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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Relativistic tidal interaction of a white dwarf with a massive black hole

We compute encounters of a realistic white dwarf model with a massive black hole in the regime where relativistic effects are important, using a three-dimensional, finite-difference, Eulerian, piecewise parabolic method (PPM) hydrodynamical code. Both disruptive and nondisruptive encounters are considered. We identify and discuss relativistic effects important for the problem: relativistic shift of the pericenter distance, time delay, relativistic precession, and the tensorial structure of the tidal forces. In the nondisruptive case, stripping of matter takes place. In the surface layers of the surviving core, complicated hydrodynamical phenomena are revealed. In both disruptive and nondispruptive encounters, material flows out in the form of two thin, S-shaped, supersonic jets. Our results provide realistic initial conditions for the subsequent investigation of the dynamics of the debris in the field of the black hole. We evaluate the critical conditions for complete disruption of the white dwarf, and compare our results with the corresponding results for nonrelativistic encounters.

Frolov, V. P.↗
NASA NTRS1996

Software Project Management and Measurement on the World-Wide-Web (WWW)

We briefly describe a system for forms-based, work-flow management that helps members of a software development team overcome geographical barriers to collaboration. Our system, called the Web Integrated Software Environment (WISE), is implemented as a World-Wide-Web service that allows for management and measurement of software development projects based on dynamic analysis of change activity in the workflow. WISE tracks issues in a software development process, provides informal communication between the users with different roles, supports to-do lists, and helps in software process improvement. WISE minimizes the time devoted to metrics collection and analysis by providing implicit delivery of messages between users based on the content of project documents. The use of a database in WISE is hidden from the users who view WISE as maintaining a personal 'to-do list' of tasks related to the many projects on which they may play different roles.

Callahan, John↗
NASA NTRS2001

A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe. The major study of a sample of z=3 and its comparison with a sample of z=0.l quasars across the whole X-ray to radio spectrum was completed and accepted for publication in ApJ Supplements. This study comprises the thesis work of Olga Kuhn. The two samples are matched in evolved luminosity, and so should be sampling the same black hole population at different z, and in different accretion states. Despite this no strong differences were found between the samples, except in the 'small bump' region of the optical/UV. This region is dominated by FeII emission, and may indicate abundance evolution in quasars. The lack of overall spectral changes argues strongly against a single population of quasars fading over cosmic time, and for a multiple generation, or multiple outburst model for quasars. A study of the total luminosity absorbed from quasars and re-emitted in the infrared produced two results (reported in two papers): The minimum intrinsic luminosity/Gpc(3) from AGN compared with the measured mass density in supermassive black holes [Gpc(-3)] requires a conversion efficiency of accreted mass into luminosity of greater than 15%. Non-rotating black holes cannot exceed 5% efficiency, while rapidly rotating black holes can reach 47%. Hence our result requires that most supermassive black holes must be rapidly rotating. The second result comes from considering the contribution that the re-radiated quasar radiation makes to the far infrared background (FIRB). The effective temperature of the re radiation is tightly constrained, but the detailed shape (e.g. line emission, range of temperature) is only of second order importance. At least 15perhaps 20-25% of the FIR background must come from AGN. This contribution significantly relieves problems in galaxy evolution that come from trying to use only starlight to make the FIRB. The third paper addresses the origin of the dust obscuration that is so widespread in AGN. The standard assumption is that the dust comes from the normal star-formation processes in galaxies and is drawn close to the nucleus along with the gas that powers the accretion. In complete contrast, using a wind outflow model for the broad emission line (BEL) region (Elvis 2000) as a basis, we show that BEL clouds will expand, cool and form dust as they flow outward, in strict analogy to the stellar winds of red supergiants.

Elvis, M.↗
NASA NTRS2001

Capillary Flow in Containers of Polygonal Section: Theory and Experiment

An improved understanding of the large-length-scale capillary flows arising in a low-gravity environment is critical to that engineering community concerned with the design and analysis of spacecraft fluids management systems. Because a significant portion of liquid behavior in spacecraft is capillary dominated it is natural to consider designs that best exploit the spontaneous character of such flows. In the present work, a recently verified asymptotic analysis is extended to approximate spontaneous capillary flows in a large class of cylindrical containers of irregular polygonal section experiencing a step reduction in gravitational acceleration. Drop tower tests are conducted using partially-filled irregular triangular containers for comparison with the theoretical predictions. The degree to which the experimental data agree with the theory is a testament to the robustness of the basic analytical assumption of predominantly parallel flow. As a result, the closed form analytical expressions presented serve as simple, accurate tools for predicting bulk flow characteristics essential to practical low-g system design and analysis. Equations for predicting corner wetting rates, total container flow rates, and transient surfaces shapes are provided that are relevant also to terrestrial applications such as capillary flow in porous media.

