Development of models for the two-dimensional, two-fluid code for sodium boiling NATOF-2D. [LMFBR
Zielinski, R.G.; Kazimi, M.S.
1981-09-01
Several features were incorporated into NATOF-2D, a two-dimensional, two fluid code developed at MIT for the purpose of analysis of sodium boiling transients under LMFBR conditions. They include improved interfacial mass, momentum and energy exchange rate models, and a cell-to-cell radial heat conduction mechanism which was calibrated by simulation of Westinghouse Blanket Heat Transfer Test Program Runs 544 and 545. Finally, a direct method of pressure field solution was implemented into a direct method of pressure field solution was implemented into NATOF-2D, replacing the iterative technique previously available, and resulted in substantially reduced computational costs.
2-d Finite Element Code Postprocessor
Energy Science and Technology Software Center (ESTSC)
1996-07-15
ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forcesmore » along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.« less
MAGNUM-2D computer code: user's guide
England, R.L.; Kline, N.W.; Ekblad, K.J.; Baca, R.G.
1985-01-01
Information relevant to the general use of the MAGNUM-2D computer code is presented. This computer code was developed for the purpose of modeling (i.e., simulating) the thermal and hydraulic conditions in the vicinity of a waste package emplaced in a deep geologic repository. The MAGNUM-2D computer computes (1) the temperature field surrounding the waste package as a function of the heat generation rate of the nuclear waste and thermal properties of the basalt and (2) the hydraulic head distribution and associated groundwater flow fields as a function of the temperature gradients and hydraulic properties of the basalt. MAGNUM-2D is a two-dimensional numerical model for transient or steady-state analysis of coupled heat transfer and groundwater flow in a fractured porous medium. The governing equations consist of a set of coupled, quasi-linear partial differential equations that are solved using a Galerkin finite-element technique. A Newton-Raphson algorithm is embedded in the Galerkin functional to formulate the problem in terms of the incremental changes in the dependent variables. Both triangular and quadrilateral finite elements are used to represent the continuum portions of the spatial domain. Line elements may be used to represent discrete conduits. 18 refs., 4 figs., 1 tab.
ENERGY LANDSCAPE OF 2D FLUID FORMS
Y. JIANG; ET AL
2000-04-01
The equilibrium states of 2D non-coarsening fluid foams, which consist of bubbles with fixed areas, correspond to local minima of the total perimeter. (1) The authors find an approximate value of the global minimum, and determine directly from an image how far a foam is from its ground state. (2) For (small) area disorder, small bubbles tend to sort inwards and large bubbles outwards. (3) Topological charges of the same sign repel while charges of opposite sign attract. (4) They discuss boundary conditions and the uniqueness of the pattern for fixed topology.
Gross, M.B.
1984-10-01
STEALTH is a family of computer codes that can be used to calculate a variety of physical processes in which the dynamic behavior of a continuum is involved. The version of STEALTH described in this volume is designed for calculations of fluid-structure interaction. This version of the program consists of a hydrodynamic version of STEALTH which has been coupled to a finite-element code, WHAMSE. STEALTH computes the transient response of the fluid continuum, while WHAMSE computes the transient response of shell and beam structures under external fluid loadings. The coupling between STEALTH and WHAMSE is performed during each cycle or step of a calculation. Separate calculations of fluid response and structural response are avoided, thereby giving a more accurate model of the dynamic coupling between fluid and structure. This volume provides the theoretical background, the finite-difference equations, the finite-element equations, a discussion of several sample problems, a listing of the input decks for the sample problems, a programmer's manual and a description of the input records for the STEALTH/WHAMSE computer program.
2D FEM Heat Transfer & E&M Field Code
Energy Science and Technology Software Center (ESTSC)
1992-04-02
TOPAZ and TOPAZ2D are two-dimensional implicit finite element computer codes for heat transfer analysis. TOPAZ2D can also be used to solve electrostatic and magnetostatic problems. The programs solve for the steady-state or transient temperature or electrostatic and magnetostatic potential field on two-dimensional planar or axisymmetric geometries. Material properties may be temperature or potential-dependent and either isotropic or orthotropic. A variety of time and temperature-dependent boundary conditions can be specified including temperature, flux, convection, and radiation.more » By implementing the user subroutine feature, users can model chemical reaction kinetics and allow for any type of functional representation of boundary conditions and internal heat generation. The programs can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in the material surrounding the enclosure. Additional features include thermal contact resistance across an interface, bulk fluids, phase change, and energy balances.« less
2D FEM Heat Transfer & E&M Field Code
1992-04-02
TOPAZ and TOPAZ2D are two-dimensional implicit finite element computer codes for heat transfer analysis. TOPAZ2D can also be used to solve electrostatic and magnetostatic problems. The programs solve for the steady-state or transient temperature or electrostatic and magnetostatic potential field on two-dimensional planar or axisymmetric geometries. Material properties may be temperature or potential-dependent and either isotropic or orthotropic. A variety of time and temperature-dependent boundary conditions can be specified including temperature, flux, convection, and radiation. By implementing the user subroutine feature, users can model chemical reaction kinetics and allow for any type of functional representation of boundary conditions and internal heat generation. The programs can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in the material surrounding the enclosure. Additional features include thermal contact resistance across an interface, bulk fluids, phase change, and energy balances.
Collective excitations in 2D hard-disc fluid.
Huerta, Adrian; Bryk, Taras; Trokhymchuk, Andrij
2015-07-01
Collective dynamics of a two-dimensional (2D) hard-disc fluid was studied by molecular dynamics simulations in the range of packing fractions that covers states up to the freezing. Some striking features concerning collective excitations in this system were observed. In particular, the short-wavelength shear waves while being absent at low packing fractions were observed in the range of high packing fractions, just before the freezing transition in a 2D hard-disc fluid. In contrast, the so-called "positive sound dispersion" typically observed in dense Lennard-Jones-like fluids, was not detected for the 2D hard-disc fluid. The ratio of specific heats in the 2D hard-disc fluid shows a monotonic increase with density approaching the freezing, resembling in this way the similar behavior in the vicinity of the Widom line in the case of supercritical fluids. PMID:25595625
A new inversion method for (T2, D) 2D NMR logging and fluid typing
NASA Astrophysics Data System (ADS)
Tan, Maojin; Zou, Youlong; Zhou, Cancan
2013-02-01
One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail.
Environmental Fluid Dynamics Code
The Environmental Fluid Dynamics Code (EFDC)is a state-of-the-art hydrodynamic model that can be used to simulate aquatic systems in one, two, and three dimensions. It has evolved over the past two decades to become one of the most widely used and technically defensible hydrodyn...
In search of a 2-dB coding gain
NASA Technical Reports Server (NTRS)
Yuen, J. H.; Vo, Q. D.
1985-01-01
A recent code search found a (15,1/5), a (14,1/6), and a (15,1/6) convolutional code which, when concatenated with a 10-bit (1023,959) Reed-Solomon (RS) code, achieves a bit-error rate (BER) of 0.000001 at a bit signal-to-noise ratio (SNR) of 0.50 dB, 0.47 dB and 0.42 B, respectively. All of these three codes outperform the Voyager communication system, our baseline, which achieves a BER of 10.000001 at bit SNR of 2.53 db, by more than 2 dB. The 2 dB coding improvement goal was exceeded.
Rheological Properties of Quasi-2D Fluids in Microgravity
NASA Technical Reports Server (NTRS)
Stannarius, Ralf; Trittel, Torsten; Eremin, Alexey; Harth, Kirsten; Clark, Noel; Maclennan, Joseph; Glaser, Matthew; Park, Cheol; Hall, Nancy; Tin, Padetha
2015-01-01
In recent years, research on complex fluids and fluids in restricted geometries has attracted much attention in the scientific community. This can be attributed not only to the development of novel materials based on complex fluids but also to a variety of important physical phenomena which have barely been explored. One example is the behavior of membranes and thin fluid films, which can be described by two-dimensional (2D) rheology behavior that is quite different from 3D fluids. In this study, we have investigated the rheological properties of freely suspended films of a thermotropic liquid crystal in microgravity experiments. This model system mimics isotropic and anisotropic quasi 2D fluids [46]. We use inkjet printing technology to dispense small droplets (inclusions) onto the film surface. The motion of these inclusions provides information on the rheological properties of the films and allows the study of a variety of flow instabilities. Flat films have been investigated on a sub-orbital rocket flight and curved films (bubbles) have been studied in the ISS project OASIS. Microgravity is essential when the films are curved in order to avoid sedimentation. The experiments yield the mobility of the droplets in the films as well as the mutual mobility of pairs of particles. Experimental results will be presented for 2D-isotropic (smectic-A) and 2D-nematic (smectic-C) phases.
TOPAZ2D heat transfer code users manual and thermal property data base
NASA Astrophysics Data System (ADS)
Shapiro, A. B.; Edwards, A. L.
1990-05-01
TOPAZ2D is a two dimensional implicit finite element computer code for heat transfer analysis. This user's manual provides information on the structure of a TOPAZ2D input file. Also included is a material thermal property data base. This manual is supplemented with The TOPAZ2D Theoretical Manual and the TOPAZ2D Verification Manual. TOPAZ2D has been implemented on the CRAY, SUN, and VAX computers. TOPAZ2D can be used to solve for the steady state or transient temperature field on two dimensional planar or axisymmetric geometries. Material properties may be temperature dependent and either isotropic or orthotropic. A variety of time and temperature dependent boundary conditions can be specified including temperature, flux, convection, and radiation. Time or temperature dependent internal heat generation can be defined locally be element or globally by material. TOPAZ2D can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in material surrounding the enclosure. Additional features include thermally controlled reactive chemical mixtures, thermal contact resistance across an interface, bulk fluid flow, phase change, and energy balances. Thermal stresses can be calculated using the solid mechanics code NIKE2D which reads the temperature state data calculated by TOPAZ2D. A three dimensional version of the code, TOPAZ3D is available.
Validation and testing of the VAM2D computer code
Kool, J.B.; Wu, Y.S. )
1991-10-01
This document describes two modeling studies conducted by HydroGeoLogic, Inc. for the US NRC under contract no. NRC-04089-090, entitled, Validation and Testing of the VAM2D Computer Code.'' VAM2D is a two-dimensional, variably saturated flow and transport code, with applications for performance assessment of nuclear waste disposal. The computer code itself is documented in a separate NUREG document (NUREG/CR-5352, 1989). The studies presented in this report involve application of the VAM2D code to two diverse subsurface modeling problems. The first one involves modeling of infiltration and redistribution of water and solutes in an initially dry, heterogeneous field soil. This application involves detailed modeling over a relatively short, 9-month time period. The second problem pertains to the application of VAM2D to the modeling of a waste disposal facility in a fractured clay, over much larger space and time scales and with particular emphasis on the applicability and reliability of using equivalent porous medium approach for simulating flow and transport in fractured geologic media. Reflecting the separate and distinct nature of the two problems studied, this report is organized in two separate parts. 61 refs., 31 figs., 9 tabs.
A discrete simulation of 2-D fluid flow on TERASYS
Mullins, P.G.; Krolak, P.D.
1995-12-01
A discrete simulation of two-dimensional (2-D) fluid flow, on a recently designed novel architecture called TERASYS is presented. The simulation uses a cellular automaton approach, implemented in a new language called data-parallel bit C (dbC). A performance comparison between our implementation on TERASYS and an implementation on the Connection Machine is discussed. We comment briefly on the suitability of the TERASYS system for modeling fluid flow using cellular automata.
Recent update of the RPLUS2D/3D codes
NASA Technical Reports Server (NTRS)
Tsai, Y.-L. Peter
1991-01-01
The development of the RPLUS2D/3D codes is summarized. These codes utilize LU algorithms to solve chemical non-equilibrium flows in a body-fitted coordinate system. The motivation behind the development of these codes is the need to numerically predict chemical non-equilibrium flows for the National AeroSpace Plane Program. Recent improvements include vectorization method, blocking algorithms for geometric flexibility, out-of-core storage for large-size problems, and an LU-SW/UP combination for CPU-time efficiency and solution quality.
AnisWave2D: User's Guide to the 2d Anisotropic Finite-DifferenceCode
Toomey, Aoife
2005-01-06
This document describes a parallel finite-difference code for modeling wave propagation in 2D, fully anisotropic materials. The code utilizes a mesh refinement scheme to improve computational efficiency. Mesh refinement allows the grid spacing to be tailored to the velocity model, so that fine grid spacing can be used in low velocity zones where the seismic wavelength is short, and coarse grid spacing can be used in zones with higher material velocities. Over-sampling of the seismic wavefield in high velocity zones is therefore avoided. The code has been implemented to run in parallel over multiple processors and allows large-scale models and models with large velocity contrasts to be simulated with ease.
ELLIPT2D: A Flexible Finite Element Code Written Python
Pletzer, A.; Mollis, J.C.
2001-03-22
The use of the Python scripting language for scientific applications and in particular to solve partial differential equations is explored. It is shown that Python's rich data structure and object-oriented features can be exploited to write programs that are not only significantly more concise than their counter parts written in Fortran, C or C++, but are also numerically efficient. To illustrate this, a two-dimensional finite element code (ELLIPT2D) has been written. ELLIPT2D provides a flexible and easy-to-use framework for solving a large class of second-order elliptic problems. The program allows for structured or unstructured meshes. All functions defining the elliptic operator are user supplied and so are the boundary conditions, which can be of Dirichlet, Neumann or Robbins type. ELLIPT2D makes extensive use of dictionaries (hash tables) as a way to represent sparse matrices.Other key features of the Python language that have been widely used include: operator over loading, error handling, array slicing, and the Tkinter module for building graphical use interfaces. As an example of the utility of ELLIPT2D, a nonlinear solution of the Grad-Shafranov equation is computed using a Newton iterative scheme. A second application focuses on a solution of the toroidal Laplace equation coupled to a magnetohydrodynamic stability code, a problem arising in the context of magnetic fusion research.
TOPAZ2D heat transfer code users manual and thermal property data base
Shapiro, A.B.; Edwards, A.L.
1990-05-01
TOPAZ2D is a two dimensional implicit finite element computer code for heat transfer analysis. This user's manual provides information on the structure of a TOPAZ2D input file. Also included is a material thermal property data base. This manual is supplemented with The TOPAZ2D Theoretical Manual and the TOPAZ2D Verification Manual. TOPAZ2D has been implemented on the CRAY, SUN, and VAX computers. TOPAZ2D can be used to solve for the steady state or transient temperature field on two dimensional planar or axisymmetric geometries. Material properties may be temperature dependent and either isotropic or orthotropic. A variety of time and temperature dependent boundary conditions can be specified including temperature, flux, convection, and radiation. Time or temperature dependent internal heat generation can be defined locally be element or globally by material. TOPAZ2D can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in material surrounding the enclosure. Additional features include thermally controlled reactive chemical mixtures, thermal contact resistance across an interface, bulk fluid flow, phase change, and energy balances. Thermal stresses can be calculated using the solid mechanics code NIKE2D which reads the temperature state data calculated by TOPAZ2D. A three dimensional version of the code, TOPAZ3D is available. The material thermal property data base, Chapter 4, included in this manual was originally published in 1969 by Art Edwards for use with his TRUMP finite difference heat transfer code. The format of the data has been altered to be compatible with TOPAZ2D. Bob Bailey is responsible for adding the high explosive thermal property data.
CBEAM. 2-D: a two-dimensional beam field code
Dreyer, K.A.
1985-05-01
CBEAM.2-D is a two-dimensional solution of Maxwell's equations for the case of an electron beam propagating through an air medium. Solutions are performed in the beam-retarded time frame. Conductivity is calculated self-consistently with field equations, allowing sophisticated dependence of plasma parameters to be handled. A unique feature of the code is that it is implemented on an IBM PC microcomputer in the BASIC language. Consequently, it should be available to a wide audience.
A velocity-dependent anomalous radial transport model for (2-D, 2-V) kinetic transport codes
NASA Astrophysics Data System (ADS)
Bodi, Kowsik; Krasheninnikov, Sergei; Cohen, Ron; Rognlien, Tom
2008-11-01
Plasma turbulence constitutes a significant part of radial plasma transport in magnetically confined plasmas. This turbulent transport is modeled in the form of anomalous convection and diffusion coefficients in fluid transport codes. There is a need to model the same in continuum kinetic edge codes [such as the (2-D, 2-V) transport version of TEMPEST, NEO, and the code being developed by the Edge Simulation Laboratory] with non-Maxwellian distributions. We present an anomalous transport model with velocity-dependent convection and diffusion coefficients leading to a diagonal transport matrix similar to that used in contemporary fluid transport models (e.g., UEDGE). Also presented are results of simulations corresponding to radial transport due to long-wavelength ExB turbulence using a velocity-independent diffusion coefficient. A BGK collision model is used to enable comparison with fluid transport codes.
Fluid Film Bearing Code Development
NASA Technical Reports Server (NTRS)
1995-01-01
The next generation of rocket engine turbopumps is being developed by industry through Government-directed contracts. These turbopumps will use fluid film bearings because they eliminate the life and shaft-speed limitations of rolling-element bearings, increase turbopump design flexibility, and reduce the need for turbopump overhauls and maintenance. The design of the fluid film bearings for these turbopumps, however, requires sophisticated analysis tools to model the complex physical behavior characteristic of fluid film bearings operating at high speeds with low viscosity fluids. State-of-the-art analysis and design tools are being developed at the Texas A&M University under a grant guided by the NASA Lewis Research Center. The latest version of the code, HYDROFLEXT, is a thermohydrodynamic bulk flow analysis with fluid compressibility, full inertia, and fully developed turbulence models. It can predict the static and dynamic force response of rigid and flexible pad hydrodynamic bearings and of rigid and tilting pad hydrostatic bearings. The Texas A&M code is a comprehensive analysis tool, incorporating key fluid phenomenon pertinent to bearings that operate at high speeds with low-viscosity fluids typical of those used in rocket engine turbopumps. Specifically, the energy equation was implemented into the code to enable fluid properties to vary with temperature and pressure. This is particularly important for cryogenic fluids because their properties are sensitive to temperature as well as pressure. As shown in the figure, predicted bearing mass flow rates vary significantly depending on the fluid model used. Because cryogens are semicompressible fluids and the bearing dynamic characteristics are highly sensitive to fluid compressibility, fluid compressibility effects are also modeled. The code contains fluid properties for liquid hydrogen, liquid oxygen, and liquid nitrogen as well as for water and air. Other fluids can be handled by the code provided that the
A 2D electrohydrodynamic model for electrorotation of fluid drops.
Feng, James Q
2002-02-01
A theoretical analysis of spontaneous electrorotation of deformable fluid drops in a DC electric field is presented with a 2D electrohydrodynamic model. The fluids in the system are assumed to be leaky dielectric and Newtonian. If the rotating flow is dominant over the cellular convection type of electrohydrodynamic flow, closed-form solutions for drops of small deformations can be obtained. Because the governing equations are in general nonlinear even when drop deformations are ignored, the general solution for even undeformed drop takes a form of infinite series and can only be evaluated by numerical means. Both closed-form solutions for special cases and numerical solutions for more general cases are obtained here to describe steady-state field variables and first-order drop deformations. In a DC electric field of strength beyond the threshold value, spontaneous electrorotation of a drop is shown to occur when charge relaxation in the surrounding fluid is faster than the fluid inside the drop. With increasing the strength of the applied electric field from the threshold for onset of electrorotation, the axis of drop contraction deviates from from that of the applied electric field in the direction of the rotating flow with an angle increasing with the field strength. PMID:16290391
Modelling RF sources using 2-D PIC codes
Eppley, K.R.
1993-03-01
In recent years, many types of RF sources have been successfully modelled using 2-D PIC codes. Both cross field devices (magnetrons, cross field amplifiers, etc.) and pencil beam devices (klystrons, gyrotrons, TWT`S, lasertrons, etc.) have been simulated. All these devices involve the interaction of an electron beam with an RF circuit. For many applications, the RF structure may be approximated by an equivalent circuit, which appears in the simulation as a boundary condition on the electric field (``port approximation``). The drive term for the circuit is calculated from the energy transfer between beam and field in the drift space. For some applications it may be necessary to model the actual geometry of the structure, although this is more expensive. One problem not entirely solved is how to accurately model in 2-D the coupling to an external waveguide. Frequently this is approximated by a radial transmission line, but this sometimes yields incorrect results. We also discuss issues in modelling the cathode and injecting the beam into the PIC simulation.
Modelling RF sources using 2-D PIC codes
Eppley, K.R.
1993-03-01
In recent years, many types of RF sources have been successfully modelled using 2-D PIC codes. Both cross field devices (magnetrons, cross field amplifiers, etc.) and pencil beam devices (klystrons, gyrotrons, TWT'S, lasertrons, etc.) have been simulated. All these devices involve the interaction of an electron beam with an RF circuit. For many applications, the RF structure may be approximated by an equivalent circuit, which appears in the simulation as a boundary condition on the electric field ( port approximation''). The drive term for the circuit is calculated from the energy transfer between beam and field in the drift space. For some applications it may be necessary to model the actual geometry of the structure, although this is more expensive. One problem not entirely solved is how to accurately model in 2-D the coupling to an external waveguide. Frequently this is approximated by a radial transmission line, but this sometimes yields incorrect results. We also discuss issues in modelling the cathode and injecting the beam into the PIC simulation.
50 CFR Table 2d to Part 679 - Species Codes-Non-FMP Species
Code of Federal Regulations, 2013 CFR
2013-10-01
... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Species Codes-Non-FMP Species 2d Table 2d to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Table 2d Table 2d to Part 679—Species Codes—Non-FMP Species General use...
50 CFR Table 2d to Part 679 - Species Codes-Non-FMP Species
Code of Federal Regulations, 2014 CFR
2014-10-01
... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Species Codes-Non-FMP Species 2d Table 2d to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Table 2d Table 2d to Part 679—Species Codes—Non-FMP Species General use...
50 CFR Table 2d to Part 679 - Species Codes-Non-FMP Species
Code of Federal Regulations, 2012 CFR
2012-10-01
... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Species Codes-Non-FMP Species 2d Table 2d to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE (CONTINUED) FISHERIES OF THE EXCLUSIVE ECONOMIC ZONE OFF ALASKA Pt. 679, Table 2d Table 2d to Part...
