| Modeling of the 105-mm Rarefaction Wave Gun |
Aug-2009 |
36 pages |
| Authors:
Terrence P Coffee; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
 | The Rarefaction wAVE guN (RAVEN) is designed to reduce the recoil momentum of a gun while having a minimal effect on the projectile velocity. The recoil reduction is achieved by venting gas out the breech through an expansion nozzle. This is similar to a recoilless rifle. The difference is that the venting is delayed until the projectile is some distance down tube. The opening of the breech creates a rarefaction ... |
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| Computation of Hypersonic Shock Wave Flows of Multi-Component Reactive Gas Mixtures Using the Generalized Boltzmann Equation |
27-Mar-2009 |
41 pages |
| Authors:
Ramesh K Agarwal; WASHINGTON UNIV ST LOUIS MO DEPT OF MECHANICAL ENGINEERING
|
| The objective of this project has been to develop a computational methodology and a code for computing hypersonic non-equilibrium shock wave flows of multi-component reactive gas mixtures of diatomic gases using the Generalized Boltzmann Equation (same as the Wang-Chang Uhlenbeck equation which accounts for the degenerate energy levels) at Knudsen numbers in transitional and rarefied flow regimes. A 3D Generalized Boltzmann Equation (GBE) solver has been developed for a Cartesian ... |
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| Surface Roughness Effects in Low Reynolds Number Channel Flows |
12 JUN 2006 |
9 pages |
| Authors:
N. Gimelsheim; J. Duncan; T. Lilly; S. Gimelshein; A. Ketsdever; I. Wysong; ERC INTERNATIONAL INC SAN DIEGO CA
|
| Rarefied helium and nitrogen flow expanding into vacuum through 150 micrometers high and 1.5 cm long channels is studied experimentally and numerically with the DSMC method. Different types of channel walls are examined, both polished and rough with well characterized roughness shaped as triangles and rectangles. The pressure varies from 200 to 13,000 Pa, with the gas mean free path being both much larger and much smaller than the roughness ... |
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| Perturbation Evolution Started by Richtmyer-Meshkov Instability in Planar Laser Targets |
2006 |
18 pages |
| Authors:
Y. Aglitskiy; N. Metzler; M. Karasik; V. Serlin; A. L. Velikovich; S. P. Obenschain; A. N. Mostovych; A. J. Schmitt; J. Weaver; J. H. Gardner; T. Walsh; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
|
| The first observations of the interaction of the Richtmyer-Meshkov (RM) instability with reflected shock and rarefaction waves in laser-driven targets are reported. The RM growth is started by a shock wave incident upon a rippled interface between low-density foam and solid plastic. Subsequent interaction of secondary rarefaction and/or shock waves arriving from the ablation front and the rear surface of the target with the RM-unstable interface stops the perturbation growth ... |
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| Gaseous Flows in Microchannels |
13 JUL 2005 |
7 pages |
| Authors:
I. A. Graur; J. G. Meolans; D. E. Zeitoun; UNIVERSITE DE PROVENCE MARSEILLE (FRANCE)
|
| The objective of this study is to broaden the fundamental understanding of the emerging field of microfluidics, especially in a long channel. The quasi gasdynamic (QGD) equations, originally developed on the basis of a kinetical model are used for numerical and analytical simulation. A two-dimensional analysis of the QGD equations with a first order slip velocity boundary condition demonstrates that both compressibility and rarefied effects are present in long microchannels. ... |
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| Nonlinear Modelling of Start-Up Phase Pressure Spectra from Optically Smoothed Induced Spatial Incoherence Laser Imprint |
2005 |
18 pages |
| Authors:
M. J. Keskinen; A. J. Schmitt; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
|
| The spectrum of early time pressure perturbations, due to optically smoothed induced spatial incoherence (ISI) laser imprint, is computed for a planar target using a forced, dissipative model. The time-dependent ISI laser deposition is computed using a time-dependent electromagnetic full wave Maxwell code. It is found that the pressure spectrum evolves into a power law in which spectral power is transferred from large to smaller scales through a nonlinear cascade ... |
