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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

A Review of Electrical Impedance Spectrometry Methods for Parametric Estimation of Physiologic Fluid Volumes

Electrical impedance spectrometry involves measurement of the complex resistance of a load at multiple frequencies. With this information in the form of impedance magnitude and phase, or resistance and reactance, basic structure or function of the load can be estimated. The "load" targeted for measurement and estimation in this study consisted of the water-bearing tissues of the human calf. It was proposed and verified that by measuring the electrical impedance of the human calf and fitting this data to a model of fluid compartments, the lumped-model volume of intracellular and extracellular spaces could be estimated, By performing this estimation over time, the volume dynamics during application of stimuli which affect the direction of gravity can be viewed. The resulting data can form a basis for further modeling and verification of cardiovascular and compartmental modeling of fluid reactions to microgravity as well as countermeasures to the headward shift of fluid during head-down tilt or spaceflight.

Dewberry, B.↗
NASA NTRS1991

Modeling of InP metalorganic chemical vapor deposition

The growth of InP by metalorganic chemical vapor deposition (MOCVD) in a horizontal reactor is being modeled with a commercially available computational fluid dynamics modeling code. The mathematical treatment of the MOCVD process has four primary areas of concern: 1) transport phenomena, 2) chemistry, 3) boundary conditions, and 4) numerical solution methods. The transport processes involved in CVD are described by conservation of total mass, momentum, energy, and atomic species. Momentum conservation is described by a generalized form of the Navier-Stokes equation for a Newtonian fluid and laminar flow. The effect of Soret diffusion on the transport of particular chemical species and on the predicted deposition rate is examined. Both gas-phase and surface chemical reactions are employed in the model. Boundary conditions are specified at the inlet and walls of the reactor for temperature, fluid flow and chemical species. The coupled set of equations described above is solved by a finite difference method over a nonuniform rectilinear grid in both two and three dimensions. The results of the 2-D computational model is presented for gravity levels of zero- and one-g. The predicted growth rates at one-g are compared to measured growth rates on fused silica substrates.

Black, Linda R.↗
NASA NTRS1994

Modeling gas exchange in a closed plant growth chamber

Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.

Cornett, J. D.↗
NASA NTRS1994

Modeling Gas Exchange in a Closed Plant Growth Chamber

Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant a growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.

Cornett, J. D.↗
NASA NTRS2011

Experimental and Numerical Investigation of Reduced Gravity Fluid Slosh Dynamics for the Characterization of Cryogenic Launch and Space Vehicle Propellants

As space programs increasingly investigate various options for long duration space missions the accurate prediction of propellant behavior over long periods of time in microgravity environment has become increasingly imperative. This has driven the development of a detailed, physics-based understanding of slosh behavior of cryogenic propellants over a range of conditions and environments that are relevant for rocket and space storage applications. Recent advancements in computational fluid dynamics (CFD) models and hardware capabilities have enabled the modeling of complex fluid behavior in microgravity environment. Historically, launch vehicles with moderate duration upper stage coast periods have contained very limited instrumentation to quantify propellant stratification and boil-off in these environments, thus the ability to benchmark these complex computational models is of great consequence. To benchmark enhanced CFD models, recent work focuses on establishing an extensive experimental database of liquid slosh under a wide range of relevant conditions. In addition, a mass gauging system specifically designed to provide high fidelity measurements for both liquid stratification and liquid/ullage position in a micro-gravity environment has been developed. This pUblication will summarize the various experimental programs established to produce this comprehensive database and unique flight measurement techniques.

Walls, Laurie K.↗
NASA NTRS1985

Constitutive modelling of lubricants in concentrated contacts at high slide to roll ratios

A constitutive lubricant friction model for rolling/sliding concentrated contacts such as gears and cams was developed, based upon the Johnson and Tevaarwerk fluid rheology model developed earlier. The friction model reported herein differs from the earlier rheological models in that very large slide to roll ratios can now be accommodated by modifying the thermal response of the model. Also the elastic response of the fluid has been omitted from the model, thereby making it much simpler for use in the high slide to roll contacts. The effects of this simplification are very minimal on the outcome of the predicted friction losses (less than 1%). In essence then the lubricant friction model developed for the high slide to roll ratios treats the fluid in the concentrated contact as consisting of a nonlinear viscous element that is pressure, temperature, and strain rate dependent in its shear response. The fluid rheological constants required for the prediction of the friction losses at different contact conditions are obtained by traction measurements on several of the currently used gear lubricants. An example calculation, using this model and the fluid parameters obtained from the experiments, shows that it correctly predicts trends and magnitude of gear mesh losses measured elsewhere for the same fluids tested here.

Tevaarwerk, J. L.↗
NASA NTRS2000

Planned Axial Reorientation Investigation on Sloshsat

This paper details the design and logic of an experimental investigation to study axial reorientation in low gravity. The Sloshsat free-flyer is described. The planned axial reorientation experiments and test matrixes are presented. Existing analytical tools are discussed. Estimates for settling range from 64 to 1127 seconds. The planned experiments are modelled using computational fluid dynamics. These models show promise in reducing settling estimates and demonstrate the ability of pulsed high thrust settling to emulate lower thrust continuous firing.