2-D skin-current toroidal-MHD-equilibrium code
Feinberg, B.; Niland, R.A.; Coonrod, J.; Levine, M.A.
1982-09-01
A two-dimensional, toroidal, ideal MHD skin-current equilibrium computer code is described. The code is suitable for interactive implementation on a minicomptuer. Some examples of the use of the code for design and interpretation of toroidal cusp experiments are presented.
CAS2D- NONROTATING BLADE-TO-BLADE, STEADY, POTENTIAL TRANSONIC CASCADE FLOW ANALYSIS CODE
NASA Technical Reports Server (NTRS)
Dulikravich, D. S.
1994-01-01
An exact, full-potential-equation model for the steady, irrotational, homoentropic, and homoenergetic flow of a compressible, inviscid fluid through a two-dimensional planar cascade together with its appropriate boundary conditions has been derived. The CAS2D computer program numerically solves an artificially time-dependent form of the actual full-potential-equation, providing a nonrotating blade-to-blade, steady, potential transonic cascade flow analysis code. Comparisons of results with test data and theoretical solutions indicate very good agreement. In CAS2D, the governing equation is discretized by using type-dependent, rotated finite differencing and the finite area technique. The flow field is discretized by providing a boundary-fitted, nonuniform computational mesh. This mesh is generated by using a sequence of conformal mapping, nonorthogonal coordinate stretching, and local, isoparametric, bilinear mapping functions. The discretized form of the full-potential equation is solved iteratively by using successive line over relaxation. Possible isentropic shocks are captured by the explicit addition of an artificial viscosity in a conservative form. In addition, a four-level, consecutive, mesh refinement feature makes CAS2D a reliable and fast algorithm for the analysis of transonic, two-dimensional cascade flows. The results from CAS2D are not directly applicable to three-dimensional, potential, rotating flows through a cascade of blades because CAS2D does not consider the effects of the Coriolis force that would be present in the three-dimensional case. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370 series computer with a central memory requirement of approximately 200K of 8 bit bytes. The CAS2D program was developed in 1980.
2-D traveling-wave patterns in binary fluid convection
Surko, C.M.; Porta, A.L.
1996-12-31
An overview is presented of recent experiments designed to study two-dimensional traveling-wave convection in binary fluid convection in a large aspect ratio container. Disordered patterns are observed when convection is initiated. As time proceeds, they evolve to more ordered patterns, consisting of several domains of traveling-waves separated by well-defined domain boundaries. The detailed character of the patterns depends sensitively on the Rayleigh number. Numerical techniques are described which were developed to provide a quantitative characterization of the traveling-wave patterns. Applications of complex demodulation techniques are also described, which make a detailed study of the structure and dynamics of the domain boundaries possible.
NASA Technical Reports Server (NTRS)
Kapoor, Kamlesh; Anderson, Bernhard H.; Shaw, Robert J.
1994-01-01
A two-dimensional computational code, PRLUS2D, which was developed for the reactive propulsive flows of ramjets and scramjets, was validated for two-dimensional shock-wave/turbulent-boundary-layer interactions. The problem of compression corners at supersonic speeds was solved using the RPLUS2D code. To validate the RPLUS2D code for hypersonic speeds, it was applied to a realistic hypersonic inlet geometry. Both the Baldwin-Lomax and the Chien two-equation turbulence models were used. Computational results showed that the RPLUS2D code compared very well with experimentally obtained data for supersonic compression corner flows, except in the case of large separated flows resulting from the interactions between the shock wave and turbulent boundary layer. The computational results compared well with the experiment results in a hypersonic NASA P8 inlet case, with the Chien two-equation turbulence model performing better than the Baldwin-Lomax model.
Automatic differentiation of the TACO2D finite element code using ADIFOR
Carle, A.; Fagan, M.
1996-04-01
The need for sensitivities in particular applications is becoming increasingly important in problems such as optimal design or control. In this study, the authors use ADIFOR to generate derivative code for TACO2D, a finite element heat transfer code. The study of TACO2D indicates that ADIFOR-generated derivatives yield accurate derivatives at a fraction of the time requirements of finite difference approximations, and space requirements proportional to the number of variables. The primary focus on TACO2D was for the design of chemical vapor deposition reactors.
2-D Three Fluid Simulation of Upstreaming Ions Above Auroral Precipitation
NASA Astrophysics Data System (ADS)
Danielides, M. A.; Lummerzheim, D.; Otto, A.; Stevens, R. J.
2006-12-01
The ionosphere is a rich reservoir of charged particles from which a variable fraction is transported to the magnetosphere. An important transport phenomena is the formation of upward ion flow above auroral structure. A primary region of the outflow is not known, but contributions come from polar cap, dayside cusp/cleft region, auroral oval, or even from mid-latitudes. In the past global magnetospheric models and fluid codes were used to simulate large scale ion outflow above, e.g., the polar-cap aurora. However, satellites orbiting at low- altitudes have repeatingly detected localized ion outflow above the auroral oval. Ionosphere-magnetosphere coupling simulations gave first insides into the small-scale dynamics of aurora. The aim of this study is the investigation of coupled plasma and neutral dynamics in smaller scale aurora to explain the generation, structure, and dynamics of vertical ion upstream. We consider auroral electron precipitation at ionospheric heights in a 2-D three fluid ionospheric-magnetospheric coupling code (Otto and Zhu, 2003). Specially we examine the effects of the electron precipitation, heat conduction and heating in field- aligned current through coulomb collisions or turbulence causing: i) electron heating, ii) electron pressure gradients, and iii) upstreaming of ions through a resulting ambipolar electric field. Our first case studies are performed for different boundary conditions and for different auroral electron precipitation parameters (variation in characteristic auroral energy, auroral energy flux and horizontal scale). The results shall clarify how auroral precipitation can drive ions upwards. Finally we discuss the effect of ion drag and the interaction of the upstreaming ions with a stable neutral constituent. Otto, O. and H. Zhu, Fluid plasma simulation of coupled systems: Ionosphere and magnetosphere, Space Plasma Simulation. Edited by J. Buechner, C. Dum, and M. Scholer., Lecture Notes in Physics, vol. 615, p.193
In situ fluid typing and quantification with 1D and 2D NMR logging.
Sun, Boqin
2007-05-01
In situ nuclear magnetic resonance (NMR) fluid typing has recently gained momentum due to data acquisition and inversion algorithm enhancement of NMR logging tools. T(2) distributions derived from NMR logging contain information on bulk fluids and pore size distributions. However, the accuracy of fluid typing is greatly overshadowed by the overlap between T(2) peaks arising from different fluids with similar apparent T(2) relaxation times. Nevertheless, the shapes of T(2) distributions from different fluid components are often different and can be predetermined. Inversion with predetermined T(2) distributions allows us to perform fluid component decomposition to yield individual fluid volume ratios. Another effective method for in situ fluid typing is two-dimensional (2D) NMR logging, which results in proton population distribution as a function of T(2) relaxation time and fluid diffusion coefficient (or T(1) relaxation time). Since diffusion coefficients (or T(1) relaxation time) for different fluid components can be very different, it is relatively easy to separate oil (especially heavy oil) from water signal in a 2D NMR map and to perform accurate fluid typing. Combining NMR logging with resistivity and/or neutron/density logs provides a third method for in situ fluid typing. We shall describe these techniques with field examples. PMID:17466778
PiCode: A New Picture-Embedding 2D Barcode.
Chen, Changsheng; Huang, Wenjian; Zhou, Baojian; Liu, Chenchen; Mow, Wai Ho
2016-08-01
Nowadays, 2D barcodes have been widely used as an interface to connect potential customers and advertisement contents. However, the appearance of a conventional 2D barcode pattern is often too obtrusive for integrating into an aesthetically designed advertisement. Besides, no human readable information is provided before the barcode is successfully decoded. This paper proposes a new picture-embedding 2D barcode, called PiCode, which mitigates these two limitations by equipping a scannable 2D barcode with a picturesque appearance. PiCode is designed with careful considerations on both the perceptual quality of the embedded image and the decoding robustness of the encoded message. Comparisons with the existing beautified 2D barcodes show that PiCode achieves one of the best perceptual qualities for the embedded image, and maintains a better tradeoff between image quality and decoding robustness in various application conditions. PiCode has been implemented in the MATLAB on a PC and some key building blocks have also been ported to Android and iOS platforms. Its practicality for real-world applications has been successfully demonstrated. PMID:27249833
Numerical simulation of ( T 2, T 1) 2D NMR and fluid responses
NASA Astrophysics Data System (ADS)
Tan, Mao-Jin; Zou, You-Long; Zhang, Jin-Yan; Zhao, Xin
2012-12-01
One-dimensional nuclear magnetic resonance (1D NMR) logging technology is limited for fluid typing, while two-dimensional nuclear magnetic resonance (2D NMR) logging can provide more parameters including longitudinal relaxation time ( T 1) and transverse relaxation time ( T 2) relative to fluid types in porous media. Based on the 2D NMR relaxation mechanism in a gradient magnetic field, echo train simulation and 2D NMR inversion are discussed in detail. For 2D NMR inversion, a hybrid inversion method is proposed based on the damping least squares method (LSQR) and an improved truncated singular value decomposition (TSVD) algorithm. A series of spin echoes are first simulated with multiple waiting times ( T W s) in a gradient magnetic field for given fluid models and these synthesized echo trains are inverted by the hybrid method. The inversion results are consistent with given models. Moreover, the numerical simulation of various fluid models such as the gas-water, light oil-water, and vicious oil-water models were carried out with different echo spacings ( T E s) and T W s by this hybrid method. Finally, the influences of different signal-to-noise ratios (SNRs) on inversion results in various fluid models are studied. The numerical simulations show that the hybrid method and optimized observation parameters are applicable to fluid typing of gas-water and oil-water models.
2D MIMO Network Coding with Inter-Route Interference Cancellation
NASA Astrophysics Data System (ADS)
Tran, Gia Khanh; Sakaguchi, Kei; Ono, Fumie; Araki, Kiyomichi
Infrastructure wireless mesh network has been attracting much attention due to the wide range of its application such as public wireless access, sensor network, etc. In recent years, researchers have shown that significant network throughput gain can be achieved by employing network coding in a wireless environment. For further improvement of network throughput in one dimensional (1D) topology, Ono et al. proposed to use multiple antenna technique combined with network coding. In this paper, being inspired by MIMO network coding in 1D topology, the authors establish a novel MIMO network coding algorithm for a 2D topology consisting of two crossing routes. In this algorithm, multiple network coded flows are spatially multiplexed. Owing to the efficient usage of radio resource of network coding and co-channel interference cancellation ability of MIMO, the proposed algorithm shows an 8-fold gain in network capacity compared to conventional methods in the best-case scenario.
NASA Astrophysics Data System (ADS)
Stone, James M.; Norman, Michael L.
1992-06-01
A detailed description of ZEUS-2D, a numerical code for the simulation of fluid dynamical flows including a self-consistent treatment of the effects of magnetic fields and radiation transfer is presented. Attention is given to the hydrodynamic (HD) algorithms which form the foundation for the more complex MHD and radiation HD algorithms. The effect of self-gravity on the flow dynamics is accounted for by an iterative solution of the sparse-banded matrix resulting from discretizing the Poisson equation in multidimensions. The results of an extensive series of HD test problems are presented. A detailed description of the MHD algorithms in ZEUS-2D is presented. A new method of computing the electromotive force is developed using the method of characteristics (MOC). It is demonstrated through the results of an extensive series of MHD test problems that the resulting hybrid MOC-constrained transport method provides for the accurate evolution of all modes of MHD wave families.
Snapshot 2D tomography via coded aperture x-ray scatter imaging
MacCabe, Kenneth P.; Holmgren, Andrew D.; Tornai, Martin P.; Brady, David J.
2015-01-01
This paper describes a fan beam coded aperture x-ray scatter imaging system which acquires a tomographic image from each snapshot. This technique exploits cylindrical symmetry of the scattering cross section to avoid the scanning motion typically required by projection tomography. We use a coded aperture with a harmonic dependence to determine range, and a shift code to determine cross-range. Here we use a forward-scatter configuration to image 2D objects and use serial exposures to acquire tomographic video of motion within a plane. Our reconstruction algorithm also estimates the angular dependence of the scattered radiance, a step toward materials imaging and identification. PMID:23842254
Field depth extension of 2D barcode scanner based on wavefront coding and projection algorithm
NASA Astrophysics Data System (ADS)
Zhao, Tingyu; Ye, Zi; Zhang, Wenzi; Huang, Weiwei; Yu, Feihong
2008-03-01
Wavefront coding (WFC) used in 2D barcode scanners can extend the depth of field into a great extent with simpler structure compared to the autofocus microscope system. With a cubic phase mask (CPM) employed in the STOP, blurred images will be obtained in charge coupled device (CCD), which can be restored by digital filters. Direct methods are used widely in real-time restoration with good computational efficiency but with details smoothed. Here, the results of direct method are firstly filtered by hard-threshold function. The positions of the steps can be detected by simple differential operators. With the positions corrected by projection algorithm, the exact barcode information is restored. A wavefront coding system with 7mm effective focal length and 6 F-number is designed as an example. Although with the different magnification, images of different object distances can be restored by one point spread function (PSF) with 200mm object distance. A QR code (Quickly Response Code) of 31mm X 27mm is used as a target object. The simulation results showed that the sharp imaging objective distance is from 80mm to 355mm. The 2D barcode scanner with wavefront coding extends field depth with simple structure, low cost and large manufacture tolerance. This combination of the direct filter and projection algorithm proposed here could get the exact 2D barcode information with good computational efficiency.
Wall surface temperature calculation in the SolEdge2D-EIRENE transport code
NASA Astrophysics Data System (ADS)
Denis, J.; Pégourié, B.; Bucalossi, J.; Bufferand, H.; Ciraolo, G.; Gardarein, J.-L.; Gaspar, J.; Grisolia, C.; Hodille, E.; Missirlian, M.; Serre, E.; Tamain, P.
2016-02-01
A thermal wall model is developed for the SolEdge2D-EIRENE edge transport code for calculating the surface temperature of the actively-cooled vessel components in interaction with the plasma. This is a first step towards a self-consistent evaluation of the recycling of particles, which depends on the wall surface temperature. The proposed thermal model is built to match both steady-state temperature and time constant of actively-cooled plasma facing components. A benchmark between this model and the Finite Element Modelling code CAST3M is performed in the case of an ITER-like monoblock. An example of application is presented for a SolEdge2D-EIRENE simulation of a medium-power discharge in the WEST tokamak, showing the steady-state wall temperature distribution and the temperature cycling due to an imposed Edge Localised Mode-like event.
Validation of a 2-D semi-coupled numerical model for fluid-structure-seabed interaction
NASA Astrophysics Data System (ADS)
Ye, Jianhong; Jeng, Dongsheng; Wang, Ren; Zhu, Changqi
2013-10-01
A 2-D semi-coupled model PORO-WSSI 2D (also be referred as FSSI-CAS 2D) for the Fluid-Structure-Seabed Interaction (FSSI) has been developed by employing RANS equations for wave motion in fluid domain, VARANS equations for porous flow in porous structures; and taking the dynamic Biot's equations (known as "u - p" approximation) for soil as the governing equations. The finite difference two-step projection method and the forward time difference method are adopted to solve the RANS, VARANS equations; and the finite element method is adopted to solve the "u - p" approximation. A data exchange port is developed to couple the RANS, VARANS equations and the dynamic Biot's equations together. The analytical solution proposed by Hsu and Jeng (1994) and some experiments conducted in wave flume or geotechnical centrifuge in which various waves involved are used to validate the developed semi-coupled numerical model. The sandy bed involved in these experiments is poro-elastic or poro-elastoplastic. The inclusion of the interaction between fluid, marine structures and poro-elastoplastic seabed foundation is a special point and highlight in this paper, which is essentially different with other previous coupled models The excellent agreement between the numerical results and the experiment data indicates that the developed coupled model is highly reliablefor the FSSI problem.
Laure, Chloé; Karamessini, Denise; Milenkovic, Olgica; Charles, Laurence; Lutz, Jean-François
2016-08-26
A 2D approach was studied for the design of polymer-based molecular barcodes. Uniform oligo(alkoxyamine amide)s, containing a monomer-coded binary message, were synthesized by orthogonal solid-phase chemistry. Sets of oligomers with different chain-lengths were prepared. The physical mixture of these uniform oligomers leads to an intentional dispersity (1st dimension fingerprint), which is measured by electrospray mass spectrometry. Furthermore, the monomer sequence of each component of the mass distribution can be analyzed by tandem mass spectrometry (2nd dimension sequencing). By summing the sequence information of all components, a binary message can be read. A 4-bytes extended ASCII-coded message was written on a set of six uniform oligomers. Alternatively, a 3-bytes sequence was written on a set of five oligomers. In both cases, the coded binary information was recovered. PMID:27484303
Systems Improved Numerical Fluids Analysis Code
NASA Technical Reports Server (NTRS)
Costello, F. A.
1990-01-01
Systems Improved Numerical Fluids Analysis Code, SINFAC, consists of additional routines added to April, 1983, version of SINDA. Additional routines provide for mathematical modeling of active heat-transfer loops. Simulates steady-state and pseudo-transient operations of 16 different components of heat-transfer loops, including radiators, evaporators, condensers, mechanical pumps, reservoirs, and many types of valves and fittings. Program contains property-analysis routine used to compute thermodynamic properties of 20 different refrigerants. Source code written in FORTRAN 77.
Chang, F.H.; Santee, G.E. Jr.; Mortensen, G.A.; Brockett, G.F.; Gross, M.B.; Silling, S.A.; Belytschko, T.
1981-03-01
This report, the second in a series of reports for RP-1065, describes the second step in the stepwise approach for developing the three-dimensional, nonlinear, fluid/structure interaction methodology to assess the hydroloads on a large PWR during the subcooled portions of a hypothetical LOCA. The second step in the methodology considers enhancements and special modifications to the 2D STEALTH-HYDRO computer program and the 2D WHAMSE computer program. The 2D STEALTH-HYDRO enhancements consist of a fluid-fluid coupling control-volume model and an orifice control-volume model. The enhancements to 2D WHAMSE include elimination of the implicit integration routines, material models, and structural elements not required for the hydroloads application. In addition the logic for coupling the 2D STEALTH-HYDRO computer program to the 2D WHAMSE computer program is discussed.
An Integrative Model of Excitation Driven Fluid Flow in a 2D Uterine Channel
NASA Astrophysics Data System (ADS)
Maggio, Charles; Fauci, Lisa; Chrispell, John
2009-11-01
We present a model of intra-uterine fluid flow in a sagittal cross-section of the uterus by inducing peristalsis in a 2D channel. This is an integrative multiscale computational model that takes as input fluid viscosity, passive tissue properties of the uterine channel and a prescribed wave of membrane depolarization. This voltage pulse is coupled to a model of calcium dynamics inside a uterine smooth muscle cell, which in turn drives a kinetic model of myosin phosphorylation governing contractile muscle forces. Using the immersed boundary method, these muscle forces are communicated to a fluid domain to simulate the contractions which occur in a human uterus. An analysis of the effects of model parameters on the flow properties and emergent geometry of the peristaltic channel will be presented.
Multipacting Simulation Study for 56 MHz Quarter Wave Resonator using 2D Code
Naik,D.; Ben-Zvi, I.
2009-01-02
A beam excited 56 MHz Radio Frequency (RF) Niobium Quarter Wave Resonator (QWR) has been proposed to enhance RHIC beam luminosity and bunching. Being a RF cavity, multipacting is expected; therefore an extensive study was carried out with the Multipac 2.1 2D simulation code. The study revealed that multipacting occurs in various bands up to peak surface electric field 50 kV/m and is concentrated mostly above the beam gap and on the outer conductor. To suppress multipacting, a ripple structure was introduced to the outer conductor and the phenomenon was successfully eliminated from the cavity.
Roton Excitations and the Fluid-Solid Phase Transition in Superfluid 2D Yukawa Bosons
NASA Astrophysics Data System (ADS)
Molinelli, S.; Galli, D. E.; Reatto, L.; Motta, M.
2016-05-01
We compute several ground-state properties and the dynamical structure factor of a zero-temperature system of Bosons interacting with the 2D screened Coulomb (2D-SC) potential. We resort to the exact shadow path integral ground state (SPIGS) quantum Monte Carlo method to compute the imaginary-time correlation function of the model, and to the genetic algorithm via falsification of theories (GIFT) to retrieve the dynamical structure factor. We provide a detailed comparison of ground-state properties and collective excitations of 2D-SC and ^4 He atoms. The roton energy of the 2D-SC system is an increasing function of density, and not a decreasing one as in ^4 He. This result is in contrast with the view that the roton is the soft mode of the fluid-solid transition. We uncover a remarkable quasi-universality of backflow and of other properties when expressed in terms of the amount of short-range order as quantified by the height of the first peak of the static structure factor.
Automated design of coupled RF cavities using 2-D and 3-D codes
Smith, Peter; Christiansen, D. W.; Greninger, P. T.; Spalek, G.
2001-01-01
Coupled RF cavities in the Accelerator Production of Tritium Project have been designed using a procedure in which a 2-D code (CCT) searches for a design that meets frequency and coupling requirements, while a 3-D code (HFSS) is used to obtain empirical factors used by CCT to characterize the coupling slot between cavities. Using assumed values of the empirical factors, CCT runs the Superfish code iteratively to solve for a trial cavity design that has a specified frequency and coupling. The frequency shifts and the coupling constant k of the slot are modeled in CCT using a perturbation theory, the results of which are adjusted using the empirical factors. Given a trial design, HFSS is run using periodic boundary conditions to obtain a mode spectrum. The mode spectrum is processed using the DISPER code to obtain values of the coupling and the frequencies with slots. These results are used to calculate a new set of empirical factors, which are fed back into CCT for another design iteration. Cold models have been fabricated and tested to validate the codes, and results will be presented.
