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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 1,027 records · Page 57

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NASA NTRS1989

Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

An experimental investigation of thermocapillary flow in droplets of a vegetable oil (partially hydrogenated soybean oil) immersed in silicone oil was conducted in a test cell with a heated top wall and a cooled bottom wall. The liquids are nearly immiscible and have equal densities at a temperature below the room temperature, thus providing a simulation of low-gravity conditions by reducing the buoyancy forces. The interfacial tension between the two oils was measured in the temperature range 20 to 50 C using a capillary tube and (d sigma)/(d T) was determined to be negative. Droplets ranging in sizes from 3 mm to 1 cm diameter were injected into the silicone oil. The vertical temperature profile in the bulk liquid (silicone oil) produces temperature variations along the interface which induce variations in the interfacial tension. The flow inside the droplet driven by the resulting interfacial shear stresses was observed using a laser light-sheet flow visualization technique. The flow direction is consistent with the sign of (d sigma)/(d T). The observed maximum surface velocities are compared to the theoretical predictions of Young et al. (1959).

Rashidnia, N.↗

NASA NTRS1991

Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

Rashidnia, N.↗

NASA NTRS1972

Natural Resource Information System, design analysis

The computer-based system stores, processes, and displays map data relating to natural resources. The system was designed on the basis of requirements established in a user survey and an analysis of decision flow. The design analysis effort is described, and the rationale behind major design decisions, including map processing, cell vs. polygon, choice of classification systems, mapping accuracy, system hardware, and software language is summarized.

Source record↗

NASA NTRS1984

The zonally averaged circulation, temperature, and compositional structure of the lower thermosphere and variations with geomagnetic activity

A zonally averaged chemical-dynamical model of the thermosphere is used to examine the effect of high-latitude particle and Joule heating on the neutral composition, temperature, and winds at solstice for solar minimum conditions. The meridional circulation forced by solar heating alone is a summer-to-winter flow, with a winter enhancement in atomic oxygen. The high-latitude heat sources drive mean circulation cells that reinforce the solar-driven circulation in the summer hemisphere and oppose this circulation in the winter hemisphere. The changes in wind and temperature caused by the high-latitude heat sources increase the relative concentration of N2 and O2 in the high-latitude upper thermosphere and decrease the O concentration in the high-latitude lower thermosphere. For prolonged moderate levels of geomagnetic activity the peak atomic oxygen density in the polar regions can decrease by factors of 2-3 from geomagnetic quiet conditions.

Roble, R. G.↗

NASA NTRS1985

State-of-charge coulometer

A coulometer for accurately measuring the state-of-charge of an open-cell battery utilizing an aqueous electrolyte, includes a current meter for measuring the battery/discharge current and a flow meter for measuring the rate at which the battery produces gas during charge and discharge. Coupled to the flow meter is gas analyzer which measures the oxygen fraction of the battery gas. The outputs of the current meter, flow meter, and gas analyzer are coupled to a programmed microcomputer which includes a CPU and program and data memories. The microcomputer calculates that fraction of charge and discharge current consumed in the generation of gas so that the actual state-of-charge can be determined. The state-of-charge is then shown on a visual display.

Rowlette, J. J.↗

NASA NTRS1988

A point implicit unstructured grid solver for the Euler and Navier-Stokes equations

An upwind finite element technique that uses cell centered quantities and implicit and/or explicit time marching has been developed for computing hypersonic laminar viscous flows using adaptive unstructured triangular grids. A structured grid of quadrilaterals is laid out near the body surface. For inviscid flows the method is stable at Courant numbers of over 100,000. A first order basic scheme and a higher order flux corrected transport (FCT) scheme have been implemented. This technique has been applied to the problem of predicting type III and IV shock wave interactions on a cylinder, with a view of simulating the pressure and heating rate augmentation caused by an impinging shock on the leading edge of a cowl lip of an engine inlet. The predictions of wall pressure and heating rates compare very well with experimental data. The flow features are very distinctly captured with a sequence of adaptively generated grids. The adaptive mesh generator and the upwind Navier-Stokes solver are combined in a set of programs called LARCNESS, an acronym for Langley Adaptive Remeshing Code and Navier-Stokes Solver.