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| NiAl Bond Coats Made by a Directed Vapor Deposition Approach |
OCT 2004 |
11 pages |
| Authors:
Z.. Yu; D. D. Hass; H. N. Wadley; VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Intermetallic, nickel aluminide alloys are widely used as bond coat materials in thermal barrier coating systems applied to nickel base super alloy components. They are usually synthesized by a solid-state reaction diffusion heat treatment following the chemical vapor deposition of aluminum on the nickel rich substrate. Here, an electron beam directed vapor deposition (EB-DVD) technique is used to simultaneously evaporate nickel and aluminum and then reactively deposit NiAl bond coats ... |
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| Numerical Simulations of Gas Cloud Expansion in Rarefied Environment |
JUN 2004 |
8 pages |
| Authors:
Virendra K. Dogra; Dean C. Wadsworth; JOHNS HOPKINS UNIV LAUREL MD APPLIED PHYSICS LAB
|
| Time accurate numerical simulations of a high temperature source cloud of gas expanding into an ambient atmosphere are performed using a multiple temperature gas model and the direct simulation Monte Carlo (DSMC) method. The multi-temperature approach uses continuum conservation equations derived from the Boltzmann equation via first-order Chapman-Enskog expansion and zero-order non-isotropic velocity distribution function. These equations are solved numerically using a kinetic flux splitting method for inviscid fluxes and ... |
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| Continuum and Particle Computations of Hypersonic Shock Interaction Flows |
30 NOV 2003 |
105 pages |
| Authors:
Graham V. Chandler; MINNESOTA UNIV MINNEAPOLIS DEPT OF AEROSPACE ENGINEERING AND MECHANICS
|
| There has been increasing interest in developing numerical methods and accurate physical models for solving computational fluid dynamics (CFD) problems of hypersonic continuum and rarefied flows. In this work, we establish a framework for validating numerical methods and physical models employed in popular CFD codes. The first main objective of this work is to assess the ability of current state-of-the-art methods to simulate challenging hypersonic flow problems by comparing to ... |
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| Internal Energy Mode Relaxation in High Speed Continuum and Rarefied Flows |
07 MAY 2003 |
20 pages |
| Authors:
Eswar Josyula; Dean C. Wadsworth; ENGINEERING RESEARCH AND CONSULTING INC(ERC INC) EDWARDS AFB CA
|
| The presence of shock waves in high speed flow of a polyatomic gas presents considerable difficulties for accurate numerical simulation of the flowfield. The shock wave redistributes the high kinetic energy of the oncoming flow into various internal energy modes, which relax relatively slowly, leading to significant chemical and thermal nonequilibrium the stagnation region. In the gas kinetic description, intermolecular collisions change the translational, rotational, vibrational, and electronic energies of ... |
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| Gas-Surface Interaction Model Evaluation for DSMC Applications |
JUL 2002 |
10 pages |
| Authors:
Dean C. Wadsworth; Douglas B. VanGilder; Virendra K. Dogra; ENGINEERING RESEARCH AND CONSULTING INCEDWARDS AFB CA
|
| The general gas surface interaction event is considered to be parameterized by the molecule's incident energy magnitude and incident angle relative to the surface normal. These parameters are used to estimate the degree of nonequilibrium that arises for typical applications, and the quality of scattering predictions made by common few-parameter models such as the Maxwell model. Experimental measurements and molecular dynamics simulations are evaluated as potential sources of data to ... |
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| Sonic Rarefaction Wave Low Recoil Gun |
JAN 2002 |
28 pages |
| Authors:
E. Kathe; R. Dillon; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| A principal challenge faced by the U.S. Army TACOM-ARDEC Benet Laboratories in the design of armaments for lightweight future fighting vehicles with lethality overmatch is mitigating the deleterious effects of large caliber cannon recoil. The sonic RArefaction waVE low recoil guN (RAVEN) is a novel invention to dramatically reduce the gas momentum contribution to recoil with absolutely no reduction in me ballistic efficiency of launch. This technology is being investigated ... |