MHDust: A 3-fluid dusty plasma code
NASA Astrophysics Data System (ADS)
Lazerson, Samuel
MHDust is a next generation 3-fluid magnetized dusty plasma code, treating the inertial dynamics of both the dust and ion components. Coded in ANSI C, the numerical method employs Leap-Frog and Dufort-Frankel integration schemes. Features include: nonlinear collisional terms, quasi-neutrality or continuity based electron densities, and dynamical dust charge number. Tests of wave-mode propagation (Acoustic and Electromagnetic) allow a comparison to linear wave mode theory. Additional nonlinear phenomena are presented including magnetic reconnection and shear-flow instabilities. Relevant parameters for the space environment are considered, allowing a comparison to be made with previous dusty plasma codes (DENISIS). The utility of the code is expanded through the possibility of small dust mass. This allows MH- Dust to be used as a 2-ion plasma code. MHDust considerably expands the range of numerical investigations into nonlinear phenomena in the field of astrophysical dusty plasmas.
Assessment of the 2D MOC solver in MPACT: Michigan parallel characteristics transport code
Collins, B.; Kochunas, B.; Downar, T.
2013-07-01
MPACT (Michigan Parallel Characteristics Transport Code) is a new reactor analysis tool being developed by researchers at the University of Michigan as an advanced pin-resolved transport capability within VERA (Virtual Environment for Reactor Analysis). VERA is the end-user reactor simulation tool being developed by the Consortium for the Advanced Simulation of Light Water Reactors (CASL). The MPACT development project is itself unique for the way it is changing how students perform research to achieve the instructional and research goals of an academic institution, while providing immediate value to the industry. One of the major computational pieces in MPACT is the 2D MOC solver. It is critical that the 2D MOC solver provide an efficient, accurate, and robust solution over a broad range of reactor operating conditions. The C5G7 benchmark is first used to test the accuracy of the method with a fixed set of cross-sections. The VERA Core Physics Progression Problems are then used to compare the accuracy of both the 2D transport solver and also the cross-section treatments. (authors)
NASA Astrophysics Data System (ADS)
Stone, James M.; Norman, Michael L.
1992-06-01
In this, the second of a series of three papers, we continue a detailed description of ZEUS-2D, a numerical code for the simulation of fluid dynamical flows in astrophysics including a self-consistent treatment of the effects of magnetic fields and radiation transfer. In this paper, we give a detailed description of the magnetohydrodynamical (MHD) algorithms in ZEUS-2D. The recently developed constrained transport (CT) algorithm is implemented for the numerical evolution of the components of the magnetic field for MHD simulations. This formalism guarantees the numerically evolved field components will satisfy the divergence-free constraint at all times. We find, however, that the method used to compute the electromotive forces must be chosen carefully to propagate accurately all modes of MHD wave families (in particular shear Alfvén waves). A new method of computing the electromotive force is developed using the method of characteristics (MOC). It is demonstrated through the results of an extensive series of MHD test problems that the resulting hybrid MOC-CT method provides for the accurate evolution of all modes of MHD wave families.
NASA Astrophysics Data System (ADS)
Kawamura, E.; Lichtenberg, A. J.; Lieberman, M. A.; Marakhtanov, A. M.
2016-06-01
A fast 2D axisymmetric fluid-analytical multifrequency capacitively coupled plasma (CCP) reactor code is used to study center high nonuniformity in a low pressure electronegative chlorine discharge. In the code, a time-independent Helmholtz wave equation is used to solve for the capacitive fields in the linearized frequency domain. This eliminates the time dependence from the electromagnetic (EM) solve, greatly speeding up the simulations at the cost of neglecting higher harmonics. However, since the code allows up to three driving frequencies, we can add the two most important harmonics to the CCP simulations as the second and third input frequencies. The amplitude and phase of these harmonics are estimated by using a recently developed 1D radial nonlinear transmission line (TL) model of a highly asymmetric cylindrical discharge (Lieberman et al 2015 Plasma Sources Sci. Technol. 24 055011). We find that at higher applied frequencies, the higher harmonics contribute significantly to the center high nonuniformity due to their shorter plasma wavelengths.
Modelling 2001 lahars at Popocatépetl volcano using FLO2D numerical code
NASA Astrophysics Data System (ADS)
Caballero, L.; Capra, L.
2013-12-01
Popocatépetl volcano is located on the central part of the Transmexican Volcanic Belt. It is one of the most active volcanoes in Mexico and endanger more than 25 million people that lives in its surroundings. In the last months, the renewal of its volcanic activity put into alert scientific community. One of the possible scenarios is the 2001 explosive activity, which was characterized by a 8 km eruptive column and the subsequent formation of pumice flows up to 4 km from the crater. Lahars were generated few hours after, remobilizing the new deposits towards NE flank of the volcano, along Huiloac Gorge, almost reaching Santiago Xalitzintla town (Capra et al., 2004). The occurrence of a similar scenario makes very important to reproduce this event to delimitate accurately lahar hazard zones. In this work, 2001 lahar deposit is modeled using FLO2D numerical code. Geophone data is used to reconstruct initial hydrograph and sediment concentration. Sensitivity study of most important parameters used by this code like Manning, and α and β coefficients was conducted in order to achieve a good simulation. Results obtained were compared with field data and demonstrated a good agreement in thickness and flow distribution. A comparison with previously published data with laharZ program (Muñoz-Salinas, 2009) is also made. Additionally, lahars with fluctuating sediment concentrations but with similar volume are simulated to observe the influence of the rheological behavior on lahar distribution.
Embedded morphological dilation coding for 2D and 3D images
NASA Astrophysics Data System (ADS)
Lazzaroni, Fabio; Signoroni, Alberto; Leonardi, Riccardo
2002-01-01
Current wavelet-based image coders obtain high performance thanks to the identification and the exploitation of the statistical properties of natural images in the transformed domain. Zerotree-based algorithms, as Embedded Zerotree Wavelets (EZW) and Set Partitioning In Hierarchical Trees (SPIHT), offer high Rate-Distortion (RD) coding performance and low computational complexity by exploiting statistical dependencies among insignificant coefficients on hierarchical subband structures. Another possible approach tries to predict the clusters of significant coefficients by means of some form of morphological dilation. An example of a morphology-based coder is the Significance-Linked Connected Component Analysis (SLCCA) that has shown performance which are comparable to the zerotree-based coders but is not embedded. A new embedded bit-plane coder is proposed here based on morphological dilation of significant coefficients and context based arithmetic coding. The algorithm is able to exploit both intra-band and inter-band statistical dependencies among wavelet significant coefficients. Moreover, the same approach is used both for two and three-dimensional wavelet-based image compression. Finally we the algorithms are tested on some 2D images and on a medical volume, by comparing the RD results to those obtained with the state-of-the-art wavelet-based coders.
A case study of fluid flow in fractured rock mass based on 2-D DFN modeling
NASA Astrophysics Data System (ADS)
Han, Jisu; Noh, Young-Hwan; Um, Jeong-Gi; Choi, Yosoon
2014-05-01
A two dimensional steady-state fluid flow through fractured rock mass of an abandoned copper mine in Korea is addressed based on discrete fracture network modeling. An injection well and three observation wells were installed at the field site to monitor the variations of total heads induced by injection of fresh water. A series of packer tests were performed to estimate the rock mass permeability. First, the two dimensional stochastic fracture network model was built and validated for a granitic rock mass using the geometrical and statistical data obtained from surface exposures and borehole logs. This validated fracture network model was combined with the fracture data observed on boreholes to generate a stochastic-deterministic fracture network system. Estimated apertures for each of the fracture sets using permeability data obtained from borehole packer tests were discussed next. Finally, a systematic procedure for fluid flow modeling in fractured rock mass in two dimensional domain was presented to estimate the conductance, flow quantity and nodal head in 2-D conceptual linear pipe channel network. The results obtained in this study clearly show that fracture geometry parameters (orientation, density and size) play an important role in the hydraulic behavior of fractured rock masses.
Gradient-Driven Vortex Motion in Nonneutral Plasmas and Ideal 2D Fluids
NASA Astrophysics Data System (ADS)
Schecter, David A.
2000-10-01
Two-dimensional (2D) turbulent flows can relax to metastable patterns without dissipation of kinetic energy. This ``rapid'' relaxation has been observed in computer simulations of ideal 2D fluids, and more recently in experiments with pure electron plasmas, which can obey similar dynamics. The late stage of relaxation often involves small vortices moving in a larger ``background'' shear-flow.(X.P. Huang et al., Phys. Rev. Lett. 74), 4424 (1995). In time, positive vortices (rotating counter-clockwise) move to peaks in background vorticity, whereas negative vortices (rotating clockwise) move to minima.(C.G. Rossby, J. Mar. Res. 7), 175 (1948); C.H. Liu and L. Ting, Comp. & Fluids 15, 77 (1987). In general, the rate of this migration increases with the magnitude of the background vorticity gradient, whereas it decreases as the background shear intensifies.\\vspace12pt Positive and negative vortices can also be classified as either prograde or retrograde, depending on whether they rotate with or against the local background shear. Surprisingly, a retrograde vortex moves up or down a background vorticity gradient orders of magnitude faster than a prograde vortex of equal strength.(D.A. Schecter and D.H.E. Dubin, Phys. Rev. Lett. 83), 2191 (1999). An accurate expression for the velocity of a weak retrograde vortex is obtained from an analytic calculation, in which the response of the background flow to the vortex is linearized. However, this linear theory fails for prograde vortices of any strength. Interestingly, the velocity of a prograde vortex can be obtained from a simple estimate, which accounts for the nonlinear ``trapping'' of background fluid around the vortex. The analytic expressions for the velocities of both prograde and retrograde vortices are in good quantitative agreement with vortex-in-cell simulations, and with electron plasma experiments, when the background shear is below a critical level. When the ratio of background shear to background vorticity
Icarus: A 2-D Direct Simulation Monte Carlo (DSMC) Code for Multi-Processor Computers
BARTEL, TIMOTHY J.; PLIMPTON, STEVEN J.; GALLIS, MICHAIL A.
2001-10-01
Icarus is a 2D Direct Simulation Monte Carlo (DSMC) code which has been optimized for the parallel computing environment. The code is based on the DSMC method of Bird[11.1] and models from free-molecular to continuum flowfields in either cartesian (x, y) or axisymmetric (z, r) coordinates. Computational particles, representing a given number of molecules or atoms, are tracked as they have collisions with other particles or surfaces. Multiple species, internal energy modes (rotation and vibration), chemistry, and ion transport are modeled. A new trace species methodology for collisions and chemistry is used to obtain statistics for small species concentrations. Gas phase chemistry is modeled using steric factors derived from Arrhenius reaction rates or in a manner similar to continuum modeling. Surface chemistry is modeled with surface reaction probabilities; an optional site density, energy dependent, coverage model is included. Electrons are modeled by either a local charge neutrality assumption or as discrete simulational particles. Ion chemistry is modeled with electron impact chemistry rates and charge exchange reactions. Coulomb collision cross-sections are used instead of Variable Hard Sphere values for ion-ion interactions. The electro-static fields can either be: externally input, a Langmuir-Tonks model or from a Green's Function (Boundary Element) based Poison Solver. Icarus has been used for subsonic to hypersonic, chemically reacting, and plasma flows. The Icarus software package includes the grid generation, parallel processor decomposition, post-processing, and restart software. The commercial graphics package, Tecplot, is used for graphics display. All of the software packages are written in standard Fortran.
Differential Sensitivity Theory applied to the MESA2D code for multi-material problems
Henninger, R.J.; Maudlin, P.J.; Harstad, E.N.
1996-05-01
The technique called Differential Sensitivity Theory (DST) is extended to the multi-component system of equations solved by the MESA2D hydrocode. DST uses adjoint techniques to determine exact sensitivity derivatives, i.e., if R is a calculation result of interest (response R) and {alpha}{sub i} is a calculation input (parameter {alpha}{sub i}), then {partial_derivative}R/{partial_derivative}{alpha}{sub i} is defined as the sensitivity. The advantage of using DST is that for an n-parameter problem {ital all} n sensitivities can be obtained by integrating the solutions from only {ital two} calculations, a MESA calculation and its corresponding adjoint calculation using an Adjoint Continuum Mechanics (ACM) code. Previous papers have described application of the technique to one-dimensional, single-material problems. This work presents the derivation and solution of the additional adjoint equations for the purpose of computing sensitivities for two-dimensional, multi-component problems. As an example, results for a multi-material flyer plate impact problem featuring an oblique impact are given. {copyright} {ital 1996 American Institute of Physics.}
Differential Sensitivity Theory applied to the MESA2D code for multi-material problems
NASA Astrophysics Data System (ADS)
Henninger, R. J.; Maudlin, P. J.; Harstad, E. N.
1996-05-01
The technique called Differential Sensitivity Theory (DST) is extended to the multi-component system of equations solved by the MESA2D hydrocode. DST uses adjoint techniques to determine exact sensitivity derivatives, i.e., if R is a calculation result of interest (response R) and αi is a calculation input (parameter αi), then ∂R/∂αi is defined as the sensitivity. The advantage of using DST is that for an n-parameter problem all n sensitivities can be obtained by integrating the solutions from only two calculations, a MESA calculation and its corresponding adjoint calculation using an Adjoint Continuum Mechanics (ACM) code. Previous papers have described application of the technique to one-dimensional, single-material problems. This work presents the derivation and solution of the additional adjoint equations for the purpose of computing sensitivities for two-dimensional, multi-component problems. As an example, results for a multi-material flyer plate impact problem featuring an oblique impact are given.
Differential sensitivity theory applied to the MESA2D code for multi-material problems
Henninger, R.J.; Maudlin, P.J.; Harstad, E.N.
1995-09-01
The technique called Differential Sensitivity Theory (DST) is extended to the multi-component system of equations solved by the MESA2D hydrocode. DST uses adjoint techniques to determine exact sensitivity derivatives, i.e., if R is a calculation result of interest (response R) and {alpha}{sub i} is a calculation input (parameter {alpha}{sub i}), then {partial_derivative}R/{partial_derivative}{alpha}{sub i} is defined as the sensitivity. The advantage of using DST is that for an n-parameter problem all n sensitivities can be obtained by integrating the solutions from only two calculations, a MESA calculation and its corresponding adjoint calculation using an Adjoint Continuum Mechanics (ACM) code. Previous papers have described application of the technique to one-dimensional, single-material problems. This work presents the derivation and solution of the additional adjoint equations for the purpose of computing sensitivities for two-dimensional, multi-component problems. As an example, results for a multi-material flyer plate impact problem featuring an oblique impact are given.
MULTI2D - a computer code for two-dimensional radiation hydrodynamics
NASA Astrophysics Data System (ADS)
Ramis, R.; Meyer-ter-Vehn, J.; Ramírez, J.
2009-06-01
Simulation of radiation hydrodynamics in two spatial dimensions is developed, having in mind, in particular, target design for indirectly driven inertial confinement energy (IFE) and the interpretation of related experiments. Intense radiation pulses by laser or particle beams heat high-Z target configurations of different geometries and lead to a regime which is optically thick in some regions and optically thin in others. A diffusion description is inadequate in this situation. A new numerical code has been developed which describes hydrodynamics in two spatial dimensions (cylindrical R-Z geometry) and radiation transport along rays in three dimensions with the 4 π solid angle discretized in direction. Matter moves on a non-structured mesh composed of trilateral and quadrilateral elements. Radiation flux of a given direction enters on two (one) sides of a triangle and leaves on the opposite side(s) in proportion to the viewing angles depending on the geometry. This scheme allows to propagate sharply edged beams without ray tracing, though at the price of some lateral diffusion. The algorithm treats correctly both the optically thin and optically thick regimes. A symmetric semi-implicit (SSI) method is used to guarantee numerical stability. Program summaryProgram title: MULTI2D Catalogue identifier: AECV_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 151 098 No. of bytes in distributed program, including test data, etc.: 889 622 Distribution format: tar.gz Programming language: C Computer: PC (32 bits architecture) Operating system: Linux/Unix RAM: 2 Mbytes Word size: 32 bits Classification: 19.7 External routines: X-window standard library (libX11.so) and corresponding heading files (X11/*.h) are
A novel 2D wavelength-time chaos code in optical CDMA system
NASA Astrophysics Data System (ADS)
Zhang, Qi; Xin, Xiangjun; Wang, Yongjun; Zhang, Lijia; Yu, Chongxiu; Meng, Nan; Wang, Houtian
2012-11-01
Two-dimensional wavelength-time chaos code is proposed and constructed for a synchronous optical code division multiple access system. The access performance is compared between one-dimensional chaos code, WDM/chaos code and the proposed code. Comparison shows that two-dimensional wavelength-time chaos code possesses larger capacity, better spectral efficiency and bit-error ratio than WDM/chaos combinations and one-dimensional chaos code.
2D fluid simulations of acoustic waves in pulsed ICP discharges: Comparison with experiments
NASA Astrophysics Data System (ADS)
Despiau-Pujo, Emilie; Cunge, Gilles; Sadeghi, Nader; Braithwaite, N. St. J.
2012-10-01
Neutral depletion, which is mostly caused by gas heating under typical material processing conditions, is an important phenomenon in high-density plasmas. In low pressure pulsed discharges, experiments show that additional depletion due to electron pressure (Pe) may have a non-negligible influence on radical transport [1]. To evaluate this effect, comparisons between 2D fluid simulations and measurements of gas convection in Ar/Cl2 pulsed ICP plasmas are reported. In the afterglow, Pe drops rapidly by electron cooling which generates a neutral pressure gradient between the plasma bulk and the reactor walls. This in turn forces the cold surrounding gas to move rapidly towards the center, thus launching an acoustic wave in the reactor. Time-resolved measurements of atoms drift velocity and gas temperature by LIF and LAS in the early afterglow are consistent with gas drifting at acoustic wave velocity followed by rapid gas cooling. Similar results are predicted by the model. The ion flux at the reactor walls is also shown to oscillate in phase with the acoustic wave due to ion-neutral friction forces. Finally, during plasma ignition, experiments show opposite phenomena when Pe rises.[4pt] [1] Cunge et al, APL 96, 131501 (2010)
A hybrid numerical fluid dynamics code for resistive magnetohydrodynamics
Energy Science and Technology Software Center (ESTSC)
2006-04-01
Spasmos is a computational fluid dynamics code that uses two numerical methods to solve the equations of resistive magnetohydrodynamic (MHD) flows in compressible, inviscid, conducting media[1]. The code is implemented as a set of libraries for the Python programming language[2]. It represents conducting and non-conducting gases and materials with uncomplicated (analytic) equations of state. It supports calculations in 1D, 2D, and 3D geometry, though only the 1D configuation has received significant testing to date. Becausemore » it uses the Python interpreter as a front end, users can easily write test programs to model systems with a variety of different numerical and physical parameters. Currently, the code includes 1D test programs for hydrodynamics (linear acoustic waves, the Sod weak shock[3], the Noh strong shock[4], the Sedov explosion[5], magnetic diffusion (decay of a magnetic pulse[6], a driven oscillatory "wine-cellar" problem[7], magnetic equilibrium), and magnetohydrodynamics (an advected magnetic pulse[8], linear MHD waves, a magnetized shock tube[9]). Spasmos current runs only in a serial configuration. In the future, it will use MPI for parallel computation.« less
Ren, X; Domier, C W; Kramer, G; Luhmann, N C; Muscatello, C M; Shi, L; Tobias, B J; Valeo, E
2014-11-01
A synthetic microwave imaging reflectometer (MIR) diagnostic employing the full-wave reflectometer code (FWR2D) has been developed and is currently being used to guide the design of real systems, such as the one recently installed on DIII-D. The FWR2D code utilizes real plasma profiles as input, and it is combined with optical simulation tools for synthetic diagnostic signal generation. A detailed discussion of FWR2D and the process to generate the synthetic signal are presented in this paper. The synthetic signal is also compared to a prescribed density fluctuation spectrum to quantify the imaging quality. An example is presented with H-mode-like plasma profiles derived from a DIII-D discharge, where the MIR focal is located in the pedestal region. It is shown that MIR is suitable for diagnosing fluctuations with poloidal wavenumber up to 2.0 cm(-1) and fluctuation amplitudes less than 5%. PMID:25430276
2D Resistive Magnetohydrodynamics Calculations with an Arbitrary Lagrange Eulerian Code
NASA Astrophysics Data System (ADS)
Rousculp, C. L.; Gianakon, T. A.; Lipnikov, K. N.; Nelson, E. M.
2015-11-01
Single fluid resistive MHD is useful for modeling Z-pinch configurations in cylindrical geometry. One such example is thin walled liners for shock physics or HEDP experiments driven by capacitor banks such as the LANL's PHELIX or Sandia-Z. MHD is also useful for modeling high-explosive-driven flux compression generators (FCGs) and their high-current switches. The resistive MHD in our arbitrary Lagrange Eulerian (ALE) code operates in one and two dimensions in both Cartesian and cylindrical geometry. It is implemented as a time-step split operator, which consists of, ideal MHD connected to the explicit hydro momentum and energy equations and a second order mimetic discretization solver for implicit solution of the magnetic diffusion equation. In a staggered grid scheme, a single-component of cell-centered magnetic flux is conserved in the Lagrangian frame exactly, while magnetic forces are accumulated at the nodes. Total energy is conserved to round off. Total flux is conserved under the ALE relaxation and remap. The diffusion solver consistently computes Ohmic heating. Both Neumann and Dirichlet boundary conditions are available with coupling to external circuit models. Example calculations will be shown.
Development of a CFD Code for Analysis of Fluid Dynamic Forces in Seals
NASA Technical Reports Server (NTRS)
Athavale, Mahesh M.; Przekwas, Andrzej J.; Singhal, Ashok K.
1991-01-01
The aim is to develop a 3-D computational fluid dynamics (CFD) code for the analysis of fluid flow in cylindrical seals and evaluation of the dynamic forces on the seals. This code is expected to serve as a scientific tool for detailed flow analysis as well as a check for the accuracy of the 2D industrial codes. The features necessary in the CFD code are outlined. The initial focus was to develop or modify and implement new techniques and physical models. These include collocated grid formulation, rotating coordinate frames and moving grid formulation. Other advanced numerical techniques include higher order spatial and temporal differencing and an efficient linear equation solver. These techniques were implemented in a 2D flow solver for initial testing. Several benchmark test cases were computed using the 2D code, and the results of these were compared to analytical solutions or experimental data to check the accuracy. Tests presented here include planar wedge flow, flow due to an enclosed rotor, and flow in a 2D seal with a whirling rotor. Comparisons between numerical and experimental results for an annular seal and a 7-cavity labyrinth seal are also included.
