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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 NTRS1975

Acoustics of attached and partially attached flow for simplified OTW configurations with 5:1 slot nozzle

The acoustics of simple engine over-the-wing configurations, with complete and partially attached jet flow to the shielding surface were studied with scale models. The nozzle used consisted of a 5:1 slot nozzle operated at a nominal jet Mach number of 0.6, with the flow directed parallel to and at angles up to 10 deg toward the shielding surface. The flow field at the trailing edge of each nozzle/surface configuration was mapped. the results indicate that, with attached flow, the jet flow field is stretched in the flow direction resulting in locally higher velocities than those for partially attached flow or nozzle only flow. The stretching of the flow field increases the noise levels for the attached flow cases compared to those with only partially attached flow. With attached flow, the shielding benefits are substantially reduced compared with fully detached flow.

Vonglahn, U.↗
NASA NTRS1975

Acoustics of attached and partially attached flow for simplified OTW configurations with 5:1 slot nozzle

The acoustics of simple engine over-the-wing configurations, with complete and partially attached jet flow to the shielding surface, were studied at model scale. The nozzle consisted of a 5:1 slot nozzle operated at a nominal jet Mach number of 0.6, with the flow directed parallel to and at angles up to 10 deg toward the shielding surface. The shielding length of the surface and the nozzle height above the surface were varied. The aerodynamic results indicate that, with attached flow, the jet flow field is stretched in the flow direction resulting in locally higher velocities than those for partially attached flow or nozzle only flow. The stretching of the flow field increased the noise levels for the attached flow cases compared to those with only partially attached flow. With attached flow, the shielding benefits were substantially reduced compared with fully detached flow. Increasing the impingement angle of the jet flow from 0 to 10 deg generally caused the noise levels to increase in the mid and high frequencies.

Von Glahn, U.↗
NASA NTRS1976

Resonance-line transfer with partial redistribution. VIII - Solution in the comoving frame for moving atmospheres

The effects of partial frequency redistribution in the scattering process for lines formed in moving atmospheres are analyzed using a general method that allows the transfer equation to be solved in the comoving frame of the gas. The same chromospheric and atomic model studied by Cannon and Vardavas (1974) is employed in the calculations, but a depth scale with logarithmically spaced points is adopted. It is found that in both static and moving atmospheres, the profiles obtained with complete and partial frequency redistribution are virtually identical. The large differences in profiles obtained by Cannon and Vardavas when they used complete and partial redistribution are shown to be spurious (and physically unreal) effects resulting from angle averaging in the observer's frame instead of the comoving frame.

Mihalas, D.↗
NASA NTRS1976

Improvement in birefringent filters. IV - The alternate partial polarizer filter

The design and performance of a birefringent filter with alternate partial polarizers are analyzed. The properties of several filter configurations with imperfect intermediate polarizers are examined. It is shown that such filters have significant advantages in transmission and profile shape over both the standard Lyot and the contrast element Lyot filters. These theoretical advantages are demonstrated by the measured properties of an actual filter using the alternate partial polarizer (APP) design. This filter is a four-module eight-crystal APP device which has been built using Polaroid HN-38 for the perfect polarizers and two laminated sheets of HN-55 for the partial polarizers. The measured characteristics of the filter are found to be in good agreement with theory.

Title, A. M.↗
NASA NTRS1976

Solutions to divergence form equations using the method of partial implicitization

Partial implicitization is well suited for use on vector-processing computers since the method is an explicit unconditionally stable numerical technique. So far equations cast in nondivergence form have been used, though equations cast in the divergence form would have inherently greater accuracy. Since the method of partial implicitization is applicable only to relaxing problems to their steady state and is not applicable to true transient problems, a simple mathematical manipulation can be carried out which will produce the desired partial implicitization solution to divergence form equations.

Graves, R. A., Jr.↗
NASA NTRS1978

The development of a three-dimensional partially elliptic flow computer program for combustor research

A three dimensional, partially elliptic, computer program was developed. Without requiring three dimensional computer storage locations for all flow variables, the partially elliptic program is capable of predicting three dimensional combustor flow fields with large downstream effects. The program requires only slight increase of computer storage over the parabolic flow program from which it was developed. A finite difference formulation for a three dimensional, fully elliptic, turbulent, reacting, flow field was derived. Because of the negligible diffusion effects in the main flow direction in a supersonic combustor, the set of finite-difference equations can be reduced to a partially elliptic form. Only the pressure field was governed by an elliptic equation and requires three dimensional storage; all other dependent variables are governed by parabolic equations. A numerical procedure which combines a marching integration scheme with an iterative scheme for solving the elliptic pressure was adopted.

