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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Hydrodynamic effects on cells in agitated tissue culture reactors

The mechanisms by which hydrodynamic forces can affect cells grown on microcarrier beads in agitated cell culture reactors were investigated by analyzing the motion of microcarriers relative to the surrounding fluid, to each other, and to moving or stationary solid surfaces. It was found that harmful effects on cell cultures that have been previously attributed to shear can be better explained as the effects of turbulence (of a size scale comparable to the microcarriers or the spacing between them) or collisions. The primary mechanisms of cell damage involve direct interaction between microcarriers and turbulent eddies, collisions between microcarriers in turbulent flow, and collisions against the impeller or other solid surfaces. The implications of these analytical results for the design of tissue culture reactors are discussed.

Cherry, R. S.↗
NASA NTRS1994

A three-dimensional structured/unstructured hybrid Navier-Stokes method for turbine blade rows

A three-dimensional viscous structured/unstructured hybrid scheme has been developed for numerical computation of high Reynolds number turbomachinery flows. The procedure allows an efficient structured solver to be employed in the densely clustered, high aspect-ratio grid around the viscous regions near solid surfaces, while employing an unstructured solver elsewhere in the flow domain to add flexibility in mesh generation. Test results for an inviscid flow over an external transonic wing and a Navier-Stokes flow for an internal annular cascade are presented.

Tsung, F.-L.↗
NASA NTRS1988

Three-dimensional unsteady transonic viscous-inviscid interaction using the Euler and boundary-layer equations

The objective of this study is the development of a numerical technique which can provide three-dimensional, time-accurate, compressible, turbulent flow solutions in a practical and relatively economical way. The approach taken is that of the method of viscous-inviscid interaction. The Euler equations are assumed to govern the outer inviscid portion of the flow, and the viscous layer close to the solid wall is described by a set of integral boundary-layer equations. The viscous solutions are obtained in a direct fashion with a weighted-average phase error scheme. The method of equivalent sources is used for viscous-inviscid coupling. Steady-state and unsteady computations for an AGARD airfoil and a wing show that satisfactory engineering solutions can be obtained for attached, high Reynolds number flows using this method. Quasi-unsteady interactions are shown to produce similar results to those provided by true-unsteady interactions. Considerable computer resources can be saved for some cases by using quasi-unsteady interactions.

Whitfield, David L.↗
NASA NTRS1963

AN AEROTHERMOCHENMCAL ANALYSIS OF EROSIVE BURNING OF SOLID PROPELLANT

In a solid propellant rocket of a side burning type, the flow rate of the hot combustion gases parallel to the burning surface is approximately proportional to the distance from the leading edge of the propellant. In the present paper, therefore, the erosive burning of the solid propellant is analyzed by tile boundary-layer approximation in aerothermochemistry for the case where the velocity, u ∞ , of the hot combustion gas stream outside the boundary layer increases linearly with the distance, x, from the leading edge of the propellant, i.e., u ∞ = Gx, and the effects of the hot gas stream on the burning rate of the propellant are examined.

GAS STREAM↗
NASA NTRS2001

Evaluation of Sulfur Flow Emplacement on Io from Galileo Data and Numerical Modeling

Galileo images of bright lava flows surrounding Emakong Patera have been analyzed and numerical modeling has been performed to assess whether these flows could have resulted from the emplacement of sulfur lavas on Io. Images from the solid-state imaging.(SSI) camera show that these bright, white to yellow Emakong flows are up to 370 km long and contain dark, sinuous features that are interpreted to be lava conduits, approx. 300-500 m wide and > 100 km long. Near-Infrared Mapping Spectrometer (NIMS) thermal emission data yield a color temperature estimate of 344 K +/- 60 K (less than or equal to 131 C) within the Emakong caldera. We suggest that these bright flows likely resulted from either sulfur lavas or silicate lavas that have undergone extensive cooling, pyroclastic mantling, and/or alteration with bright sulfurous materials. The Emakong bright flows have estimated volumes of approx. 250-350 cu km, similar to some of the smaller Columbia River Basalt flows. If the Emakong flows did result from effusive sulfur eruptions, then they are orders of magnitude greater in volume than any terrestrial sulfur flows. Our numerical modeling results show that sulfur lavas on Io could have been emplaced as turbulent flows, which were capable of traveling tens to hundreds of kilometers, consistent with the predictions of Sagan [ 19793 and Fink et al. [ 19831. Our modeled flow distances are also consistent with the measured lengths of the Emakong channels and bright flows. Modeled thermal erosion rates are approx. 1-4 m/d for flows erupted at approx. 140-180 C, which are consistent with the melting rates of Kieffer et al. [2000]. The Emakong channels could be thermal erosional in nature; however, the morphologic signatures of thermal erosion channels cannot be discerned from available images. There are planned Galileo flybys of Io in 2001 which provide excellent opportunities to obtain high-resolution morphologic and color data of Emakong Patera. Such observations could, along with further modeling, provide additional information to better constrain whether sulfur lavas produced the Emakong flows.

