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LASNEX modeling of target expansion in the ETA-II experiment

Description: We have used the hydrodynamics code LASNEX to model the hydro-expansion of the tantalum target for the ETA-II experiment. The electron beam has kinetic energy of 6 MeV and has a total energy ranges from 720 to 1440 J. The electron beam profile resembles that of a Bennett pinch. The radius for the full-width-at-half-maximum ranges from 1 to 3 mm. For all these parameters, simulations show that the electron beam is able to ablate the central portion of the target. The expansion velocity of the target ranges from about 10� to 5 x 105 cm/s. The target is hot enough so that the surrounding low-density air is ionized and is expanding at a considerably higher velocity than the target itself. Therefore, care must be taken during the experiment to ensure that the measurement is for the tantalum and not for the ionized air.
Date: May 20, 1998
Creator: Ho, D D-M
Partner: UNT Libraries Government Documents Department

Centrality dependence of multiplicity, transverse energy, and elliptic flow from hydrodynamics

Description: The centrality dependence of the charged multiplicity, transverse energy, and elliptic flow coefficient is studied in a hydrodynamic model, using a variety of different initializations which model the initial energy or entropy production process as a hard or soft process, respectively. While the charged multiplicity depends strongly on the chosen initialization, the p{sub T}-integrated elliptic flow for charged particles as a function of charged particle multiplicity and the p{sub T}-differential elliptic flow for charged particles in minimum bias events turn out to be almost independent of the initialization.
Date: March 21, 2001
Creator: Kolb, Peter F.; Heinz, Ulrich; Huovinen, Pasi; Eskola, Kari J. & Tuominen, Kimmo
Partner: UNT Libraries Government Documents Department

Development of a Hydrodynamic Model of Puget Sound and Northwest Straits

Description: The hydrodynamic model used in this study is the Finite Volume Coastal Ocean Model (FVCOM) developed by the University of Massachusetts at Dartmouth. The unstructured grid and finite volume framework, as well as the capability of wetting/drying simulation and baroclinic simulation, makes FVCOM a good fit to the modeling needs for nearshore restoration in Puget Sound. The model domain covers the entire Puget Sound, Strait of Juan de Fuca, San Juan Passages, and Georgia Strait at the United States-Canada Border. The model is driven by tide, freshwater discharge, and surface wind. Preliminary model validation was conducted for tides at various locations in the straits and Puget Sound using National Oceanic and Atmospheric Administration (NOAA) tide data. The hydrodynamic model was successfully linked to the NOAA oil spill model General NOAA Operational Modeling Environment model (GNOME) to predict particle trajectories at various locations in Puget Sound. Model results demonstrated that the Puget Sound GNOME model is a useful tool to obtain first-hand information for emergency response such as oil spill and fish migration pathways.
Date: December 10, 2007
Creator: Yang, Zhaoqing & Khangaonkar, Tarang P.
Partner: UNT Libraries Government Documents Department

Hydrodynamic Modeling Analysis of Union Slough Restoration Project in Snohomish River, Washington

Description: A modeling study was conducted to evaluate additional project design scenarios at the Union Slough restoration/mitigation site during low tide and to provide recommendations for finish-grade elevations to achieve desired drainage. This was accomplished using the Snohomish River hydrodynamic model developed previously by PNNL.
Date: December 20, 2010
Creator: Yang, Zhaoqing & Wang, Taiping
Partner: UNT Libraries Government Documents Department

Mutiscale Modeling of Segregation in Granular Flows

Description: Modeling and simulation of segregation phenomena in granular flows are investigated. Computational models at different scales ranging from particle level (microscale) to continuum level (macroscale) are employed in order to determine the important microscale physics relevant to macroscale modeling. The capability of a multi-fluid model to capture segregation caused by density difference is demonstrated by simulating grain-chaff biomass flows in a laboratory-scale air column and in a combine harvester. The multi-fluid model treats gas and solid phases as interpenetrating continua in an Eulerian frame. This model is further improved by incorporating particle rotation using kinetic theory for rapid granular flow of slightly frictional spheres. A simplified model is implemented without changing the current kinetic theory framework by introducing an effective coefficient of restitution to account for additional energy dissipation due to frictional collisions. The accuracy of predicting segregation rate in a gas-fluidized bed is improved by the implementation. This result indicates that particle rotation is important microscopic physics to be incorporated into the hydrodynamic model. Segregation of a large particle in a dense granular bed of small particles under vertical. vibration is studied using molecular dynamics simulations. Wall friction is identified as a necessary condition for the segregation. Large-scale force networks bearing larger-than-average forces are found with the presence of wall friction. The role of force networks in assisting rising of the large particle is analyzed. Single-point force distribution and two-point spatial force correlation are computed. The results show the heterogeneity of forces and a short-range correlation. The short correlation length implies that even dense granular flows may admit local constitutive relations. A modified minimum spanning tree (MST) algorithm is developed to asymptotically recover the force statistics in the force networks. This algorithm provides a possible route to constructing a continuum model with microstructural information supplied from it. Microstructures in ...
Date: August 3, 2007
Creator: Sun, Jin
Partner: UNT Libraries Government Documents Department