Pan, Y. S.↗
NASA NTRS1979

A partial oxidation staging concept for gas turbines using broadened specification fuels

A concept is described for using a very fuel-rich partial oxidation process as the first stage of a two-stage combustion system for onboard processing of broadened specification fuels to improve their combustion characteristics. Results of an initial step in the experimental verification of the concept are presented, where the basic benefits of H2 enrichment are shown to provide extended lean-combustion limits and permit simultaneous achievement of ultralow levels of NOx, CO, and HC emissions. The H2 required to obtain these results is within the range available from a partial oxidation precombustion stage. Operation of a catalytic partial oxidation reactor using a conventional aviation turbine fuel (JP5) and an unconventional fuel (blend of JP5/xylene) is shown to produce a 'fuel gas' stream with near-theoretical equilibrium H2 content. However, a number of design considerations indicate that the precombustion stage should be incorporated as a thermal reaction.

Clayton, R. M.↗
NASA NTRS1982

Preliminary modeling of high pressure partial melting - Implications for early lunar differentiation

A quantitative model is presented for equilibrium crystallization of lunar magmas at high pressure, which, viewed in reverse, is equivalent to equilibrium partial melting. Data are extrapolated from simple systems, mare basalt systems, and from experiments on terrestrial compositions. Liquidus phase equilibria in a portion of the CaO-MgO-Al2O3-SiO2 system serve as a guide for predicting phase equilibria in the natural system. High pressure partial melting sequences are calculated for several proposed whole moon compositions at nominal pressure of 10 and 20 kb. Results show that compositions with chondritic Ca/Al have quite different melting paths from those with subchondritic Ca/Al, and as a result the types of magmas produced are quite different. If the moon possesses a chondritic Ca/Al ratio, models which rely on small degrees of partial melting to produce the early lunar magnetism are suspect.

Longhi, J.↗
NASA NTRS1982

New advances in the partial-reflection-drifts experiment using microprocessors

Improvements to the partial reflection drifts experiment are completed. The results of the improvements include real time processing and simultaneous measurements of the D region with coherent scatter. Preliminary results indicate a positive correlation between drift velocities calculated by both methods during a two day interval. The possibility now exists for extended observations between partial reflection and coherent scatter. In addition, preliminary measurements could be performed between partial reflection and meteor radar to complete a comparison of methods used to determine velocities in the D region.

Ruggerio, R. L.↗
NASA NTRS1983

A partially molten magma ocean model

Under the assumption that the outer 300-400 km of the moon was at first only partially, rather than fully molten, an explanation of the properties of the lunar crust and upper mantle is obtained according to which nuclei of anorthositic crust formed over localized bodies of magma segregated from the partial melt, and then grew peripherally until fully covering the moon. Over most of its growth period, the anorthosite crust floated on a layer of magma whose thickness was regulated by the opposing forces of (1) loss of material by fractional crystallization, and (2) addition of magma from the partial melt below. The clustering of Eu, Sr and Mg values found among pristine ferroan anorthosites are predicted by this model.

Shirley, D. N.↗
NASA NTRS1985

The evolution of partially differentiated planetesimals Evidence from iron meteorite groups IAB and IIICD

Some of the properties of IAB and IIICD iron meteorites thought to be derived from partially differentiated planetesimals are summarized, and the physical aspects that may have controlled parent body differentiation and affected the composition of the sulfide melt are outlined. The chemical evolution of the parent body is then discussed, and observations supporting the partial differentiation model are examined. Finally, an attempt is made to reinterpret barometric and chronometric data in light of the partial differentiation model, and tentative conclusions are presented.