Weislogel, Mark M.↗
NASA NTRS1995

Stokes problems for moving half-planes

New exact solutions of the Navier-Stokes equations are obtained for the unbounded and bounded oscillatory and impulsive tangential edgewise motion of touching half-infinite plates in their own plane. In contrast to Stokes classical solutions for the harmonic and impulsive motion of an infinite plane wall, where the solutions are separable or have a simple similarity form, the present solutions have a two-dimensional structure in the near region of the contact between the half-infinite plates. Nevertheless, it is possible to obtain relatively simple closed-form solutions for the flow field in each case by defining new variables which greatly simplify the r- and theta- dependence of the solutions in the vicinity of the contact region. These solutions for flow in a half-infinite space are then extended to bounded flows in a channel using an image superposition technique. The impulsive motion has application to the motion near geophysical faults, whereas the oscillatory motion has arisen in the design of a novel oscillating half-plate flow chamber for examining the effect of fluid shear stress on cultured cell monolayers.

NASA Discipline Musculoskeletal↗
NASA NTRS2006

Global Aspects of Heliosphere-Geosphere Coupling

The magnetosphere serves both to hold off the solar wind and to couple it selectively to the Earth through the auroral zones. It has long been understood that the plasmasphere consists of geogenic plasmas that expand out of the sunlit low latitude ionosphere, but it was initially assumed that the hot low density plasma beyond the plasmasphere is largely of solar wind origin with a minor admixture of ionospheric plasmas, discovered via mass spectrometric observations in the early 70's. Since then, elaborate simulation models have been developed that have taken us from an era of cartoon physics to a new era of quantitative global comparisons between observations and theory. In most current global circulation models of the magnetosphere, the ionospheric load on the system is taken to lie exclusively in the thin F layer of the ionosphere. This layer is coupled with solar wind and magnetospheric plasmas via Maxwell stresses communicated by field aligned current systems, and with the thermosphere via ion-neutral charge exchange and Coulomb collisions. However, recent observations have shown us that ionospheric plasmas flow sporadically in various forms into the plasmasphere and up into the high latitude circulation cells of the outer magnetosphere, as driven by the solar wind and its variable intensity and magnetic field. Under some conditions, ionospheric material is observed to be the principal component of plasmas at the dayside magnetopause and in the plasma sheet and ring current regions. Given a global model of magnetospheric circulation, it is relatively straightforward to investigate the behaviors of ionospheric plasmas in response to solar wind drivers, and we report the results of such efforts here. We find that ionospheric plasmas dominate the plasma pressure in the magnetosphere in some regions, particularly when the solar wind is especially intense and-or southward directed. This result violates the assumption that the ionospheric load is confined to the F layer, and shows that the ionosphere is often an important dynamic element of the solar wind-ionosphere system throughout the magnetosphere, especially during larger geospace storms. This means that future global circulation models must account for ionospheric plasma inertia, heat capacity, and pressure, to be quantitatively credible.

Moore, Thomas E.↗
NASA NTRS2007

New Observations of the Heliospheric Magnetic Field from the Voyager Spacecraft

We review recent observations of variations of the heliospheric magnetic field B(t) made by Voyager 1 and 2 (V1 and V2), and we discuss the boundary conditions needed for models to explain the observations. Usually, observations from a spacecraft close to the Sun, such as ACE, WIND or Ulysses are used as input to a time-dependent model. Generally, the predicted profile B(t) can be compared directly with the observed profile only when either V1 or V2 is approximately radially aligned with a near-Sun spacecraft; this happens rarely and only for a brief time interval. The Bastille Day events illustrate this situation. In the absence of radial alignment of the spacecraft it is possible to predict the development of a global structure (a GMIR) with data from ACE or WIND, if they obtain a representative sample the flows that merge to form a GMIR. When latitudinal gradients are small and when there is statistical homogeneity in the azimuthal direction, it is possible to predict the statistical properties of the large-scale fluctuations of B(t) observed by V1 or V2 during a year or so. We illustrate this situation with observations from the recent solar maximum and the declining phase of the solar cycle. Predictions of detailed observations made by V1 and V2 under general conditions (e.g., when there is a large latitudinal gradient) require boundary conditions as a function of time on a surface, such as a Sun-centered sphere with a radius of 1 AU. These conditions can only be provided by global solar observations. We suggest the feasibility of such an approach, using V2 observations for 2005 and 2006. The prediction of observations in the heliosheath requires the solution of the 3-D boundary problem for the supersonic solar wind and propagation of solar wind through the termination shock into the heliosphere. The properties of B(t) observed in the heliosheath have not yet been predicted.