Code Differentiation for Hydrodynamic Model Optimization

Description: Use of a hydrodynamics code for experimental data fitting purposes (an optimization problem) requires information about how a computed result changes when the model parameters change. These so-called sensitivities provide the gradient that determines the search direction for modifying the parameters to find an optimal result. Here, the authors apply code-based automatic differentiation (AD) techniques applied in the forward and adjoint modes to two problems with 12 parameters to obtain these gradients and compare the computational efficiency and accuracy of the various methods. They fit the pressure trace from a one-dimensional flyer-plate experiment and examine the accuracy for a two-dimensional jet-formation problem. For the flyer-plate experiment, the adjoint mode requires similar or less computer time than the forward methods. Additional parameters will not change the adjoint mode run time appreciably, which is a distinct advantage for this method. Obtaining ''accurate'' sensitivities for the j et problem parameters remains problematic.
Date: June 27, 1999
Creator: Henninger, R.J. & Maudlin, P.J.
Partner: UNT Libraries Government Documents Department

Progress in collective flow studies from the onset to Bevalac/SIS

Description: Collective flow in heavy ion collisions was first observed experimentally more than a decade ago at the Bevalac by the Plastic Ball collaboration. Although early calculations had suggested that measurement of the flow would place tight constraints on the nuclear equation of state, uncertainties in other input parameters of microscopic models, which also affect the flow, led to large ambiguities in the equation of state. This talk will discuss recent flow studies that attempt to overcome these difficulties. The EOS and FOPI experiments at the Bevalac and SIS accelerators have measured flow in the 200--2000 A-MeV bombarding energy range with better acceptance, particle identification, and systematics than was previously available. Meanwhile, programs at MSU and GANIL are studying the disappearance of flow around 50 A-MeV. Systematic comparison of these data with predictions of microscopic models is beginning to reduce the ambiguities in the extraction of physics quantities. Also, new directions in flow studies, such as the flow of produced particles and radial flow, offer the possibility of further information from flow studies. Recent accomplishments and new directions in flow studies are discussed, and areas where further study is needed are pointed out.
Date: March 1, 1995
Creator: Lisa, M.A.
Partner: UNT Libraries Government Documents Department

MASS2, Modular Aquatic Simulation System in Two Dimensions, User Guide and Reference

Description: The Modular Aquatic Simulation System in Two Dimensions (MASS2) is a two-dimensional, depth-averaged hydrodynamics and transport model. The model simulates time varying distributions of depth-averaged velocities, water surface elevations, and water quality constituents. This manual documents the use of MASS2. It is the second of two reports on MASS2. The first report documents the theory and numerical methods used in MASS2, and is often referred to herein as the Theory Manual. MASS2 is applicable to a wide variety of environmental analyses of rivers and estuaries where vertical variations in the water column are negligible or unimportant.
Date: July 1, 2007
Creator: Perkins, William A. & Richmond, Marshall C.
Partner: UNT Libraries Government Documents Department

MASS2, Modular Aquatic Simulation System in Two Dimensions, Theory and Numerical Methods

Description: The Modular Aquatic Simulation System in Two Dimensions (MASS2) is a two-dimensional, depth-averaged hydrodynamics and transport model. The model simulates time varying distributions of depth-averaged velocities, water surface elevations, and water quality constituents. MASS2 uses a structured, multi-block, boundary-fitted, curvilinear computational mesh, which allows the simulation of very complex riverine or estuarine networks. The blocks may be of varying resolution, which allows high resolution to be used only where needed. MASS2 can simulate a wide variety of hydrodynamic conditions, including supercritical flow and hydraulic jumps. It can also simulate a wide variety of water quality conditions, including sediment, conservative or decaying contaminants, sediment-sorbed contaminants, water temperature, and total dissolved gas. Any number of these constituents may be simulated simultaneously. In addition, transport simulations may be performed using pre-calculated hydrodynamic conditions, allowing long-term transport simulations unencumbered by the more intensive hydrodynamic calculations, or repeated transport simulations without re-simulating hydrodynamics. This report documents the theory and numerical methods used in MASS2. In addition, the results are presented from several of hydrodynamic and transport validation tests to which MASS2 was subjected. The companion user manual documents the application of MASS2.
Date: July 1, 2007
Creator: Perkins, William A. & Richmond, Marshall C.
Partner: UNT Libraries Government Documents Department