SINFAC - SYSTEMS IMPROVED NUMERICAL FLUIDS ANALYSIS CODE
NASA Technical Reports Server (NTRS)
Costello, F. A.
1994-01-01
The Systems Improved Numerical Fluids Analysis Code, SINFAC, consists of additional routines added to the April 1983 revision of SINDA, a general thermal analyzer program. The purpose of the additional routines is to allow for the modeling of active heat transfer loops. The modeler can simulate the steady-state and pseudo-transient operations of 16 different heat transfer loop components including radiators, evaporators, condensers, mechanical pumps, reservoirs and many types of valves and fittings. In addition, the program contains a property analysis routine that can be used to compute the thermodynamic properties of 20 different refrigerants. SINFAC can simulate the response to transient boundary conditions. SINFAC was first developed as a method for computing the steady-state performance of two phase systems. It was then modified using CNFRWD, SINDA's explicit time-integration scheme, to accommodate transient thermal models. However, SINFAC cannot simulate pressure drops due to time-dependent fluid acceleration, transient boil-out, or transient fill-up, except in the accumulator. SINFAC also requires the user to be familiar with SINDA. The solution procedure used by SINFAC is similar to that which an engineer would use to solve a system manually. The solution to a system requires the determination of all of the outlet conditions of each component such as the flow rate, pressure, and enthalpy. To obtain these values, the user first estimates the inlet conditions to the first component of the system, then computes the outlet conditions from the data supplied by the manufacturer of the first component. The user then estimates the temperature at the outlet of the third component and computes the corresponding flow resistance of the second component. With the flow resistance of the second component, the user computes the conditions down stream, namely the inlet conditions of the third. The computations follow for the rest of the system, back to the first component
NASA Astrophysics Data System (ADS)
Leboeuf, Jean-Noel; Decyk, Viktor; Newman, David; Sanchez, Raul
2012-03-01
The massively parallel, nonlinear, 3D, toroidal, electrostatic, gyrokinetic, PIC, Cartesian geometry UCAN code, with particle ions and adiabatic electrons, has been successfully exercised to identify non-diffusive transport characteristics in DIII-D-like tokamak discharges. The limitation in applying UCAN to larger scale discharges is the 1D domain decomposition in the toroidal (or z-) direction for massively parallel implementation using MPI which has restricted the calculations to a few hundred ion Larmor radii per minor radius. To exceed these sizes, we have implemented 2D domain decomposition in UCAN with the addition of the y-direction to the processor mix. This has been facilitated by use of relevant components in the 2D domain decomposed PLIB2 library of field and particle management routines developed for UCLA's UPIC framework of conventional PIC codes. The gyro-averaging in gyrokinetic codes has necessitated the use of replicated arrays for efficient charge accumulation and particle push. The 2D domain-decomposed UCAN2 code reproduces the original 1D domain results within roundoff. Production calculations at large system sizes have been performed with UCAN2 on 131072 processors of the Cray XE6 at NERSC.
A 2-D orientation-adaptive prediction filter in lifting structures for image coding.
Gerek, Omer N; Cetin, A Enis
2006-01-01
Lifting-style implementations of wavelets are widely used in image coders. A two-dimensional (2-D) edge adaptive lifting structure, which is similar to Daubechies 5/3 wavelet, is presented. The 2-D prediction filter predicts the value of the next polyphase component according to an edge orientation estimator of the image. Consequently, the prediction domain is allowed to rotate +/-45 degrees in regions with diagonal gradient. The gradient estimator is computationally inexpensive with additional costs of only six subtractions per lifting instruction, and no multiplications are required. PMID:16435541
NASA Astrophysics Data System (ADS)
Zhao, Yaqin; Zhong, Xin; Wu, Di; Zhang, Ye; Ren, Guanghui; Wu, Zhilu
2013-09-01
Optical code-division multiple access (OCDMA) systems usually allocate orthogonal or quasi-orthogonal codes to the active users. When transmitting through atmospheric scattering channel, the coding pulses are broadened and the orthogonality of the codes is worsened. In truly asynchronous case, namely both the chips and the bits are asynchronous among each active user, the pulse broadening affects the system performance a lot. In this paper, we evaluate the performance of a 2D asynchronous hard-limiting wireless OCDMA system through atmospheric scattering channel. The probability density function of multiple access interference in truly asynchronous case is given. The bit error rate decreases as the ratio of the chip period to the root mean square delay spread increases and the channel limits the bit rate to different levels when the chip period varies.
NASA Astrophysics Data System (ADS)
Sharapov, V. N.; Cherepanov, A. N.; Popov, V. N.; Bykova, V. G.
2012-11-01
A model describing two-dimensional (2D) dynamics of heat transfer in the fluid systems with a localized sink of a magmatic fluid into local fractured zones above the roof of crystallizing crustal intrusions is suggested. Numerical modeling of the migration of the phase boundaries in 2D intrusive chambers under retrograde boiling of magma with relatively high initial water content in the melt shows that, depending on the character of heat dissipation from a magmatic fluid into the host rock, two types of fluid magmatic systems can arise. (1) At high heat losses, the zoning of fluidogenic ore formation is determined by the changes in temperature of the rocks within the contact aureole of the intrusive bodies. These temperature variations are controlled by the migration of the phase boundaries in the cooling melt towards the center of the magmatic bodies from their contacts. (2) In the case of a localized sink of the magmatic fluid in different parts of the top of the intrusive chambers, a specific characteristic scenario of cooling of the magmatic bodies is probably implemented. In 2D systems with a heat transfer coefficient α k < 5 × 104 W/m2 K, an area with quasi-stationary phase boundaries develops close to the region of fluid drainage through the fractured zone in the intrusion. Therefore, as the phase boundaries contract to the sink zone of a fluid, specific thermal tubes arise, whose characteristics depend on the width of the fluid-conductive zone and the heat losses into the side rocks. (3) The time required for the intrusion to solidify varies depending on the particular position of the fluid conductor above the top of the magmatic body.
SAGE 2D and 3D Simulations of the Explosive Venting of Supercritical Fluids Through Porous Media
NASA Astrophysics Data System (ADS)
Weaver, R.; Gisler, G.; Svensen, H.; Mazzini, A.
2008-12-01
Magmatic intrusive events in large igneous provinces heat sedimentary country rock leading to the eventual release of volatiles. This has been proposed as a contributor to climate change and other environmental impacts. By means of numerical simulations, we examine ways in which these volatiles can be released explosively from depth. Gases and fluids cooked out of country rock by metamorphic heating may be confined for a time by impermeable clays or other barriers, developing high pressures and supercritical fluids. If confinement is suddenly breached (by an earthquake for example) in such a way that the fluid has access to porous sediments, a violent eruption of a non-magmatic mixture of fluid and sediment may result. Surface manifestations of these events could be hydrothermal vent complexes, kimberlite pipes, pockmarks, or mud volcanoes. These are widespread on Earth, especially in large igneous provinces, as in the Karoo Basin of South Africa, the North Sea off the Norwegian margin, and the Siberian Traps. We have performed 2D and 3D simulations with the Sage hydrocode (from Los Alamos and Science Applications International) of supercritical venting in a variety of geometries and configurations. The simulations show several different patterns of propagation and fracturing in porous or otherwise weakened overburden, dependent on depth, source conditions (fluid availability, temperature, and pressure), and manner of confinement breach. Results will be given for a variety of 2D and 3D simulations of these events exploring the release of volatiles into the atmosphere.
NASA Astrophysics Data System (ADS)
Krause, M.; Camenzind, M.
2001-12-01
In the present paper, we examine the convergence behavior and inter-code reliability of astrophysical jet simulations in axial symmetry. We consider both pure hydrodynamic jets and jets with a dynamically significant magnetic field. The setups were chosen to match the setups of two other publications, and recomputed with the MHD code NIRVANA. We show that NIRVANA and the two other codes give comparable, but not identical results. We explain the differences by the different application of artificial viscosity in the three codes and numerical details, which can be summarized in a resolution effect, in the case without magnetic field: NIRVANA turns out to be a fair code of medium efficiency. It needs approximately twice the resolution as the code by Lind (Lind et al. 1989) and half the resolution as the code by Kössl (Kössl & Müller 1988). We find that some global properties of a hydrodynamical jet simulation, like e.g. the bow shock velocity, converge at 100 points per beam radius (ppb) with NIRVANA. The situation is quite different after switching on the toroidal magnetic field: in this case, global properties converge even at 10 ppb. In both cases, details of the inner jet structure and especially the terminal shock region are still insufficiently resolved, even at our highest resolution of 70 ppb in the magnetized case and 400 ppb for the pure hydrodynamic jet. The magnetized jet even suffers from a fatal retreat of the Mach disk towards the inflow boundary, which indicates that this simulation does not converge, in the end. This is also in definite disagreement with earlier simulations, and challenges further studies of the problem with other codes. In the case of our highest resolution simulation, we can report two new features: first, small scale Kelvin-Helmholtz instabilities are excited at the contact discontinuity next to the jet head. This slows down the development of the long wavelength Kelvin-Helmholtz instability and its turbulent cascade to smaller
50 CFR Table 2d to Part 679 - Species Codes-Non-FMP Species
Code of Federal Regulations, 2011 CFR
2011-10-01
... (unspecified) 625 Lamprey, pacific 600 Lingcod 130 Lumpsucker 216 Pacific flatnose 260 Pacific hagfish 212 Pacific hake 112 Pacific lamprey 600 Pacific saury 220 Pacific tomcod 250 Poacher (Family Algonidae) 219... description Code Arctic char, anadromous 521 Dolly varden, anadromous 531 Eels or eel-like fish 210 Eel,...
TOPAZ - a finite element heat conduction code for analyzing 2-D solids
Shapiro, A.B.
1984-03-01
TOPAZ is a two-dimensional implicit finite element computer code for heat conduction analysis. This report provides a user's manual for TOPAZ and a description of the numerical algorithms used. Sample problems with analytical solutions are presented. TOPAZ has been implemented on the CRAY and VAX computers.
NASA Astrophysics Data System (ADS)
Pan, Li-Hua; Hou, Peng-Fei; Chen, Jia-Yun
2016-08-01
The 2D steady-state solutions regarding the expressions of stress and strain for fluid-saturated, orthotropic, poroelastic plane are derived in this paper. For this object, the general solutions of the corresponding governing equation are first obtained and expressed in harmonic functions. Based on these compact general solutions, the suitable harmonic functions with undetermined constants for line fluid source in the interior of infinite poroelastic body and a line fluid source on the surface of semi-infinite poroelastic body are presented, respectively. The fundamental solutions can be obtained by substituting these functions into the general solution, and the undetermined constants can be obtained by the continuous conditions, equilibrium conditions and boundary conditions.
Vlasov Fluid stability of a 2-D plasma with a linear magnetic field null
Kim, J.S.
1984-01-01
Vlasov Fluid stability of a 2-dimensional plasma near an O type magnetic null is investigated. Specifically, an elongated Z-pinch is considered, and applied to Field Reversed Configurations at Los Alamos National Laboratory by making a cylindrical approximation of the compact torus. The orbits near an elliptical O type null are found to be very complicated; the orbits are large and some are stochastic. The kinetic corrections to magnetohydrodynamics (MHD) are investigated by evaluating the expectation values of the growth rates of a Vlasov Fluid dispersion functional by using a set of trial functions based on ideal MHD. The dispersion functional involves fluid parts and orbit dependent parts. The latter involves phase integral of two time correlations. The phase integral is replaced by the time integral both for the regular and for the stochastic orbits. Two trial functions are used; one has a large displacement near the null and the other away from the null.
NASA Astrophysics Data System (ADS)
Yamada, Susumu; Kitamura, Akihiro; Kurikami, Hiroshi; Machida, Masahiko
2015-04-01
Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on March 2011 released significant quantities of radionuclides to atmosphere. The most significant nuclide is radioactive cesium isotopes. Therefore, the movement of the cesium is one of the critical issues for the environmental assessment. Since the cesium is strongly sorbed by soil particles, the cesium transport can be regarded as the sediment transport which is mainly brought about by the aquatic system such as a river and a lake. In this research, our target is the sediment transport on Ogaki dam reservoir which is located in about 16 km northwest from FDNPP. The reservoir is one of the principal irrigation dam reservoirs in Fukushima Prefecture and its upstream river basin was heavily contaminated by radioactivity. We simulate the sediment transport on the reservoir using 2-D river simulation code named Nays2D originally developed by Shimizu et al. (The latest version of Nays2D is available as a code included in iRIC (http://i-ric.org/en/), which is a river flow and riverbed variation analysis software package). In general, a 2-D simulation code requires a huge amount of calculation time. Therefore, we parallelize the code and execute it on a parallel computer. We examine the relationship between the behavior of the sediment transport and the height of the reservoir exit. The simulation result shows that almost all the sand that enter into the reservoir deposit close to the entrance of the reservoir for any height of the exit. The amounts of silt depositing within the reservoir slightly increase by raising the height of the exit. However, that of the clay dramatically increases. Especially, more than half of the clay deposits, if the exit is sufficiently high. These results demonstrate that the water level of the reservoir has a strong influence on the amount of the clay discharged from the reservoir. As a result, we conclude that the tuning of the water level has a possibility for controlling the
2D numerical modelling of fluid percolation in the subduction zone
NASA Astrophysics Data System (ADS)
Dymkova, D.; Gerya, T.; Podladchikov, Y.
2012-04-01
Subducting slab dehydration and resulting aqueous fluid percolation triggers partial melting in the mantle wedge and is accompanied with the further melt percolation through the porous space to the region above the slab. This problem is a complex coupled chemical, thermal and mechanical process responsible for the magmatic arcs formation and change of the mantle wedge properties. We have created a two-dimensional model of a two-phase flow in a porous media solving a coupled Darcy-Stokes system of equations for two incompressible media for the case of nonlinear visco-plastic rheology of solid matrix. Our system of equation is expanded for the high-porosity limits and stabilized for the case of high porosity contrasts. We use a finite-difference method with fully staggered grid in a combination with marker-in-cell technique for advection of fluid and solid phase. We performed a comparison with a benchmark of a thermal convection in a porous media in a bottom-heated box to verify the interdependency of Rayleigh and Nusselt numbers with earlier obtained ones (Cherkaoui & Wilcock, 1999). We have demonstrated the stability and robustness of the algorithm in case of strongly non-linear visco-plastic rheology of solid including cases with localization of both deformation and porous flow along spontaneously forming shear bands. We have checked our model for the forming of localized porous channels under a simple shear stress (Katz et al, 2006). We have developed a setup of a self-initiating due to gravitational instability subduction. With our coupled fluid-solid flow we have achieved a self-consistent water downward suction by a slab bending predicted by the other models with a simplified fluid kinematical motion implementation (Faccenda et al, 2009). With this setup we have obtained a self-consistent upper crust weakening by a porous fluid pressure which was theoretically assumed in the previously existing subduction models (Gerya & Meilick, 2011; Faccenda et al, 2009
2-D Circulation Control Airfoil Benchmark Experiments Intended for CFD Code Validation
NASA Technical Reports Server (NTRS)
Englar, Robert J.; Jones, Gregory S.; Allan, Brian G.; Lin, Johb C.
2009-01-01
A current NASA Research Announcement (NRA) project being conducted by Georgia Tech Research Institute (GTRI) personnel and NASA collaborators includes the development of Circulation Control (CC) blown airfoils to improve subsonic aircraft high-lift and cruise performance. The emphasis of this program is the development of CC active flow control concepts for both high-lift augmentation, drag control, and cruise efficiency. A collaboration in this project includes work by NASA research engineers, whereas CFD validation and flow physics experimental research are part of NASA s systematic approach to developing design and optimization tools for CC applications to fixed-wing aircraft. The design space for CESTOL type aircraft is focusing on geometries that depend on advanced flow control technologies that include Circulation Control aerodynamics. The ability to consistently predict advanced aircraft performance requires improvements in design tools to include these advanced concepts. Validation of these tools will be based on experimental methods applied to complex flows that go beyond conventional aircraft modeling techniques. This paper focuses on recent/ongoing benchmark high-lift experiments and CFD efforts intended to provide 2-D CFD validation data sets related to NASA s Cruise Efficient Short Take Off and Landing (CESTOL) study. Both the experimental data and related CFD predictions are discussed.
Efficient simulation of pitch angle collisions in a 2+2-D Eulerian Vlasov code
NASA Astrophysics Data System (ADS)
Banks, Jeff; Berger, R.; Brunner, S.; Tran, T.
2014-10-01
Here we discuss pitch angle scattering collisions in the context of the Eulerian-based kinetic code LOKI that evolves the Vlasov-Poisson system in 2+2-dimensional phase space. The collision operator is discretized using 4th order accurate conservative finite-differencing. The treatment of the Vlasov operator in phase-space uses an approach based on a minimally diffuse, fourth-order-accurate discretization (Banks and Hittinger, IEEE T. Plasma Sci. 39, 2198). The overall scheme is therefore discretely conservative and controls unphysical oscillations. Some details of the numerical scheme will be presented, and the implementation on modern highly concurrent parallel computers will be discussed. We will present results of collisional effects on linear and non-linear Landau damping of electron plasma waves (EPWs). In addition we will present initial results showing the effect of collisions on the evolution of EPWs in two space dimensions. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the LDRD program at LLNL under project tracking code 12-ERD-061.
A 2D forward and inverse code for streaming potential problems
NASA Astrophysics Data System (ADS)
Soueid Ahmed, A.; Jardani, A.; Revil, A.
2013-12-01
The self-potential method corresponds to the passive measurement of the electrical field in response to the occurrence of natural sources of current in the ground. One of these sources corresponds to the streaming current associated with the flow of the groundwater. We can therefore apply the self- potential method to recover non-intrusively some information regarding the groundwater flow. We first solve the forward problem starting with the solution of the groundwater flow problem, then computing the source current density, and finally solving a Poisson equation for the electrical potential. We use the finite-element method to solve the relevant partial differential equations. In order to reduce the number of (petrophysical) model parameters required to solve the forward problem, we introduced an effective charge density tensor of the pore water, which can be determined directly from the permeability tensor for neutral pore waters. The second aspect of our work concerns the inversion of the self-potential data using Tikhonov regularization with smoothness and weighting depth constraints. This approach accounts for the distribution of the electrical resistivity, which can be independently and approximately determined from electrical resistivity tomography. A numerical code, SP2DINV, has been implemented in Matlab to perform both the forward and inverse modeling. Three synthetic case studies are discussed.
Comparing a 2D fluid model of the DC planar magnetron cathode to experiments
Garcia, M.
1996-05-01
Planar magnetron cathodes have arching magnetic field lines which concentrate plasma density near the electrode surface. This enhances the ion bombardment of the surface and the yield of sputtered atoms. Magnetron cathodes are used in the Plasma Electrode Pockels Cell (PEPC) devices of the Laser Program because they provide for significantly higher conduction than do glow discharges. An essential feature of magnetron cathodes is that the vector product of the perpendicular electric field, E[sub y], with the parallel component of the magnetic field, B[sub x], forms a closed track with a circulating current along the cathode surface. An analytical, 2D, two component, quasi-neutral, continuum model yields formulas for the plasma density, the total and component current densities, the electric field, and the positive electrical potential, between the cathode surface and a distant, uniform plasma. For a specific gas, the free parameters are electron temperature, gas number density, and total current. The model is applied to the interpretation of experimental data from the PEPC device, as well as a small vacuum facility for testing magnetron cathodes. Finally, the model has been applied to generate cross sectional views of a PEPC magnetron cathode track.
Anomalous diffusion of an ellipsoid in quasi-2D active fluids
NASA Astrophysics Data System (ADS)
Peng, Yi; Yang, Ou; Tang, Chao; Cheng, Xiang
Enhanced diffusion of a tracer particle is a unique feature in active fluids. Here, we studied the diffusion of an ellipsoid in a free-standing film of E. coli. Particle diffusion is linearly enhanced at low bacterial concentrations, whereas a non-linear enhancement is observed at high bacterial concentrations due to the giant fluctuation. More importantly, we uncover an anomalous coupling between the translational and rotational degrees of freedom that is strictly prohibited in the classical Brownian diffusion. Combining experiments with theoretical modeling, we show that such an anomaly arises from the stretching flow induced by the force dipole of swimming bacteria. Our work illustrates a novel universal feature of active matter and transforms the understanding of fundamental transport processes in microbiological systems. ACS Petroleum Research Fund #54168-DNI9, NSF Faculty Early Career Development Program, DMR-1452180.
A New Cell-Centered Implicit Numerical Scheme for Ions in the 2-D Axisymmetric Code Hall2de
NASA Technical Reports Server (NTRS)
Lopez Ortega, Alejandro; Mikellides, Ioannis G.
2014-01-01
We present a new algorithm in the Hall2De code to simulate the ion hydrodynamics in the acceleration channel and near plume regions of Hall-effect thrusters. This implementation constitutes an upgrade of the capabilities built in the Hall2De code. The equations of mass conservation and momentum for unmagnetized ions are solved using a conservative, finite-volume, cell-centered scheme on a magnetic-field-aligned grid. Major computational savings are achieved by making use of an implicit predictor/multi-corrector algorithm for time evolution. Inaccuracies in the prediction of the motion of low-energy ions in the near plume in hydrodynamics approaches are addressed by implementing a multi-fluid algorithm that tracks ions of different energies separately. A wide range of comparisons with measurements are performed to validate the new ion algorithms. Several numerical experiments with the location and value of the anomalous collision frequency are also presented. Differences in the plasma properties in the near-plume between the single fluid and multi-fluid approaches are discussed. We complete our validation by comparing predicted erosion rates at the channel walls of the thruster with measurements. Erosion rates predicted by the plasma properties obtained from simulations replicate accurately measured rates of erosion within the uncertainty range of the sputtering models employed.
