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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 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Fluid Dynamics of Bubbly Liquids

Experiments have been performed to study the average flow properties of inertially dominated bubbly liquids which may be described by a novel analysis. Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The suspension was produced using a bank of 900 glass capillaries with inner diameter of about 100 microns in a quasi-steady fashion. In addition, salt was added to the suspension to prevent bubble-bubble coalescence. As a result, a nearly monodisperse suspension of bubble was produced. By increasing the inclination angle, we were able to explore an increasing amount of shear to buoyancy motion. A pipe flow experiment with the liquid being recirculated is under construction. This will provide an even larger range of shear to buoyancy motion. We are planning a microgravity experiment in which a bubble suspension is subjected to shearing in a couette cell in the absence of a buoyancy-driven relative motion of the two phases. By employing a single-wire, hot film anemometer, we were able to obtain the liquid velocity fluctuations. The shear stress at the wall was measured using a hot film probe flush mounted on the wall. The gas volume fraction, bubble velocity, and bubble velocity fluctuations were measured using a homemade, dual impedance probe. In addition, we also employed a high-speed camera to obtain the bubble size distribution and bubble shape in a dilute suspension. A rapid decrease in bubble velocity for a dilute bubble suspension is attributed to the effects of bubble-wall collisions. The more gradual decrease of bubble velocity as gas volume fraction increases, due to subsequent hindering of bubble motion, is in qualitative agreement with the predictions of Spelt and Sangani for the effects of potential-flow bubble-bubble interactions on the mean velocity. The ratio of the bubble velocity variance to the square of the mean is 0(0.1). For these conditions Spelt and Sangani predicted that the homogeneous suspension would be unstable and clustering into horizontal rafts will take place. Evidence for bubble clustering is obtained by analysis of video images. The liquid velocity variance is larger than would be expected for a homogeneous suspension and the liquid velocity frequency spectrum indicates the presence of velocity fluctuations that are slow compared with the time for the passage of an individual bubble. These observations provide further evidence for bubble clustering.

Tsang, Y. H.↗
DOE OSTI2023

Lime slurry treatment of soils developing on abandoned coal mine spoil: Linking contaminant transport from the micrometer to pedon-scale

Historical and abandoned coal mine spoil continues to generate acid- and metal(loid)-rich porewaters and represents a geographically large and diffuse non-point source of contamination to local watersheds. A potentially inexpensive approach to treat these materials and soils developing on them is through the application of lime slurries, to neutralize acidity and encourage the (co)precipitation of metal(loids) with Fe(III)-(oxy)hydroxides, and potentially other metal-oxides and/or Ca-bearing phases. Here, the efficacy of this approach was evaluated through parallel field application and laboratory-based flow-through column experiments. The field site is Huff Run sub-watershed 25 located in Tuscarawas County, Ohio and was chosen in part because it was previously classified as one of the most highly AMD-impacted sub-watersheds in the region. Two locations with historical spoil were chosen and suction lysimeters were installed at 25 and 75 cm depth to monitor porewater composition on two sides at the base of each pile. Half of each slope received seven lime slurry treatments from June through October of 2017. A suite of aqueous (ICP-OES, IC, and TOC-L) and solid phase geochemical and mineralogical approaches (quantitative SEM-EDS and synchrotron μ-XRF) were used to determine how composition, texture, morphology, and spatial distribution of mineral coatings differ in pre- and post-lime treated soils, and how that impacts the distribution and transport of trace metal(loid)s. Mine spoil porewater at site 1 was slightly less alkaline (pH ranging from 7.04 to 7.37) than at site 2 (ranging from 7.55 to 7.71), and average electrical conductivity values at site 1 (316–405 μS cm —1 ) were slightly lower than at site 2 (358–464 μS cm —1 ), although differences between the sites were not significant. Porewater pH and electrical conductivity in all lysimeters decreased over the course of the field season but there was no obvious response to lime treatment at either site or any depth. At site 1, both treatment and depth were significant factors affecting Ca, K, Ni, SO 4 2— , and DOC concentrations while only treatment effects were significant for dissolved Al and Cu (p < 0.05). For all soils, there were no trends in metal concentration observed over time although DOC and SO 4 2— decreased over the field season. Pedon-scale changes in metal porewater concentrations in response to treatment were linked to micrometer-scale changes in mineral surface coatings; specifically, higher concentrations of Ca, Fe, Mn, and Zn were observed in the coatings and no changes were observed in Fe redox speciation, whereas total S decreased likely due to oxidation of S in coal fragments. In contrast to the field experiment, the column experiments exhibited a much greater response in effluent composition with respect to lime treatment. The untreated columns had approximately an order of magnitude more H + leached over the course of the experiment (p < 0.001) and resulted in greater Ca, Al, Cu, and DIC leached and less Mn, Zn, and SO 4 2— . Soils treated with the lime slurry in the column experiments exhibited larger and thicker secondary Fe-coatings, including the addition of Fe-sulfates. Despite clear trends in the laboratory-based column experiment where the lime-to-soil ratio was higher, the effects were either muted or undetected in the field pilot project, suggesting that a higher application rate of lime in the field is needed to achieve a similar effect. This work provides evidence that a less alkaline lime slurry could be a practical and inexpensive method of treating coal mine spoil-impacted soils and represents an important step in linking laboratory-based remediation studies to implemented field-based studies.