Anisotropic flow nu2 in Au + Au collisions at RHIC

Description: Using the RQMD model, transverse momentum dependence of the anisotropic flow v{sub 2} for {pi}, K, nucleon, {phi}, and {lambda}, are studied for Au + Au collisions at {radical}s{sub NN} = 200 GeV. Both hydrodynamic hadron-mass hiragracy (hhmh) at low p{sub T} region and particle type dependence (baryon versus meson) at the intermediate p{sub T} region are reproduced with the model calculations although the model underpredicted the overall values of v{sub 2} by a factor of 2-3. As expected, when the rescatterings are turned off, all v{sub 2} becomes zero. The failure of the hadronic model in predicting the absolute values of hadron v{sub 2} clearly demonstrate the need of early dense partonic interaction in heavy-ion collisions at RHIC. At the intermediate p{sub T}, the hadron type dependence cold also be explained by the vacume hadronic cross sections within the frame of the model. The measurements of collective motion of hadrons from high-energy nuclear collisions can provide information on the dynamical equation of state information of the system [1, 2, 3]. Specifically, the strange and multi-strange hadron flow results have demonstrated the partonic collectivity [5] and the heavy-flavor flow will test the hypothesis of early thermalization in such collisions [4]. At RHIC, the measurements [6, 7] of elliptic flow v{sub 2} and nuclear modification factor r{sub AA} has lead to the conclusion that hadrons were formed via the coalescence/recombination of massive quarks [8, 9, 10]. This finding is directly related to the key issue in high-energy nuclear collisions such as deconfinement and chiral symmetry restoration. In addition, it also touched the important problem of hadronization process in high-energy collisions. Therefore a systematic study with different approaches becomes necessary. In this report, using a hadronic transport model UrQMD(v2.2)/RQMD(v2.4) [11, 12], we study the v{sub 2} of {pi}, K, p, {phi}, and ...
Date: August 20, 2005
Creator: Lu, Y.; Bleicher, M.; Liu, F.; Kiu, Z.; Sorensen, P.; Stocker,H. et al.
Partner: UNT Libraries Government Documents Department

3-D HYDRODYNAMIC MODELING IN A GEOSPATIAL FRAMEWORK

Description: 3-D hydrodynamic models are used by the Savannah River National Laboratory (SRNL) to simulate the transport of thermal and radionuclide discharges in coastal estuary systems. Development of such models requires accurate bathymetry, coastline, and boundary condition data in conjunction with the ability to rapidly discretize model domains and interpolate the required geospatial data onto the domain. To facilitate rapid and accurate hydrodynamic model development, SRNL has developed a pre- and post-processor application in a geospatial framework to automate the creation of models using existing data. This automated capability allows development of very detailed models to maximize exploitation of available surface water radionuclide sample data and thermal imagery.
Date: August 24, 2006
Creator: Bollinger, J; Alfred Garrett, A; Larry Koffman, L & David Hayes, D
Partner: UNT Libraries Government Documents Department

Assessment of Energy Removal Impacts on Physical Systems: Hydrodynamic Model Domain Expansion and Refinement, and Online Dissemination of Model Results

Description: In this report we describe the 1) the expansion of the PNNL hydrodynamic model domain to include the continental shelf along the coasts of Washington, Oregon, and Vancouver Island; and 2) the approach and progress in developing the online/Internet disseminations of model results and outreach efforts in support of the Puget Sound Operational Forecast System (PS-OPF). Submittal of this report completes the work on Task 2.1.2, Effects of Physical Systems, Subtask 2.1.2.1, Hydrodynamics, for fiscal year 2010 of the Environmental Effects of Marine and Hydrokinetic Energy project.
Date: August 1, 2010
Creator: Yang, Zhaoqing; Khangaonkar, Tarang & Wang, Taiping
Partner: UNT Libraries Government Documents Department