Williams, David A.↗
NASA NTRS2001

Evaluation of Sulfur Flow Emplacement on Io from Galileo Data and Numerical Modeling

Galileo images of bright lava flows surrounding Emakong Patera have bee0 analyzed and numerical modeling has been performed to assess whether these flows could have resulted from the emplacement of sulfur lavas on Io. Images from the solid-state imaging (SSI) camera show that these bright, white to yellow Emakong flows are up to 370 km long and contain dark, sinuous features that are interpreted to be lava conduits, -300-500 m wide and >lo0 km lorig. Neiu-Infrared Mapping S estimate of 344 K f 60 G131'C) within the Bmakong caldera. We suggest that these bright flows likely resulted from either sulfur lavas or silicate lavas that have undergone extensive cooling, pyroclastic mantling, and/or alteration with bright sulfurous materials. The Emakoag bright flows have estimated volume of -250-350 km', similar to some of the smaller Columbia River Basalt flows, If the Emakong flows did result from effusive sulfur eruptions, then they are orders of magnitude reater in volume than any terrestrial sulfur flows. Our numerical modeling capable of traveling tens to hundreds of kilometers, consistent with the predictions of Sagan. Our modeled flow distances are also consistent with the measured lengths of the Emakong channels and bright flows.

Williams, David A.↗
NASA NTRS1997

Direct Measurement of Internal Flow Velocities in a Star-Slot Model

This paper presents the results of a cold flow experiment to make direct measurements of the velocity distribution in a model of a solid rocket motor star grain propellant slot. The experimental procedure utilizes a multi-component laser Doppler velocimeter (LDV) and an apparatus for seeding the flow with aluminum particles to determine the velocity components at various discrete locations within the star slot. The test article used in this investigation was a one-tenth scale, cold flow model based on the geometry of the Space Shuttle solid rocket motor head-end section. The results obtained for the direct measurements of velocity are compared to velocities calculated from measured pressure distributions to data obtained from oil smear experiments and flow visualization videos, and to heat transfer calorimeter data.

Foster, Winfred A., Jr.↗
NASA NTRS1987

Numerical grid generation and flow simulation in SSME thrust chamber

The development of liquid and solid rocket engines for future space projects demands a detailed optimization process for highly efficient performance and cost reasons. Also, testing of full size engines may not be feasible when the large size requires test facilities which are cost prohibitive or if vacuum operation cannot be acquired. For such situations only scaling from small test scale measurements or accurate analytical predictions will provide the performance prior to actually flying the mission. A rigorous approach for simulating the combustion processes in liquid rocket engines by employing a direct solution of Navier-Stokes equations within the entire volume of the thrust chambers is presented. This method is illustrated in the solution of reactive flow in the Space Shuttle Main Engine (SSME) thrust chamber. The objective is to review recent improvements in the mathematical model and to present the grid generation methodology suitable for rocket thrust chamber geometries.

Gross, K. W.↗
NASA NTRS1986

Explicit expression to predict the erosive burning rate of solid propellants

Using the theory of gas dynamics and heat transfer from a turbulent gas flow to the burning surface of propellant along a permeable wall, an explicit expression is derived to predict the burning rate of the solid propellant with crossflow. Results of the calculation have been compared with experimental data and proved to be correct.