Thareja, Rajiv R.↗

NASA NTRS1991

A fast upwind solver for the Euler equations on three-dimensional unstructured meshes

An upwind scheme is presented for solving the three-dimensional Euler equations on unstructured tetrahedral meshes. Spatial discretization is accomplished by a cell-centered finite-volume formulation using flux-difference splitting. Higher-order differences are formed by a novel cell reconstruction process which results in computational times per cell comparable to those of structured codes. The approach yields highly resolved solutions in regions of smooth flow while avoiding oscillations across shocks without explicit limiting. Solutions are advanced in time by a 3-stage Runge-Kutta time-stepping scheme with convergence accelerated to steady state by local time stepping and implicit residual smoothing. Solutions are presented for a range of configurations in the transonic speed regime to demonstrate code accuracy, speed, and robustness. The results include an assessment of grid sensitivity and convergence acceleration by mesh sequencing.

Frink, Neal T.↗

NASA NTRS1993

Separation of biogenic materials by electrophoresis under zero gravity (L-3)

Electrophoresis separates electrically charged materials by imposing a voltage between electrodes. Though free-flow electrophoresis is used without carriers such as colloids to separate and purify biogenic materials including biogenic cells and proteins in blood, its resolving power and separation efficiency is very low on Earth due to sedimentation, flotation, and thermal convection caused by the specific gravity differences between separated materials and buffer solutions. The objective of this experiment is to make a comparative study of various electrophoresis conditions on the ground and in zero-gravity in order to ultimately develop a method for separating various important 'vial' components which are difficult to separate on the ground.

Kuroda, Masao↗

NASA NTRS2004

A Fast Upwind Solver for the Euler Equations on Three-Dimensional Unstructured Meshes

Frink, Neal T.↗

NASA NTRS2007

Convergence Acceleration of Runge-Kutta Schemes for Solving the Navier-Stokes Equations

The convergence of a Runge-Kutta (RK) scheme with multigrid is accelerated by preconditioning with a fully implicit operator. With the extended stability of the Runge-Kutta scheme, CFL numbers as high as 1000 can be used. The implicit preconditioner addresses the stiffness in the discrete equations associated with stretched meshes. This RK/implicit scheme is used as a smoother for multigrid. Fourier analysis is applied to determine damping properties. Numerical dissipation operators based on the Roe scheme, a matrix dissipation, and the CUSP scheme are considered in evaluating the RK/implicit scheme. In addition, the effect of the number of RK stages is examined. Both the numerical and computational efficiency of the scheme with the different dissipation operators are discussed. The RK/implicit scheme is used to solve the two-dimensional (2-D) and three-dimensional (3-D) compressible, Reynolds-averaged Navier-Stokes equations. Turbulent flows over an airfoil and wing at subsonic and transonic conditions are computed. The effects of the cell aspect ratio on convergence are investigated for Reynolds numbers between 5:7 x 10(exp 6) and 100 x 10(exp 6). It is demonstrated that the implicit preconditioner can reduce the computational time of a well-tuned standard RK scheme by a factor between four and ten.

Swanson, Roy C., Jr.↗

NASA NTRS2009

Liquid Oxygen/Liquid Methane Test Results of the RS-18 Lunar Ascent Engine at Simulated Altitude Conditions at NASA White Sands Test Facility

