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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Discrete element simulations of gravitational volcanic deformation: Deformation structures and geometries - 1

We have carried out two-dimensional particle dynamics simulations of granular piles subject to frictional Coulomb failure criteria to gain a first-order understanding of different modes of gravitational deformation within volcanoes. Under uniform basal and internal strength conditions, granular piles grow self-similarly, developing distinctive stratigraphies, morphologies, and structures. Piles constructed upon cohesive substrates exhibit particle avalanching, forming outward dipping strata and angle of repose slopes. Systematic decreases in basal strength lead to progressively deeper and steeper internal detachment faults and slip along a basal decollement; landslide forms grade from shallow slumps to deep-seated landslide and, finally, to axial subsidence and outward flank displacements, or volcanic spreading. Surface slopes decrease and develop concave up morphologies with decreasing decollement strength; depositional layers tilt progressively inward. Spatial variations in basal strength cause lateral transitions in pile structure, stratigraphy, and morphology. This approximation of volcanoes as Coulomb granular piles reproduces the richness of deformational structures and surface morphologies in many volcanic settings. The gentle slopes of Hawaiian volcanoes and Olympus Mons on Mars suggest weak basal decollements that enable volcanic spreading. High-angle normal faults, favored above weak decollements, are interpreted in both settings and may explain catastrophic sector collapse in Hawaii and broad aureole deposits surrounding Olympus Mons. In contrast, steeper slopes and shallow detachment faults predominate in the Canary Islands, thought to lack a weak decollement, favoring smaller, more frequent slope failures than predicted for Hawaii. The numerical results provide a useful predictive tool for interpreting dynamic behavior and associated geologic hazards of active volcanoes.

Morgan, Julia K.↗
NASA NTRS1993

Probabilistic simulation of fragment dynamics and their surface impacts in the SSME turbopump

Numerical simulations are used to model the dynamics of solid fragments in the high pressure fuel turbopump of the space shuttle main engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.

Hamed, A.↗
NASA NTRS1991

Probabilistic simulation of fragment dynamics and their surface impacts in the SSME turbopump

Numerical simulations are used to model the dynamics of solid fragments in the high-pressure fuel turbopump of the Space Shuttle Main Engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.

Hamed, A.↗
NASA NTRS2010

DEM Solutions Develops Answers to Modeling Lunar Dust and Regolith

With the proposed return to the Moon, scientists like NASA-KSC's Dr. Calle are concerned for a number of reasons. We will be staying longer on the planet's surface, future missions may include dust-raising activities, such as excavation and handling of lunar soil and rock, and we will be sending robotic instruments to do much of the work for us. Understanding more about the chemical and physical properties of lunar dust, how dust particles interact with each other and with equipment surfaces and the role of static electricity build-up on dust particles in the low-humidity lunar environment is imperative to the development of technologies for removing and preventing dust accumulation, and successfully handling lunar regolith. Dr. Calle is currently working on the problems of the electrostatic phenomena of granular and bulk materials as they apply to planetary surfaces, particularly to those of Mars and the Moon, and is heavily involved in developing instrumentation for future planetary missions. With this end in view, the NASA Kennedy Space Center's Innovative Partnerships Program Office partnered with OEM Solutions, Inc. OEM Solutions is a global leader in particle dynamics simulation software, providing custom solutions for use in tackling tough design and process problems related to bulk solids handling. Customers in industries such as pharmaceutical, chemical, mineral, and materials processing as well as oil and gas production, agricultural and construction, and geo-technical engineering use OEM Solutions' EDEM(TradeMark) software to improve the design and operation of their equipment while reducing development costs, time-to-market and operational risk. EDEM is the world's first general-purpose computer-aided engineering (CAE) tool to use state-of-the-art discrete element modeling technology for the simulation and analysis of particle handling and manufacturing operations. With EDEM you'can quickly and easily create a parameterized model of your granular solids system. Computer-aided design (CAD) models of real particles can be imported to obtain an accurate representation of their shape. EDEM(TradeMark) uses particle-scale behavior models to simulate bulk solids behavior. In addition to particle size and shape, the models can account for physical properties of particles along with interaction between particles and with equipment surfaces and surrounding media, as needed to define the physics of a particular process.

