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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Instability of time-periodic flows

The instabilities of some spatially and/or time-periodic flows are discussed, in particular, flows with curved streamlines which can support Taylor-Gortler vortices are described in detail. The simplest flow where this type of instability can occur is that due to the torsional oscillations of an infinitely long circular cylinder. For more complicated spatially varying time-periodic flows, a similar type of instability can occur and is spatially localized near the most unstable positions. When nonlinear effects are considered it is found that the instability modifies the steady streaming boundary layer induced by the oscillatory motion. It is shown that a rapidly rotating cylinder in a uniform flow is susceptible to a related type of instability; the appropriate stability equations are shown to be identical to those which govern the instability of a boussinesq fluid of Prandtl number unity heated time periodically from below.

Hall, P.↗
NASA NTRS1987

Instability of time-periodic flows

The instabilities of some spatially and/or time-periodic flows are discussed, in particular, flows with curved streamlines which can support Taylor-Gortler vortices are described in detail. The simplest flow where this type of instability can occur is that due to the torsional oscillations of an infinitely long circular cylinder. For more complicated spatially varying time-periodic flows, a similar type of instability can occur and is spatially localized near the most unstable positions. When nonlinear effects are considered it is found that the instability modifies the steady streaming boundary layer induced by the oscillatory motion. It is shown that a rapidly rotating cylinder in a uniform flow is susceptible to a related type of instability; the appropriate stability equations are shown to be identical to those which govern the instability of a Boussinesq fluid of Prandtl number unity heated time periodically from below.

Hall, Philip↗
NASA NTRS2003

Rayleigh-Benard Instability in a Vertical Cylinder with a Rotating Magnetic Field

This paper presents a linear stability analysis for the Rayleigh-Benard convection in a finite-length, vertical cylinder with a rotating magnetic field. The vertical wall of the cylinder is adiabatic, and planar top and bottom walls are isothermal with a higher temperature at the bottom. The stabilizing effects of the rotating magnetic field are studied for four values of the Prandtl number. Results for one Prandtl number are compared to previously published experimental results.

Walker, J. S.↗
NASA NTRS1988

Primitive numerical simulation of circular Couette flow - Carrousel wind tunnel nonturbulent solutions

The azimuthal-invariant, three-dimensional cylindrical, incompressible Navier-Stokes equations are solved to steady state for a finite-length, physically realistic model. The numerical method relies on an alternating-direction implicit scheme that is formally second-order accurate in space and first-order accurate in time. The equations are linearized and uncoupled by evaluating variable coefficients at the previous time iteration. Wall grid clustering is provided by a Roberts transformation in radial and axial directions. A vorticity-velocity formulation is found to be preferable to a vorticity-streamfunction approach. Subject to no-slip, Dirichlet boundary conditions, except for the inner cylinder rotation velocity (impulsive start-up) and zero-flow initial conditions, nonturbulent solutions are obtained for sub- and supercritical Reynolds numbers of 100 to 400 for a finite geometry where R(outer)/R(inner) = 1.5, H/R(inner) = 0.73, and H/Delta-R = 1.5. An axially-stretched model solution is shown to asymptotically approach the one-dimensional analytic Couette solution at the cylinder midheight. Flowfield change from laminar to Taylor-vortex flow is discussed as a function of Reynolds number. Three-dimensional velocities, vorticity, and streamfunction are presented via two-dimensional graphs and three-dimensional surface and contour plots.

Hasiuk, Jan↗
NASA NTRS1993

Numerical study of compressible boundary-level transition between two concentric cylinders

The period of support of this Cooperative Agreement was from April 15, 1990 to October 31, 1992, with a no-cost extension to October 31, 1993 to complete some unfinished tasks. Within this period, research associate Dr. Kai-Hsiung Kao has made tremendous contributions to this project and has produced an impressive amount of publications. At the early stage of the research, he spent some time on the extension of his doctoral thesis in a subject closely related to the present project. His major research effort was devoted to the investigation of stability of a viscous flow between two differentially rotating cylinders, with an emphasis on the effects of compressibility and heat transfer. Actually, the research topics were not restricted to those described by the title of this Agreement, as reflected in some of the more recent publications.

