Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “flow lines”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Rewet Temperature Correlations for Liquid-Nitrogen Boiling Pipe Flows Across Varying Flow Conditions and Orientations

In many convective liquid-vapor phase change heat transfer engineering applications, cryogenic fluids are widely used in industrial processes, spacecraft and cryosurgery systems, and so on. For example, cryogens are usually used as liquid fuels such as liquid hydrogen and oxygen in the rocket industry, liquid nitrogen (LN2) and helium are frequently used to cool superconducting magnetic device for medical applications. In these systems, proper transport, handling, and storage of cryogenic fluids are of extreme importance. Among all the cryogenic transport processes performed in room temperatures, quenching, also termed chilldown, is a unavoidable initial, transient phase-change heat transfer process that brings the system down to the cryogenic condition. The Leidenfrost temperature or rewet temperature that signals the end of film boiling is practically considered the completion point of a quenching process. Therefore, rewet temperature has been considered the most important parameter for the engineering design of cryogenic thermal management systems. As most of the previous correlations for predicting the Leidenfrost temperature and the rewet temperature have been basically developed for water, they are shown to disagree with recent liquid nitrogen pipe chilldown experiments in upward and downward flow directions over a wide range of flow rates, pressures, and degrees of inlet subcooling. In addition to a complete review of the literature, two new correlations are presented in this work, one based on bubble growth and another based on the theoretical maximum limit of superheat. Each correlation performs well over the entire data set.

liquid nitrogen↗
NASA NTRS2022

Validation of a High-Fidelity Supersonic Parachute Inflation Dynamics Model and Best Practice

The parachute inflation dynamics (PID) of a Disk-Gap-Band (DGB) parachute system travelling at supersonic velocities in the high-altitude Earth atmosphere is simulated using a high-fidelity, multiphysics, massively-parallel computational framework. The sensitivity of the simulation results with respect to critical modelling and simulation parameters, including the fluid mechanical governing equations (Euler vs Navier-Stokes with RANS turbulence closure vs Navier-Stokes with LES turbulence closer), the interaction between the flow and the suspension lines (accounted for vs not accounted for), the dynamics of the payload (restrained vs free), and the material model of the heterogeneous fabric canopy (Saint-Venant Kirchoff vs mechanics-informed multiscale neural network), is extensively investigated. The parameter investigation is enabled by advancements to the state-of-the-art in the modelling and simulation of the supersonic parachute inflation process, which are presented as part of the computational framework. The predictive quality of the computational framework in the context of supersonic PID is validated by comparison of the simulation results with the experimental results from NASA’s Advanced Supersonic Parachute Research (ASPIRE) project. Through the validation, best practices for the modelling and simulation of supersonic PID are developed and proposed.

Rabinovitch, Jason↗
DOE OSTI2015

Methods for isolation and viability assessment of biological organisms

Isolation of biological or chemical organisms can be accomplished using a surface enhanced Raman scattering (SERS) system. The SERS system can be a single or a stacked plurality of photonic crystal membranes with noble-metal lined through pores for flowing analyte potentially containing the biological or chemical organisms. The through pores can be adapted to trap individual biological or chemical organisms and emit SERS spectra, which can then be detected by a detector and further analyzed for viability of the biological or chemical organism.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Highlights from Sherwood 2014. International Sherwood Fusion Theory Conference, March 24-26, Bahia Resort Hotel, San Diego, California

Rob Goldston (PPPL) kicked off the Sherwood meeting with his review talk, “Understanding and innovation in magnetic fusion”. He covered a history of results from tokamak experiments in the areas of core confinement, stability, sustainment – tying the paradigms for understanding all three to the plasma edge, where outstanding questions remain. Two other review talks were given by Russel Caflisch (UCLA) on “Accelerated simulation of coulomb collisions in plasmas”, and Dan Barnes (Tri Alpha) on “Plasma theory as private enterprise”. Altogether, there were 15 invited talks spanning the field of fusion theory on topics such as nonlinear gyrokinetic simulations of the tokamak edge, plasma-wall modelling, toroidal rotation, zonal flows, magnetic field-line reconnection, coulomb collisions, and intrinsic momentum transport. Author-provided summaries of several of the invited talks are included on pages 7 to 14 of this document. There was a very strong showing by graduate students, postdocs, and young scientists at the meeting. More than 25 students from around the world presented papers. A list of all participating students can be found on page 5 of this document

Source record↗
NASA NTRS1993

Evidence for siphon flows with shocks in solar magnetic flux tubes

We synthesize profiles of the infrared line Fe I 15648.5 A (g = 3) for a recently developed theoretical model of siphon flows along photospheric magnetic loops. The synthesized line profiles are compared with the observations from which Rueedi et al. (1992) deduced the presence of such flows across the neutral line of an active region plage. This comparison supports the interpretation of Rueedi et al. (1992). It also suggests that the average footpoint separation of the observed loops carrying the siphon flow is 8-15 sec and that the siphon flow experiences a standing tube shock in the downstream leg near the top of the arch.