58 GEOSCIENCES↗
DOE OSTI2024

Interactions of laser-driven tin ejecta microjets over phase transition boundaries

Ejecta microjets offer an experimental methodology to study high-speed particle laden-flow interactions, as microjets consist of millions of particulates traveling at velocities of several kilometers per second and are easily generated by most common shock drives. Previous experiments on the OMEGA Extended Performance laser found that collisions between two counter-propagating laser-driven tin ejecta microjets varied as a function of drive pressure; jets generated near shock pressures of 10 GPa passed through each other without interacting, whereas jets generated at shock pressures of over 100 GPa interacted strongly, forming a cloud around the center interaction point. In this paper, we present a more systematic scan of tin ejecta microjet collisions over intermediate pressure regimes to identify how and at what shock pressure interaction behavior onsets. Radiographs of interacting microjets at five different laser drive energies qualitatively demonstrate that interaction behavior onsets slowly as a function of laser drive energy. Quantitative mass and density metrics from each radiograph provide trends on jet characteristics and collisional mass dispersion. It is observed that jetting mass, jet densities, and mass dispersion increase with increasing drive pressures and that the increased jet density at the higher drive energies may account for the increased mass dispersion. This work provides an important step in the understanding of tin ejecta microjet collisions and paves the way for future studies on the physics dominating high-speed particle-laden flow interactions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Techno-Economic Wind Blade Manufacturing Model to Identify Opportunities for Cost Improvements Phase II IACMI Project 4.6/4.8

In IACMI Project 4.6 and IACMI Project 4.8, an Excel-based Techno-Economic Model (TEM) of the manufacturing process for composite wind turbine blades and a DELMIA Factory Flow Simulation of a generic wind blade manufacturing facility was developed. Together, these two tools provide a combined economic modeling capability that accounts for the material, labor, overhead and full-lifecycle operating costs associated with wind blade manufacturing as well as the impact of process flow and factory layout on overall manufacturing efficiency. The tools provide a novel means of detailed comparative analysis of the economic feasibility of proposed technologies and process changes for blade manufacturing. The modeling tools were developed with close support from members of industry and visits to multiple blade manufacturing facilities. With industry oversight, a detailed generalized manufacturing process plan and facility layout were developed with manufacturing parameters, material costs and economic factors based on historical data. Dassault Systèmes and the University of Texas at Dallas (UTD) contributed to the development of the Techno-Economic Model by providing macros to enable the generation of Bill of Material (BOM) data from a 3D blade design in either CATIA or NuMAD format, respectively. The TEM was built with the capability to directly import a Bill of Materials for economic analysis, and with the addition of the macros provided by Dassault and UTD, the TEM can directly import blade designs from both CATIA and NuMAD file formats. The modeling tools developed in Project 4.6 were used to investigate four wind blade manufacturing concepts in detail and select one to explore with laboratory-scale experimentation in Project 4.8. The four manufacturing concepts that were investigated were down-selected by the full project team from a larger list of concepts. The selections were made based on a number of criteria ranking viability and level of interest for each concept. The ‘One-Step Close’ manufacturing concept was ultimately selected for investigation in Project 4.8 and the demonstration was performed at the NREL CoMET facility. The TPI advanced manufacturing facility in Warren, RI contributed the production of several prototype components, the designs for which were developed by Janicki Industries. The demonstration project provided clear indication of the viability of the One-Step Close manufacturing concept for blade manufacturing and good validation of the Techno-Economic Model’s prediction of its economic impact.