Chato, David J.↗
NASA NTRS2018

Aerodynamic Conceptual Design of Boundary Layer Ingestion Propulsor Systems: A Quasi-2D Through Flow Analysis Method and Multi-Fidelity Propulsor Design Framework

A propulsor design framework for maximizing the benefits of boundary layer ingestion is presented. The performance of BLI is strongly affected by all propulsor components, including the boundary layer characteristics (displacement thickness and form factor) of the ingested boundary layer at the inlet, the radical loading characteristics if the fan and exit guide vane (EGV), the area contraction from inlet to nozzle, and flow expansion at the exhaust cone. A strategy and it's associated multi-fidelity design framework are proposed for an efficient conceptual design of the BLI proplusor which inherently differs from the conventional engine. In the frame work, a quasi-2D through flow model served as the underlying fidelity model is introduced to incorporate the radial effect of the boundary layer entering the propulsor. Multi-fidelity design work is conducted to maximize the predefined performance metrics. On top of this efficient quasi-2D model. computational fluid dynamics based 3-D propulsor models are implemented to refine and validate the design. A BLI propulsion system integrated with fuselage is designed to showcase the framework. The performance of the resulting BLI propulsor system is evaluated via body-force model in unstructured Reynolds-Averaged Navier-Stoke (RANS) CFD and improvement is presented.

Lee, B. J.↗
NASA NTRS1986

Constraints on geomagnetic secular variation modeling from electromagnetism and fluid dynamics of the Earth's core

A spherical harmonic representation of the geomagnetic field and its secular variation for epoch 1980, designated GSFC(9/84), is derived and evaluated. At three epochs (1977.5, 1980.0, 1982.5) this model incorporates conservation of magnetic flux through five selected patches of area on the core/mantle boundary bounded by the zero contours of vertical magnetic field. These fifteen nonlinear constraints are included like data in an iterative least squares parameter estimation procedure that starts with the recently derived unconstrained field model GSFC (12/83). Convergence is approached within three iterations. The constrained model is evaluated by comparing its predictive capability outside the time span of its data, in terms of residuals at magnetic observatories, with that for the unconstrained model.

Benton, E. R.↗
NASA NTRSDate not supplied

Addressing CFM Modeling Gaps for Application into NASA’S Future Cutting Edge Missions

NASA, the US industry, and international partners are crafting frameworks to enable sustaining lunar missions. The ongoing programs, led by the agency, and prominent industry players, encompass plans for the sustained use of cryogenic propellants in lunar landers and in-space propellant refueling depots. NASA’s proactive funding initiatives have fueled the advancement of predictive computational models tailored to enhance the storage and transfer of cryogenic propellant. This paper aims to spotlight the latest advancements in this arena and delve into the collaborative efforts surrounding predictive model development within internal NASA programs as well as current and previous collaborations with industry and international partners. The paper presents an overview of recent advancements in cryogenic fluid management model development, along with their correlation with recent microgravity and large-scale cryogenic ground tests. The tests include key experiments such as the ISS Zero-Boil-Off Tank (ZBOT) series of experiments and the (Robotic Refueling Mission 3) RRM3 test during which liquid methane was stored on-orbit for an extended period of five months. The paper also highlights the anchoring of propellant tank pressurized drain tests involving sloshing that were conducted with liquid methane propellant during the Apollo/Saturn Era. Additionally, the paper discusses model anchoring against more recent sloshing tests carried out with liquid hydrogen propellant. Notable large-scale tests, such as a liquid oxygen propellant transfer test conducted by SpaceX were also used to help correlate a two-phase propellant transfer model using the valuable data measured during the test. The paper further showcases model correlations against a substantial oxygen liquefaction test undertaken by NASA to validate In-Situ-Resource-Utilization (ISRU) technologies that will prove pivotal for a sustained lunar presence.

Low-gravity fluid modeling↗
NASA NTRS1992

Analysis of fluid/mechanical systems using EASY5

This paper illustrates how the use of a general analysis package can simplify modeling and analyzing fluid/mechanical systems. One such package is EASY5, a Boeing Computer Services product. The basic transmission line equations for modeling piped fluid systems are presented, as well as methods of incorporating these equations into the EASY5 environment. The paper describes how this analysis tool has been used to model several fluid subsystems of the Space Shuttle Orbiter.