Degenhardt, D.↗
DOE OSTI2015

Age and the means of bypassing stasis influence the intrinsic subtype of immortalized human mammary epithelial cells

Based on molecular features, breast cancers are grouped into intrinsic subtypes that have different prognoses and therapeutic response profiles. With increasing age, breast cancer incidence increases, with hormone receptor-positive and other luminal-like subtype tumors comprising a majority of cases. It is not known at what stage of tumor progression subtype specification occurs, nor how the process of aging affects the intrinsic subtype. We examined subtype markers in immortalized human mammary epithelial cell lines established following exposure of primary cultured cell strains to a two-step immortalization protocol that targets the two main barriers to immortality: stasis (stress-associated senescence) and replicative senescence. Cell lines derived from epithelial cells obtained from non-tumorous pre- and post-menopausal breast surgery tissues were compared. Additionally, comparisons were made between lines generated using two different genetic interventions to bypass stasis: transduction of either an shRNA that down-regulated p16INK4A, or overexpressed constitutive active cyclin D1/CDK2. In all cases, the replicative senescence barrier was bypassed by transduction of c-Myc. Cells from all resulting immortal lines exhibited normal karyotypes. Immunofluorescence, flow cytometry, and gene expression analyses of lineage-specific markers were used to categorize the intrinsic subtypes of the immortalized lines. Bypassing stasis with p16 shRNA in young strains generated cell lines that were invariably basal-like, but the lines examined from older strains exhibited some luminal features such as keratin 19 and estrogen receptor expression. Overexpression of cyclin D1/CDK2 resulted in keratin 19 positive, luminal-like cell lines from both young and old strains, and the lines examined from older strains exhibited estrogen receptor expression. Thus age and the method of bypassing stasis independently influence the subtype of immortalized human mammary epithelial cells.

59 BASIC BIOLOGICAL SCIENCES↗
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 NTRS1995

Development of a quiet supersonic wind tunnel with a cryogenic adaptive nozzle

Low-disturbance or 'quiet' wind tunnels are now considered an essential part of meaningful boundary layer transition research. Advances in Supersonic Laminar Flow Control (SLFC) technology for swept wings depends on a better understanding of the receptivity of the transition phenomena to attachment-line contamination and cross-flows. This need has provided the impetus for building the Laminar Flow Supersonic Wind Tunnel (LFSWT) at NASA-Ames, as part of the NASA High Speed Research Program (HSRP). The LFSWT was designed to provide NASA with an unequaled capability for transition research at low supersonic Mach numbers (<2.5). The following are the objectives in support of the new Fluid Mechanic Laboratory (FML) quiet supersonic wind tunnel: (I) Develop a unique injector drive system using the existing FML indraft compressor; (2) Develop an FML instrumentation capability for quiet supersonic wind tunnel evaluation and transition studies at NASA-Ames; (3) Determine the State of the Art in quiet supersonic wind tunnel design; (4) Build and commission the LFSWT; (5) Make detailed flow quality measurements in the LFSWT; (6) Perform tests of swept wing models in the LFSWT in support of the NASA HSR program; and (7) Provide documentation of research progress.

Wolf, Stephen W. D.↗
NASA NTRS2010

Formation and Reconnection of Three-Dimensional Current Sheets in the Solar Corona

