procedure are shown to be stable and accurate.

Frankel, J. I.↗
NASA NTRS1994

An analytic solution of the radiative transfer equation for a gray scattering atmosphere in motion

We provide a formal analytic solution of the radiative transfer equation for a gray moving atmosphere in a plane parallel geometry. A formal solution in the diffusion and the free-streaming limit is also provided in the case of a spherically extended atmosphere. The formal solutions are written explicitly for scattering atmospheres in which the density and the velocity fields are given by a power law. A self-consistent temperature profile accurate to O(Beta = v/c) is provided for the case in which the absorption or the scattering are temperature independent. The gray extinction temperature profile is considerably simplified in the case of a scattering atmosphere. Steady state flow and homologous expansion are special cases that are considered in detail.

Pistinner, Shlomi↗
NASA NTRS1985

Turbine Vane External Heat Transfer. Volume 2. Numerical Solutions of the Navier-stokes Equations for Two- and Three-dimensional Turbine Cascades with Heat Transfer

The application of the time-dependent ensemble-averaged Navier-Stokes equations to transonic turbine cascade flow fields was examined. In particular, efforts focused on an assessment of the procedure in conjunction with a suitable turbulence model to calculate steady turbine flow fields using an O-type coordinate system. Three cascade configurations were considered. Comparisons were made between the predicted and measured surface pressures and heat transfer distributions wherever available. In general, the pressure predictions were in good agreement with the data. Heat transfer calculations also showed good agreement when an empirical transition model was used. However, further work in the development of laminar-turbulent transitional models is indicated. The calculations showed most of the known features associated with turbine cascade flow fields. These results indicate the ability of the Navier-Stokes analysis to predict, in reasonable amounts of computation time, the surface pressure distribution, heat transfer rates, and viscous flow development for turbine cascades operating at realistic conditions.

Yang, R. J.↗