The simulation of a criticality accident excursion occurring in a simple fast metal system using the coupled neutronic-hydrodynamic method

Description: Analysis of a criticality accident scenario occuring in a simple fast metal system using the coupled neutronic-hydrodynamic method is demonstrated by examining the last Godiva-I criticality accident. The basis tools and information for creating a coupled neutronic-hydrodynamic code are presented. Simplifying assumptions and approximations for creating an idealized model for the Godiva-I system are discussed. Estimates of the total energy generation and the maximum attainable kinetic energy yield are the most important results that are obtained from the code. With modifications, the methodology presented in this paper can be extended to analyze criticality accident excursions in other kinds of nuclear systems.
Date: December 31, 1996
Creator: Myers, W.L.
Partner: UNT Libraries Government Documents Department

Resistive Instabilities in Hall Current Plasma Discharge

Description: Plasma perturbations in the acceleration channel of a Hall thruster are found to be unstable in the presence of collisions. Both electrostatic lower-hybrid waves and electromagnetic Alfven waves transverse to the applied electric and magnetic field are found to be unstable due to collisions in the E X B electron flow. These results are obtained assuming a two-fluid hydrodynamic model in slab geometry. The characterisitic frequencies of these modes are consistent with experimental observations in Hall current plasma thrusters.
Date: November 16, 2000
Creator: Litvak, Andrei A. & Fisch, Nathaniel J.
Partner: UNT Libraries Government Documents Department

Direct observation of resonance effects in laser cluster interactions

Description: Time resolved dynamics of high intensity laser interactions with atomic clusters have been studied with both theoretical analysis and experiment. A short-pulse Ti:sapphire laser system, which could produce 50 mJ of energy in a 50 fs pulse, was built to perform these experiments. The laser used a novel single grating stretcher and was pumped, in part, by a custom Nd:YLF laser system, including 19 mm Nd:YLF amplifiers. It was found that there is an optimal pulse width to maximize absorption for a given cluster size. This optimal pulse width ranged from 400 fs for 85 A radius xenon clusters to 1.2 ps for 205 {angstrom} radius xenon clusters. Using a pump-probe configuration, the absorption of the probe radiation was observed to reach a maximum for a particular time delay between pump and probe, dependent on the cluster size. The delay for peak absorption was 800, 1400, and 2100 fs for 85 {angstrom}, 130 {angstrom}, and 170 {angstrom} radius xenon clusters respectively. Model calculations suggest that these effects are due to resonant heating of the spherical plasma in agreement with the hydrodynamic interpretation of cluster interactions. While this simple hydrodynamic code produces reasonable agreement with data, it does not include bulk plasma or non-linear propagation effects and is limited to the regime where resonant behavior dominates. We also measured the scattered laser light from the laser-cluster interaction. Similar to the absorption measurements, there is an optimal pulse width which maximizes the scattered signal. This pulse width is larger than the optimal pulse width for absorption. This disagrees with model calculations which show both pulse widths being similar. Further experiments measuring the scattered light in a pump-probe configuration should help to resolve this disagreement.
Date: June 1, 1999
Creator: Zweiback, J
Partner: UNT Libraries Government Documents Department

Experimental and computational studies of hydrodynamics in three-phase and two-phase fluidized beds

Description: The objective of the present study was to investigate the hydrodynamics of three-phase fluidized beds, their rheology, and experimentally verify a predictive three fluid hydrodynamic model developed at the Illinois Institute of Technology, Chicago. The recent reviews show that there exist no such models in the literature. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid, and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. In this thesis, a three fluid model is presented. The input into the model can be particulate viscosities either measured with a Brookfield viscometer or derived using the mathematical techniques of kinetic theory of granular flows pioneered by Savage and others. The computer simulation of a three-phase fluidized bed in an asymmetric mode qualitatively predicts the gas, liquid and solid hold-ups (volume fractions) and flow patterns in the industrially important churn-turbulent (bubbly coalesced) regimes. The computations in a fluidized bed with a symmetric distributor incorrectly showed no bubble coalescence. A combination of X-ray and {gamma}-ray densitometers was used to measure the solids and the liquid volume fractions in a two dimensional bed in the bubble coalesced regime. There is a good agreement between the theory for an asymmetric distributor and the experiments.
Date: December 1, 1994
Creator: Bahary, M.
Partner: UNT Libraries Government Documents Department