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| Internal Ballistics Analysis for the Raven Propulson System |
26 APR 2001 |
11 pages |
| Authors:
S. Dunn; J. French; D. Coats; E. Kathe; R. Dillon; S. Sopok; M. Witherell; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| The recently proposed light Future Combat System (FCS) vehicles require a highly lethal cannon with greatly reduced recoil momentum. A novel approach to this problem was proposed by Kathe, which utilizes a RArefaction waVE guN (RAVEN) propulsion system to significantly reduce the recoil momentum and barrel heating. To accurately assess the effectiveness of this approach, a Navier-Stokes flow solver was developed to calculate the internal ballistics of this unconventional hybrid ... |
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| Rarefaction Wave Gun Propulsion |
APR 2001 |
23 pages |
| Authors:
E. Kathe; R. Dillon; S. Sopok; M. Witherell; S. Dunn; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| RArefaction waVE guN (RAVEN) propulsion constitutes a novel means to dramatically reduce the recoil momentum and heat imparted to future cannons during firing. The method may be considered a hybrid propulsion technology with features common to both closed-breech cannons and recoilless rifles. Reduction of recoil and gun heating would greatly facilitate large caliber gun integration within light future combat system (FCS) vehicles. Analysis of a RAVEN launcher comparable to the ... |
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| Eu's Generalized Hydrodynamics as the Basis of a New Computational Model for Rarefied and Microscale Gasdynamics |
09 JUL 2000 |
9 pages |
| Authors:
R. S. Myong; MINNESOTA UNIV ST PAUL INST FOR MATHEMATICS AND ITS APPLICATIONS
|
| A new computational model based on Eu's generalized hydrodynamics, which has been recently proposed for describing the motion of gases in non- equilibrium state and is shown to be consistent with the second law of thermodynamics, is presented. The general understanding of Eu's generalized hydrodynamics, which employs the cumulant expansion for the Boltzmann collision integral instead of the BGK approximation, is also obtained by considering three fundamental flows; compressed gas ... |
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| Numerical and Experimental Investigations of Channel Flows in a Disk- Type Drag Pump |
09 JUL 2000 |
9 pages |
| Authors:
Young-Kyu Hwang; Joong-Sik Heo; Wook-Jin Choi; SUNGKYUNK UNIV SUWON (SOUTH KOREA) SCHOOL OF MECHANICAL ENGINEERING
|
| Pumping performance of a disk-type drag pump is studied numerically and experimentally. Molecular transition and slip flows that arise in a spiral channel on the rotating disk are simulated by using particle and continuum methods. The particle approach employs the direct simulation Monte Carlo (DSMC) method, and the continuum approach solves the Navier-Stokes (N-S) equations. A new DSMC code that can handle noninertial effects existing in the rotating frame of ... |
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| A 1-D Granular Gas as a Knudsen Gas |
09 JUL 2000 |
9 pages |
| Authors:
Patricio COrdero; Jose M. Pasini; Rosa Ramirez; CHILE UNIV SANTIAGO DEPT DE FISICA
|
| We study a one-dimensional system of inelastic hard particles driven by thermal walls. For low dissipation in collisions the system may be treated as a perturbation on a non-interacting system, being thus conceptually similar to a Knudsen gas. When the quasielastic system is subjected to gravity a kinetic theory approach is suitable, giving a faithful description of results stemming from Newtonian molecular dynamics simulations. Effects derived from the finite size ... |
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| Direct Numerical Simulation and Linear Analysis of Stability of Nonequilibrium Hypersonic Boundary Layers |
05 OCT 1998 |
31 pages |
| Authors:
Xiaolin Zhong; CALIFORNIA UNIV LOS ANGELES DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
|