Clark, Robert W., Jr.↗
NASA NTRSDate not supplied

Low-cost Quantification of Fluid Flow Parameter Sensitivity using Reduced-order Modeling

Uncertainty quantification of computational fluid dynamics (CFD) simulations is a complicated procedure which still relies in many cases on engineering judgment and factors of safety. This is in part because the computational cost of measuring the simulation's sensitivity to all meaningful parameters (e.g., body surface roughness) and hyperparameters (e.g., subiteration convergence criterion) is intractable for even a single simulation. Reduced-order modeling dramatically lowers this computational cost of simulating fluid flows, but usually only where similar data is already available. In this work, fluid reduced-order models are utilized to quantify a flow's sensitivity to certain physical parameters for the purposes of improved uncertainty quantification. Characteristic observability and sensitivity are both explored. The resulting sensitivity quantifications enable more informed CFD frameworks and more rigorous uncertainty bounds on the resulting data.

uncertainty quantification↗
NASA NTRSDate not supplied

Low-cost Quantification of Fluid Flow Parameter Sensitivity using Reduced-order Modeling

Uncertainty quantification of computational fluid dynamics (CFD) simulations is a complicated procedure which still relies in many cases on engineering judgment and factors of safety. This is in part because the computational cost of measuring the simulation's sensitivity to all meaningful parameters (e.g., body surface roughness) and hyperparameters (e.g., subiteration convergence criterion) is intractable for even a single simulation. Reduced-order modeling dramatically lowers this computational cost of simulating fluid flows, but usually only where similar data is already available. In this work, fluid reduced-order models are utilized to quantify a flow's sensitivity to certain physical parameters for the purposes of improved uncertainty quantification. Characteristic observability and sensitivity are both explored. The resulting sensitivity quantifications enable more informed CFD frameworks and more rigorous uncertainty bounds on the resulting data.

uncertainty quantification↗
NASA NTRS2005

A New Unsteady Model for Dense Cloud Cavitation in Cryogenic Fluids

A new unsteady, cavitation model is presented wherein the phase change process (bubble growth/collapse) is coupled to the acoustic field in a cryogenic fluid. It predicts the number density and radius of bubbles in vapor clouds by tracking both the aggregate surface area and volume fraction of the cloud. Hence, formulations for the dynamics of individual bubbles (e.g. Rayleigh-Plesset equation) may be integrated within the macroscopic context of a dense vapor cloud i.e. a cloud that occupies a significant fraction of available volume and contains numerous bubbles. This formulation has been implemented within the CRUNCH CFD, which has a compressible real fluid formulation, a multi-element, unstructured grid framework, and has been validated extensively for liquid rocket turbopump inducers. Detailed unsteady simulations of a cavitating ogive in liquid nitrogen are presented where time-averaged mean cavity pressure and temperature depressions due to cavitation are compared with experimental data. The model also provides the spatial and temporal history of the bubble size distribution in the vapor clouds that are shed, an important physical parameter that is difficult to measure experimentally and is a significant advancement in the modeling of dense cloud cavitation.

Hosangadi, A.↗
NASA NTRS2007

Mars Sulfate Formation Sourced in Sulfide-Enriched Subsurface Fluids: The Rio Tinto Model

The extensive evidence for sulfate deposits on Mars provided by analyses of MER and Mars Express data shows that the sulfur played an essential role in the geochemical cycles of the planet, including reservoirs in the atmosphere, hydro-sphere and geosphere. Overall the data are consistent with a fluvial/lacustrine-evaporative origin of at least some of the sulfate deposits, with mineral precipitation through oversaturation of salty acidic fluids enriched in sulfates. This scenario requires reservoirs of sulfur and associated cations, as well as an acidic and oxidizing hydrochemistry which could be provided by surface and subsurface catching of meteoric waters resulting in the presence of sulfur-bearing gases and steam photochemistry. In this work we suggest a new scenario for the extensive generation of sulfates in Mars based on the observation of seasonal changes in the redox and pH of subsurface waters enriched in sulfur that supply the acidic Mars process analog of Rio Tinto. This model considers the long-term subsurface storage of sulfur during most of Noachian and its release from the late Noachian to Hesperian time through weathering by meteoric fluids that would acidify and oxidize the sulfur bearing compounds stored in the subsurface.

Fernandez-Remolar, D. C.↗
NASA NTRS1994

Modeling dynamically coupled fluid-duct systems with finite line elements

Structural analysis of piping systems, especially dynamic analysis, typically considers the duct structure and the contained fluid column separately. Coupling of these two systems, however, forms a new dynamic system with characteristics not necessarily described by the superposition of the two component system's characteristics. Methods for modeling the two coupled components simultaneously using finite line elements are presented. Techniques for general duct intersections, area or direction changes, long radius bends, hydraulic losses, and hydraulic impedances are discussed. An example problem and results involving time transients are presented. Additionally, a program to enhance post-processing of line element models is discussed.

Saxon, J. B.↗
NASA NTRS2000

DyFK Simulation of Field-Aligned Ion Flows Observed by POLAR within Convecting Flux Over the Polar Ionosphere

Ion (O+ and H+) parallel flows along antisunward convecting flux tubes across the polar ionosphere from day to night side are simulated by an extended Dynamic Fluid semiKinetic (DyFK) model. The collision dominated portion of the flux tubes is treated with a moment-based fluid model for altitudes from 120 ?1100 km, while the generalized semikinetic model is used for the topside through 3 RE region. The effects of cleft/auroral soft electron precipitation and wave-driven transverse ion heating are incorporated into the generalized semi-kinetic treatment of topside ionosphere. The simulated evolution of field-aligned ion flow parameters is compared with observations made by the Thermal Ion Dynamics Experiment (TIDE) on board the POLAR satellite near 5000 km altitude over the southern hemisphere polar ionosphere.

Tu, J.-N.↗