Radial and elliptic flow at RHIC: Further predictions

Description: Using a hydrodynamic model, we predict the transverse momentum dependence of the spectra and the elliptic flow for different hadrons in Au+Au collisions at sqrt(s)=130 AGeV. The dependence of the differential and p{_}t-integrated elliptic flow on the hadron mass, equation of state and freeze-out temperature is studied both numerically and analytically.
Date: January 30, 2001
Creator: Huovinen, Pasi; Kolb, Peter F.; Heinz, Ulrich; Ruuskanen, P.V. & Voloshin, Sergei A.
Partner: UNT Libraries Government Documents Department

Puget Sound Dissolved Oxygen Modeling Study: Development of an Intermediate-Scale Hydrodynamic Model

Description: The Washington State Department of Ecology contracted with Pacific Northwest National Laboratory to develop an intermediate-scale hydrodynamic and water quality model to study dissolved oxygen and nutrient dynamics in Puget Sound and to help define potential Puget Sound-wide nutrient management strategies and decisions. Specifically, the project is expected to help determine 1) if current and potential future nitrogen loadings from point and non-point sources are significantly impairing water quality at a large scale and 2) what level of nutrient reductions are necessary to reduce or dominate human impacts to dissolved oxygen levels in the sensitive areas. In this study, an intermediate-scale hydrodynamic model of Puget Sound was developed to simulate the hydrodynamics of Puget Sound and the Northwest Straits for the year 2006. The model was constructed using the unstructured Finite Volume Coastal Ocean Model. The overall model grid resolution within Puget Sound in its present configuration is about 880 m. The model was driven by tides, river inflows, and meteorological forcing (wind and net heat flux) and simulated tidal circulations, temperature, and salinity distributions in Puget Sound. The model was validated against observed data of water surface elevation, velocity, temperature, and salinity at various stations within the study domain. Model validation indicated that the model simulates tidal elevations and currents in Puget Sound well and reproduces the general patterns of the temperature and salinity distributions.
Date: November 30, 2010
Creator: Yang, Zhaoqing; Khangaonkar, Tarang; Labiosa, Rochelle G. & Kim, Taeyun
Partner: UNT Libraries Government Documents Department

Hydrodynamic Modeling of Air Blast Propagation from the Humble Redwood Chemical High Explosive Detonations Using GEODYN

Description: Two-dimensional axisymmetric hydrodynamic models were developed using GEODYN to simulate the propagation of air blasts resulting from a series of high explosive detonations conducted at Kirtland Air Force Base in August and September of 2007. Dubbed Humble Redwood I (HR-1), these near-surface chemical high explosive detonations consisted of seven shots of varying height or depth of burst. Each shot was simulated numerically using GEODYN. An adaptive mesh refinement scheme based on air pressure gradients was employed such that the mesh refinement tracked the advancing shock front where sharp discontinuities existed in the state variables, but allowed the mesh to sufficiently relax behind the shock front for runtime efficiency. Comparisons of overpressure, sound speed, and positive phase impulse from the GEODYN simulations were made to the recorded data taken from each HR-1 shot. Where the detonations occurred above ground or were shallowly buried (no deeper than 1 m), the GEODYN model was able to simulate the sound speeds, peak overpressures, and positive phase impulses to within approximately 1%, 23%, and 6%, respectively, of the actual recorded data, supporting the use of numerical simulation of the air blast as a forensic tool in determining the yield of an otherwise unknown explosion.
Date: September 20, 2011
Creator: Chipman, V D
Partner: UNT Libraries Government Documents Department

Review of Systematic Investigations of the Rout/Rside ratio in HBT at RHIC

Description: We review the significant difference in the ratio R{sub out}/R{sub side} between experiment and theory in heavy-ion collisions at RHIC. This ratio is expected to be strongly correlated with the pion emission duration. Hydrodynamic models typically calculate a value that approximately equal to 1.5 and moderately dependent on k{sub T} whereas the experiments report a value close to unity and independent of k{sub T}. We review those calculations in which systematic variations in the theoretical assumptions were reported. We find that the scenario of second order phase transition or cross-over has been given insufficient attention, and may play an important role in resolving this discrepancy.
Date: January 6, 2005
Creator: Soltz, R. A.
Partner: UNT Libraries Government Documents Department

Quantifying the Behavioral Response of Spawning Chum Salmon to Elevated Discharges from Bonneville Dam, Columbia River : Annual Report 2005-2006.