NASA Astrophysics Data System (ADS)
Velioǧlu, Deniz; Cevdet Yalçıner, Ahmet; Zaytsev, Andrey
2016-04-01
Tsunamis are huge waves with long wave periods and wave lengths that can cause great devastation and loss of life when they strike a coast. The interest in experimental and numerical modeling of tsunami propagation and inundation increased considerably after the 2011 Great East Japan earthquake. In this study, two numerical codes, FLOW 3D and NAMI DANCE, that analyze tsunami propagation and inundation patterns are considered. Flow 3D simulates linear and nonlinear propagating surface waves as well as long waves by solving three-dimensional Navier-Stokes (3D-NS) equations. NAMI DANCE uses finite difference computational method to solve 2D depth-averaged linear and nonlinear forms of shallow water equations (NSWE) in long wave problems, specifically tsunamis. In order to validate these two codes and analyze the differences between 3D-NS and 2D depth-averaged NSWE equations, two benchmark problems are applied. One benchmark problem investigates the runup of long waves over a complex 3D beach. The experimental setup is a 1:400 scale model of Monai Valley located on the west coast of Okushiri Island, Japan. Other benchmark problem is discussed in 2015 National Tsunami Hazard Mitigation Program (NTHMP) Annual meeting in Portland, USA. It is a field dataset, recording the Japan 2011 tsunami in Hilo Harbor, Hawaii. The computed water surface elevation and velocity data are compared with the measured data. The comparisons showed that both codes are in fairly good agreement with each other and benchmark data. The differences between 3D-NS and 2D depth-averaged NSWE equations are highlighted. All results are presented with discussions and comparisons. Acknowledgements: Partial support by Japan-Turkey Joint Research Project by JICA on earthquakes and tsunamis in Marmara Region (JICA SATREPS - MarDiM Project), 603839 ASTARTE Project of EU, UDAP-C-12-14 project of AFAD Turkey, 108Y227, 113M556 and 213M534 projects of TUBITAK Turkey, RAPSODI (CONCERT_Dis-021) of CONCERT
Kawamura, E.; Verboncoeur, J.P.; Birdsall, C.K.
1996-12-31
The goal is to obtain the ion angular and energy distributions at the wafer of inductive and capacitive discharges. To do this on a standard uniform mesh with particle codes alone would be impractical because of the long time scale nature of the problem (i.e., 10{sup 6} time steps). A solution is to use a fluid code to simulate the bulk source region, while using a particle-in-cell code to simulate the sheath region. Induct95 is a 2d fluid code which can simulate inductive and capacitive discharges. Though it does not resolve the sheath region near the wafer, it provides diagnostics for the collisional bulk plasma (i.e., potentials, temperatures, fluxes, etc.). Also, fluid codes converge to equilibrium much faster than particle codes in collisional regimes PDP1 is a 1d3v particle-in-cell code which can simulate rf discharges. It can resolve the sheath region and obtain the ion angular and energy distributions at the wafer target. The overall running time is expected to be that of the fluid code.
NASA Astrophysics Data System (ADS)
Choquard, Ph.; Vuffray, M.
2014-10-01
The coupling between dilatation and vorticity, two coexisting and fundamental processes in fluid dynamics (Wu et al., 2006, pp. 3, 6) is investigated here, in the simplest cases of inviscid 2D isotropic Burgers and pressureless Euler-Coriolis fluids respectively modeled by single vortices confined in compressible, local, inertial and global, rotating, environments. The field equations are established, inductively, starting from the equations of the characteristics solved with an initial Helmholtz decomposition of the velocity fields namely a vorticity free and a divergence free part (Wu et al., 2006, Sects. 2.3.2, 2.3.3) and, deductively, by means of a canonical Hamiltonian Clebsch like formalism (Clebsch, 1857, 1859), implying two pairs of conjugate variables. Two vector valued fields are constants of the motion: the velocity field in the Burgers case and the momentum field per unit mass in the Euler-Coriolis one. Taking advantage of this property, a class of solutions for the mass densities of the fluids is given by the Jacobian of their sum with respect to the actual coordinates. Implementation of the isotropy hypothesis entails a radial dependence of the velocity potentials and of the stream functions associated to the compressible and to the rotational part of the fluids and results in the cancellation of the dilatation-rotational cross terms in the Jacobian. A simple expression is obtained for all the radially symmetric Jacobians occurring in the theory. Representative examples of regular and singular solutions are shown and the competition between dilatation and vorticity is illustrated. Inspired by thermodynamical, mean field theoretical analogies, a genuine variational formula is proposed which yields unique measure solutions for the radially symmetric fluid densities investigated. We stress that this variational formula, unlike the Hopf-Lax formula, enables us to treat systems which are both compressible and rotational. Moreover in the one
Hallquist, J.O.
1982-02-01
This revised report provides an updated user's manual for DYNA2D, an explicit two-dimensional axisymmetric and plane strain finite element code for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. A contact-impact algorithm permits gaps and sliding along material interfaces. By a specialization of this algorithm, such interfaces can be rigidly tied to admit variable zoning without the need of transition regions. Spatial discretization is achieved by the use of 4-node solid elements, and the equations-of motion are integrated by the central difference method. An interactive rezoner eliminates the need to terminate the calculation when the mesh becomes too distorted. Rather, the mesh can be rezoned and the calculation continued. The command structure for the rezoner is described and illustrated by an example.
NASA Astrophysics Data System (ADS)
Shaari, M. F.; Abu Bakar, H.; Nordin, N.; Saw, S. K.; Samad, Z.
2013-12-01
Contractile body is an alternative mechanism instead of rotating blade propeller to generate water jet for locomotion. The oscillating motion of the actuator at different frequencies varies the pressure and volume of the pressure chamber in time to draw in and jet out the water at a certain mass flow rate. The aim of this research was to analyze the influence of the actuating frequency of the fluid flow in the pressure chamber of the thruster during this inflation-deflation process. A 70mm × 70mm × 18mm (L × W × T) 2D water jet thruster was fabricated for this purpose. The contractile function was driven using two lateral pneumatic actuators where the fluid flow analysis was focused on the X-Y plane vector. Observation was carried out using a video camera and Matlab image measurement technique to determine the volume of the flowing mass. The result demonstrated that the greater actuating frequency decreases the fluid flow rate and the Reynolds number. This observation shows that the higher frequency would give a higher mass flow rate during water jet generation.
Eyler, L.L.; Budden, M.J.
1985-03-01
The objective of this work is to assess prediction capabilities and features of the MAGNUM-2D computer code in relation to its intended use in the Basalt Waste Isolation Project (BWIP). This objective is accomplished through a code verification and benchmarking task. Results are documented which support correctness of prediction capabilities in areas of intended model application. 10 references, 43 figures, 11 tables.
Code verification for unsteady 3-D fluid-solid interaction problems
NASA Astrophysics Data System (ADS)
Yu, Kintak Raymond; Étienne, Stéphane; Hay, Alexander; Pelletier, Dominique
2015-12-01
This paper describes a procedure to synthesize Manufactured Solutions for Code Verification of an important class of Fluid-Structure Interaction (FSI) problems whose behaviors can be modeled as rigid body vibrations in incompressible fluids. We refer this class of FSI problems as Fluid-Solid Interaction problems, which can be found in many practical engineering applications. The methodology can be utilized to develop Manufactured Solutions for both 2-D and 3-D cases. We demonstrate the procedure with our numerical code. We present details of the formulation and methodology. We also provide the reasonings behind our proposed approach. Results from grid and time step refinement studies confirm the verification of our solver and demonstrate the versatility of the simple synthesis procedure. In addition, the results also demonstrate that the modified decoupled approach to verify flow problems with high-order time-stepping schemes can be employed equally well to verify code for multi-physics problems (here, those of the Fluid-Solid Interaction) when the numerical discretization is based on the Method of Lines.
LUDWIG: A parallel Lattice-Boltzmann code for complex fluids
NASA Astrophysics Data System (ADS)
Desplat, Jean-Christophe; Pagonabarraga, Ignacio; Bladon, Peter
2001-03-01
This paper describes Ludwig, a versatile code for the simulation of Lattice-Boltzmann (LB) models in 3D on cubic lattices. In fact, Ludwig is not a single code, but a set of codes that share certain common routines, such as I/O and communications. If Ludwig is used as intended, a variety of complex fluid models with different equilibrium free energies are simple to code, so that the user may concentrate on the physics of the problem, rather than on parallel computing issues. Thus far, Ludwig's main application has been to symmetric binary fluid mixtures. We first explain the philosophy and structure of Ludwig which is argued to be a very effective way of developing large codes for academic consortia. Next we elaborate on some parallel implementation issues such as parallel I/O, and the use of MPI to achieve full portability and good efficiency on both MPP and SMP systems. Finally, we describe how to implement generic solid boundaries, and look in detail at the particular case of a symmetric binary fluid mixture near a solid wall. We present a novel scheme for the thermodynamically consistent simulation of wetting phenomena, in the presence of static and moving solid boundaries, and check its performance.
Code System for Fluid-Structure Interaction Analysis.
Energy Science and Technology Software Center (ESTSC)
2001-05-30
Version 00 PELE-IC is a two-dimensional semi-implicit Eulerian hydrodynamics program for the solution of incompressible flow coupled to flexible structures. The code was developed to calculate fluid-structure interactions and bubble dynamics of a pressure-suppression system following a loss-of-coolant accident (LOCA). The fluid, structure, and coupling algorithms have been verified by calculation of benchmark problems and air and steam blowdown experiments. The code is written for both plane and cylindrical coordinates. The coupling algorithm is generalmore » enough to handle a wide variety of structural shapes. The concepts of void fractions and interface orientation are used to track the movement of free surfaces, allowing great versatility in following fluid-gas interfaces both for bubble definition and water surface motion without the use of marker particles.« less
Experimental methodology for computational fluid dynamics code validation
Aeschliman, D.P.; Oberkampf, W.L.
1997-09-01
Validation of Computational Fluid Dynamics (CFD) codes is an essential element of the code development process. Typically, CFD code validation is accomplished through comparison of computed results to previously published experimental data that were obtained for some other purpose, unrelated to code validation. As a result, it is a near certainty that not all of the information required by the code, particularly the boundary conditions, will be available. The common approach is therefore unsatisfactory, and a different method is required. This paper describes a methodology developed specifically for experimental validation of CFD codes. The methodology requires teamwork and cooperation between code developers and experimentalists throughout the validation process, and takes advantage of certain synergisms between CFD and experiment. The methodology employs a novel uncertainty analysis technique which helps to define the experimental plan for code validation wind tunnel experiments, and to distinguish between and quantify various types of experimental error. The methodology is demonstrated with an example of surface pressure measurements over a model of varying geometrical complexity in laminar, hypersonic, near perfect gas, 3-dimensional flow.
Fluid-Rock Interaction Models: Code Release and Results
NASA Astrophysics Data System (ADS)
Bolton, E. W.
2006-12-01
Numerical models our group has developed for understanding the role of kinetic processes during fluid-rock interaction will be released free to the public. We will also present results that highlight the importance of kinetic processes. The author is preparing manuals describing the numerical methods used, as well as "how-to" guides for using the models. The release will include input files, full in-line code documentation of the FORTRAN source code, and instructions for use of model output for visualization and analysis. The aqueous phase (weathering) and supercritical (mixed-volatile metamorphic) fluid flow and reaction models for porous media will be released separately. These codes will be useful as teaching and research tools. The codes may be run on current generation personal computers. Although other codes are available for attacking some of the problems we address, unique aspects of our codes include sub-grid-scale grain models to track grain size changes, as well as dynamic porosity and permeability. Also, as the flow field can change significantly over the course of the simulation, efficient solution methods have been developed for the repeated solution of Poisson-type equations that arise from Darcy's law. These include sparse-matrix methods as well as the even more efficient spectral-transform technique. Results will be presented for kinetic control of reaction pathways and for heterogeneous media. Codes and documentation for modeling intra-grain diffusion of trace elements and isotopes, and exchange of these between grains and moving fluids will also be released. The unique aspect of this model is that it includes concurrent diffusion and grain growth or dissolution for multiple mineral types (low-diffusion regridding has been developed to deal with the moving-boundary problem at the fluid/mineral interface). Results for finite diffusion rates will be compared to batch and fractional melting models. Additional code and documentation will be released
NASA Astrophysics Data System (ADS)
Kirnev, G.; Fundamenski, W.; Corrigan, G.
2007-06-01
The scrape-off layer (SOL) of the JET tokamak has been modelled using a two-dimensional plasma/neutral code, EDGE2D/NIMBUS, with variable transport coefficients, chosen according to nine candidate theories for radial heat transport in the SOL. Comparison of the radial power width on the outer divertor plates, λq, predicted by modelling and measured experimentally in L-mode and ELM-averaged H-mode at JET is presented. Transport coefficients based on classical and neo-classical ion conduction are found to offer the best agreement with experimentally measured λq magnitude and scaling with target power, upstream density and toroidal field. These results reinforce the findings of an earlier study, based on a simplified model of the SOL (Chankin 1997 Plasma Phys. Control. Fusion 39 1059), and support the earlier estimate of the power width at the entrance of the outer divertor volume in ITER, λq ap 4 mm mapped to the outer mid-plane (Fundamenski et al 2004 Nucl. Fusion 44 20).
High-Performance Java Codes for Computational Fluid Dynamics
NASA Technical Reports Server (NTRS)
Riley, Christopher; Chatterjee, Siddhartha; Biswas, Rupak; Biegel, Bryan (Technical Monitor)
2001-01-01
The computational science community is reluctant to write large-scale computationally -intensive applications in Java due to concerns over Java's poor performance, despite the claimed software engineering advantages of its object-oriented features. Naive Java implementations of numerical algorithms can perform poorly compared to corresponding Fortran or C implementations. To achieve high performance, Java applications must be designed with good performance as a primary goal. This paper presents the object-oriented design and implementation of two real-world applications from the field of Computational Fluid Dynamics (CFD): a finite-volume fluid flow solver (LAURA, from NASA Langley Research Center), and an unstructured mesh adaptation algorithm (2D_TAG, from NASA Ames Research Center). This work builds on our previous experience with the design of high-performance numerical libraries in Java. We examine the performance of the applications using the currently available Java infrastructure and show that the Java version of the flow solver LAURA performs almost within a factor of 2 of the original procedural version. Our Java version of the mesh adaptation algorithm 2D_TAG performs within a factor of 1.5 of its original procedural version on certain platforms. Our results demonstrate that object-oriented software design principles are not necessarily inimical to high performance.
Mosleh-Shirazi, Mohammad Amin; Zarrini-Monfared, Zinat; Karbasi, Sareh; Zamani, Ali
2014-01-01
Two-dimensional (2D) arrays of thick segmented scintillators are of interest as X-ray detectors for both 2D and 3D image-guided radiotherapy (IGRT). Their detection process involves ionizing radiation energy deposition followed by production and transport of optical photons. Only a very limited number of optical Monte Carlo simulation models exist, which has limited the number of modeling studies that have considered both stages of the detection process. We present ScintSim1, an in-house optical Monte Carlo simulation code for 2D arrays of scintillation crystals, developed in the MATLAB programming environment. The code was rewritten and revised based on an existing program for single-element detectors, with the additional capability to model 2D arrays of elements with configurable dimensions, material, etc., The code generates and follows each optical photon history through the detector element (and, in case of cross-talk, the surrounding ones) until it reaches a configurable receptor, or is attenuated. The new model was verified by testing against relevant theoretically known behaviors or quantities and the results of a validated single-element model. For both sets of comparisons, the discrepancies in the calculated quantities were all <1%. The results validate the accuracy of the new code, which is a useful tool in scintillation detector optimization. PMID:24600168
Mosleh-Shirazi, Mohammad Amin; Zarrini-Monfared, Zinat; Karbasi, Sareh; Zamani, Ali
2014-01-01
Two-dimensional (2D) arrays of thick segmented scintillators are of interest as X-ray detectors for both 2D and 3D image-guided radiotherapy (IGRT). Their detection process involves ionizing radiation energy deposition followed by production and transport of optical photons. Only a very limited number of optical Monte Carlo simulation models exist, which has limited the number of modeling studies that have considered both stages of the detection process. We present ScintSim1, an in-house optical Monte Carlo simulation code for 2D arrays of scintillation crystals, developed in the MATLAB programming environment. The code was rewritten and revised based on an existing program for single-element detectors, with the additional capability to model 2D arrays of elements with configurable dimensions, material, etc., The code generates and follows each optical photon history through the detector element (and, in case of cross-talk, the surrounding ones) until it reaches a configurable receptor, or is attenuated. The new model was verified by testing against relevant theoretically known behaviors or quantities and the results of a validated single-element model. For both sets of comparisons, the discrepancies in the calculated quantities were all <1%. The results validate the accuracy of the new code, which is a useful tool in scintillation detector optimization. PMID:24600168
Methodology for computational fluid dynamics code verification/validation
Oberkampf, W.L.; Blottner, F.G.; Aeschliman, D.P.
1995-07-01
The issues of verification, calibration, and validation of computational fluid dynamics (CFD) codes has been receiving increasing levels of attention in the research literature and in engineering technology. Both CFD researchers and users of CFD codes are asking more critical and detailed questions concerning the accuracy, range of applicability, reliability and robustness of CFD codes and their predictions. This is a welcomed trend because it demonstrates that CFD is maturing from a research tool to the world of impacting engineering hardware and system design. In this environment, the broad issue of code quality assurance becomes paramount. However, the philosophy and methodology of building confidence in CFD code predictions has proven to be more difficult than many expected. A wide variety of physical modeling errors and discretization errors are discussed. Here, discretization errors refer to all errors caused by conversion of the original partial differential equations to algebraic equations, and their solution. Boundary conditions for both the partial differential equations and the discretized equations will be discussed. Contrasts are drawn between the assumptions and actual use of numerical method consistency and stability. Comments are also made concerning the existence and uniqueness of solutions for both the partial differential equations and the discrete equations. Various techniques are suggested for the detection and estimation of errors caused by physical modeling and discretization of the partial differential equations.
Code Verification of the HIGRAD Computational Fluid Dynamics Solver
Van Buren, Kendra L.; Canfield, Jesse M.; Hemez, Francois M.; Sauer, Jeremy A.
2012-05-04
The purpose of this report is to outline code and solution verification activities applied to HIGRAD, a Computational Fluid Dynamics (CFD) solver of the compressible Navier-Stokes equations developed at the Los Alamos National Laboratory, and used to simulate various phenomena such as the propagation of wildfires and atmospheric hydrodynamics. Code verification efforts, as described in this report, are an important first step to establish the credibility of numerical simulations. They provide evidence that the mathematical formulation is properly implemented without significant mistakes that would adversely impact the application of interest. Highly accurate analytical solutions are derived for four code verification test problems that exercise different aspects of the code. These test problems are referred to as: (i) the quiet start, (ii) the passive advection, (iii) the passive diffusion, and (iv) the piston-like problem. These problems are simulated using HIGRAD with different levels of mesh discretization and the numerical solutions are compared to their analytical counterparts. In addition, the rates of convergence are estimated to verify the numerical performance of the solver. The first three test problems produce numerical approximations as expected. The fourth test problem (piston-like) indicates the extent to which the code is able to simulate a 'mild' discontinuity, which is a condition that would typically be better handled by a Lagrangian formulation. The current investigation concludes that the numerical implementation of the solver performs as expected. The quality of solutions is sufficient to provide credible simulations of fluid flows around wind turbines. The main caveat associated to these findings is the low coverage provided by these four problems, and somewhat limited verification activities. A more comprehensive evaluation of HIGRAD may be beneficial for future studies.
Numerical model of water flow and solute accumulation in vertisols using HYDRUS 2D/3D code
NASA Astrophysics Data System (ADS)
Weiss, Tomáš; Dahan, Ofer; Turkeltub, Tuvia
2015-04-01
boundary to the wall of the crack (so that the solute can accumulate due to evaporation on the crack block wall, and infiltrating fresh water can push the solute further down) - in order to do so, HYDRUS 2D/3D code had to be modified by its developers. Unconventionally, the main fitting parameters were: parameter a and n in the soil water retention curve and saturated hydraulic conductivity. The amount of infiltrated water (within a reasonable range), the infiltration function in the crack and the actual evaporation from the crack were also used as secondary fitting parameters. The model supports the previous findings that significant amount (~90%) of water from rain events must infiltrate through the crack. It was also noted that infiltration from the crack has to be increasing with depth and that the highest infiltration rate should be somewhere between 1-3m. This paper suggests a new way how to model vertisols in semi-arid regions. It also supports the previous findings about vertisols: especially, the utmost importance of soil cracks as preferential pathways for water and contaminants and soil cracks as deep evaporators.
Wind tunnel requirements for computational fluid dynamics code verification
NASA Technical Reports Server (NTRS)
Marvin, Joseph G.
1987-01-01
The role of experiment in the development of Computational Fluid Dynamics (CFD) for aerodynamic flow field prediction is discussed. Requirements for code verification from two sources that pace the development of CFD are described for: (1) development of adequate flow modeling, and (2) establishment of confidence in the use of CFD to predict complex flows. The types of data needed and their accuracy differs in detail and scope and leads to definite wind tunnel requirements. Examples of testing to assess and develop turbulence models, and to verify code development, are used to establish future wind tunnel testing requirements. Versatility, appropriate scale and speed range, accessibility for nonintrusive instrumentation, computerized data systems, and dedicated use for verification were among the more important requirements identified.
NASA Technical Reports Server (NTRS)
Hanson, Donald B.
1994-01-01
A two dimensional linear aeroacoustic theory for rotor/stator interaction with unsteady coupling was derived and explored in Volume 1 of this report. Computer program CUP2D has been written in FORTRAN embodying the theoretical equations. This volume (Volume 2) describes the structure of the code, installation and running, preparation of the input file, and interpretation of the output. A sample case is provided with printouts of the input and output. The source code is included with comments linking it closely to the theoretical equations in Volume 1.
This study is a part of an ongoing research project that aims at assessing the environmental benefits of DNAPL removal. The laboratory part of the research project is to examine the functional relationship between DNAPL architecture, mass removal and contaminant mass flux in 2-D ...
nMHDust: A 4-Fluid Partially Ionized Dusty Plasma Code
NASA Astrophysics Data System (ADS)
Lazerson, Samuel
2008-11-01
nMHDust is a next generation 4-fluid partially ionized magnetized dusty plasma code, treating the inertial dynamics of dust, ion and neutral components. Coded in ANSI C, the numerical method is based on the MHDust 3-fluid fully ionized dusty plasma code. This code expands the features of the MHDust code to include ionization/recombination effects and the netCDF data format. Tests of this code include: ionization instabilities, wave mode propagation (electromagnetic and acoustic), shear-flow instabilities, and magnetic reconnection. Relevant parameters for the space environment are considered, allowing a comparison to be made with previous dusty plasma codes (MHDust and DENISIS). The utility of the code is expanded through the possibility of a small dust mass. This allows nMHDust to be used as a 2-ion plasma code. nMHDust completes the array of fluid dusty plasma codes available for numerical investigations into nonlinear phenomena in the field of astrophysical dusty plasmas.