Current-sheet formation and magnetic reconnection are believed to be the basic physical processes responsible for much of the activity observed in astrophysical plasmas, such as the Sun s corona. We investigate these processes for a magnetic configuration consisting of a uniform background field and an embedded line dipole, a topology that is expected to be ubiquitous in the corona. This magnetic system is driven by a uniform horizontal flow applied at the line-tied photosphere. Although both the initial field and the driver are translationally symmetric, the resulting evolution is calculated using a fully three-dimensional magnetohydrodynamic (3D MHD) simulation with adaptive mesh refinement that resolves the current sheet and reconnection dynamics in detail. The advantage of our approach is that it allows us to apply directly the vast body of knowledge gained from the many studies of 2D reconnection to the fully 3D case. We find that a current sheet forms in close analogy to the classic Syrovatskii 2D mechanism, but the resulting evolution is different than expected. The current sheet is globally stable, showing no evidence for a disruption or a secondary instability even for aspect ratios as high as 80:1. The global evolution generally follows the standard Sweet- Parker 2D reconnection model except for an accelerated reconnection rate at a very thin current sheet, due to the tearing instability and the formation of magnetic islands. An interesting conclusion is that despite the formation of fully 3D structures at small scales, the system remains close to 2D at global scales. We discuss the implications of our results for observations of the solar corona. Subject Headings: Sun: corona Sun: magnetic fields Sun: reconnection

Edmondson, J. K.↗
NASA NTRS1987

A mapped finite difference study of noise propagation in nonuniform ducts with mean flow

The primary objective of this work is to study noise propagation in acoustically lined variable area ducts with mean fluid flow. The method of study is numerical in nature and involves a body-fitted grid mapping procedure in conjunction with a factored-implicit finite difference technique. The mean fluid flow model used is two-dimensional, inviscid, irrotational, incompressible, and nonheat conducting. Fully-coupled solutions of the linearized gasdynamic equations are obtained for both positive and negative Mach numbers as well as for hard and soft wall conditions. The factored-implicit finite difference technique used did give rise to short wavelength perturbations, but these were dampened by the introduction of higher order artificial dissipation terms into the scheme. Results compared favorably with available numerical and experimental data.

Raad, Peter E.↗
DOE OSTI2022

Flow Channels and the Generation of Alfvénic Turbulence Along Storm‐Time Inner Magnetospheric Field‐Lines

Abstract A feature of Earth's storm‐time magnetosphere outside the plasmapause is the occurrence of broad‐spectrum Alfvénic fluctuations. In this letter observations from the Van Allen Probes are compared with 3‐D fluid‐kinetic simulations of an evolving convective flow channel to investigate the mechanisms generating the observed spectrum. It is shown how narrow channels of fast convection are unstable to the Kelvin‐Helmholtz instability which on closed field‐lines initiates a cascade to small scales. Sustained driving of the flow combined with reflection from the topside ionosphere leads to the generation of an intensified spectrum of electromagnetic structures having similar spectral and morphological characteristics to those observed. This process couples enhanced magnetospheric convection to kinetic scale electromagnetic fluctuations that drive particle transport, scattering and energization through the outer radiation belt and ring current during geomagnetic storms.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1984

Numerical simulation of the tip vortex off a low-aspect-ratio wing at transonic speed

The viscous transonic flow around a low-aspect-ratio wing has been computed using an implicit, three-dimensional, 'thin-layer' Navier-Stokes solver. The grid around the geometry of interest is obtained numerically as a solution to a Dirichlet problem for the cube. The geometry chosen for this study is a low-aspect-ratio wing with large sweep, twist, taper, and camber. The topology chosen to wrap the mesh around the wing with good tip resolution is a C-O type mesh. Using this grid, the flow around the wing was computed for a free-stream Mach number of 0.82 at an angle of attack of 5 deg. At this Mach number, an oblique shock forms on the upper surface of the wing, and a tip vortex and three-dimensional flow separation off the wing surface are observed. Particle path lines indicate that the three-dimensional flow separation on the wing surface is part of the roots of the tip-vortex formation. The lifting of the tip vortex before the wing trailing edge is clearly observed by following the trajectory of particles released around the wing tip.

Mansour, N. N.↗
NASA NTRS2011

Numerical Prediction of Radiation Measurements Taken in the X2 Facility for Mars and Titan Gas Mixtures