Chow, Chuen-Yen↗
NASA NTRS1990

Mathematical modeling of the flow field and particle motion in a rotating bioreactor at unit gravity and microgravity

The biotechnology group at NASA Johnson Space Center is developing systems for culturing mammalian cells that stimulate some aspect of microgravity and provide a low shear environment for microgravity-based studies on suspension and anchorage dependent cells. The design of these vessels for culturing cells is based on the need to suspend cells and aggregates of cells and microcarrier beads continually in the culturing medium. The design must also provide sufficient circulation for adequate mass transfer of nutrients to the cells and minimize the total force on the cells. Forces, resulting from sources such as hydrodynamic fluid shear and collisions of cells and walls of the vessels, may damage delicate cells and degrade the formation of three dimensional structures. This study examines one particular design in both unit gravity and microgravity based on two concentric cylinders rotating in the same direction at different speeds to create a Couette flow between them. A numerical simulation for the flow field and the trajectories of particles in the vessel. The flow field for the circulation of the culturing medium is modeled by the Navier-Stokes equations. The forces on a particle are assumed to be drag from the fluid's circulation, buoyancy from the gravitational force and centrifugal force from the rotation of the vessel. The problem requires first solving the system of partial differential equations for the fluid flow by a finite difference method and then solving the system of ordinary differential equations for the trajectories by Gear's stiff method. Results of the study indicate that the trajectories in unit gravity and microgravity are very similar except for small spatial deviations on the fast time scale in unit gravity. The total force per unit cross sectional area on a particle in microgravity, however, is significantly smaller than the corresponding value in unit gravity, which is also smaller than anticipated. Hence, this study indicates that this design for a bioreactor with optimal rates of rotation can provide a good environment for culturing cells in microgravity with adequate circulation and minimal force on the cells.

Boyd, Ernest J.↗
DOE OSTI2025

Electrolyzers in focus: advances in CO 2 electrolyzer designs

Electrochemical CO 2 reduction (ECR) remains a viable method to reintegrate anthropogenic CO 2 into current energy infrastructures through its conversion into commodity chemicals. To facilitate the integration of ECR, electrochemical devices called electrolyzers must be implemented to overcome the inherent limitations that exist in current ECR experiments, namely kinetics and mass transport. In this review, we outline the current and advancing designs in ECR electrolyzers, with a focus on the following five electrochemical devices: membrane electrode assemblies (MEA), flow cell (FC), rotating disk electrode (RDE), rotating ring-disk electrode (RRDE), and rotating cylinder electrode (RCE). We highlight the tunable components of each electrolyzer with a forward outlook on the optimization and relevance of electrolyzer designs in upcoming ECR applications.

CO2 reduction↗
NASA NTRS1926

First experiences with the rotating laboratory

This report describes experiences with a rotating cylinder to explore the effects of motion and flow upon human sensory organs. One observation was that the variation of the resultant line of gravity (from gravity and centrifugal force) was not felt so strongly as might be expected. The impressions produced by the physical effects on the members of the body, especially the ones caused by the deflecting force (Coriolis force), are exactly what the laws of physics would lead us to expect, although somewhat surprising when observed in one's own body.

ROTATING↗
DOE OSTI2025

Lithium Divertor Targets and Walls for the ASTER Liquid Stellarator Reactor, Distributed Divertor

Stellarators may have advantages for certain liquid metal options as Plasma Facing Components (PFC) for divertor targets and first walls due to the wide range of possible magnetic configurations, which additionally are free of disruptions and fast field variations. In a previous work (V. Queral et al., IEEE Trans. Plasma Sci. 52, 2024), a concept of stellarator reactor (ASTER-CP) based on swirling Li-molten salts and liquid lithium floating on the molten salt as PFC was presented. The divertor matters were not studied then and, thus, they are being studied and experimentally tested now. The ASTER-CP reactor concept, the initial liquid metal experiments and potential concepts for the ASTER-CP divertor and first wall are reported. Concerning the experiments, several small scale experiments of galinstan in a small rotating cylinder under magnetic field have been produced, including one experiment with high viscosity galinstan-mixture for increased thickness of layer. An experiment of floating lithium on the molten salt LiCl-PbCl2 gave fast volatilization/decomposition of the molten salt. Particularly for divertors, the traditional free-flow, Capillary Porous Systems and ‘divertorlets’ have been studied for application to ASTER-CP. Surface waves (hot spots), lack of enough surface fluid turbulence and excessive fluid speed are the main issues found in fast free-flow. The perhaps original concept of Distributed Divertor and Equi-power Surface is tentatively proposed and studied, taking advantage of stellarator fields and low recycling regime.

distributed divertor↗
DOE OSTI2024

On a High-Mirror Stellarator Reactor Exploratory Concept With Neutrons Concentrated on Centrifuge Liquids