| The goal of this research project is to develop new advanced numerical methods and to perform direct numerical simulation (DNS) studies of transient hypersonic reacting flows over full 3-D maneuvering vehicles. The DNS tools and supporting theoretical approaches are used to gain new fundamental understanding of transition phenomena of 3-D chemically-reacting hypersonic boundary layers. Our research accomplishments in the report period can be classified into three areas. First, we have ... |
|
| Micromachined Shear Sensors for Fluid Flows |
15 MAY 97 |
102 pages |
| Authors:
Kenneth S. Breuer; Martin A. Schmidt; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING AND COMPU TER SCIENCE
|
| The three year program focused on modeling of fluid mechanics in micromachined systems. The program supported a graduate student at MIT (Ed Piekos). The program was successful in exploring the effects of rarefaction and the use of different computational tools for analyzing and simulating flows in MEMS devices. |
|
| Capsule Aerothermodynamics (L' Aerothermodynamique des Capsules) |
MAY 97 |
|
| Authors:
ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT NEUILLY-SUR-SEINE (FRAN CE)
|
 | This report is a compilation of the edited proceedings for the 'Capsule Aerothermodynamics' course held at the von Karman Institute for Fluid Dynamics (VKI) in Rhode-Saint-Genese, Belgium, 20-22 March 1995. At present, on a world scale, different capsules and penetrators are being considered for planetary entry, such as the Huygens probe to Titan, the Intermarsnet to Mars, and a probe attached to the Mercury orbiter to Venus. In addition, conceptual ... |
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| Numerical Studies of Low-Density Two-Dimensional Hypersonic Flows by Using the Navier-Stokes and Burnett Equations with Nonequilibrium Real Gas Effects |
24 JAN 97 |
33 pages |
| Authors:
Xiaolin Zhong; CALIFORNIA UNIV LOS ANGELES DEPT OF MECHANICAL AEROSPACE AND NUCLEAR ENGINEER ING
|
| The goal of this research is to study the laminar turbulent transition and other transient flow phenomena of 3-D chemically reacting hypersonic boundary layers by direct numerical simulation (DNS) and by linear stability analysis. The research in the report period was focused on developing new numerical methods for such studies and studying several fundamental transient hypersonic flow phenomena. First, several new efficient and high-order accurate numerical methods for DNS of ... |
|
| Development and Calibration of a Super Large Scale Gap Test (SLSGT) |
AUG 1996 |
|
| Authors:
J. G. Glenn; Stephen A. Aubert; Michael E. Gunger; WRIGHT LAB EGLIN AFB FL
|
| Numerical simulations of eight inch (203 mm) diameter gap test experiments employing heavily confined donors have been conducted. They reveal that strong convergence of lateral rarefaction waves results in transmitted shocks with latent high pressure regions which exceed the amplitude of the leading edge of the shock wave, and are transmitted into the gap attenuator. Since gap tests are calibrated using TOA measurement of the transmitted shock wave, into the ... |
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| Wave Interactions and Variation Estimates For Self-Similar Viscous Limits in Systems of Conservation Laws |
FEB 95 |
66 pages |
| Authors:
Athanasios E. Tzavaras; WISCONSIN UNIV-MADISON CENTER FOR MATHEMATICAL SCIENCES
|
| We consider the problem of self similar viscous limits for general systems of conservation laws. First, we give conditions so that the resulting boundary value problem admits solutions. In particular this covers the class of symmetric hyperbolic systems. Second, we show that if the system is strictly hyperbolic and the Riemann data are sufficiently close then the resulting family of solutions is of uniformly bounded variation and oscillation. Third, we ... |
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| A Study of Fluid Problems Requiring a Direct Particle Simulation |
28 NOV 94 |
30 pages |
| Authors:
Donald Baganoff; STANFORD UNIV CA
|
| This final report is for work carried out under Grant No. F49620-93- 1-0143 during the 18-month period from 1 April, 1993 to 30 September, 1994. The principal objective of the research was to make use of a parallel computer code recently developed by our group, for Bird's direct simulation Monte Carlo (DSMC) method, and to gain experience in simulating various rarefied three- dimensional flows about bodies having reasonably complex geometries, ... |