Wang, S.↗
NASA NTRS2003

A 3-D CFD Analysis of the Space Shuttle RSRM With Propellant Fins @ 1 sec. Burn-Back

In this study 3-D Computational Fluid Dynamic (CFD) runs have been made for the Space Shuttle RSRM using 2 different grids and 4 different turbulent models, which were the Standard KE, the RNG KE, the Realizable KE, and the Reynolds stress model. The RSRM forward segment consists of 11 fins. By taking advantage of the forward fin symmetry only half of one fin along the axis had to be used in making the grid. This meant that the 3-D model consisted of a pie slice that encompassed 1/22nd of the motor circumference and went along the axis of the entire motor. The 3-D flow patterns in the forward fin region are of particular interest. Close inspection of these flow patterns indicate that 2 counter-rotating axial vortices emerge from each submerged solid propellant fin. Thus, the 3-D CFD analysis allows insight into complicated internal motor flow patterns that are not available from the simpler 2-D axi-symmetric studies. In addition, a comparison is made between the 3-D bore pressure drop and the 2-D axi-symmetric pressure drop.

Morstadt, Robert A.↗
NASA NTRS2006

Influence of Processing Parameters on the Flow Path in Friction Stir Welding

Friction stir welding (FSW) is a solid phase welding process that unites thermal and mechanical aspects to produce a high quality joint. The process variables are rpm, translational weld speed, and downward plunge force. The strain-temperature history of a metal element at each point on the cross-section of the weld is determined by the individual flow path taken by the particular filament of metal flowing around the tool as influenced by the process variables. The resulting properties of the weld are determined by the strain-temperature history. Thus to control FSW properties, improved understanding of the processing parameters on the metal flow path is necessary.

Schneider, J. A.↗
NASA NTRS1984

An experimental investigation of gas jets in confined swirling air flow

The fluid dynamics of jets in confined swirling flows which is of importance to designers of turbine combustors and solid fuel ramjets used to power missiles fired from cannons were examined. The fluid dynamics of gas jets of different densities in confined swirling flows were investigated. Mean velocity and turbulence measurements are made with a one color, one component laser velocimeter operating in the forward scatter mode. It is shown that jets in confined flow with large area ratio are highly dissipative which results in both air and helium/air jet centerline velocity decays. For air jets, the jet like behavior in the tube center disappears at about 20 diameters downstream of the jet exit. This phenomenon is independent of the initial jet velocity. The turbulence field at this point also decays to that of the background swirling flow. A jet like behavior in the tube center is noticed even at 40 diameters for the helium/air jets. The subsequent flow and turbulence field depend highly on the initial jet velocity. The jets are fully turbulent, and the cause of this difference in behavior is attributed to the combined action swirl and density difference. This observation can have significant impact on the design of turbine combustors and solid fuel ramjets subject to spin.

Mongia, H.↗
NASA NTRS2004

Validation of an Impedance Education Method in Flow

This paper reports results of a research effort to validate a method for educing the normal incidence impedance of a locally reacting liner, located in a grazing incidence, nonprogressive acoustic wave environment with flow. The results presented in this paper test the ability of the method to reproduce the measured normal incidence impedance of a solid steel plate and two soft test liners in a uniform flow. The test liners are known to be locally react- ing and exhibit no measurable amplitude-dependent impedance nonlinearities or flow effects. Baseline impedance spectra for these liners were therefore established from measurements in a conventional normal incidence impedance tube. A key feature of the method is the expansion of the unknown impedance function as a piecewise continuous polynomial with undetermined coefficients. Stewart's adaptation of the Davidon-Fletcher-Powell optimization algorithm is used to educe the normal incidence impedance at each Mach number by optimizing an objective function. The method is shown to reproduce the measured normal incidence impedance spectrum for each of the test liners, thus validating its usefulness for determining the normal incidence impedance of test liners for a broad range of source frequencies and flow Mach numbers. Nomenclature

Watson, Willie R.↗
NASA NTRS1988

Automated Water-Purification System

Reverse-osmosis system operates and maintains itself with minimal human attention, using programmable controller. In purifier, membranes surround hollow cores through which clean product water flows out of reverse-osmosis unit. No chemical reactions or phase changes involved. Reject water, in which dissolved solids concentrated, emerges from outer membrane material on same side water entered. Flow controls maintain ratio of 50 percent product water and 50 percent reject water. Membranes expected to last from 3 to 15 years.