17 WIND ENERGY↗
NASA NTRS1978

The relation between temporal and spatial stability in three-dimensional flows

An analysis is presented of the nonparallel spatial or temporal stability of three-dimensional incompressible, isothermal boundary-layer flows taking into account the transverse velocity component as well as the axial and crossflow variations of the mean flow. The method of multiple scales is used to derive partial differential equations that describe the axial and crossflow variations of the disturbance amplitude, phase and wavenumbers. This equation is used to derive the expressions that relate the temporal and spatial instabilities. These relations are functions of the complex group velocities. Moreover, this equation is used to derive the expression that relates the spatial amplification in any direction to a calculated amplification in any other direction. These relations are verified by numerical results obtained for two- and three-dimensional disturbances in two- and three-dimensional flows.

Nayfeh, A. H.↗
DOE OSTI2022

A particle resolved simulation approach for studying shock interactions with moving, colliding solid particles

This work applies a new combination of techniques for the fully resolved simulation of compressible, gas–particle multiphase flows. Here, the adaptive wavelet collocation method is used to dynamically, and efficiently, adapt the computational grid to localized flow features and the particles. A characteristic-based volume penalization method that imposes arbitrary Dirichlet, Neumann, or Robin-type immersed boundary conditions, is used to enforce the no-slip condition at particle surfaces. A hard-sphere collision model is applied to capture the particle–particle collisions. Proof of concept test cases are presented, showcasing the dynamic grid adaptation and fully resolved two-way coupling between the phases that is possible with this approach. Results for a shock-driven single cylinder under viscous and inviscid conditions are presented along with a demonstration of a shock interacting with a cloud of randomly distributed cylinders and spheres.

42 ENGINEERING↗
NASA NTRS2000

Computations of Boiling in Microgravity

The absence (or reduction) of gravity, can lead to major changes in boiling heat transfer. On Earth, convection has a major effect on the heat distribution ahead of an evaporation front, and buoyancy determines the motion of the growing bubbles. In microgravity, convection and buoyancy are absent or greatly reduced and the dynamics of the growing vapor bubbles can change in a fundamental way. In particular, the lack of redistribution of heat can lead to a large superheat and explosive growth of bubbles once they form. While considerable efforts have been devoted to examining boiling experimentally, including the effect of microgravity, theoretical and computational work have been limited. Here, the growth of boiling bubbles is studied by direct numerical simulations where the flow field is fully resolved and the effects of inertia, viscosity, surface deformation, heat conduction and convection, as well as the phase change, are fully accounted for. Boiling involves both fluid flow and heat transfer and thus requires the solution of the Navier-Stokes and the energy equations. The numerical method is based on writing one set of governing transport equations which is valid in both the liquid and vapor phases. This local, single-field formulation incorporates the effect of the interface in the governing equations as source terms acting only at the interface. These sources account for surface tension and latent heat in the equations for conservation of momentum and energy as well as mass transfer across the interface due to phase change. The single-field formulation naturally incorporates the correct mass, momentum and energy balances across the interface. Integration of the conservation equations across the interface directly yields the jump conditions derived in the local instant formulation for two-phase systems. In the numerical implementation, the conservation equations for the whole computational domain (both vapor and liquid) are solved using a stationary grid and the phase boundary is followed by a moving unstructured two-dimensional grid. While two-dimensional simulations have been used for preliminary studies and to examine the resolution requirement, the focus is on fully three-dimensional simulations. The numerical methodology, including the parallelization and grid refinement strategy is discussed, and preliminary results shown. For buoyancy driven flow, the heat transfer is in good agreement with experimental correlations. The changes when gravity is turned off and/or fluid shear is added are discussed, as well as the difference between simulations of a layer freely releasing bubbles versus simulations using only one wavelength initial perturbation. Figure 1 shows the early stages of the formation of a three-dimensional bubble from a thin vapor layer. The boundary conditions are periodic in the x and y direction, the bottom is a hot and the top allows a free outflow. The jagged edge of the surface close to the bottom of the computational domain is due to some of the surface elements being on the other side of the domain and some elements not plotted by our plotting routine. In the second figure, we show the temperature distribution through two perpendicular planes.