Tests were conducted with the RS-18 rocket engine using liquid oxygen (LO2) and liquid methane (LCH4) propellants under simulated altitude conditions at NASA Johnson Space Center White Sands Test Facility (WSTF). This project is part of NASA's Propulsion and Cryogenics Advanced Development (PCAD) project. "Green" propellants, such as LO2/LCH4, offer savings in both performance and safety over equivalently sized hypergolic propulsion systems in spacecraft applications such as ascent engines or service module engines. Altitude simulation was achieved using the WSTF Large Altitude Simulation System, which provided altitude conditions equivalent up to ~122,000 ft (~37 km). For specific impulse calculations, engine thrust and propellant mass flow rates were measured. LO2 flow ranged from 5.9 - 9.5 lbm/sec (2.7 - 4.3 kg/sec), and LCH4 flow varied from 3.0 - 4.4 lbm/sec (1.4 - 2.0 kg/sec) during the RS-18 hot-fire test series. Propellant flow rate was measured using a coriolis mass-flow meter and compared with a serial turbine-style flow meter. Results showed a significant performance measurement difference during ignition startup due to two-phase flow effects. Subsequent cold-flow testing demonstrated that the propellant manifolds must be adequately flushed in order for the coriolis flow meters to give accurate data. The coriolis flow meters were later shown to provide accurate steady-state data, but the turbine flow meter data should be used in transient phases of operation. Thrust was measured using three load cells in parallel, which also provides the capability to calculate thrust vector alignment. Ignition was demonstrated using a gaseous oxygen/methane spark torch igniter. Test objectives for the RS-18 project are 1) conduct a shakedown of the test stand for LO2/methane lunar ascent engines, 2) obtain vacuum ignition data for the torch and pyrotechnic igniters, and 3) obtain nozzle kinetics data to anchor two-dimensional kinetics codes. All of these objectives were met with the RS-18 data and additional testing data from subsequent LO2/methane test programs in 2009 which included the first simulated-altitude pyrotechnic ignition demonstration of LO2/methane.

Melcher, John C., IV↗

NASA NTRS2020

AQUIFER Nano-Electrofuel Energy Economy and Powered Aircraft Operations

The Aqueous, QUick-charging battery Integration For Electric flight Research project is explained and the major subsystems are described, including nano-electric fluid, rim-driven motors, and integration concepts. The nano-electric fluid concept is a new type of aqueous flow battery that could reduce or retire the fire and explosion hazards of conventional batteries and fuel cells. The nano-electric fluid itself could enable energy storage and increased available energy per fuel weight ratios. The rim-driven motor is being developed to improve propulsion system safety and stability and to reduce noise. The rim-driven motor concept could enable motors that are more efficient both electrically and aerodynamically. The Energy Economy of the project concept is presented as a potential renewable or green energy sustainment for utilizing in-place infrastructure. The nano-electric fluid energy charge-use-recharge cycle is presented using renewable energy input from solar, wind, and hydroelectricity. Powered aircraft operations are presented, and the logistics of the new nano-electric fluid technology are explored. Powered aircraft operations topics include weight and balance, fueling, recharging, safety, and derivative considerations.

Lechniak, Jason A.↗

NASA NTRS1980

Flow measurements in a model swirl combustor

Flow measurements in a model combustor composed of two confined coaxial swirling jets under noncombusting conditions are presented. Mean flow results are obtained for five different flow conditions to determine the effect of outer swirl on the recirculation zone (which is used for flame stabilization under combustion conditions). As the outer swirl magnitude is first decreased from maximum counter-swirl to zero and then increased to give co-swirl conditions, the size and the reverse flow velocity in the recirculation zone diminish. Detailed time mean and fluctuating flow measurements are obtained for a co-swirl and a counter-swirl condition with a directional pitot probe and hot-wire anenometry. For these two cases, recirculation zone occurs only with counter-swirl, near the exit of the inner jet. The recirculation zone is in the form of a one celled toroidal vortex having very low swirl velocity. Axial development of fluctuation levels, energy dissipation rates and turbulence length scales are described for the two flow conditions. Spectral analysis reveals periodic oscillations in both flows. The oscillations originate from the inner jet and up to 4 harmonics are observed. The fundamental frequencies are comparable to the rotational frequencies of the inner jets at the exit which are approximately under solid body rotation. The significance of the present results for the combustion process is discussed.