Shapiro, A.B.
1983-08-01
The computer code FACET calculates the radiation geometric view factor (alternatively called shape factor, angle factor, or configuration factor) between surfaces for axisymmetric, two-dimensional planar and three-dimensional geometries with interposed third surface obstructions. FACET was developed to calculate view factors for input to finite-element heat-transfer analysis codes. The first section of this report is a brief review of previous radiation-view-factor computer codes. The second section presents the defining integral equation for the geometric view factor between two surfaces and the assumptions made in its derivation. Also in this section are the numerical algorithms used to integrate this equation for the various geometries. The third section presents the algorithms used to detect self-shadowing and third-surface shadowing between the two surfaces for which a view factor is being calculated. The fourth section provides a user's input guide followed by several example problems.
Kasinathan, N.; Rajakumar, A.; Vaidyanathan, G.; Chetal, S.C.
1995-09-01
Post shutdown decay heat removal is an important safety requirement in any nuclear system. In order to improve the reliability of this function, Liquid metal (sodium) cooled fast breeder reactors (LMFBR) are equipped with redundant hot pool dipped immersion coolers connected to natural draught air cooled heat exchangers through intermediate sodium circuits. During decay heat removal, flow through the core, immersion cooler primary side and in the intermediate sodium circuits are also through natural convection. In order to establish the viability and validate computer codes used in making predictions, a 1:20 scale experimental model called RAMONA with water as coolant has been built and experimental simulation of decay heat removal situation has been performed at KfK Karlsruhe. Results of two such experiments have been compiled and published as benchmarks. This paper brings out the results of the numerical simulation of one of the benchmark case through a 1D/2D coupled code system, DHDYN-1D/THYC-2D and the salient features of the comparisons. Brief description of the formulations of the codes are also included.
VFLOW2D - A Vorte-Based Code for Computing Flow Over Elastically Supported Tubes and Tube Arrays
WOLFE,WALTER P.; STRICKLAND,JAMES H.; HOMICZ,GREGORY F.; GOSSLER,ALBERT A.
2000-10-11
A numerical flow model is developed to simulate two-dimensional fluid flow past immersed, elastically supported tube arrays. This work is motivated by the objective of predicting forces and motion associated with both deep-water drilling and production risers in the oil industry. This work has other engineering applications including simulation of flow past tubular heat exchangers or submarine-towed sensor arrays and the flow about parachute ribbons. In the present work, a vortex method is used for solving the unsteady flow field. This method demonstrates inherent advantages over more conventional grid-based computational fluid dynamics. The vortex method is non-iterative, does not require artificial viscosity for stability, displays minimal numerical diffusion, can easily treat moving boundaries, and allows a greatly reduced computational domain since vorticity occupies only a small fraction of the fluid volume. A gridless approach is used in the flow sufficiently distant from surfaces. A Lagrangian remap scheme is used near surfaces to calculate diffusion and convection of vorticity. A fast multipole technique is utilized for efficient calculation of velocity from the vorticity field. The ability of the method to correctly predict lift and drag forces on simple stationary geometries over a broad range of Reynolds numbers is presented.
NASA Astrophysics Data System (ADS)
Ji, Jianhua; Wang, Yanfen; Wang, Ke; Xu, Ming; Zhang, Zhipeng; Yang, Shuwen
2013-09-01
A new two-dimensional OOC (optical orthogonal codes) named PC/MOCS is constructed, using PC (prime code) for time spreading and MOCS (modified one-coincidence sequence) for wavelength hopping. Compared with PC/PC, the number of wavelengths for PC/MOCS is not limited to a prime number. Compared with PC/OCS, the length of MOCS need not be expanded to the same length of PC. PC/MOCS can be constructed flexibly, and also can use available wavelengths effectively. Theoretical analysis shows that PC/MOCS can reduce the bit error rate (BER) of OCDMA system, and can support more users than PC/PC and PC/OCS.
NASA Astrophysics Data System (ADS)
Lopes Filho, Milton C.; Nussenzveig Lopes, Helena J.; Titi, Edriss S.; Zang, Aibin
2015-06-01
The second-grade fluid equations are a model for viscoelastic fluids, with two parameters: α > 0, corresponding to the elastic response, and , corresponding to viscosity. Formally setting these parameters to 0 reduces the equations to the incompressible Euler equations of ideal fluid flow. In this article we study the limits of solutions of the second-grade fluid system, in a smooth, bounded, two-dimensional domain with no-slip boundary conditions. This class of problems interpolates between the Euler- α model (), for which the authors recently proved convergence to the solution of the incompressible Euler equations, and the Navier-Stokes case ( α = 0), for which the vanishing viscosity limit is an important open problem. We prove three results. First, we establish convergence of the solutions of the second-grade model to those of the Euler equations provided , as α → 0, extending the main result in (Lopes Filho et al., Physica D 292(293):51-61, 2015). Second, we prove equivalence between convergence (of the second-grade fluid equations to the Euler equations) and vanishing of the energy dissipation in a suitably thin region near the boundary, in the asymptotic regime , as α → 0. This amounts to a convergence criterion similar to the well-known Kato criterion for the vanishing viscosity limit of the Navier-Stokes equations to the Euler equations. Finally, we obtain an extension of Kato's classical criterion to the second-grade fluid model, valid if , as . The proof of all these results relies on energy estimates and boundary correctors, following the original idea by Kato.
TRAC code assessment using data from SCTF Core-III, a large-scale 2D/3D facility
Boyack, B.E.; Shire, P.R.; Harmony, S.C.; Rhee, G.
1988-01-01
Nine tests from the SCTF Core-III configuration have been analyzed using TRAC-PF1/MOD1. The objectives of these assessment activities were to obtain a better understanding of the phenomena occurring during the refill and reflood phases of a large-break loss-of-coolant accident, to determine the accuracy to which key parameters are calculated, and to identify deficiencies in key code correlations and models that provide closure for the differential equations defining thermal-hydraulic phenomena in pressurized water reactors. Overall, the agreement between calculated and measured values of peak cladding temperature is reasonable. In addition, TRAC adequately predicts many of the trends observed in both the integral effect and separate effect tests conducted in SCTF Core-III. The importance of assessment activities that consider potential contributors to discrepancies between the measured and calculated results arising from three sources are described as those related to (1) knowledge about the facility configuration and operation, (2) facility modeling for code input, and (3) deficiencies in code correlations and models. An example is provided. 8 refs., 7 figs., 2 tabs.
ZORNOC: a 1 1/2-D tokamak data analysis code for studying noncircular high beta plasmas
Zurro, B.; Wieland, R.M.; Murakami, M.; Swain, D.W.
1980-03-01
A new tokamak data analysis code, ZORNOC, was developed to study noncircular, high beta plasmas in the Impurity Study Experiment (ISX-B). These plasmas exhibit significant flux surface shifts and elongation in both ohmically heated and beam-heated discharges. The MHD equilibrium flux surface geometry is determined by solving the Grad-Shafranov equation based on: (1) the shape of the outermost flux surface, deduced from the magnetic loop probes; (2) a pressure profile, deduced by means of Thomson scattering data (electrons), charge exchange data (ions), and a Fokker-Planck model (fast ions); and (3) a safety factor profile, determined from the experimental data using a simple model (Z/sub eff/ = const) that is self-consistently altered while the plasma equilibrium is iterated. For beam-heated discharches the beam deposition profile is determined by means of a Monte Carlo scheme and the slowing down of the fast ions by means of an analytical solution of the Fokker-Planck equation. The code also carries out an electron power balance and calculates various confinement parameters. The code is described and examples of its operation are given.
Viriato: A Fourier-Hermite spectral code for strongly magnetized fluid-kinetic plasma dynamics
NASA Astrophysics Data System (ADS)
Loureiro, N. F.; Dorland, W.; Fazendeiro, L.; Kanekar, A.; Mallet, A.; Vilelas, M. S.; Zocco, A.
2016-09-01
We report on the algorithms and numerical methods used in Viriato, a novel fluid-kinetic code that solves two distinct sets of equations: (i) the Kinetic Reduced Electron Heating Model (KREHM) equations (Zocco and Schekochihin, 2011) (which reduce to the standard Reduced-MHD equations in the appropriate limit) and (ii) the kinetic reduced MHD (KRMHD) equations (Schekochihin et al., 2009). Two main applications of these equations are magnetized (Alfvénic) plasma turbulence and magnetic reconnection. Viriato uses operator splitting (Strang or Godunov) to separate the dynamics parallel and perpendicular to the ambient magnetic field (assumed strong). Along the magnetic field, Viriato allows for either a second-order accurate MacCormack method or, for higher accuracy, a spectral-like scheme composed of the combination of a total variation diminishing (TVD) third order Runge-Kutta method for the time derivative with a 7th order upwind scheme for the fluxes. Perpendicular to the field Viriato is pseudo-spectral, and the time integration is performed by means of an iterative predictor-corrector scheme. In addition, a distinctive feature of Viriato is its spectral representation of the parallel velocity-space dependence, achieved by means of a Hermite representation of the perturbed distribution function. A series of linear and nonlinear benchmarks and tests are presented, including a detailed analysis of 2D and 3D Orszag-Tang-type decaying turbulence, both in fluid and kinetic regimes.
Litvinenko, I. A.; Lykov, V. A.
1997-04-15
The results of numerical simulation of fast electrons motion and generated electro-magnetic fields at the picosecond pulse laser interaction with flat target are presented. The calculations were performed with PM2D code, where relativistic equation of electron motion joint with Maxwell equations is solved by particle method in cells. The efficiency of fast electrons energy conversion to the transverse electromagnetic wave of picosecond duration can reach the value 10{sup -4} for the intensity of ultrashort laser pulse at the target 10{sup 16}-10{sup 17} W/cm{sup 2}.
NASA Technical Reports Server (NTRS)
Hicks, Raymond M.; Cliff, Susan E.
1991-01-01
Full-potential, Euler, and Navier-Stokes computational fluid dynamics (CFD) codes were evaluated for use in analyzing the flow field about airfoils sections operating at Mach numbers from 0.20 to 0.60 and Reynolds numbers from 500,000 to 2,000,000. The potential code (LBAUER) includes weakly coupled integral boundary layer equations for laminar and turbulent flow with simple transition and separation models. The Navier-Stokes code (ARC2D) uses the thin-layer formulation of the Reynolds-averaged equations with an algebraic turbulence model. The Euler code (ISES) includes strongly coupled integral boundary layer equations and advanced transition and separation calculations with the capability to model laminar separation bubbles and limited zones of turbulent separation. The best experiment/CFD correlation was obtained with the Euler code because its boundary layer equations model the physics of the flow better than the other two codes. An unusual reversal of boundary layer separation with increasing angle of attack, following initial shock formation on the upper surface of the airfoil, was found in the experiment data. This phenomenon was not predicted by the CFD codes evaluated.
HT2DINV: A 2D forward and inverse code for steady-state and transient hydraulic tomography problems
NASA Astrophysics Data System (ADS)
Soueid Ahmed, A.; Jardani, A.; Revil, A.; Dupont, J. P.
2015-12-01
Hydraulic tomography is a technique used to characterize the spatial heterogeneities of storativity and transmissivity fields. The responses of an aquifer to a source of hydraulic stimulations are used to recover the features of the estimated fields using inverse techniques. We developed a 2D free source Matlab package for performing hydraulic tomography analysis in steady state and transient regimes. The package uses the finite elements method to solve the ground water flow equation for simple or complex geometries accounting for the anisotropy of the material properties. The inverse problem is based on implementing the geostatistical quasi-linear approach of Kitanidis combined with the adjoint-state method to compute the required sensitivity matrices. For undetermined inverse problems, the adjoint-state method provides a faster and more accurate approach for the evaluation of sensitivity matrices compared with the finite differences method. Our methodology is organized in a way that permits the end-user to activate parallel computing in order to reduce the computational burden. Three case studies are investigated demonstrating the robustness and efficiency of our approach for inverting hydraulic parameters.
An IPOT meshless method using DC PSE approximation for fluid flow equations in 2D and 3D geometries
NASA Astrophysics Data System (ADS)
Bourantas, G. C.; Loukopoulos, V. C.; Skouras, E. D.; Burganos, V. N.; Nikiforidis, G. C.
2016-06-01
Navier-Stokes (N-S) equations, in their primitive variable (u-v-p) formulation, are numerically solved using the Implicit Potential (IPOT) numerical scheme in the context of strong form Meshless Point Collocation (MPC) method. The unknown field functions are computed using the Discretization Correction Particle Strength Exchange (DC PSE) approximation method. The latter makes use of discrete moment conditions to derive the operator kernels, which leads to low condition number for the moment matrix compared to other meshless interpolation methods and increased stability for the numerical solution. The proposed meshless scheme is applied on 2D and 3D spatial domains, using uniform or irregular set of nodes to represent the domain. The numerical results obtained are compared against those obtained using well-established methods.
Lappala, E.G.; Healy, R.W.; Weeks, E.P.
1987-01-01
This report documents FORTRAN computer code for solving problems involving variably saturated single-phase flow in porous media. The flow equation is written with total hydraulic potential as the dependent variable, which allows straightforward treatment of both saturated and unsaturated conditions. The spatial derivatives in the flow equation are approximated by central differences, and time derivatives are approximated either by a fully implicit backward or by a centered-difference scheme. Nonlinear conductance and storage terms may be linearized using either an explicit method or an implicit Newton-Raphson method. Relative hydraulic conductivity is evaluated at cell boundaries by using either full upstream weighting, the arithmetic mean, or the geometric mean of values from adjacent cells. Nonlinear boundary conditions treated by the code include infiltration, evaporation, and seepage faces. Extraction by plant roots that is caused by atmospheric demand is included as a nonlinear sink term. These nonlinear boundary and sink terms are linearized implicitly. The code has been verified for several one-dimensional linear problems for which analytical solutions exist and against two nonlinear problems that have been simulated with other numerical models. A complete listing of data-entry requirements and data entry and results for three example problems are provided. (USGS)
A MARS-based method for estimating regional 2-D ionospheric VTEC and receiver differential code bias
NASA Astrophysics Data System (ADS)
Kao, Szu-Pyng; Chen, Yao-Chung; Ning, Fang-Shii
2014-01-01
The geometry-free linear combination of dual-frequency GNSS reference station ground observations are currently used to build the Vertical Total Electron Content (VTEC) model of the ionosphere. As it is known, besides ionospheric delays, there are differential code bias (DCB) of satellite (SDCB) and receiver (RDCB) in the geometry-free observation equation. The SDCB can be obtained using the International GNSS Service (IGS) analysis centers, but the RDCB for regional and local network receivers are not provided. Therefore, estimating the RDCB and VTEC model accurately and simultaneously is a critical factor investigated by researchers. This study uses Multivariate Adaptive Regression Splines (MARS) to estimate the VTEC approximate model and then substitutes this model in the observation equation to form the normal equation. The least squares method is used to solve the RDCB and VTEC model together. The research findings show that this method has good modeling effectiveness and the estimated RDCB has good reliability. The estimated VTEC model applied to GPS single-frequency precise point positioning has better positioning accuracy in comparison to the IGS global ionosphere map (GIM).
NASA Astrophysics Data System (ADS)
Kim, Ho Jun; Lee, Hae June
2016-06-01
The wide applicability of capacitively coupled plasma (CCP) deposition has increased the interest in developing comprehensive numerical models, but CCP imposes a tremendous computational cost when conducting a transient analysis in a three-dimensional (3D) model which reflects the real geometry of reactors. In particular, the detailed flow features of reactive gases induced by 3D geometric effects need to be considered for the precise calculation of radical distribution of reactive species. Thus, an alternative inclusive method for the numerical simulation of CCP deposition is proposed to simulate a two-dimensional (2D) CCP model based on the 3D gas flow results by simulating flow, temperature, and species fields in a 3D space at first without calculating the plasma chemistry. A numerical study of a cylindrical showerhead-electrode CCP reactor was conducted for particular cases of SiH4/NH3/N2/He gas mixture to deposit a hydrogenated silicon nitride (SiN x H y ) film. The proposed methodology produces numerical results for a 300 mm wafer deposition reactor which agree very well with the deposition rate profile measured experimentally along the wafer radius.
Two-Phase Acto-Cytosolic Fluid Flow in a Moving Keratocyte: A 2D Continuum Model.
Nikmaneshi, M R; Firoozabadi, B; Saidi, M S
2015-09-01
The F-actin network and cytosol in the lamellipodia of crawling cells flow in a centripetal pattern and spout-like form, respectively. We have numerically studied this two-phase flow in the realistic geometry of a moving keratocyte. Cytosol has been treated as a low viscosity Newtonian fluid flowing through the high viscosity porous medium of F-actin network. Other involved phenomena including myosin activity, adhesion friction, and interphase interaction are also discussed to provide an overall view of this problem. Adopting a two-phase coupled model by myosin concentration, we have found new accurate perspectives of acto-cytosolic flow and pressure fields, myosin distribution, as well as the distribution of effective forces across the lamellipodia of a keratocyte with stationary shape. The order of magnitude method is also used to determine the contribution of forces in the internal dynamics of lamellipodia. PMID:26403420
NASA Astrophysics Data System (ADS)
Berger, Richard; Chapman, T.; Banks, J. W.; Brunner, S.
2015-11-01
We present 2D+2V Vlasov simulations of Ion Acoustic waves (IAWs) driven by an external traveling-wave potential, ϕ0 (x , t) , with frequency, ω, and wavenumber, k, obeying the kinetic dispersion relation. Both electrons and ions are treated kinetically. Simulations with ϕ0 (x , t) , localized transverse to the propagation direction, model IAWs driven in a laser speckle. The waves bow with a positive or negative curvature of the wave fronts that depends on the sign of the nonlinear frequency shift ΔωNL , which is in turn determined by the magnitude of ZTe /Ti where Z is the charge state and Te , i is the electron, ion temperature. These kinetic effects result can cause modulational and self-focusing instabilities that transfer wave energy to kinetic energy. Linear dispersion properties of IAWs are used in laser propagation codes that predict the amount of light reflected by stimulated Brillouin scattering. At high enough amplitudes, the linear dispersion is invalid and these kinetic effects should be incorporated. Including the spatial and time scales of these instabilities is computationally prohibitive. We report progress including kinetic models in laser propagation codes. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 15.
NASA Astrophysics Data System (ADS)
Chen, K.; You, Y.; Noblesse, F.
2016-07-01
Experiments are conducted in a linear stratified fluid with a momentum source modeled via a nozzle jet moving horizontally. The generation mechanism of the quasi-two-dimensional dipolar vortex streets is investigated and their evolution characteristics are analyzed. Observation shows that the formation of a dipolar vortex street requires a nonzero motion of the nozzle in addition to conditions of the Reynolds and Froude number (Re, Fr). The (Re, Fr) condition that the dipolar vortex streets can be generated is determined via experimental measurements. The explanation for the absence of such a vortex street can be the low energy of the jet and the strong body-effect disturbance of the solid nozzle. The dependence of the vortex street dimensionless formation time τ and the Strouhal number St on the Froude number Fr or the Reynolds number Re is analyzed. This analysis shows that τ and St appear to be independent of Re and approximately have power-law relations with Fr via data fitting. The exponents of Fr in the two power-law functions are -0.27 for τ and -0.21 for St, while the constant coefficients are 65 and 0.21.
Application of computational fluid dynamics methods to improve thermal hydraulic code analysis
NASA Astrophysics Data System (ADS)
Sentell, Dennis Shannon, Jr.
A computational fluid dynamics code is used to model the primary natural circulation loop of a proposed small modular reactor for comparison to experimental data and best-estimate thermal-hydraulic code results. Recent advances in computational fluid dynamics code modeling capabilities make them attractive alternatives to the current conservative approach of coupled best-estimate thermal hydraulic codes and uncertainty evaluations. The results from a computational fluid dynamics analysis are benchmarked against the experimental test results of a 1:3 length, 1:254 volume, full pressure and full temperature scale small modular reactor during steady-state power operations and during a depressurization transient. A comparative evaluation of the experimental data, the thermal hydraulic code results and the computational fluid dynamics code results provides an opportunity to validate the best-estimate thermal hydraulic code's treatment of a natural circulation loop and provide insights into expanded use of the computational fluid dynamics code in future designs and operations. Additionally, a sensitivity analysis is conducted to determine those physical phenomena most impactful on operations of the proposed reactor's natural circulation loop. The combination of the comparative evaluation and sensitivity analysis provides the resources for increased confidence in model developments for natural circulation loops and provides for reliability improvements of the thermal hydraulic code.
NASA Astrophysics Data System (ADS)
Nissen-Meyer, Tarje; Fournier, Alexandre; Dahlen, F. A.
2008-09-01
We portray a dedicated spectral-element method to solve the elastodynamic wave equation upon spherically symmetric earth models at the expense of a 2-D domain. Using this method, 3-D wavefields of arbitrary resolution may be computed to obtain Fréchet sensitivity kernels, especially for diffracted arrivals. The meshing process is presented for varying frequencies in terms of its efficiency as measured by the total number of elements, their spacing variations and stability criteria. We assess the mesh quantitatively by defining these numerical parameters in a general non-dimensionalized form such that comparisons to other grid-based methods are straightforward. Efficient-mesh generation for the PREM example and a minimum-messaging domain decomposition and parallelization strategy lay foundations for waveforms up to frequencies of 1 Hz on moderate PC clusters. The discretization of fluid, solid and respective boundary regions is similar to previous spectral-element implementations, save for a fluid potential formulation that incorporates the density, thereby yielding identical boundary terms on fluid and solid sides. We compare the second-order Newmark time extrapolation scheme with a newly implemented fourth-order symplectic scheme and argue in favour of the latter in cases of propagation over many wavelengths due to drastic accuracy improvements. Various validation examples such as full moment-tensor seismograms, wavefield snapshots, and energy conservation illustrate the favourable behaviour and potential of the method.
Energy Science and Technology Software Center (ESTSC)
2005-07-01
Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.