Ahlstrom, Harlow G.↗
NASA NTRS1996

Bubble Dynamics on a Heated Surface

In this work, we study the combined thermocapillary and natural convective flow generated by a bubble on a heated solid surface. The interaction between gas and vapor bubbles with the surrounding fluid is of interest for both space and ground-based processing. On earth, the volumetric forces are dominant, especially, in apparatuses with large volume to surface ratio. But in the reduced gravity environment of orbiting spacecraft, surface forces become more important and the effects of Marangoni convection are easily unmasked. In order to delineate the roles of the various interacting phenomena, a combined numerical-experimental approach is adopted. The temperature field is visualized using Mach-Zehnder interferometry and the flow field is observed by a laser sheet flow visualization technique. A finite element numerical model is developed which solves the two-dimensional momentum and energy equations and includes the effects of bubble surface deformation. Steady state temperature and velocity fields predicted by the finite element model are in excellent qualitative agreement with the experimental results. A parametric study of the interaction between Marangoni and natural convective flows including conditions pertinent to microgravity space experiments is presented. Numerical simulations clearly indicate that there is a considerable difference between 1-g and low-g temperature and flow fields induced by the bubble.

Kassemi, Mohammad↗
NASA NTRS1993

Heat Transfer from Radiatively Heated Material in a Low Reynolds Number Microgravity Environment

A mathematical model of the transient three-dimensional heat transfer between a slowly moving ambient gas stream and a thermally thick or thin flat surface heated by external radiation in a microgravity environment is presented. The problem is motivated in part by fire safety issues in spacecraft. The gas phase is represented by variable property convection-diffusion energy and mass conservation equations valid at low Reynolds numbers. The absence of gravity and low Reynolds number together permit the flow to be represented by a self-consistent velocity potential determined by the ambient velocity and the thermal expansion in the gas. The solid exchanges energy with the gas by conduction/convection and with the surroundings by surface absorption and re-emission of radiation. Heat conduction in the solid is assumed to be one dimensional at each point on the surface as a consequence of the limited times (of order of 10 seconds) of interest in these simulations. Despite the apparent simplicity of the model, the results show a complex thermally induced flow near the heated surface. The thermal exchange between the gas and solid produces an outward sourcelike flow upstream of the center of the irradiated area and a sinklike flow downstream. The responses of the temperature fields and the associated flows to changes in the intensity of the external radiation and the ambient velocity are discussed.

Yamashita, H.↗
NASA NTRS1998

Magnetic Damping of Solid Solution Semiconductor Alloys

The objective of this study is to conduct the Earth-based research sufficient to successfully propose a flight experiment (1) to experimentally test the validity of the modeling predictions applicable to the magnetic damping of convective flows in conductive melts as this applies to the bulk growth of solid solution semiconducting materials in the reduced gravitational levels available in low Earth orbit and (2) to assess the effectiveness of steady magnetic fields in reducing the fluid flows occurring in these materials during space processing. To achieve the objectives of this investigation, we are carrying out a comprehensive program in the Bridgman and floating-zone configurations using the solid solution alloy system Ge-Si. This alloy system was chosen because it has been studied extensively in environments that have not simultaneously included both low gravity and an applied magnetic field. Also, all compositions have a high electrical conductivity, and the materials parameters permit high growth rates compared to many other commonly studied alloy semiconductors. An important supporting investigation is determining the role, if any, that thermoelectromagnetic convection (TEMC) plays during growth of these materials in a magnetic field. Some compositional anomalies observed by us in magnetic grown crystals can only be explained by TEMC; this has significant implications for the deployment of a Magnetic Damping Furnace in space. This effect will be especially important in solid solutions where the growth interface is, in general, neither isothermal nor isoconcentrational. It could be important in single melting point materials, also, if faceting takes place producing a non-isothermal interface.

Szofran, Frank R.↗
NASA NTRS1975

Shock wave relations in lunar ash flow

A detailed analysis of steady normal shock waves in a layer of lunar ash by the theory of two phase flow of a mixture of a gas and small solid particles is presented. New terms of pressure gradient and virtual mass forces in the particle momentum equation and the particle kinetic energy and work done in the particle energy equation are included in the fundamental equations and their influences are investigated. The flow variables as functions of the free stream Mach number, initial particle volume fraction and the density ratio G are presented. The thickness of the relaxation zone is found to increase with decreasing initial particle volume fraction and almost independent of G for any given values of free stream Mach number. A new empirical relation of the drag coefficient for the spherical particles in the mixture is proposed to fit experimental data.

Pai, S. I.↗