Description: In unimpounded rivers, Pacific salmon (Oncorhynchus spp.) typically spawn under relatively stable stream flows, with exceptions occurring during periodic precipitation events. In contrast, hydroelectric development has often resulted in an artificial hydrograph characterized by rapid changes in discharge and tailwater elevation that occur on a daily, or even an hourly basis, due to power generation (Cushman 1985; Moog 1993). Consequently, populations of Pacific salmon that are known to spawn in main-stem habitats below hydroelectric dams face the risks of changing habitat suitability, potential redd dewatering, and uncertain spawning success (Hamilton and Buell 1976; Chapman et al. 1986; Dauble et al. 1999; Garland et al. 2003; Connor and Pflug 2004; McMichael et al. 2005). Although the direct effects of a variable hydrograph, such as redd dewatering are apparent, specific effects on spawning behavior remain largely unexplored. Chum salmon (O. keta) that spawn below Bonneville Dam on the Columbia River are particularly vulnerable to the effects of water level fluctuations. Although chum salmon generally spawn in smaller tributaries (Johnson et al. 1997), many fish spawn in main-stem habitats below Bonneville Dam near Ives Island (Tomaro et al. 2007; Figure 1). The primary spawning area near Ives Island is shallow and sensitive to changes in water level caused by hydroelectric power generation at Bonneville Dam. In the past, fluctuating water levels have dewatered redds and changed the amount of available spawning habitat (Garland et al. 2003). To minimize these effects, fishery managers attempt to maintain a stable tailwater elevation at Bonneville Dam of 3.5 m (above mean sea level) during spawning, which ensures adequate water is provided to the primary chum salmon spawning area below the mouth of Hamilton Creek (Figure 1). Given the uncertainty of winter precipitation and water supply, this strategy has been effective at restricting spawning to a specific riverbed ...
Date: December 1, 2008
Creator: Tiffan, Kenneth F.; Haskell, Craig A. & Kock, Tobias J.
Partner: UNT Libraries Government Documents Department

The Role of Viscosity in TATB Hot Spot Ignition

Description: The role of dissipative effects, such as viscosity, in the ignition of high explosive pores is investigated using a coupled chemical, thermal, and hydrodynamic model. Chemical reactions are tracked with the Cheetah thermochemical code coupled to the ALE3D hydrodynamic code. We perform molecular dynamics simulations to determine the viscosity of liquid TATB. We also analyze shock wave experiments to obtain an estimate for the shock viscosity of TATB. Using the lower bound liquid-like viscosities, we find that the pore collapse is hydrodynamic in nature. Using the upper bound viscosity from shock wave experiments, we find that the pore collapse is closest to the viscous limit.
Date: August 2, 2011
Creator: Fried, L E; Zepeda-Ruis, L; Howard, W M; Najjar, F & Reaugh, J E
Partner: UNT Libraries Government Documents Department

A model of meteoroid atmospheric entry with implications for the neohazard and the impact of comet Shoemaker-Levy 9 on Jupiter

Description: A new semianalytical model describing the entry and deformation of meteoroids entering planetary atmospheres has been developed and calibrated against numerical simulations performed using the CTH shock-physics computational hydrocode. The model starts with the classical treatment of meteoroid ablation which is modified to include an explicit treatment of energy conservation during the ablative process. This is reconciled with terrestrial observations by modeling the formation of a vapor/debris layer (the visible bolide) surrounding the central meteoroid. A mechanical deformation model based on long-wavelength hydrodynamic instability growth is added and calibrated against numerical simulations performed with CTH. The analytical model provides initial conditions for numerical fireball simulations which are compared with observations of the Comet Shoemaker-Levy 9 impact on Jupiter and can be used to assess the terrestrial impact hazard.
Date: May 1, 1996
Creator: Crawford, D.A. & Boslough, M.B.
Partner: UNT Libraries Government Documents Department

Effects of Segmented Electrode in Hall Current Plasma Thrusters

Description: Segmented electrodes with a low secondary electron emission are shown to alter significantly plasma flow in the ceramic channel of the Hall thruster. The location of the axial acceleration region relative to the magnetic field can be moved. The radial potential distribution can also be altered near the channel walls. A hydrodynamic model shows that these effects are consistent with a lower secondary electron emission of the segmented electrode as compared to ceramic channel walls.
Date: December 3, 2001
Creator: Raitses, Y.; Keidar, M.; Staack, D. & Fisch, N.J.
Partner: UNT Libraries Government Documents Department