Scaglione, S; Wendt, D; Miggino, S; Papadimitropoulos, A; Fato, M; Quarto, R; Martin, I
2008-08-01
In this study, we investigated the effect of the long-term (10 days) application of a defined and uniform level of fluid flow (uniform shear stress of 1.2 x 10(-3) N/m(2)) on human bone marrow stromal cells (BMSC) cultured on different substrates (i.e., uncoated glass or calcium phosphate coated glass, Osteologictrade mark) in a 2D parallel plate model. Both exposure to flow and culture on Osteologic significantly reduced the number of cell doublings. BMSC cultured under flow were more intensely stained for collagen type I and by von Kossa for mineralized matrix. BMSC exposed to flow displayed an increased osteogenic commitment (i.e., higher mRNA expression of cbfa-1 and osterix), although phenotype changes in response to flow (i.e., mRNA expression of osteopontin, osteocalcin and bone sialoprotein) were dependent on the substrate used. These findings highlight the importance of the combination of physical forces and culture substrate to determine the functional state of differentiating osteoblastic cells. The results obtained using a simple and controlled 2D model system may help to interpret the long-term effects of BMSC culture under perfusion within 3D porous scaffolds, where multiple experimental variables cannot be easily studied independently, and shear stresses cannot be precisely computed. PMID:17969030
A 3D-CFD code for accurate prediction of fluid flows and fluid forces in seals
NASA Astrophysics Data System (ADS)
Athavale, M. M.; Przekwas, A. J.; Hendricks, R. C.
1994-01-01
Current and future turbomachinery requires advanced seal configurations to control leakage, inhibit mixing of incompatible fluids and to control the rotodynamic response. In recognition of a deficiency in the existing predictive methodology for seals, a seven year effort was established in 1990 by NASA's Office of Aeronautics Exploration and Technology, under the Earth-to-Orbit Propulsion program, to develop validated Computational Fluid Dynamics (CFD) concepts, codes and analyses for seals. The effort will provide NASA and the U.S. Aerospace Industry with advanced CFD scientific codes and industrial codes for analyzing and designing turbomachinery seals. An advanced 3D CFD cylindrical seal code has been developed, incorporating state-of-the-art computational methodology for flow analysis in straight, tapered and stepped seals. Relevant computational features of the code include: stationary/rotating coordinates, cylindrical and general Body Fitted Coordinates (BFC) systems, high order differencing schemes, colocated variable arrangement, advanced turbulence models, incompressible/compressible flows, and moving grids. This paper presents the current status of code development, code demonstration for predicting rotordynamic coefficients, numerical parametric study of entrance loss coefficients for generic annular seals, and plans for code extensions to labyrinth, damping, and other seal configurations.
Icarus: A 2D direct simulation Monte Carlo (DSMC) code for parallel computers. User`s manual - V.3.0
Bartel, T.; Plimpton, S.; Johannes, J.; Payne, J.
1996-10-01
Icarus is a 2D Direct Simulation Monte Carlo (DSMC) code which has been optimized for the parallel computing environment. The code is based on the DSMC method of Bird and models from free-molecular to continuum flowfields in either cartesian (x, y) or axisymmetric (z, r) coordinates. Computational particles, representing a given number of molecules or atoms, are tracked as they have collisions with other particles or surfaces. Multiple species, internal energy modes (rotation and vibration), chemistry, and ion transport are modelled. A new trace species methodology for collisions and chemistry is used to obtain statistics for small species concentrations. Gas phase chemistry is modelled using steric factors derived from Arrhenius reaction rates. Surface chemistry is modelled with surface reaction probabilities. The electron number density is either a fixed external generated field or determined using a local charge neutrality assumption. Ion chemistry is modelled with electron impact chemistry rates and charge exchange reactions. Coulomb collision cross-sections are used instead of Variable Hard Sphere values for ion-ion interactions. The electrostatic fields can either be externally input or internally generated using a Langmuir-Tonks model. The Icarus software package includes the grid generation, parallel processor decomposition, postprocessing, and restart software. The commercial graphics package, Tecplot, is used for graphics display. The majority of the software packages are written in standard Fortran.
The development of an intelligent interface to a computational fluid dynamics flow-solver code
NASA Technical Reports Server (NTRS)
Williams, Anthony D.
1988-01-01
Researchers at NASA Lewis are currently developing an 'intelligent' interface to aid in the development and use of large, computational fluid dynamics flow-solver codes for studying the internal fluid behavior of aerospace propulsion systems. This paper discusses the requirements, design, and implementation of an intelligent interface to Proteus, a general purpose, 3-D, Navier-Stokes flow solver. The interface is called PROTAIS to denote its introduction of artificial intelligence (AI) concepts to the Proteus code.
The development of an intelligent interface to a computational fluid dynamics flow-solver code
NASA Technical Reports Server (NTRS)
Williams, Anthony D.
1988-01-01
Researchers at NASA Lewis are currently developing an 'intelligent' interface to aid in the development and use of large, computational fluid dynamics flow-solver codes for studying the internal fluid behavior of aerospace propulsion systems. This paper discusses the requirements, design, and implementation of an intelligent interface to Proteus, a general purpose, three-dimensional, Navier-Stokes flow solver. The interface is called PROTAIS to denote its introduction of artificial intelligence (AI) concepts to the Proteus code.
NASA Astrophysics Data System (ADS)
Innocenti, M.; Beck, A.; Lapenta, G.; Markidis, S.
2012-12-01
The kinetic simulation of intrinsically multi scale processes such as magnetic reconnection events with realistic mass ratios is a daunting task for explicit Particle In Cell (PIC) codes, which require to use resolutions of the order of the electron Debye length even when simulating dramatically bigger domains. As an example, a simulation of reconnection in the magnetotail, with domain sizes of the order of 20 di x 10 di (˜ 7.2 106 m x 3.6 106 m, with di being the ion skin depth) and a resolution of λD,e= 687 m, with λD,e the electron Debye length, requires the astounding number of 10500 x 5240 cells. Higher grid spacings can be used if the simulation is performed with an implicit PIC code, which substitutes a much less strict accuracy constraint to the stability constraint of explicit PIC codes. The same reconnection problem as before can be simulated, with an implicit PIC code resolving the scale of interest of de /2 instead of the electron Debye length (de is the electron skin depth), with the much more manageable number of 1920 x 958 cells. However, an even smaller number of cells can be used if, instead of using the same, high resolution on the entire domain, the domain to simulate is divided into subdomains each resolved with a grid spacing related to the physical scale of interest in the specific subdomain. In the case of reconnection, the division which immediately springs to mind is between electron diffusion region, ion diffusion region and outer region, where resolutions respectively of the order of fractions of the electron skin depth, of the ion skin depth and bigger can be used. We present here a new Multi Level Multi Domain (MLMD) Implicit Moment Method (IMM) Particle In Cell (PIC) code, Parsek2D-MLMD, able to perform simulations of magnetic reconnection where the expensive high resolutions are used only when needed, while the rest of the domain is simulated with grid spacings chosen according to the local scales of interest. The major difference
Mitri, F G
2015-09-01
The classical Resonance Scattering Theory (RST) for plane waves in acoustics is generalized for the case of a 2D arbitrarily-shaped beam incident upon an elastic cylinder with arbitrary location that is immersed in a nonviscous fluid. The formulation is valid for an elastic (or viscoelastic) cylinder (or a cylindrical shell, a layered cylinder/shell, or a multilayered cylindrical shell, etc.) of any size and material. Partial-wave series expansions (PWSEs) for the incident, internal and scattered fields are derived, and numerical examples illustrate the theory. The wave-fields are expressed using a generalized PWSE involving the beam-shape coefficients (BSCs) and the scattering coefficients of the cylinder. When the beam is shifted off the center of the cylinder, the off-axial BSCs are evaluated by performing standard numerical integration. Acoustic resonance scattering directivity diagrams are calculated by subtracting an appropriate background from the expression of the scattered pressure field. The properties related to the arbitrary scattering of a zeroth-order quasi-Gaussian cylindrical beam (chosen as an example) by an elastic brass cylinder centered on the axis of wave propagation of the beam, and shifted off-axially are analyzed and discussed. Moreover, the total and resonance backscattering form function moduli are numerically computed, and the results discussed with emphasis on the contribution of the surface waves circumnavigating the cylinder circular surface to the resonance backscattering. Furthermore, the analysis is extended to derive general expressions for the axial and transverse acoustic radiation force functions for the cylinder in any 2D beam of arbitrary shape. Examples are provided for a zeroth-order quasi Gaussian cylindrical beam with different waist. Potential applications are in underwater and physical acoustics, however, ongoing research in biomedical ultrasound, non-destructive evaluation, imaging, manufacturing, instrumentation, and
Korecka, Magdalena; Waligorska, Teresa; Figurski, Michal; Toledo, Jon B; Arnold, Steven E; Grossman, Murray; Trojanowski, John Q; Shaw, Leslie M
2014-01-01
The primary aims of this work were to: 1) establish a calibrator surrogate matrix for quantification of amyloid-β (Aβ)42 in human cerebrospinal fluid (CSF) and preparation of quality control samples for LC-MS-MS methodology, 2) validate analytical performance of the assay, and 3) evaluate its diagnostic utility and compare it with the AlzBio3 immunoassay. The analytical methodology was based on a 2D-UPLC-MS-MS platform. Sample pretreatment used 5 M guanidine hydrochloride and extraction on μElution SPE columns as previously described. A column cleaning procedure involved gradual removal of aqueous solvents by acetonitrile assured consistent long-term chromatography performance. Receiver-operator characteristic (ROC) curve and correlation analyses evaluated the diagnostic utility of UPLC-MS-MS compared to AlzBio3 immunoassay for detection of Alzheimer's disease (AD). The surrogate matrix, artificial CSF containing 4 mg/mL of BSA, provides linear and reproducible calibration comparable to human pooled CSF as calibration matrix. Appropriate cleaning of the trapping and analytical columns provided every-day, trouble-free runs. Analyses of CSF Aβ42 showed that UPLC-MS-MS distinguished neuropathologically-diagnosed AD subjects from healthy controls with at least equivalent diagnostic utility to AlzBio3. Comparison of ROC curves for these two assays showed no statistically significant difference (p = 0.2229). Linear regression analysis of Aβ42 concentrations measured by this mass spectrometry-based method compared to the AlzBio3 immunoassay showed significantly higher but highly correlated results. In conclusion, the newly established surrogate matrix for 2D-UPLC-MS-MS measurement of Aβ42 provides selective, reproducible, and accurate results. The documented analytical performance and diagnostic performance for AD versus controls supports consideration as a candidate reference method. PMID:24625802
Issues in computational fluid dynamics code verification and validation
Oberkampf, W.L.; Blottner, F.G.
1997-09-01
A broad range of mathematical modeling errors of fluid flow physics and numerical approximation errors are addressed in computational fluid dynamics (CFD). It is strongly believed that if CFD is to have a major impact on the design of engineering hardware and flight systems, the level of confidence in complex simulations must substantially improve. To better understand the present limitations of CFD simulations, a wide variety of physical modeling, discretization, and solution errors are identified and discussed. Here, discretization and solution errors refer to all errors caused by conversion of the original partial differential, or integral, conservation equations representing the physical process, to algebraic equations and their solution on a computer. The impact of boundary conditions on the solution of the partial differential equations and their discrete representation will also be discussed. Throughout the article, clear distinctions are made between the analytical mathematical models of fluid dynamics and the numerical models. Lax`s Equivalence Theorem and its frailties in practical CFD solutions are pointed out. Distinctions are also made between the existence and uniqueness of solutions to the partial differential equations as opposed to the discrete equations. Two techniques are briefly discussed for the detection and quantification of certain types of discretization and grid resolution errors.
NASA Astrophysics Data System (ADS)
Key, K.
2013-12-01
This work announces the public release of an open-source inversion code named MARE2DEM (Modeling with Adaptively Refined Elements for 2D Electromagnetics). Although initially designed for the rapid inversion of marine electromagnetic data, MARE2DEM now supports a wide variety of acquisition configurations for both offshore and onshore surveys that utilize electric and magnetic dipole transmitters or magnetotelluric plane waves. The model domain is flexibly parameterized using a grid of arbitrarily shaped polygonal regions, allowing for complicated structures such as topography or seismically imaged horizons to be easily assimilated. MARE2DEM efficiently solves the forward problem in parallel by dividing the input data parameters into smaller subsets using a parallel data decomposition algorithm. The data subsets are then solved in parallel using an automatic adaptive finite element method that iterative solves the forward problem on successively refined finite element meshes until a specified accuracy tolerance is met, thus freeing the end user from the burden of designing an accurate numerical modeling grid. Regularized non-linear inversion for isotropic or anisotropic conductivity is accomplished with a new implementation of Occam's method referred to as fast-Occam, which is able to minimize the objective function in much fewer forward evaluations than the required by the original method. This presentation will review the theoretical considerations behind MARE2DEM and use a few recent offshore EM data sets to demonstrate its capabilities and to showcase the software interface tools that streamline model building and data inversion.
User's manual for PELE3D: a computer code for three-dimensional incompressible fluid dynamics
McMaster, W H
1982-05-07
The PELE3D code is a three-dimensional semi-implicit Eulerian hydrodynamics computer program for the solution of incompressible fluid flow coupled to a structure. The fluid and coupling algorithms have been adapted from the previously developed two-dimensional code PELE-IC. The PELE3D code is written in both plane and cylindrical coordinates. The coupling algorithm is general enough to handle a variety of structural shapes. The free surface algorithm is able to accommodate a top surface and several independent bubbles. The code is in a developmental status since all the intended options have not been fully implemented and tested. Development of this code ended in 1980 upon termination of the contract with the Nuclear Regulatory Commission.
Predictions of bubbly flows in vertical pipes using two-fluid models in CFDS-FLOW3D code
Banas, A.O.; Carver, M.B.; Unrau, D.
1995-09-01
This paper reports the results of a preliminary study exploring the performance of two sets of two-fluid closure relationships applied to the simulation of turbulent air-water bubbly upflows through vertical pipes. Predictions obtained with the default CFDS-FLOW3D model for dispersed flows were compared with the predictions of a new model (based on the work of Lee), and with the experimental data of Liu. The new model, implemented in the CFDS-FLOW3D code, included additional source terms in the {open_quotes}standard{close_quotes} {kappa}-{epsilon} transport equations for the liquid phase, as well as modified model coefficients and wall functions. All simulations were carried out in a 2-D axisymmetric format, collapsing the general multifluid framework of CFDS-FLOW3D to the two-fluid (air-water) case. The newly implemented model consistently improved predictions of radial-velocity profiles of both phases, but failed to accurately reproduce the experimental phase-distribution data. This shortcoming was traced to the neglect of anisotropic effects in the modelling of liquid-phase turbulence. In this sense, the present investigation should be considered as the first step toward the ultimate goal of developing a theoretically sound and universal CFD-type two-fluid model for bubbly flows in channels.
Energy Science and Technology Software Center (ESTSC)
2004-08-01
AnisWave2D is a 2D finite-difference code for a simulating seismic wave propagation in fully anisotropic materials. The code is implemented to run in parallel over multiple processors and is fully portable. A mesh refinement algorithm has been utilized to allow the grid-spacing to be tailored to the velocity model, avoiding the over-sampling of high-velocity materials that usually occurs in fixed-grid schemes.
NASA Astrophysics Data System (ADS)
Baudon, Catherine; Gillet, Hervé; Cremer, Michel
2013-04-01
High-quality bathymetric, 2D seismic and Chirp data located in the southern parts of the Bay of Biscay, France, collected by the University of Bordeaux 1 (Cruises ITSAS 2, 2001; PROSECAN 3, 2006 and SARGASS, 2010) have recently been compiled. The survey area widely covers the Capbreton Canyon, which lies on the boundary between two major structural zones: the Aquitanian passive margin to the North, and the Basque-Cantabrian margin to the South which corresponds to the offshore Pyrenean front. The dataset revealed a large number of key seafloor features potentially associated with focused fluid-flow processes and subsurface sediment-remobilization. Focused fluid migration through sub-seabed sediments is a common phenomenon on continental margins worldwide and has widespread implications from both industrial and fundamental perspectives, from seafloor marine environmental issues to petroleum exploration and hazard assessments. Our study analyses the relationships between seafloor features, deeper structures and fluid migration through the Plio-Quaternary sedimentary pile. The geometrical characteristics, mechanisms of formation and kinematics of four main groups of seabed features have been investigated. (i) A 150km2 field of pockmarks can be observed on the Basque margin. These features are cone-shaped circular or elliptical depressions that are either randomly distributed as small pockmarks (diameter < 20m) or aligned in trains of large pockmarks (ranging from 200 to 600m in diameter) along shallow troughs leading downstream to the Capbreton Canyon. Seismic data show that most pockmarks reach the seabed through vertically staked V-shaped features but some are buried and show evidence of lateral migration through time. (ii) A second field of widely-spaced groups of pockmarks pierce the upper slope of the Aquitanian margin. These depressions are typically a few hundred meters in diameter and seem to be preferentially located in the troughs or on the stoss sides of
Benchmark studies of the gyro-Landau-fluid code and gyro-kinetic codes on kinetic ballooning modes
NASA Astrophysics Data System (ADS)
Tang, T. F.; Xu, X. Q.; Ma, C. H.; Bass, E. M.; Holland, C.; Candy, J.
2016-03-01
A Gyro-Landau-Fluid (GLF) 3 + 1 model has been recently implemented in BOUT++ framework, which contains full Finite-Larmor-Radius effects, Landau damping, and toroidal resonance [Ma et al., Phys. Plasmas 22, 055903 (2015)]. A linear global beta scan has been conducted using the JET-like circular equilibria (cbm18 series), showing that the unstable modes are kinetic ballooning modes (KBMs). In this work, we use the GYRO code, which is a gyrokinetic continuum code widely used for simulation of the plasma microturbulence, to benchmark with GLF 3 + 1 code on KBMs. To verify our code on the KBM case, we first perform the beta scan based on "Cyclone base case parameter set." We find that the growth rate is almost the same for two codes, and the KBM mode is further destabilized as beta increases. For JET-like global circular equilibria, as the modes localize in peak pressure gradient region, a linear local beta scan using the same set of equilibria has been performed at this position for comparison. With the drift kinetic electron module in the GYRO code by including small electron-electron collision to damp electron modes, GYRO generated mode structures and parity suggest that they are kinetic ballooning modes, and the growth rate is comparable to the GLF results. However, a radial scan of the pedestal for a particular set of cbm18 equilibria, using GYRO code, shows different trends for the low-n and high-n modes. The low-n modes show that the linear growth rate peaks at peak pressure gradient position as GLF results. However, for high-n modes, the growth rate of the most unstable mode shifts outward to the bottom of pedestal and the real frequency of what was originally the KBMs in ion diamagnetic drift direction steadily approaches and crosses over to the electron diamagnetic drift direction.
NASA Astrophysics Data System (ADS)
Aeschliman, D. P.; Oberkampf, W. L.; Blottner, F. G.
Verification, calibration, and validation (VCV) of Computational Fluid Dynamics (CFD) codes is an essential element of the code development process. The exact manner in which code VCV activities are planned and conducted, however, is critically important. It is suggested that the way in which code validation, in particular, is often conducted--by comparison to published experimental data obtained for other purposes--is in general difficult and unsatisfactory, and that a different approach is required. This paper describes a proposed methodology for CFD code VCV that meets the technical requirements and is philosophically consistent with code development needs. The proposed methodology stresses teamwork and cooperation between code developers and experimentalists throughout the VCV process, and takes advantage of certain synergisms between CFD and experiment. A novel approach to uncertainty analysis is described which can both distinguish between and quantify various types of experimental error, and whose attributes are used to help define an appropriate experimental design for code VCV experiments. The methodology is demonstrated with an example of laminar, hypersonic, near perfect gas, 3-dimensional flow over a sliced sphere/cone of varying geometrical complexity.
Aeschliman, D.P.; Oberkampf, W.L.; Blottner, F.G.
1995-07-01
Verification, calibration, and validation (VCV) of Computational Fluid Dynamics (CFD) codes is an essential element of the code development process. The exact manner in which code VCV activities are planned and conducted, however, is critically important. It is suggested that the way in which code validation, in particular, is often conducted--by comparison to published experimental data obtained for other purposes--is in general difficult and unsatisfactory, and that a different approach is required. This paper describes a proposed methodology for CFD code VCV that meets the technical requirements and is philosophically consistent with code development needs. The proposed methodology stresses teamwork and cooperation between code developers and experimentalists throughout the VCV process, and takes advantage of certain synergisms between CFD and experiment. A novel approach to uncertainty analysis is described which can both distinguish between and quantify various types of experimental error, and whose attributes are used to help define an appropriate experimental design for code VCV experiments. The methodology is demonstrated with an example of laminar, hypersonic, near perfect gas, 3-dimensional flow over a sliced sphere/cone of varying geometrical complexity.
Sandia National Laboratories environmental fluid dynamics code : sediment transport user manual.
Grace, Matthew D.; Thanh, Phi Hung X.; James, Scott Carlton
2008-09-01
This document describes the sediment transport subroutines and input files for the Sandia National Laboratories Environmental Fluid Dynamics Code (SNL-EFDC). Detailed descriptions of the input files containing data from Sediment Erosion at Depth flume (SEDflume) measurements are provided along with the description of the source code implementing sediment transport. Both the theoretical description of sediment transport employed in SNL-EFDC and the source code are described. This user manual is meant to be used in conjunction with the EFDC manual (Hamrick 1996) because there will be no reference to the hydrodynamics in EFDC. Through this document, the authors aim to provide the necessary information for new users who wish to implement sediment transport in EFDC and obtain a clear understanding of the source code.
ReA Fluid Code with Wave-Particle Trapping Effects
NASA Astrophysics Data System (ADS)
Mattor, Nathan
1999-11-01
A fluid code is presented that contains nonlinear wave-particle resonance effects, such as trapping and scattering. Generally it is thought that such effects require kinetic equations, but recent studies have called this into question.(S.E. Parker and D. Carati, Phys. Rev. Lett. 75,) 441 (1995) This code is a practical demonstration of these assertions. The code solves electrostatic one dimensional equations, and in principle applies to the same plasma as the classic code ``ES1.''(Plasma Physics via Computer Simulation,) by C. K. Birdsall and A. B. Langdon (c. 1985, McGraw-Hill, New York). Various nonlinear wave-particle resonance effects, approximations, and timings are discussed. Work performed at Lawrence Livermore National Laboratory under DoE Contract No. W7405-ENG-48.