|
| DNA/WES Ground Motion Test Facility-Results and Analysis of Impact Tests Against Masonry and Socorro Plaster Sand Testbeds |
APR 94 |
155 pages |
| Authors:
Howard G. White; John T. Byrne; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS STRUCTURES LAB
|
| The DNA/WES Ground Motion Test Facility is a vertical gas gun with a 4-ft diameter projectile. This report describes use of this facility for conducting tests with sand testbeds. A description of testbed construction and testing procedures is discussed. Stress and velocity histories are presented from each test. Analysis of the data includes determination of the propagation velocity of the loading and rarefaction waves in a test article. A method ... |
|
| Simulating Sympathetic Detonation Effects |
SEP 93 |
38 pages |
| Authors:
J. G. Glenn; ORLANDO TECHNOLOGY INC SHALIMAR FL
|
| In an effort, to understand the mechanism causing sympathetic detonation, a concurrent calculational/experimental research program was initiated. The primary objective of this work was to predict the propensity of a given energetic formulation to sympathetically detonate in the storage configuration, Results from initial testing suggested the primary energy transfer mechanism associated with sympathetic detonation events involve flyer plate-like impact To accurately describe the initial shock environment at the acceptor, accounting ... |
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| Wave Structure Induced by Fluid Dynamic Limits in the Broadwell Model |
JUL 93 |
44 pages |
| Authors:
Athanasios E. Tzavaras; WISCONSIN UNIV-MADISON CENTER FOR MATHEMATICAL SCIENCES
|
| Consider the fluid dynamic limit problem for the Broadwell system of the kinetic theory of gases, for Riemann, Maxwellian initial data. The formal limit is the Riemann problem for a pair of conservation laws and is invariant under dilations of coordinates. The approach of self-similar fluid dynamic limits consists in replacing the mean free path in the Broadwell model so that the resulting problem preserves the invariance under dilations. The ... |
|
| Geometric Theory of Infinite Dimensional Dynamical Systems |
14 MAY 92 |
9 pages |
| Authors:
Mallet-Paret Dafermos; Strauss Souganidis; BROWN UNIV PROVIDENCE RI DIV OF APPLIED MATHEMATICS
|
| A subject of investigation was the extent to which an entropy inequality (i.e., the Second Law of Thermodynamics) induces stabilization of solutions of hyperbolic systems of conservation laws. It was shown that the entropy inequality guarantees uniqueness of Lipschitz solutions within the class of BV solutions, provided that the entropy is convex just in certain directions compatible with the natural invariance of the system expressed in terms of involutions . ... |
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| Theory of Electron Beam Tracking in Reduced-Density Channels |
02 APR 91 |
|
| Authors:
R. F. Fernsler; S. P. Slinker; R. F. Hubbard; NAVAL RESEARCH LAB WASHINGTON DC
|
| A theory is presented for the guiding of relativistic electron beams by rarefied gaseous channels. The analysis is based on analytic computations of the transverse force felt by a rigid-rod beam propagating off-axis from a channel or reduced gas density. The density gradients produce an attractive channel force that can be surprisingly robust, even though it develops from relatively subtle gas chemistry properties. Static numerical calculations support the analytic work. ... |
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| Particle Simulation of Hypersonic Flow |
24 APR 90 |
|
| Authors:
Donald Baganoff; STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS
|
| A limitation of the DSMC method is that it does not allow efficient use of vector architectures that are predominate in current supercomputers. A new selection rule for collisions between simulated molecules is developed which is highly compatible with vectorization. The collision-selection rule is shown to give identical results to the DSMC method in predicting shock-wave structure and in predicting the correct mean-free path variation with density and temperature for ... |
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| An Optical Study of the Flow Start-Up Process in Four Convergent- Divergent Nozzles |