Burlaga, Leonard F.↗
NASA NTRS2006

Rapid Aeroelastic Analysis of Blade Flutter in Turbomachines

The LINFLUX-AE computer code predicts flutter and forced responses of blades and vanes in turbomachines under subsonic, transonic, and supersonic flow conditions. The code solves the Euler equations of unsteady flow in a blade passage under the assumption that the blades vibrate harmonically at small amplitudes. The steady-state nonlinear Euler equations are solved by a separate program, then equations for unsteady flow components are obtained through linearization around the steady-state solution. A structural-dynamics analysis (see figure) is performed to determine the frequencies and mode shapes of blade vibrations, a preprocessor interpolates mode shapes from the structural-dynamics mesh onto the LINFLUX computational-fluid-dynamics mesh, and an interface code is used to convert the steady-state flow solution to a form required by LINFLUX. Then LINFLUX solves the linearized equations in the frequency domain to calculate the unsteady aerodynamic pressure distribution for a given vibration mode, frequency, and interblade phase angle. A post-processor uses the unsteady pressures to calculate generalized aerodynamic forces, response amplitudes, and eigenvalues (which determine the flutter frequency and damping). In comparison with the TURBO-AE aeroelastic-analysis code, which solves the equations in the time domain, LINFLUX-AE is 6 to 7 times faster.

Trudell, J. J.↗
NASA NTRS2016

Metallic Thin-Film Bonding and Alloy Generation

Diffusion bonding a stack of aluminum thin films is particularly challenging due to a stable aluminum oxide coating that rapidly forms on the aluminum thin films when they are exposed to atmosphere and the relatively low meting temperature of aluminum. By plating the individual aluminum thin films with a metal that does not rapidly form a stable oxide coating, the individual aluminum thin films may be readily diffusion bonded together using heat and pressure. The resulting diffusion bonded structure can be an alloy of choice through the use of a carefully selected base and plating metals. The aluminum thin films may also be etched with distinct patterns that form a microfluidic fluid flow path through the stack of aluminum thin films when diffusion bonded together.

Fryer, Jack Merrill↗
NASA NTRS2016

High Leverage Technologies for In-Space Assembly of Complex Structures

In-space assembly (ISA), the ability to build structures in space, has the potential to enable or support a wide range of advanced mission capabilities. Many different individual assembly technologies would be needed in different combinations to serve many mission concepts. The many-to-many relationship between mission needs and technologies makes it difficult to determine exactly which specific technologies should receive priority for development and demonstration. Furthermore, because enabling technologies are still immature, no realistic, near-term design reference mission has been described that would form the basis for flowing down requirements for such development and demonstration. This broad applicability without a single, well-articulated mission makes it difficult to advance the technology all the way to flight readiness. This paper reports on a study that prioritized individual technologies across a broad field of possible missions to determine priority for future technology investment.

Hamill, Doris↗
NASA NTRSDate not supplied

Preliminary Development of Multi-Vehicle (m:N) Operations with NASA Langley’s Remote Vehicle Operations Center

To achieve the vision of Advanced Air Mobility (AAM), a transition from localized operations of aircraft to remote operations is being pursued across many use cases. This transition will allow fewer human operators to manage more increasingly autonomous aircraft (i.e., m operators managing N vehicles, or m:N). To study this operational concept, the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) has developed a prototype remote vehicle operations center and ground control station (GCS) software to conduct research with simulated and real flight operations. To date, flight operations at LaRC have been limited to one vehicle per operator. However, the current paper describes initial development and considerations for enabling m:N flight operations at LaRC. Further, the research described in this paper provides the foundation for a concept of operations (ConOps) that will be developed to support remote operators managing multiple increasingly autonomous vehicles, with the goal of exploring human-autonomy teaming (HAT) concepts that enable more advanced m:N operations. Two key enablers have been identified to facilitate successful m:N operations: GCS software updates for multi-vehicle management and procedural updates for vehicle handoffs during off-nominal events. Additionally, specific modifications were identified across five key areas: technology and software, team structure, inter-team communication, contingency plans, and operator decision flows. Next steps in forming the LaRC m:N ConOps will include working with subject-matter experts to identify off-nominal scenarios, implementing the recommended GCS functionality for m:N operations, and performing integration testing of facility capabilities and new operational procedures. Although the future m:N ConOps will be tailored to the NASA LaRC remote operations facility and flight range, it is intended to be a transparent, accessible, and reality-based exemplar for external organizations seeking to create or evaluate their own m:N operational concepts.