Vu, B. T.↗

NASA NTRS2009

Microwave Sterilization and Depyrogenation System

A fully functional, microgravity-compatible microwave sterilization and depyrogenation system (MSDS) prototype was developed that is capable of producing medical-grade water (MGW) without expendable supplies, using NASA potable water that currently is available aboard the International Space Station (ISS) and will be available for Lunar and planetary missions in the future. The microwave- based, continuous MSDS efficiently couples microwaves to a single-phase, pressurized, flowing water stream that is rapidly heated above 150 C. Under these conditions, water is rapidly sterilized. Endotoxins, significant biological toxins that originate from the cell walls of gram-negative bacteria and which represent another defining MGW requirement, are also deactivated (i.e., depyrogenated) albeit more slowly, with such deactivation representing a more difficult challenge than sterilization. Several innovations culminated in the successful MSDS prototype design. The most significant is the antenna-directed microwave heating of a water stream flowing through a microwave sterilization chamber (MSC). Novel antenna designs were developed to increase microwave transmission efficiency. These improvements resulted in greater than 95-percent absorption of incident microwaves. In addition, incorporation of recuperative heat exchangers (RHxs) in the design reduced the microwave power required to heat a water stream flowing at 15 mL/min to 170 C to only 50 W. Further improvements in energy efficiency involved the employment of a second antenna to redirect reflected microwaves back into the MSC, eliminating the need for a water load and simplifying MSDS design. A quick connect (QC) is another innovation that can be sterilized and depyrogenated at temperature, and then cooled using a unique flow design, allowing collection of MGW at atmospheric pressure and 80 C. The final innovation was the use of in-line mixers incorporated in the flow path to disrupt laminar flow and increase contact time at a given flow rate. These technologies can be employed in small-scale systems for efficient production of MGW in the laboratory or in a range of larger systems that meet various industrial requirements. The microwave antennas can also be adapted to selectively sterilize vulnerable connections to ultra-pure water production facilities or biologically vulnerable systems where microorganisms may intrude.

Akse, James R.↗

NASA NTRS2017

Cause and Cure-Deterioration in Accuracy of CFD Simulations with Use of High-Aspect-Ratio Triangular/Tetrahedral Grids

In the multi-dimensional space-time conservation element and solution element16 (CESE) method, triangles and tetrahedral mesh elements turn out to be the most natural building blocks for 2D and 3D spatial grids, respectively. As such, the CESE method is naturally compatible with the simplest 2D and 3D unstructured grids and thus can be easily applied to solve problems with complex geometries. However, because (a) accurate solution of a high-Reynolds number flow field near a solid wall requires that the grid intervals along the direction normal to the wall be much finer than those in a direction parallel to the wall and, as such, the use of grid cells with extremely high aspect ratio (103 to 106) may become mandatory, and (b) unlike quadrilateral hexahedral grids, it is well-known that accuracy of gradient computations involving triangular tetrahedral grids tends to deteriorate rapidly as cell aspect ratio increases. As a result, the use of triangular tetrahedral grid cells near a solid wall has long been deemed impractical by CFD researchers. In view of (a) the critical role played by triangular tetrahedral grids in the CESE development, and (b) the importance of accurate resolution of high-Reynolds number flow field near a solid wall, as will be presented in the main paper, a comprehensive and rigorous mathematical framework that clearly identifies the reasons behind the accuracy deterioration as described above has been developed for the 2D case involving triangular cells. By avoiding the pitfalls identified by the 2D framework, and its 3D extension, it has been shown numerically.

CFD↗

NASA NTRS1990

An upwind-biased, point-implicit relaxation algorithm for viscous, compressible perfect-gas flows

An upwind-biased, point-implicit relaxation algorithm for obtaining the numerical solution to the governing equations for three-dimensional, viscous, compressible, perfect-gas flows is described. The algorithm is derived using a finite-volume formulation in which the inviscid components of flux across cell walls are described with Roe's averaging and Harten's entropy fix with second-order corrections based on Yee's Symmetric Total Variation Diminishing scheme. Viscous terms are discretized using central differences. The relaxation strategy is well suited for computers employing either vector or parallel architectures. It is also well suited to the numerical solution of the governing equations on unstructured grids. Because of the point-implicit relaxation strategy, the algorithm remains stable at large Courant numbers without the necessity of solving large, block tri-diagonal systems. Convergence rates and grid refinement studies are conducted for Mach 5 flow through an inlet with a 10 deg compression ramp and Mach 14 flow over a 15 deg ramp. Predictions for pressure distributions, surface heating, and aerodynamics coefficients compare well with experiment data for Mach 10 flow over a blunt body.