MAR 90 |
|
| Authors:
Heinz Reichenbach; Klaus O. Opalka; FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E V FREI- BU RG (GERMANY F R) ERNST-MACH-INST
|
| Large blast simulators (LBS) are specialized shock tunnels for generating decaying blast waves such as are associated with nuclear explosions. Blast simulators employ convergent-divergent nozzles at the driver exit to retard the outflow of the high-pressure driver gas and generate long flow durations. The LBS nozzle design in this study differs from the nozzle design used in previous studies in that it has the flow-initiating diaphragm mounted in the throat ... |
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| A Modified LaGrange Pressure Gradient for the Regenerative Liquid Propellant Gun |
JAN 90 |
|
| Authors:
Walter F. Morrison; Terence P. Coffee; ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| A modified Lagrange gradient model for use in lumped parameter simulations of the regenerative liquid propellant gun is presented. The model accounts for the non-zero gas velocity at the barrel entrance and the rarefaction wave traveling along the barrel toward the projectile base after 'all-burnt' in a regenerative liquid propellant gun (RLPG). Computer simulations of a high velocity cannon have been conducted using a lumped parameter code with the modified ... |
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| The Aerodynamic Characteristics of Power-Law Bodies in Continuum and Transitional Hypersonic Flow |
AUG 89 |
|
| Authors:
M. F. Westby; J. D. Regan; ROYAL AEROSPACE ESTABLISHMENT FARNBOROUGH (ENGLAND)
|
| This Memorandum describes experimental studies carried out at the RAE in the Low Density Tunnel and Gun Tunnel to determine the aerodynamic characteristics of a series of power-law bodies of constant fineness ratio over a Reynolds number range covering both continuum and transitional rarefied flow. The tests were carried out at Mach numbers of 10 in the Low Density Tunnel and 12.8 in the Gun Tunnel at angles of incidence ... |
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| Design and Operation of a Free Molecule Heat Transfer Probe |
DEC 88 |
|
| Authors:
Frank G. Collins; TENNESSEE UNIV SPACE INST TULLAHOMA
|
| This report describes the development of a free molecule hot wire probe unique design. When the probe is coupled with an independent measurement of number density or pitot pressure, it is capable of determining all of the flow properties at a point in a rarefied flow field. It has good spatial resolution and large dynamic range, and it is capable of obtaining measurements at densities below which some techniques, such ... |
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| Transitional Waves for Conservation Laws |
DEC 88 |
|
| Authors:
Eli L. Isaacson; Dan Marchesin; Bradley J. Plohr; WISCONSIN UNIV-MADISON CENTER FOR MATHEMATICAL SCIENCES
|
| A new class of fundamental waves arises in conservation laws that are not strictly hyperbolic. These waves serve as transitions between wave groups associated with particular characteristic families. Transitional shock waves are discontinuous solutions that possess viscous profiles but do not conform to the Lax characteristic criterion; they are sensitive to the precise form of the physical viscosity. Transitional rarefaction waves are rarefaction fans across which the characteristic family changes ... |
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| Solar Rocket Plume/Mirror Interactions |
FEB 88 |
|
| Authors:
Charles L. Merkle; Sheng-Tao Yu; PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF MECHANICAL ENGINEERING
|
| The extent to which the plume from a solar thermal rocket will impinge on the solar collector is studied by flowfield analysis. Such interaction can adversely affect collector performance through fouling, excessive heat loading, or pressure loads that deform the delicate structures. The geometrical shape of the collector is such that only the flow from the nozzle boundary layer can reach it, but the thrust levels of interest lead to ... |
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| Ambient Scattering from Ring-Symmetric Spacecraft Exhaust Plume |
APR 87 |
|
| Authors:
Joseph Falcovitz; FALCOVITZ (JOSEPH) HAIFA (ISRAEL)
|