Tryggvason, G.↗
NASA NTRS2008

Design and Calibration of Custom Flowfield/Rake for the F-15B Propulsion Flight Test Fixture

The Propulsion Flight Test Fixture (PFTF) system at NASA Dryden Flight Research Center (DFRC) provides an innovative and cost effective method of flight testing advanced propulsion concepts and components in a relevant environment using DFRC's F-15B #836. The PFTF attaches to the centerline pylon of the aircraft and Has an integrated 6 axis force balance for flight testing of propulsion experiments The PTFF has undergone two previous flight validation test phases: (1)The Local Mach Investigation (LMT) flights, in which an air data boom was attached to a cylinder with a conical nose cap . This flight test phase quantified the local Mach number and the local flow angle at a single point under the F-155B/PFTF. (2) The Cone Drag Experiment (CDE), in which the cylinder / nosecap assembly was tested in order to validate the PFTF's integral 6-component force balance. The next test phase with the PFTF is the flight test of the channeled centerbody axisymmetric inlet. However, for the flight data from this test to be valid, more information must be gathered concerning the quality of the flow through the aerodynamic interface plane of the inlet. The flow angularity and Mach number must be known at multiple locations on the interface plane. Flight data will be gathered using a custom-design flowfield rake to probe the flow underneath the F-15B at the design flight conditions.

Flynn, Darin C.↗
NASA NTRSDate not supplied

Flow Boiling in Microgap Coolers - Suborbital Flight Results

Flow Boiling in Microgap Coolers (FBMC) is a thermal management technique that provides embedded, on-site heat removal for power dense electronic components and systems. The dielectric coolant undergoes liquid-to-vapor phase change as it passes through channels integrated within or between devices. By facilitating direct contact between the coolant and heat-generating devices and relying on phase change, the system provides tight temperature control, hot spot mitigation, very high heat transfer coefficients, and low pumping power. Ground tests demonstrated removal of high heat fluxes (up to 500 kW/m2), very high coefficients of performance (up to 40 W of heat transferred per W of pumping power), and consistent performance across five evaporator orientations under the appropriate conditions. As a follow-on study and to better assess the role of gravity on such two-phase systems, the FBMC payload was developed and flown twice aboard the Blue Origin New Shepard space vehicle in January and May 2019. Each flight exposed the payload to weightlessness (150 seconds below 0.01 g) and shorter periods of high-g during ascent (up to 3 g) and descent (up to 5 g). The flow boiling performance was consistent independent of the acceleration levels, which provides confidence that such systems will provide consistent performance when tested on the ground, orbiting or traveling through weightlessness, and operating on the surface of the Moon, Mars, and other planetary bodies. Details of the flight results, payload development, flight environment, and planned future testing will be presented.