m:N↗
DOE OSTI2025

Systems Innovation: Modernization & Efficiencies for ESH&Q Reviews

Environmental compliance reviews at INL have traditionally been managed through fragmented systems, relying on multiple spreadsheets and manual processes. This inefficiency led to time-consuming status updates and redundant tasks, such as manually sending reminder emails and transferring data from Excel to the Environmental Review Process (ERP). Initial attempts to streamline these processes using Power Automate and Excel revealed significant limitations, necessitating a more comprehensive solution. To address these immediate inefficiencies, automated workflows were developed using Power Automate. These workflows were designed to send scheduled status update reminders and capture responses through standardized forms, with submitted data flowing directly into centralized Excel trackers. This automation reduced the administrative burden, improved data accuracy, and enabled faster, more consistent reporting. Specifically, email automation achieved a 65% efficiency gain, while data integration saw a 48% improvement, resulting in 91% of project statuses being updated within two months. Despite the improvements brought by Power Automate, the fragmented nature of the review processes persisted. To further enhance efficiency and accuracy, the Integrated Review Tool (IRT) was developed. The IRT aims to centralize review initiation and connect team systems, creating an interconnected data infrastructure that preserves team autonomy while enhancing overall efficiency. This tool automates email reminders, centralizes reviews, and streamlines data integration, significantly improving the accuracy and efficiency of environmental compliance reviews. The design and development of the IRT involved advanced systems methodology, process mapping, project management, and collaboration with subject matter experts. The minimum viable product design is 100% complete, and system development is currently underway, with expected outcomes including a centralized entry point for all ESH&Q reviews, automated routing, real-time tracking and analytics, AI integration, and a user-friendly interface. This project demonstrates the potential of leveraging automation and integrated systems to enhance efficiency, accuracy, and decision-making in environmental reporting and compliance processes at INL.

99 - GENERAL AND MISCELLANEOUS↗
NASA NTRS2002

Interchange Method in Compressible Magnetized Couette Flow: Magnetorotational and Magnetoconvective Instabilities

We obtain the general forms of the axisymmetric stability criteria in a magnetized compressible Couette flow using an energy variational principle, the so-called interchange or Chandrasekhar s met hod, which we applied successfully in the incompressible case. This formulation accounts for the simultaneous presence of gravity, rotation, a toroidal magnetic field, a weak axial magnetic field, entropy gradients, and density gradients in the initial equilibrium state. The power of the method lies in its simplicity which allows us to derive extremely compact and physically clear expressions for the relevant stability criteria despite the inclusion of so many physical effects. In the implementation of the method, all the applicable conservation laws are explicitly taken into account during the variations of a quantity with dimensions of energy which we call the free energy function. As in the incompressible case, the presence of an axial field invalidates the conservation laws of angular momentum and azimuthal magnetic flux and introduces instead isorotation and axial current conservation along field lines. Our results are therefore markedly different depending on whether an axial magnetic field is present, and generalize in two simple expressions all previously known, partial stability criteria for the appearance of magnetorotational instability. Furthermore, the coupling between magnetic tension and buoyancy and its influence to the dynamics of nonhomoentropic magnetized flows becomes quite clear from our results. In the limits of plane-parallel atmospheres and homoentropic flows, our formulation easily recovers the stability criteria for suppression of convective and Parker instabilities, as well as some related special cases studied over 40 years ago by Newcomb and Tserkovnikov via laborious variational techniques.

Christodoulou, Dimitris M.↗
NASA NTRS1991

Development of a steady potential solver for use with linearized, unsteady aerodynamic analyses

A full potential steady flow solver (SFLOW) developed explicitly for use with an inviscid unsteady aerodynamic analysis (LINFLO) is described. The steady solver uses the nonconservative form of the nonlinear potential flow equations together with an implicit, least squares, finite difference approximation to solve for the steady flow field. The difference equations were developed on a composite mesh which consists of a C grid embedded in a rectilinear (H grid) cascade mesh. The composite mesh is capable of resolving blade to blade and far field phenomena on the H grid, while accurately resolving local phenomena on the C grid. The resulting system of algebraic equations is arranged in matrix form using a sparse matrix package and solved by Newton's method. Steady and unsteady results are presented for two cascade configurations: a high speed compressor and a turbine with high exit Mach number.