| We present a first-collision model for the evaluation of return flux from the exhaust plume of a ring-symmeric HF/DF laser in LEO, generated by an incident flux of ambient molecules traveling at orbital speed. The steady plume is bounded by a pair of lip-centered rarefaction fans, and unless spacecraft attitude enables incident air molecules to reach the plume through the cavition through the cavitation regions that extend beyond these fans, ... |
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| Analytical and Numerical Computation of Ring-Symmetric Spacecraft Exhaust Plumes |
DEC 86 |
|
| Authors:
Joseph Falcovitz; FALCOVITZ (JOSEPH) HAIFA (ISRAEL)
|
| A doubleheader approach to the computation of a ring-symmetric spacecraft exhaust plume is presented. We plan to use the present analytic approximation in conjunction with a model for backflow from the exhaust plume of an orbiting spacecraft, induced by oncoming ambient molecules. This process takes place in the regions of centered rarefaction waves (CRW) that flank the central plume. A semi-inverse marching characteristic scheme (SIMA) is formulated specifically for accurate ... |
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| Control of Ion-Velocity Distributions in Laser-Target Interaction Experiments |
06 OCT 86 |
|
| Authors:
J. Grun; R. Stellingwerf; B. H. Ripin; MISSION RESEARCH CORP ALBUQUERQUE NM
|
| The width of ion velocity distributions from laser produced plasmas can be controlled experimentally by varying the size of the laser spot. The ion velocity width is determined primarily by whether the ions are mostly in the rarefraction or steady state regime. It is not dominated by the thermal distribution of the ions, as is often assumed. Keywords: Laser fusion; Plasma; Fusion; Laser plasma interactions; Ions; Ablation. |
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| The Classification of Solutions of Quadratic Riemann Problems. I |
DEC 85 |
|
| Authors:
E. Isaacson; D. Marchesin; B. Plohr; B. Temple; WISCONSIN UNIV-MADISON MATHEMATICS RESEARCH CENTER
|
| We are interested in classifying the solutions of Riemann problems for the 2 x 2 conservation laws which have homogeneous quadratic flux functions. Such flux functions approximate an arbitrary 2 x 2 system in a neighborhood of an isolated point where strict hyperbolicity fails. This problem was motivated by Marchesin and Paes-Leme who discovered such a singularity in a system of equations arising in oil reservoir simulation. Schaeffer, Shearer, Marchesin ... |
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| A Computational Blast Valve Study |
FEB 85 |
|
| Authors:
D. M. Hisley; ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The BRL Q1D code was modified to include a diaphragm blast valve model. The diaphragm/blast valve model was verified and used to computationally determine the suitability of using a fast-acting (blast) valve to replace diaphragm-breaking as the means of initiation flow in a large shock. For a 1- dimensional model of the Centre d'Etudes de Gramat shock tube, it was determined that a blast valve which opens in less than ... |
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| Reflected Overpressure Impulse on a Finite Structure, |
AUG 1984 |
|
| Authors:
G. A. Coulter; C. N. Kingery; ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| This paper presents the effect of angle of incidence of the shock front on reflected impulse loading on a finite structure. Impulse reflection factors have been developed for angles of incidence from zero to ninety degrees. Reflected impulse on a finite structure is much less than reflected impulse on an infinite plane because of the unloading due to rarefaction waves propagating from the sides of the structure which lowers the ... |
|
| Feasibility Study of Shock Wave Modification in the BRL 2.44 m Blast Simulator |
MAR 1984 |
|
| Authors:
G. A. Coulter; G. Bulmash; C. Kingery; ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| Four types of driver sections (short driver, baffled driver, single pipe, and multiple pipe driver) were designed and tested on a 1/48th scale model of the BRL 2.44 m shock tube. Pressures were monitored along the test section with piezoelectric transducers to determine waveshape as a function of drivers. Pressure-time waveforms are compared to computer predictions produced by the NASA-Ames one-dimensional hydrocode. Predictions are given for the performance of the ... |