In the framework of fusion energy research based on magnetic confinement, stellarators allow numerous degrees of freedom for the design of the magnetic trap and plasma shape. Taking advantage of these features, some plasma shapes might benefit several of the many integrated elements involved in commercial fusion reactors, like, e.g., decreasing the number, mass and complexity of replaced activated in-vessel components (IVC) (i.e., by using liquids), extraction of large power, tritium generation, and remote maintenance. Certainly, free-surface liquid materials were proposed for tokamaks and field-reversed configuration (FRC) to try to improve some of such elements, i.e., in advanced power extraction (APEX) studies. Some reactor-relevant quasi-isodynamic (QI) magnetic configurations exhibit a relatively straight sector of plasma and high magnetic mirror. The combination of those elements and possibilities in a single stellarator reactor concept might have some advantages, in spite of the uncertainties due to the current low technological readiness level (TRL). The proposed and studied reactor concept is based on a vacuum vessel having short curved sectors and longer wide cylindrical sectors, which encloses a high-mirror low-vertical-excursion magnetic configuration, and swirling liquids or rotating cylinders, which centrifuge molten Li salts located at the low field region. Thus, the molten salts (if possible covered by a thin layer of liquid lithium) would be located on the internal perimeter of the cylinder, to act as particle exhaust (except for helium), neutron power extractor, and tritium breeder. The high-mirror feature tries to concentrate the neutron power at the cylindrical sectors, which might avoid using breeding materials at the curved sectors. The different elements of the concept are exploratorily studied and defined, and the difficulties assessed.

centrifuge↗
NASA NTRS1965

Transition in circular couette flow.

Stability and transition in Couette flow between concentric rotating cylinders including design and instrumentation of experimental machines

COUETTE FLOW↗
NASA NTRS1972

Application of quasi-linearization techniques to the analysis of aerodynamic-noise fields

The method of parametric differentiation was used as a means of obtaining solutions which describe aerodynamically generated sound fields, and which are valid over an increased range of a specific parameter. Details of applying the method to the problem of calculating the sound field of two rectilinear vortices rotating about an axis between them in a compressible medium are discussed. Pressure distribution in the far field are obtained. Parametric differentiation was also applied to the calculation of aerodynamic sound generated by a rotating cylinder in a viscous, compressible medium. The formulation of this problem in parametric space is given, and a procedure for obtaining a solution is outlined.

Harris, W. L., Sr.↗
NASA NTRS1973

Motion compensator for holographic motion picture camera

When reference beam strikes target it undergoes Doppler shift dependent upon target velocity. To compensate, object beam is first reflected from rotating cylinder that revolves in direction opposite to target but at same speed. When beam strikes target it is returned to original frequency and is in phase with reference beam. Alternatively this motion compensator may act on reference beam.

Kurtz, R. L.↗
NASA NTRS1975

Correlation of low speed wind tunnel and flight test data for V/STOL aircraft

The XV-5B fan-in-wing aircraft and the Y0V-10 RCF rotating cylinder flap aircraft were subjected to wind tunnel tests. These tests were conducted specifically to provide for correlation between wind tunnel and inflight aerodynamics and noise test data. Correlation between aerodynamic and noise data are presented and testing techniques that are related to the accuracy of the data, or that might affect the correlations, are discussed.

Cook, W. L.↗
NASA NTRS1975

Analysis of a heat transfer device for measuring film coefficients

A heat transfer device consisting of a heated rotating cylinder in a bath was analyzed for its effectiveness to determine heat transfer coefficient of fluids. A time dependent analysis shows that the performance is insensitive to the value of heat transfer coefficient with the given rig configuration.

Medrow, R. A.↗
NASA NTRS1976

Correlation of low speed wind tunnel and flight test data for V/STOL aircraft

The availability of wind tunnel test data for correlation purposes of the same V/STOL aircraft tested in flight is very limited. This is due in a large part to size limitations of wind tunnels and the number of wind tunnels available for testing of full-scale aircraft. Wind tunnel tests are described for two research aircraft - the XV-5B fan-in-wing aircraft and the YOV-10 RCF (rotating cylinder flap) aircraft - in the NASA Ames 40- by 80-foot wind tunnel. The tests were conducted specifically to provide for correlation between wind tunnel and in-flight aerodynamics and noise test data. Correlation between aerodynamic and noise data are presented and testing techniques that are related to the accuracy of the data, or that might affect the correlations, are discussed. The correlation of noise measurements made with a J-85 engine mounted on a F-106 aircraft during low altitude flyovers with the same J-85 engine mounted on a model and tested in the Ames 40- by 80-foot wind tunnel are also reported.

Cook, W. L.↗