Dunn, Carol Anne↗
NASA NTRS2011

TPSAS-NF1676L-12354-DND

This work deals with performance properties of a dynamic traffic model, the Air Traffic Monotonic Lagrangian Grid (ATMLG), which can be used to evaluate new control strategies for conflict avoidance, separation assurance, and traffic management. The model is based on an algorithm and data structure called the Monotonic Lagrangian Grid (MLG), originally developed at NRL in the mid 1980s and since then used as an underpinning for various particle dynamics simulations. The MLG stores positions and other data needed to describe N moving objects, where N can be very large. The MLG algorithm involves sorting and ordering objects. A stationary grid is an alternative to the dynamic grid of MLG. Stationary grids can be attractive in that they do not require sorting. We investigate and report on the relative performances of air traffic simulations based on dynamic (MLG) and static (lat-long) grids.

C Kaplan↗
NASA NTRS2011

TPSAS-NF1676L-12301-DND

This work deals with performance properties of a dynamic traffic model, the Air Traffic Monotonic Lagrangian Grid (ATMLG), which can be used to evaluate new control strategies for conflict avoidance, separation assurance, and traffic management. The model is based on an algorithm and data structure called the Monotonic Lagrangian Grid (MLG), originally developed at NRL in the mid 1980s and since then used as an underpinning for various particle dynamics simulations. The MLG stores positions and other data needed to describe N moving objects, where N can be very large. The MLG algorithm involves sorting and ordering objects. A stationary grid is an alternative to the dynamic grid of MLG. Stationary grids can be attractive in that they do not require sorting. We investigate and report on the relative performances of air traffic simulations based on dynamic (MLG) and static (lat-long) grids.

Carolyn Kaplan↗
NASA NTRS2020

Dynamical Evolution of Simulated Particles Ejected from Asteroid Bennu

In early 2019, the OSIRIS-REx spacecraft discovered small particles being ejected from the surface of the near-Earth asteroid Bennu. Although they were seen to be ejected at slow speeds, on the order of tens of cm/s, a number of particles were surprisingly seen to orbit for multiple revolutions and days, which requires a dynamical mechanism to quickly and substantially modify the orbit to prevent re-impact upon their first periapse passage. This paper demonstrates that, based on simulations constrained by the conditions of the observed events, the combined effects of gravity, solar radiation pressure, and thermal radiation pressure from Bennu can produce many sustained orbits for ejected particles. Furthermore, the simulated populations exhibit two interesting phenomena that could play an important role in the geophysical evolution of bodies such as Bennu. First, small particles (< 1 cm radius) are preferentially removed from the system, which could lead to a deficit of such particles on the surface. Second, re-impacting particles preferentially land near or on the equatorial bulge of Bennu. Over time, this can lead to crater in-filling and growth of the equatorial radius without requiring landslides.

Jay W. McMahon↗
NASA NTRS1994

Numerical simulations of particle orbits around 2060 Chiron

Scattered light from orbiting or coorbiting dust is a primary signature by which Earth-based observers study the activity and atmosphere of the unusual outer solar system object 2060 Chiron. Therefore, it is important to understand the lifetime, dynamics, and loss rates of dust in its coma. We report here dynamical simulations of particles in Chiron's collisionless coma. The orbits of 17,920 dust particles were numerically integrated under the gravitational influence of Chiron, the Sun, and solar radiation pressure. These simulations show that particles ejected from Chiron are more likely to follow suborbital trajectories, or to escape altogether, than to enter quasistable orbits. Significant orbital lifetimes can only be achieved for very specific launch conditions. These results call into question models of a long-term, bound coma generated by discrete outbursts, and instead suggest that Chiron's coma state is closely coupled to the nearly instantaneous level of Chiron's surface activity.

Stern, S. A.↗
NASA NTRS1992

Parallel implementation of a particle simulation for modeling rarefied gas dynamic flow

When the conditions of flow are rarefied and hypersonic, a more suitable alternative to the use of the Navier-Stokes equations for developing a numerical solution is the Direct Simulation Monte Carlo method (DSMC), a method of simulation which employs a large number of particles in modeling a rarefied gas. The performance of a parallel DSMC code developed for the Intel iPSC/860 Touchstone Gamma prototype computer is studied and the scaleup is found to be very nearly over the range of 16-128 processors.

Fallavollita, M. A.↗
NASA NTRS2002

A Theoretical Study of the Global Geospace System Simulations

This report describes work undertaken by the principal investigator (PI) and her colleagues in three areas of research: Relativistic Electron Dynamics, Solar Energetic Particle Study, and ULF Wave Statistical Study. The researchers conducted three dimensional modeling of relativistic electron dynamics, simulated Solar Energetic Particles (SEP) trapping using a magnetohydrodynamic (MHD) code, and a study of Pc 5 magnetic pulsations.