Gnoffo, Peter A.↗

NASA NTRS1996

Fluid flow stimulates rapid and continuous release of nitric oxide in osteoblasts

Interstitial fluid flow may mediate skeletal remodeling in response to mechanical loading. Because nitric oxide (NO) has been shown to be an osteoblast mitogen and inhibitor of osteoclastic resorption, we investigated and characterized the role of fluid shear on the release of NO in osteoblasts. Rat calvarial cells in a stationary culture produced undetectable levels of NO. Fluid shear stress (6 dyn/cm2) rapidly increased NO release rate to 9.8 nmol.h-1.mg protein-1 and sustained this production for 12 h of exposure to flow. Cytokine treatment also induced NO synthesis after a 12-h lag phase of zero production, followed by a production rate of 0.6 nmol.h-1.mg protein-1. Flow-induced NO production was blocked by the NO synthase (NOS) inhibitor NG-amino-L-arginine, but not by dexamethasone, which suggests that the flow stimulated a constitutive NOS isoform. This is the first time that a functional constitutively present NOS isoform has been identified in osteoblasts. Moreover, fluid flow represents the most potent stimulus of NO release in osteoblasts reported to date. Fluid flow-induced NO production may therefore play a primary role in bone maintenance and remodeling.

NASA Discipline Cell Biology↗

NASA NTRS2012

Progress Toward Affordable High Fidelity Combustion Simulations Using Filtered Density Functions for Hypersonic Flows in Complex Geometries

Significant progress has been made in the development of subgrid scale (SGS) closures based on a filtered density function (FDF) for large eddy simulations (LES) of turbulent reacting flows. The FDF is the counterpart of the probability density function (PDF) method, which has proven effective in Reynolds averaged simulations (RAS). However, while systematic progress is being made advancing the FDF models for relatively simple flows and lab-scale flames, the application of these methods in complex geometries and high speed, wall-bounded flows with shocks remains a challenge. The key difficulties are the significant computational cost associated with solving the FDF transport equation and numerically stiff finite rate chemistry. For LES/FDF methods to make a more significant impact in practical applications a pragmatic approach must be taken that significantly reduces the computational cost while maintaining high modeling fidelity. An example of one such ongoing effort is at the NASA Langley Research Center, where the first generation FDF models, namely the scalar filtered mass density function (SFMDF) are being implemented into VULCAN, a production-quality RAS and LES solver widely used for design of high speed propulsion flowpaths. This effort leverages internal and external collaborations to reduce the overall computational cost of high fidelity simulations in VULCAN by: implementing high order methods that allow reduction in the total number of computational cells without loss in accuracy; implementing first generation of high fidelity scalar PDF/FDF models applicable to high-speed compressible flows; coupling RAS/PDF and LES/FDF into a hybrid framework to efficiently and accurately model the effects of combustion in the vicinity of the walls; developing efficient Lagrangian particle tracking algorithms to support robust solutions of the FDF equations for high speed flows; and utilizing finite rate chemistry parametrization, such as flamelet models, to reduce the number of transported reactive species and remove numerical stiffness. This paper briefly introduces the SFMDF model (highlighting key benefits and challenges), and discusses particle tracking for flows with shocks, the hybrid coupled RAS/PDF and LES/FDF model, flamelet generated manifolds (FGM) model, and the Irregularly Portioned Lagrangian Monte Carlo Finite Difference (IPLMCFD) methodology for scalable simulation of high-speed reacting compressible flows.

Drozda, Tomasz G.↗