Kracher, A.↗
NASA NTRS1985

Partial rotor-to-stator rub demonstration

A rotor radial rub typically occurs in seals or at a blade tip or shroud when there is insufficient clearance, high vibration, or the shaft equilibrium position has been displaced to effectively limit the clearance (eccentricity). There are two extreme cases of radial rubs: full annular rub, when the rotor maintains continuous contact with the seal, etc.; and a partial rub, when the contact occurs during a fraction of the precession period. They both involve similar physical phenomena such as friction and modification of stiffness. In partial rubs with consecutive impacts, a significant average value of radial force is generated. This results in shaft average displacement in the direction opposite the rub location. The rotor rig demonstrates the characteristics of a partial lateral rub of varying severity and location. These characteristics include: (1) subharmonic components as a function of rotative speed/first balance resonance ratio and radial force; (2) higher harmonic content as a function of severity; (3) increased average rotor stiffness resulting in increased first balance resonance speed; and (4) change in overall orbital pattern as a sum of the unbalance response (1x) and subharmonic response (1nx).

Grissom, R.↗
NASA NTRS1985

Tidally forced viscous heating in a partially molten Io

Models of Io that generate most of their heat by viscous dissipation in a partially molten (perhaps nearly liquid) asthenosphere are developed: a partially molten asthenosphere model and a partially molten interior model. An approximate thermal analysis is carried out, suggesting the possibility of a stable steady state. The models are consistent with observations of widely dispersed hot spots on the Io surface that radiate most of Io's heat loss. The hot spots imply that magmas carry most of the dissipative heating that is naturally accounted for in the models.

Ross, M. N.↗
NASA NTRS1986

Partial and Interaction Spline Models for the Semiparametric Estimation of Functions of Several Variables

A partial spline model is a model for a response as a function of several variables, which is the sum of a smooth function of several variables and a parametric function of the same plus possibly some other variables. Partial spline models in one and several variables, with direct and indirect data, with Gaussian errors and as an extension of GLIM to partially penalized GLIM models are described. Application to the modeling of change of regime in several variables is described. Interaction splines are introduced and described and their potential use for modeling non-linear interactions between variables by semiparametric methods is noted. Reference is made to recent work in efficient computational methods.

Wahba, Grace↗
NASA NTRS1989

Optimal moving grids for time-dependent partial differential equations

Various adaptive moving grid techniques for the numerical solution of time-dependent partial differential equations were proposed. The precise criterion for grid motion varies, but most techniques will attempt to give grids on which the solution of the partial differential equation can be well represented. Moving grids are investigated on which the solutions of the linear heat conduction and viscous Burgers' equation in one space dimension are optimally approximated. Precisely, the results of numerical calculations of optimal moving grids for piecewise linear finite element approximation of partial differential equation solutions in the least squares norm.

Wathen, A. J.↗
NASA NTRS1991

Applications of singular value analysis and partial-step algorithm for nonlinear orbit determination

An adaptive method in which cruise and nonlinear orbit determination problems can be solved using a single program is presented. It involves singular value decomposition augmented with an extended partial step algorithm. The extended partial step algorithm constrains the size of the correction to the spacecraft state and other solve-for parameters. The correction is controlled by an a priori covariance and a user-supplied bounds parameter. The extended partial step method is an extension of the update portion of the singular value decomposition algorithm. It thus preserves the numerical stability of the singular value decomposition method, while extending the region over which it converges. In linear cases, this method reduces to the singular value decomposition algorithm with the full rank solution. Two examples are presented to illustrate the method's utility.

Ryne, Mark S.↗
NASA NTRS1992

Partially exposed polymer dispersed liquid crystals for boundary layer investigations

A new configuration termed partially exposed polymer dispersed liquid crystal in which the liquid crystal microdroplets dispersed in a rigid polymer matrix are partially entrapped on the free surface of the thin film deposited on a glass substrate is reported. Optical transmission characteristics of the partially exposed polymer dispersed liquid crystal thin film in response to an air flow induced shear stress field reveal its potential as a sensor for gas flow and boundary layer investigations.

Parmar, Devendra S.↗
NASA NTRS1993

Experimental partial melting of the Allende (CV) and Murchison (CM) chondrites and the origin of asteroidal basalt

Following the investigation of Jurewicz et al. (1991) on the composition of partial melts of eucrites and angrites, this study investigates partial melts of the Allende and Murchison chondrites and details the anhydrous phase relations of both chondrites at 1 atm, under temperatures and oxygen fugacities plausigle for the formation of basaltic meteorites. It was found that, in general, ambient oxygen fugacity exerts a strong influence on the compositions of partial melts of chondrites by controlling the amount of FeO available to the silicate system. At high f(O2), angritic magmas are produced, whereas eucritic melts are produced at low levels of f(O2).

Jurewicz, A. J. G.↗