Hudson, Mary K.↗
NASA NTRS1991

Molecular dynamics computations of two dimensional supersonic rarefied gas flow past blunt bodies

This paper presents results of molecular dynamics computations of supersonic flow past a circular cylinder and past a flat plate perpendicular to a supersonic stream. The results are for Mach numbers of approximately 5 and 10, for several Knudsen numbers and several ratios of surface to free stream temperatures. A special feature of the computations is the use of relatively small numbers of particles in the molecular dynamics simulation, and an examination of the adequacy of using small numbers of particles to obtain physically useful results.

Greber, Isaac↗
NASA NTRS1992

The dynamics of low-beta plasma clouds as simulated by a three-dimensional, electromagnetic particle code

A 3D electromagnetic and relativistic particle simulation code is used to investigate the dynamics of low-beta plasma clouds moving perpendicular to an ambient magnetic field in vacuum and in a background plasma. The simulations show the formation of the space charge sheaths at the sides of the cloud with the associated polarization electric field which facilitate the cross-field propagation, as well as the sheaths at the front and rear end of the cloud caused by the larger ion Larmor radius, which allows ions to move ahead and lag behind the electrons as they gyrate. It is found that, in a background plasma, electron and ion sheaths expand along the magnetic field at the same rate, whereas in vacuum the electron sheath expands much faster than the ion sheath. Sheath clouds are accelerated up to relativistic energies, which indicates that artificial plasma clouds released in the ionosphere or magnetosphere may generate optical emissions as energetic sheath electrons scatter in the upper atmosphere.

Neubert, T.↗
NASA NTRS2000

Fast Particle Methods for Multiscale Phenomena Simulations

We are developing particle methods oriented at improving computational modeling capabilities of multiscale physical phenomena in : (i) high Reynolds number unsteady vortical flows, (ii) particle laden and interfacial flows, (iii)molecular dynamics studies of nanoscale droplets and studies of the structure, functions, and evolution of the earliest living cell. The unifying computational approach involves particle methods implemented in parallel computer architectures. The inherent adaptivity, robustness and efficiency of particle methods makes them a multidisciplinary computational tool capable of bridging the gap of micro-scale and continuum flow simulations. Using efficient tree data structures, multipole expansion algorithms, and improved particle-grid interpolation, particle methods allow for simulations using millions of computational elements, making possible the resolution of a wide range of length and time scales of these important physical phenomena.The current challenges in these simulations are in : [i] the proper formulation of particle methods in the molecular and continuous level for the discretization of the governing equations [ii] the resolution of the wide range of time and length scales governing the phenomena under investigation. [iii] the minimization of numerical artifacts that may interfere with the physics of the systems under consideration. [iv] the parallelization of processes such as tree traversal and grid-particle interpolations We are conducting simulations using vortex methods, molecular dynamics and smooth particle hydrodynamics, exploiting their unifying concepts such as : the solution of the N-body problem in parallel computers, highly accurate particle-particle and grid-particle interpolations, parallel FFT's and the formulation of processes such as diffusion in the context of particle methods. This approach enables us to transcend among seemingly unrelated areas of research.

Koumoutsakos, P.↗
NASA NTRSDate not supplied

Cathode Modeling of Solid-State Batteries

The search for safe, reliable, and compact high-capacity energy storage devices has led to increased interest in all-solid-state battery research. The use of solid electrolytes provides enhanced safety and durability due to their reduced flammability and increased mechanical strength compared to organic liquid electrolytes. Still, the use of solid electrolytes remains challenging. Computational modeling plays a substantial role in addressing these challenges. A particle dynamics electromechanical model for simulating electrochemical processes in a solid-state battery cathode will be presented. The model presents cathode microstructure at the particle level as a mixture of ionically conductive solid electrolyte particles, electrically conductive carbon additives, and cathodic reactant particles. After densification, the particle connectivity is analyzed to reconstruct the complex electric network connecting reactant particles with an anodic and cathodic current collectors through the electrolyte and carbon particles. The Kirchhoff’s matrix equation describing this electric network, is solved to obtain values of various critical parameters, such as the overall conductivity of the cathode for lithium ions and electrons, cathodic reactant material utilization, and the distribution of the electric current and voltages within the cathode. In addition, by representing the reactant particles as electrolyte or galvanic microcells governed by the Butler-Volmer electrochemical equation, the overall performance of battery cells during charge or discharge processes, respectively, can be predicted for a given cathodic powder composition. The presented model, executed on a high-performance computing architecture, essentially provides a valuable guidance in designing and developing future solid-state batteries.