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| Are Detonations Steady? |
FEB 1984 |
|
| Authors:
A. A. Oyediran; G. S. S. Ludford; CORNELL UNIV ITHACA NY DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A generic problem in the transition from deflagration to detonation is the overtaking of a steady deflagration wave by a steady shock wave. Such a collision produces a detonation wave (as well as a contact discontinuity, a back shock, and sometimes a rarefaction wave). Work reported at the 27th Conference of Army Mathematicians showed that, for small heat release in the deflagration, the detonation wave cannot be steady. Here we ... |
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| Reflected Overpressure Impulse on a Finite Structure |
DEC 1983 |
|
| Authors:
C. N. Kingery; G. A. Coulter; ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The effect of angle of incidence of the shock front on reflected impulse loading on a finite structure is presented in this report. Impulse reflection factors have been developed for angles of incidence from zero to ninety degrees. Reflected impulse on a finite structure is much less than reflected impulse on an infinite plane because of the unloading due to rarefaction waves propagation from the sides of the structure which ... |
|
| An Asymptotic Theory of Deflagrations and Detonations. I. The Steady Solutions |
JUN 1983 |
|
| Authors:
A. K. Kapila; B. J. Matkowsky; A. Van Harten; RENSSELAER POLYTECHNIC INST TROY NY DEPT OF MATHEMATICAL SCIENCES
|
|
| On the Determination of the Gas Temperature From the Velocity of the Muzzle Rarefaction Wave |
FEB 1983 |
|
| Authors:
Paul S. Gough; GOUGH (PAUL) ASSOCIATES INC PORTSMOUTH NH
|
| The temperature of the propellant gas as it flows out of the muzzle of a gun is a principal factor in respect to the strength of the air blast which accompanies the discharge of the projectile. The temperature also plays a dominant role in respect to the occurrence of secondary combustion of flash. We discuss the fundamental basis for a method of determining the temperature from measurements of the velocity ... |
|
| EBS Amplifier with Cold Cathode. |
27 JAN 1983 |
|
| Authors:
Bernard Smith; Stanley DuBuske; DEPARTMENT OF THE ARMY WASHINGTON DC
|
| The cold cathode EBS device is fabricated through solution of several problem factors which have plagued fabrication and application of such devices until now. Judicious choice of materials to be employed within the vacuum tube and careful preprocessing of all materials before assembly have significantly minimized the effect of the above mentioned undesirable factors. Considered most important in this regard is identification of getters for use within the vacuum envelope, ... |
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| Mach 10/14 Operations in the NSWC Hypervelocity Wind Tunnel Number 9 (Vertical Heater Vessel Leg) |
16 JUL 1982 |
|
| Authors:
NAVAL SURFACE WEAPONS CENTER SILVER SPRING MD
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| The original design of the Tunnel No. 9 Hypervelocity Facility called for three distinct Mach number capabilities; namely Mach 10, Mach 15, and Mach 20. The Mach 15 (now Mach 14) and Mach 10 legs are operational. However, problems have been encountered in using horizontal heater vessel to store hot test gas in the Mach 10 leg. A potential solution was to use the existing Mach 10 nozzle in combination ... |
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| Interaction of Oblique Shock and Detonation Waves |
FEB 1982 |
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| Authors:
Y. Sheng; J. P. Sislian; TORONTO UNIV DOWNSVIEW (ONTARIO) INST FOR AEROSPACE STUDIES
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| The interaction of an oblique shock wave and an oblique detonation wave which deflect the flow in the same direction is analyzed. The detonation wave is assumed to be an exothermic gasdynamic discontinuity. A criterion is developed and used to determine whether or not a theoretical solution of the problem describes a physically realizable interaction configuration. It is found that the reflected wave is, in general, a rarefaction wave. Only ... |
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