Flow boiling↗
NASA NTRS1988

Scientific support for an orbiter middeck experiment on solid surface combustion

The objective is to determine the mechanism of gas-phase flame spread over solid fuel surfaces in the absence of any buoyancy or externally imposed gas-phase flow. Such understanding can be used to improve the fire safety aspects of space travel by providing information that will allow judicious selections of spacecraft materials and environments to be made. The planned experiment consists of measuring the flame spread rate over thermally thin and thermally thick fuels in a closed container in the low-gravity environment of the Space Shuttle. Measurements consist of flame spread rate and shape obtained from two views of the process as recorded on movie film and surface and gas-phase temperatures obtained from fine-wire thermocouples. The temperature measurements along with appropriate modeling provide information about the gas-to-solid heat flux. Environmental parameters to be varied are the oxygen concentration and pressure.

Altenkirch, Robert A.↗
NASA NTRS1975

NO sub x deposited in the stratosphere by the space shuttle, phase 1

The results of calculations to determine the amount of NOx deposited in the stratosphere by space shuttle solid rocket motors (SRM) are presented. Flow properties and chemical composition in the exhaust nozzle and plume were analyzed. The nozzle calculations show that about 4.5 lbm/sec of NOx leaves the two SRMs. The total amount of NOx deposited in the stratosphere is related to the amount leaving the nozzle via an overall plume enhancement factor (OPEF), which depends upon the influence of afterburning and shocks in enhancing the exit plane NOx mole fraction. Calculations show that the OPEF is approximately 2, indicating the mass flow of NOx in the plume to be approximately l0 lbm/sec at 30 km altitude with a possible error factor of 4. For a vehicle velocity of 3750 ft/sec, therefore, the NOx deposition rate in the stratosphere is about 2.7 x 10(-3) lbm/ft.

Pergament, H. S.↗
NASA NTRS1988

Improved numerical methods for turbulent viscous flows aerothermal modeling program, phase 2

The details of a study to develop accurate and efficient numerical schemes to predict complex flows are described. In this program, several discretization schemes were evaluated using simple test cases. This assessment led to the selection of three schemes for an in-depth evaluation based on two-dimensional flows. The scheme with the superior overall performance was incorporated in a computer program for three-dimensional flows. To improve the computational efficiency, the selected discretization scheme was combined with a direct solution approach in which the fluid flow equations are solved simultaneously rather than sequentially.

Karki, K. C.↗
NASA NTRS1991

Mechanisms of microgravity flame spread over a thin solid fuel - Oxygen and opposed flow effects

Microgravity tests varying oxygen concentration and forced flow velocity have examined the importance of transport processes on flame spread over very thin solid fuels. Flame spread rates, solid phase temperature profiles and flame appearance for these tests are measured. A flame spread map is presented which indicates three distinct regions where different mechanisms control the flame spread process. In the near-quenching region (very low characteristic relative velocities) a new controlling mechanism for flame spread - oxidizer transport-limited chemical reaction - is proposed. In the near-limit, blowoff region, high opposed flow velocities impose residence time limitations on the flame spread process. A critical characteristic relative velocity line between the two near-limit regions defines conditions which result in maximum flammability both in terms of a peak flame spread rate and minimum oxygen concentration for steady burning. In the third region, away from both near-limit regions, the flame spread behavior, which can accurately be described by a thermal theory, is controlled by gas-phase conduction.