solid-state battery↗
NASA NTRSDate not supplied

Modeling of Particle Transport and Impact in Transient, Multiphase Oxidizer-Rich Environments Using Computational Fluid Dynamics and Lagrangian Particle Tracking

Particle impacts from foreign object debris (FOD) in an oxidizer-rich environment have been shown to be a credible and significant risk for ignition and failure of components and vehicles. The risk of particle ignition is dependent on many factors, including particle impact velocity/energy and fluid composition (i.e. fluid phase, species presence, and state). Prediction of particle transport and particle impacts in relevant environments, including transient, multiphase flows, is important for assessing the risk and avoiding repeated expensive system level tests. The capability to model both the fluid dynamics and particle transport in complex three-dimensional geometries and multiphase environments has been developed at Marshall Space Flight Center (MSFC) in the propulsion fluid dynamic branch (ER42) by utilizing computational fluid dynamics (CFD) simulations and Lagrangian particle tracking. Using CFD tools, including density-based Loci/CHEM with a cavitation model and pressure-based Loci/STREAM with a volume of fluids model, MSFC/ER42 has provided particle impact predictions to multiple projects for oxidizer compatibility assessments. Simulations of transient, multiphase environments such as liquid slugs flowing through tubing and cavitating flow in valves have been completed alongside one-way coupled Lagrangian particle tracking to predict particle impacts.

M.V. Fischels↗
NASA NTRS2001

Carbon Nanotubes in Water: MD Simulations of Internal and External Flow, Self Organization

We have developed computational tools, based on particle codes, for molecular dynamics (MD) simulation of carbon nanotubes (CNT) in aqueous environments. The interaction of CNTs with water is envisioned as a prototype for the design of engineering nano-devices, such as artificial sterocillia and molecular biosensors. Large scale simulations involving thousands of water molecules are possible due to our efficient parallel MD code that takes long range electrostatic interactions into account. Since CNTs can be considered as rolled up sheets of graphite, we expect the CNT-water interaction to be similar to the interaction of graphite with water. However, there are fundamental differences between considering graphite and CNTs, since the curvature of CNTs affects their chemical activity and also since capillary effects play an important role for both dynamic and static behaviour of materials inside CNTs. In recent studies Gordillo and Marti described the hydrogen bond structure as well as time dependent properties of water confined in CNTs. We are presenting results from the development of force fields describing the interaction of CNTs and water based on ab-initio quantum mechanical calculations. Furthermore, our results include both water flows external to CNTs and the behaviour of water nanodroplets inside heated CNTs. In the first case (external flows) the hydrophobic behaviour of CNTs is quantified and we analyze structural properties of water in the vicinity of CNTs with diagnostics such as hydrogen bond distribution, water dipole orientation and radial distribution functions. The presence of water leads to attractive forces between CNTs as a result of their hydrophobicity. Through extensive simulations we quantify these attractive forces in terms of the number and separation of the CNT. Results of our simulations involving arrays of CNTs indicate that these exhibit a hydrophobic behaviour that leads to self-organising structures capable of trapping water clusters. In the second case (internal flows) we study the behaviour of water droplets confined inside CNTs. Constant temperature simulations allow us to capture structural properties such as the contact angles and density profiles of the equilibrated drops. By heating and subsequently cooling of the CNT, we are able to measure the evaporation and the condensation rate of the entrapped water.

Jaffe, Richard L.↗
NASA NTRS1983

Simulation of transport and removal processes of the Saharan dust

A planetary boundary layer (PBL) model has been modified to include a Saharan air layer containing the bulk of Saharan dust. The Saharan air layer is recognized as a deep mixed layer, which extends up to 4-6 km during hot summer months and is characterized by high potential temperature and high dust concentration. Microphysical processes of particle coagulation and sedimentation have been coupled with dynamic processes to simulate the evolution of dust particles. In agreement with observations, simulations indicate that dust particles greater than 10 micron radius can be produced and transported in the Sahara air layer across the Atlantic Ocean, while dust concentrations in the PBL over the Atlantic Ocean are smaller by a factor of two or more than in the Saharan air layer.

Lee, I.-Y.↗