Hoyniak, Daniel↗
NASA NTRS1987

Simple numerical method for predicting steady compressible flows

The present numerical method for the solution of the isenthalpic form of the governing equations for compressible viscous and inviscid flows has its basis in the concept of flux vector splitting in its implicit form, and has been tested in the cases of several difficult viscous and inviscid configurations. An acceleration of time-marching to steady state is accomplished by implementing a multigrid procedure which effectively increases the convergence rate. The steady state results obtained are largely of good quality, and required only short computational times.

Von Lavante, E.↗
NASA NTRS1982

Three-dimensional inviscid analysis of the scramjet inlet flow field

A computer code has been developed to analyze the inviscid flow field in a supersonic combustion ramjet (scramjet) inlet. The code uses the three-dimensional Euler equations in full conservation form to describe the inlet flow. An algebraic numerical coordinate transformation is used to generate a set of boundary-fitted curvilinear coordinates. The governing equations are solved by a time-asymptotic, unsplit, two-step, finite-difference method. This method is highly efficient on the vector processing computers for which the current code is written. Detailed results are presented for two scramjet inlet configurations over a range of Mach numbers. The calculated results are compared with the available experimental and theoretical results.

Kumar, A.↗
DOE OSTI2021

Preliminary Implementation of Two-Dimensional Cartesian Solver in CTF-R

Sub-channel codes are one of the the modeling and simulation tools used for thermal-hydraulic analysis of nuclear reactors. A few examples of such sub-channel codes are the COolant Boiling in Rod Arrays (COBRA) family of codes. The approximations that are used to simplify the fluid conservation equations into sub-channel form, mainly that of axially-dominated flow, lead to noticeable limitations on sub-channels solvers for problems with significant flow in lateral directions. In this report, a two-dimensional Cartesian solver is developed and implemented within CTF-R, which is the residual solver in the North Carolina State University version of COBRA-TF (CTF). The new solver will enable CTF to simulate flow that is not axially-dominated. The appropriate Cartesian forms of the conservation equations are derived and implemented in the solver. Once the conservation equations are established, the process of constructing the matrix system was altered to solve a two-dimensional staggered grid system. A simple case was used to test that the two-dimensional Cartesian solver is accurate. The test problem does not include any source terms or flow in the lateral direction. The results show that the solver was able to run the simple case and converge to a steady-state solution. Future work will focus on testing existing capabilities by using test cases that include transients and equation cross-terms. Future work will also include adding additional capabilities such as enabling the solver to include cases with source terms and three dimensional cases.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS2012

Implementation of a Transition Model in a NASA Code and Validation Using Heat Transfer Data on a Turbine Blade

The purpose of this report is to summarize and document the work done to enable a NASA CFD code to model laminar-turbulent transition process on an isolated turbine blade. The ultimate purpose of the present work is to down-select a transition model that would allow the flow simulation of a variable speed power turbine to be accurately performed. The flow modeling in its final form will account for the blade row interactions and their effects on transition which would lead to accurate accounting for losses. The present work only concerns itself with steady flows of variable inlet turbulence. The low Reynolds number k- model of Wilcox and a modified version of the same model will be used for modeling of transition on experimentally measured blade pressure and heat transfer. It will be shown that the k- model and its modified variant fail to simulate the transition with any degree of accuracy. A case is thus made for the adoption of more accurate transition models. Three-equation models based on the work of Mayle on Laminar Kinetic Energy were explored. The three-equation model of Walters and Leylek was thought to be in a relatively mature state of development and was implemented in the Glenn-HT code. Two-dimensional heat transfer predictions of flat plate flow and two-dimensional and three-dimensional heat transfer predictions on a turbine blade were performed and reported herein. Surface heat transfer rate serves as sensitive indicator of transition. With the newly implemented model, it was shown that the simulation of transition process is much improved over the baseline k- model for the single Reynolds number and pressure ratio attempted; while agreement with heat transfer data became more satisfactory. Armed with the new transition model, total-pressure losses of computed three-dimensional flow of E3 tip section cascade were compared to the experimental data for a range of incidence angles. The results obtained, form a partial loss bucket for the chosen blade. In time the loss bucket will be populated with losses at additional incidences. Results obtained thus far will be discussed herein.

Ameri, Ali A.↗