Olson, S. L.↗
DOE OSTI2021

Exactness of OPF Relaxation on Three-phase Radial Networks with Delta Connections

Simulations have shown that while semi-definite relaxations of AC optimal power flow (AC-OPF) on three-phase radial networks with only wye connections tend to be exact, the presence of delta connections seem to render them inexact. This paper shows that such inexactness originates from the non-uniqueness of relaxation solutions and numerical errors amplified by the non-uniqueness. This finding motivates two algorithms to recover the exact solution of AC-OPF in unbalanced distribution networks featuring both wye and delta connections. In simulations using IEEE 13, 37 and 123-bus systems, the proposed algorithms provide exact optimal solutions up to numerical precision.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2018

Geologic CO 2 sequestration monitoring design: A machine learning and uncertainty quantification based approach

Monitoring is a crucial aspect of geologic carbon dioxide (CO 2 ) sequestration risk management. Effective monitoring is critical to ensure CO 2 is safely and permanently stored throughout the life-cycle of a geologic CO 2 sequestration project. Effective monitoring involves deciding: (i) where is the optimal location to place the monitoring well(s), and (ii) what type of data (pressure, temperature, CO 2 saturation, etc.) should be measured taking into consideration the uncertainties at geologic sequestration sites. We have developed a filtering-based data assimilation procedure to design effective monitoring approaches. To reduce the computational cost of the filtering-based data assimilation process, a machine-learning algorithm: Multivariate Adaptive Regression Splines is used to derive computationally effcient reduced order models from results of full-physics numerical simulations of CO 2 injection in saline aquifer and subsequent multi-phase fluid flow. We use example scenarios of CO 2 leakage through legacy wellbore and demonstrate a monitoring strategy can be selected with the aim of reducing uncertainty in metrics related to CO 2 leakage. We demonstrate the proposed framework with two synthetic examples: a simple validation case and a more complicated case including multiple monitoring wells. The examples demonstrate that the proposed approach can be effective in developing monitoring approaches that take into consideration uncertainties.

58 GEOSCIENCES↗
DOE OSTI2021

Robust hierarchical dispatch for residential distribution network management considering home thermal flexibility and model predictive control

In the transactive energy (TE) paradigm, the devices of participative consumers, or prosumers, may be aggregated and employed to drive operational objectives at the network level. Home heating, ventilation and air-conditioning (HVAC) systems in particular are well-suited to modulate their behaviours based on both home thermal flexibility and requests from the utility grid. This paper develops a robust, hierarchical power dispatch scheme in the context of a residential distribution network. The formulation couples a unique, multiphase linear distribution optimal power flow (OPF) at the upper level with model predictive control (MPC)-based HVAC fleet controllers at the lower level. The proposed approach is tested on nearly 2000 homes with a three-phase distribution network in an intraday market setting, where two major applications are explored and analysed.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1986

Coherent structures in a turbulent boundary layer. I - Generation of 'artificial' bursts

In an effort to better understand the physics and structure of coherent events in a turbulent boundary layer, an attempt is made to produce 'artificial' bursts. These are generated in a turbulent boundary layer developed on a flat plate towed in an 18 m water channel and thus with negligible freestream turbulence. The burstlike events are produced by either withdrawing near-wall fluid from two minute holes separated in the spanwise direction or by pitching a miniature delta wing that is flush-mounted to the wall. Either of these two actions generates a hairpinlike vortex and low-speed streak that resemble naturally occurring structures. The resulting sequence of events that occur at a given location can be uniquely controlled, thus allowing detailed examination via phase-locked measurements and flow visualization. In this paper, the proof of concept of artificial burst generation is established by comparing the artificial events with natural, random bursts using flow visualization and hot-film signals.

Gad-El-hak, M.↗
NASA NTRS1986

Dynamics, statistics and predictability of planetary flow regimes

Consideration is given to regimes of low-frequency variability in large-scale atmospheric dynamics. The model utilized is the fully-nonlinear, equivalent-baratropic vorticity equation on the sphere, with simplified forcing, dissipation and topography. It is found that certain limited regions in the system's phase space are visited repeatedly and for extended periods by model solutions. Flow patterns coupled with these regions correspond to synoptically-defined zonal and blocked Northern Hemisphere midlatitude flows. It is shown that the system's macrodynamics can be depicted by two or more planetary flow regimes, the expected residence time in each regime, and the transition properties from one regime to another. These model-derived ideas are also applied to a time series of atmospheric data from the Southern Hemisphere.

Ghil, Michael↗