Thermochemical relaxation behind a normal shock in Mars and Titan gas mixtures is simulated using a CFD solver, DPLR, for a hemisphere of 1 m radius; the thermochemical relaxation along the stagnation streamline is considered equivalent to the flow behind a normal shock. Flow simulations are performed for a Titan gas mixture (98% N2, 2% CH4 by volume) for shock speeds of 5.7 and 7.6 km/s and pressures ranging from 20 to 1000 Pa, and a Mars gas mixture (96% CO2, and 4% N2 by volume) for a shock speed of 8.6 km/s and freestream pressure of 13 Pa. For each case, the temperatures and number densities of chemical species obtained from the CFD flow predictions are used as an input to a line-by-line radiation code, NEQAIR. The NEQAIR code is then used to compute the spatial distribution of volumetric radiance starting from the shock front to the point where thermochemical equilibrium is nominally established. Computations of volumetric spectral radiance assume Boltzmann distributions over radiatively linked electronic states of atoms and molecules. The results of these simulations are compared against experimental data acquired in the X2 facility at the University of Queensland, Australia. The experimental measurements were taken over a spectral range of 310-450 nm where the dominant contributor to radiation is the CN violet band system. In almost all cases, the present approach of computing the spatial variation of post-shock volumetric radiance by applying NEQAIR along a stagnation line computed using a high-fidelity flow solver with good spatial resolution of the relaxation zone is shown to replicate trends in measured relaxation of radiance for both Mars and Titan gas mixtures.

Palmer, Grant↗
NASA NTRS1984

Spectral formation in compact X-ray sources

The gas flows responsible for X-ray spectral emission in compact X-ray sources are complex and likely to be optically thick. In galactic sources these flows include: stellar wind, accretion disk and corona, magnetosphere, and shock at the compact object surface. Active galactic nuclei are surrounded by many dense clouds responsible for the broad optical and UV emission lines. The nature of these flows can be discovered through observations of their X-ray spectra and time variability. Theoretical models for the formation of line and continuum spectra in these sources are described, emphasizing atomic photoabsorption, line emission, and Comptonization. Current observations of X-ray and UV spectra of compact galactic sources and active galactic nuclei are interpreted in terms of these models. Great advances in the understanding of these systems will result from future missions capable of observing their spectra at higher resolution. Observations of the complex of iron K-alpha lines at 6.4-6.7 keV will be particularly valuable.

Mccray, R.↗
DOE OSTI2024

Measurement of the thermal effects in the dispersion relation of the dust acoustic wave in the presence of a magnetic field

This award supported an experimental study of the properties of the dust acoustic wave, low-frequency, l ongitudinal wave mode that propagates through the dust component of a dusty plasma system and is self-excited by the free energy from the ion streaming p ast the dust, in the presence of a high magnetic fiel d. In particular, this project measured the thermal state of dusty plasma system by measuring the dispersi on relation of the dust acoustic wave while varying (1) the strength and direction of the magnetic field relative to the propagation direction of the wave and (2) the neutral gas pressure. By exploiting the unique ability of the MDPX facility to generate a dusty plasma in a high magnetic field environment, it is possible to create a preferential ion flow along the magnetic field lines as the ions become magnetized. In this way, the magnetic field strength can be used to control t he strength of the ion flow through the dust cloud an d provide insight into the contribution that one of the physical mechanisms, a two-stream ion-dust instability, thought to be responsible for high temperatures that have been previously observed might have. This work was completed over two, one-week long runs o n the Magnetized Dusty Plasma eXperiment (MDPX) in the Magnetized Plasma Research Laboratory at Auburn University and supported by work at Wittenberg University (development of an electrode system that would allow for the wave mode to propagate in th e direction of gravity as the orientation of the magnetic field is changed by rotating the magnets on the M DPX device, analysis of data acquired during the experimental campaigns, testing alternative strategies to form a dust cloud based on what was learned the first experimental campaign, etc.).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2000

Anomalous Flows at Dayside High-Latitude Magnetopause as Observed by Interball Tail Probe

We analyze magnetopause crossings at high latitudes dayside magnetopause as observed by Interball Tail probe. High time resolution plasma data show strong short-time flows near magnetopause that strongly deviate from surrounding magnetosheath flow. Several quasi- periodic velocity variations are observed at times. Plasma parameters, such as number density, temperature and bulk velocity-of these flows are close to magnetosheath values. These anomalous flows are observed almost at every magnetopause crossing in this region. The ion velocity distributions in these regions indicate the presence of open field lines. Observed properties of these flows suggest their association with reconnection at high latitudes.

Vaisberg, O. L.↗
NASA NTRS1988

Identification of RNO 43 and B335 as two highly collimated bipolar flows oriented nearly in the plane of the sky

An analysis of CO and CS line observations shows that RNO 43 and B335 are single highly collimated bipolar flows oriented nearly in the plane of the sky. The angle between the line of sight and the flow axis is estimated to be 85 deg in RNO 43 and 82 deg in B335. The results indicate that each of these flows must have a significant expansion velocity perpendicular to its axis, and that the flow in B335 must be driven by a mostly nonmolecular wind component.

Cabrit, Sylvie↗