A Parallel Two-fluid Code for Global Magnetic Reconnection Studies
J.A. Breslau; S.C. Jardin
2001-08-09
This paper describes a new algorithm for the computation of two-dimensional resistive magnetohydrodynamic (MHD) and two-fluid studies of magnetic reconnection in plasmas. It has been implemented on several parallel platforms and shows good scalability up to 32 CPUs for reasonable problem sizes. A fixed, nonuniform rectangular mesh is used to resolve the different spatial scales in the reconnection problem. The resistive MHD version of the code uses an implicit/explicit hybrid method, while the two-fluid version uses an alternating-direction implicit (ADI) method. The technique has proven useful for comparing several different theories of collisional and collisionless reconnection.
A proposed framework for computational fluid dynamics code calibration/validation
Oberkampf, W.L.
1993-12-31
The paper reviews the terminology and methodology that have been introduced during the last several years for building confidence n the predictions from Computational Fluid Dynamics (CID) codes. Code validation terminology developed for nuclear reactor analyses and aerospace applications is reviewed and evaluated. Currently used terminology such as ``calibrated code,`` ``validated code,`` and a ``validation experiment`` is discussed along with the shortcomings and criticisms of these terms. A new framework is proposed for building confidence in CFD code predictions that overcomes some of the difficulties of past procedures and delineates the causes of uncertainty in CFD predictions. Building on previous work, new definitions of code verification and calibration are proposed. These definitions provide more specific requirements for the knowledge level of the flow physics involved and the solution accuracy of the given partial differential equations. As part of the proposed framework, categories are also proposed for flow physics research, flow modeling research, and the application of numerical predictions. The contributions of physical experiments, analytical solutions, and other numerical solutions are discussed, showing that each should be designed to achieve a distinctively separate purpose in building confidence in accuracy of CFD predictions. A number of examples are given for each approach to suggest methods for obtaining the highest value for CFD code quality assurance.
NASA Astrophysics Data System (ADS)
Polukhin, V. A.; Kurbanova, E. D.
2016-02-01
Molecular dynamics simulation is used to study the thermal stability of the interfacial states of metallic Al, Ag, Sn, Pb, and Hg films (i.e., the structural elements of superconductor composites and conducting electrodes) reinforced by 2D graphene and silicene crystals upon heating up to disordering and to analyze the formation of nonautonomous fluid pseudophases in interfaces. The effect of perforation defects in reinforcing 2D-C and 2D-Si planes with passivated edge covalent bonds on the atomic dynamics is investigated. As compared to Al and Ag, the diffusion coefficients in Pd and Hg films increase monotonically with temperature during thermally activated disordering processes, the interatomic distances decrease, the sizes decrease, drops form, and their density profile grows along the normal. The coagulation of Pb and Hg drops is accompanied by a decrease in the contact angle, the reduction of the interface contact with graphene, and the enhancement of its corrugation (waviness).
NASA Astrophysics Data System (ADS)
Fiantini, Rosalina; Umar, Efrizon
2010-06-01
Common energy crisis has modified the national energy policy which is in the beginning based on natural resources becoming based on technology, therefore the capability to understanding the basic and applied science is needed to supporting those policies. National energy policy which aims at new energy exploitation, such as nuclear energy is including many efforts to increase the safety reactor core condition and optimize the related aspects and the ability to build new research reactor with properly design. The previous analysis of the modification TRIGA 2000 Reactor design indicates that forced convection of the primary coolant system put on an effect to the flow characteristic in the reactor core, but relatively insignificant effect to the flow velocity in the reactor core. In this analysis, the lid of reactor core is closed. However the forced convection effect is still presented. This analysis shows the fluid flow velocity vector in the model area without exception. Result of this analysis indicates that in the original design of TRIGA 2000 reactor, there is still forced convection effects occur but less than in the modified TRIGA 2000 design.
Fiantini, Rosalina; Umar, Efrizon
2010-06-22
Common energy crisis has modified the national energy policy which is in the beginning based on natural resources becoming based on technology, therefore the capability to understanding the basic and applied science is needed to supporting those policies. National energy policy which aims at new energy exploitation, such as nuclear energy is including many efforts to increase the safety reactor core condition and optimize the related aspects and the ability to build new research reactor with properly design. The previous analysis of the modification TRIGA 2000 Reactor design indicates that forced convection of the primary coolant system put on an effect to the flow characteristic in the reactor core, but relatively insignificant effect to the flow velocity in the reactor core. In this analysis, the lid of reactor core is closed. However the forced convection effect is still presented. This analysis shows the fluid flow velocity vector in the model area without exception. Result of this analysis indicates that in the original design of TRIGA 2000 reactor, there is still forced convection effects occur but less than in the modified TRIGA 2000 design.
A Mathematical Model and MATLAB Code for Muscle-Fluid-Structure Simulations.
Battista, Nicholas A; Baird, Austin J; Miller, Laura A
2015-11-01
This article provides models and code for numerically simulating muscle-fluid-structure interactions (FSIs). This work was presented as part of the symposium on Leading Students and Faculty to Quantitative Biology through Active Learning at the society-wide meeting of the Society for Integrative and Comparative Biology in 2015. Muscle mechanics and simple mathematical models to describe the forces generated by muscular contractions are introduced in most biomechanics and physiology courses. Often, however, the models are derived for simplifying cases such as isometric or isotonic contractions. In this article, we present a simple model of the force generated through active contraction of muscles. The muscles' forces are then used to drive the motion of flexible structures immersed in a viscous fluid. An example of an elastic band immersed in a fluid is first presented to illustrate a fully-coupled FSI in the absence of any external driving forces. In the second example, we present a valveless tube with model muscles that drive the contraction of the tube. We provide a brief overview of the numerical method used to generate these results. We also include as Supplementary Material a MATLAB code to generate these results. The code was written for flexibility so as to be easily modified to many other biological applications for educational purposes. PMID:26337187
Development Of Sputtering Models For Fluids-Based Plasma Simulation Codes
NASA Astrophysics Data System (ADS)
Veitzer, Seth; Beckwith, Kristian; Stoltz, Peter
2015-09-01
Rf-driven plasma devices such as ion sources and plasma processing devices for many industrial and research applications benefit from detailed numerical modeling. Simulation of these devices using explicit PIC codes is difficult due to inherent separations of time and spatial scales. One alternative type of model is fluid-based codes coupled with electromagnetics, that are applicable to modeling higher-density plasmas in the time domain, but can relax time step requirements. To accurately model plasma-surface processes, such as physical sputtering and secondary electron emission, kinetic particle models have been developed, where particles are emitted from a material surface due to plasma ion bombardment. In fluid models plasma properties are defined on a cell-by-cell basis, and distributions for individual particle properties are assumed. This adds a complexity to surface process modeling, which we describe here. We describe the implementation of sputtering models into the hydrodynamic plasma simulation code USim, as well as methods to improve the accuracy of fluids-based simulation of plasmas-surface interactions by better modeling of heat fluxes. This work was performed under the auspices of the Department of Energy, Office of Basic Energy Sciences Award #DE-SC0009585.
Algorithm for Wave-Particle Resonances in Fluid Codes - Final Report
Mattor, N.
2000-03-03
We review the work performed under LDRD ER grant 98-ERD-099. The goal of this work is to write a subroutine for a fluid turbulence code that allows it to incorporate wave-particle resonances (WPR). WPR historically have required a kinetic code, with extra dimensions needed to evolve the phase space distribution function, f(x, v, t). The main results accomplished under this grant have been: (1) Derivation of a nonlinear closure term for 1D electrostatic collisionless fluid; (2) Writing of a 1D electrostatic fluid code, ''es1f,'' with a subroutine to calculate the aforementioned closure term; (3) derivation of several methods to calculate the closure term, including Eulerian, Euler-local, fully local, linearized, and linearized zero-phase-velocity, and implementation of these in es1f; (4) Successful modeling of the Landau damping of an arbitrary Langmuir wave; (5) Successful description of a kinetic two-stream instability up to the point of the first bounce; and (6) a spin-off project which uses a mathematical technique developed for the closure, known as the Phase Velocity Transform (PVT) to decompose turbulent fluctuations.
NASA Astrophysics Data System (ADS)
Caballero, L.; Capra, L.
2014-07-01
Lahar modelling represents an excellent tool to design hazard maps. It allows the definition of potential inundation zones for different lahar magnitude scenarios and sediment concentrations. Here we present the results obtained for the 2001 syneruptive lahar at Popocatépetl volcano, based on simulations performed with FLO2D software. An accurate delineation of this event is needed since it is one of the possible scenarios considered during a volcanic crisis. One of the main issues for lahar simulation using FLO2D is the calibration of the input hydrograph and rheologic flow properties. Here we verified that geophone data can be properly calibrated by means of peak discharge calculations obtained by superelevation method. Simulation results clearly show the influence of concentration and rheologic properties on lahar depth and distribution. Modifying rheologic properties during lahar simulation strongly affect lahar distribution. More viscous lahars have a more restricted aerial distribution, thicker depths, and resulting velocities are noticeable smaller. FLO2D proved to be a very successful tool to delimitate lahar inundation zones as well as to generate different lahar scenarios not only related to lahar volume or magnitude but also to take into account different sediment concentrations and rheologies widely documented to influence lahar prone areas.
NASA Astrophysics Data System (ADS)
Caballero, L.; Capra, L.
2014-12-01
Lahar modeling represents an excellent tool for designing hazard maps. It allows the definition of potential inundation zones for different lahar magnitude scenarios and sediment concentrations. Here, we present the results obtained for the 2001 syneruptive lahar at Popocatépetl volcano, based on simulations performed with FLO2D software. An accurate delineation of this event is needed, since it is one of the possible scenarios considered if magmatic activity increases its magnitude. One of the main issues for lahar simulation using FLO2D is the calibration of the input hydrograph and rheological flow properties. Here, we verified that geophone data can be properly calibrated by means of peak discharge calculations obtained by the superelevation method. Digital elevation model resolution also resulted as an important factor in defining the reliability of the simulated flows. Simulation results clearly show the influence of sediment concentrations and rheological properties on lahar depth and distribution. Modifying rheological properties during lahar simulation strongly affects lahar distribution. More viscous lahars have a more restricted aerial distribution and thicker depths, and resulting velocities are noticeably smaller. FLO2D proved to be a very successful tool for delimitating lahar inundation zones as well as generating different lahar scenarios not only related to lahar volume or magnitude, but also taking into account different sediment concentrations and rheologies widely documented as influencing lahar-prone areas.
James, Scott Carlton; Roberts, Jesse D.
2014-03-01
This document describes the marine hydrokinetic (MHK) input file and subroutines for the Sandia National Laboratories Environmental Fluid Dynamics Code (SNL-EFDC), which is a combined hydrodynamic, sediment transport, and water quality model based on the Environmental Fluid Dynamics Code (EFDC) developed by John Hamrick [1], formerly sponsored by the U.S. Environmental Protection Agency, and now maintained by Tetra Tech, Inc. SNL-EFDC has been previously enhanced with the incorporation of the SEDZLJ sediment dynamics model developed by Ziegler, Lick, and Jones [2-4]. SNL-EFDC has also been upgraded to more accurately simulate algae growth with specific application to optimizing biomass in an open-channel raceway for biofuels production [5]. A detailed description of the input file containing data describing the MHK device/array is provided, along with a description of the MHK FORTRAN routine. Both a theoretical description of the MHK dynamics as incorporated into SNL-EFDC and an explanation of the source code are provided. This user manual is meant to be used in conjunction with the original EFDC [6] and sediment dynamics SNL-EFDC manuals [7]. Through this document, the authors provide information for users who wish to model the effects of an MHK device (or array of devices) on a flow system with EFDC and who also seek a clear understanding of the source code, which is available from staff in the Water Power Technologies Department at Sandia National Laboratories, Albuquerque, New Mexico.
Inlet-Compressor Analysis Performed Using Coupled Computational Fluid Dynamics Codes
NASA Technical Reports Server (NTRS)
Cole, Gary L.; Suresh, Ambady; Townsend, Scott
1999-01-01
A thorough understanding of dynamic interactions between inlets and compressors is extremely important to the design and development of propulsion control systems, particularly for supersonic aircraft such as the High-Speed Civil Transport (HSCT). Computational fluid dynamics (CFD) codes are routinely used to analyze individual propulsion components. By coupling the appropriate CFD component codes, it is possible to investigate inlet-compressor interactions. The objectives of this work were to gain a better understanding of inlet-compressor interaction physics, formulate a more realistic compressor-face boundary condition for time-accurate CFD simulations of inlets, and to take a first step toward the CFD simulation of an entire engine by coupling multidimensional component codes. This work was conducted at the NASA Lewis Research Center by a team of civil servants and support service contractors as part of the High Performance Computing and Communications Program (HPCCP).
Technology Transfer Automated Retrieval System (TEKTRAN)
Food-grade tracers were printed with two-dimensional Data Matrix (DM) barcode so that they could carry simulated identifying information about grain as part of a prospective traceability system. The key factor in evaluating the tracers was their ability to be read with a code scanner after being rem...
Scaling in the 2D SU(3) × SU(3) spin model as a test of a new coding method for SU(3) matrices
NASA Astrophysics Data System (ADS)
Bunk, B.; Sommer, R.
1985-02-01
We present a Monte Carlo measurement of the magnetic susceptibility in the SU(3) × SU(3) spin model in two dimensions. Asymptotic scaling is verified on a 20 × 20 lattice. This laboratory is then used to test a new method for coding SU(3) variables in one (60 bit)- word of computer memory. In this approach, real numbers are truncated to fit into a 5-bit representation.
NASA Technical Reports Server (NTRS)
Hardman, R. R.; Mahan, J. R.; Smith, M. H.; Gelhausen, P. A.; Van Dalsem, W. R.
1991-01-01
The need for a validation technique for computational fluid dynamics (CFD) codes in STOVL applications has led to research efforts to apply infrared thermal imaging techniques to visualize gaseous flow fields. Specifically, a heated, free-jet test facility was constructed. The gaseous flow field of the jet exhaust was characterized using an infrared imaging technique in the 2 to 5.6 micron wavelength band as well as conventional pitot tube and thermocouple methods. These infrared images are compared to computer-generated images using the equations of radiative exchange based on the temperature distribution in the jet exhaust measured with the thermocouple traverses. Temperature and velocity measurement techniques, infrared imaging, and the computer model of the infrared imaging technique are presented and discussed. From the study, it is concluded that infrared imaging techniques coupled with the radiative exchange equations applied to CFD models are a valid method to qualitatively verify CFD codes used in STOVL applications.
Sandia National Laboratories environmental fluid dynamics code : pH effects user manual.
Janardhanam, Vijay; James, Scott Carlton
2012-02-01
This document describes the implementation level changes in the source code and input files of Sandia National Laboratories Environmental Fluid Dynamics Code (SNL-EFDC) that are necessary for including pH effects into algae-growth dynamics. The document also gives a brief introduction to how pH effects are modeled into the algae-growth model. The document assumes that the reader is aware of the existing algae-growth model in SNL-EFDC. The existing model is described by James, Jarardhanam and more theoretical considerations behind modeling pH effects are presented therein. This document should be used in conjunction with the original EFDC manual and the original water-quality manual.
Sandia National Laboratories Environmental Fluid Dynamics Code V. 1 0.0 (Beta)
2015-10-20
The DOE has funded Sandia National Labs (SNL) to develop an open-source modeling tool to guide the design and layout of marine hydrokinetic (MHK) arrays to maximize power production while minimizing environmental effects. This modeling framework simulates flows through and around MHK arrays while quantifying environmental responses. As an augmented version of US EPA's Environmental Fluid Dynamics Code (EFDC), SNL-EFDC includes: (1) a new module that simulates energy conversion (momentum withdrawal) by MHK devices with commensurate changes in the turbulent kinetic energy and its dissipation rate, (2) new, advanced sediment dynamics routines, and (3) augmented water quality modules.
Sandia National Laboratories Environmental Fluid Dynamics Code V. 1 0.0 (Beta)
Energy Science and Technology Software Center (ESTSC)
2015-10-20
The DOE has funded Sandia National Labs (SNL) to develop an open-source modeling tool to guide the design and layout of marine hydrokinetic (MHK) arrays to maximize power production while minimizing environmental effects. This modeling framework simulates flows through and around MHK arrays while quantifying environmental responses. As an augmented version of US EPA's Environmental Fluid Dynamics Code (EFDC), SNL-EFDC includes: (1) a new module that simulates energy conversion (momentum withdrawal) by MHK devices withmore » commensurate changes in the turbulent kinetic energy and its dissipation rate, (2) new, advanced sediment dynamics routines, and (3) augmented water quality modules.« less
On the application of computational fluid dynamics codes for liquefied natural gas dispersion.
Luketa-Hanlin, Anay Josephine; Koopman, Ronald P.; Ermak, Donald
2006-02-01
Computational fluid dynamics (CFD) codes are increasingly being used in the liquefied natural gas (LNG) industry to predict natural gas dispersion distances. This paper addresses several issues regarding the use of CFD for LNG dispersion such as specification of the domain, grid, boundary and initial conditions. A description of the k-{var_epsilon} model is presented, along with modifications required for atmospheric flows. Validation issues pertaining to the experimental data from the Burro, Coyote, and Falcon series of LNG dispersion experiments are also discussed. A description of the atmosphere is provided as well as discussion on the inclusion of the Coriolis force to model very large LNG spills.
TEMPEST: A computer code for three-dimensional analysis of transient fluid dynamics
Fort, J.A.
1995-06-01
TEMPEST (Transient Energy Momentum and Pressure Equations Solutions in Three dimensions) is a powerful tool for solving engineering problems in nuclear energy, waste processing, chemical processing, and environmental restoration because it analyzes and illustrates 3-D time-dependent computational fluid dynamics and heat transfer analysis. It is a family of codes with two primary versions, a N- Version (available to public) and a T-Version (not currently available to public). This handout discusses its capabilities, applications, numerical algorithms, development status, and availability and assistance.
NASA Astrophysics Data System (ADS)
Rodríguez-Sánchez, Rafael; Martínez, José Luis; Cock, Jan De; Fernández-Escribano, Gerardo; Pieters, Bart; Sánchez, José L.; Claver, José M.; de Walle, Rik Van
2013-12-01
The H.264/AVC video coding standard introduces some improved tools in order to increase compression efficiency. Moreover, the multi-view extension of H.264/AVC, called H.264/MVC, adopts many of them. Among the new features, variable block-size motion estimation is one which contributes to high coding efficiency. Furthermore, it defines a different prediction structure that includes hierarchical bidirectional pictures, outperforming traditional Group of Pictures patterns in both scenarios: single-view and multi-view. However, these video coding techniques have high computational complexity. Several techniques have been proposed in the literature over the last few years which are aimed at accelerating the inter prediction process, but there are no works focusing on bidirectional prediction or hierarchical prediction. In this article, with the emergence of many-core processors or accelerators, a step forward is taken towards an implementation of an H.264/AVC and H.264/MVC inter prediction algorithm on a graphics processing unit. The results show a negligible rate distortion drop with a time reduction of up to 98% for the complete H.264/AVC encoder.
Winters, W.S.
1984-01-01
An overview of the computer code TOPAZ (Transient-One-Dimensional Pipe Flow Analyzer) is presented. TOPAZ models the flow of compressible and incompressible fluids through complex and arbitrary arrangements of pipes, valves, flow branches and vessels. Heat transfer to and from the fluid containment structures (i.e. vessel and pipe walls) can also be modeled. This document includes discussions of the fluid flow equations and containment heat conduction equations. The modeling philosophy, numerical integration technique, code architecture, and methods for generating the computational mesh are also discussed.
Hodgdon, M.L.; Oona, H.; Martinez, A.R.; Salon, S.; Wendling, P.; Krahenbuhl, L.; Nicolas, A.; Nicolas, L.
1989-01-01
We present herein the results of three electromagnetic field problems for compressed magnetic field generators and their associated power flow channels. The first problem is the computation of the transient magnetic field in a two-dimensional model of helical generator during loading. The second problem is the three-dimensional eddy current patterns in a section of an armature beneath a bifurcation point of a helical winding. Our third problem is the calculation of the three-dimensional electrostatic fields in a region known as the post-hole convolute in which a rod connects the inner and outer walls of a system of three concentric cylinders through a hole in the middle cylinder. While analytic solutions exist for many electromagnetic field problems in cases of special and ideal geometries, the solutions of these and similar problems for the proper analysis and design of compressed magnetic field generators and their related hardware require computer simulations. In earlier studies, computer models have been proposed, several based on research oriented hydrocodes to which uncoupled or partially coupled Maxwell's equations solvers are added. Although the hydrocode models address the problem of moving, deformable conductors, they are not useful for electromagnetic analysis, nor can they be considered design tools. For our studies, we take advantage of the commercial, electromagnetic computer-aided design software packages FLUX2D nd PHI3D that were developed for motor manufacturers and utilities industries. 4 refs., 6 figs.
Simulating Gyrokinetic/fluid hybrid electromagnetic modes in the total-f gyrokinetic code XGC1
NASA Astrophysics Data System (ADS)
Lang, Jianying; Hager, Robert; Ku, Seung-Hoe; Chang, Choong-Seock
2015-11-01
XGC1 code has been extended to include the electronmagnetic capability using the hybrid model with gyrokinetic ions and fluid electrons. This feature will enable a more complete description of the MHD/fluid type mode activities including ELMs and low-n tearing modes. Their interaction with the kinetic neoclassical and microturbulence dynamics needs to be simulated together. Evolution of the background profile should also be captured self-consistently. We report recent development and verification of this hybrid model in the limit of small delta-B. The code has been verified for Alfven waves and ITG/KBM transition, and low-n resistive tearing modes. The KBM capability of XGC1 has been verified against the published results from Gyro, GEM, GS2, Gene, and GTC. Detailed verification of resistive tearing modes and kink modes in the toroidal geometry will be also presented. An implicit method is implemented in XGC1 to bypass the Courant condition caused by fast Alfven oscillations. Work supported by US DOE OFES and OASCR.
Nichols, B. D.; Mueller, C.; Necker, G. A.; Travis, J. R.; Spore, J. W.; Lam, K. L.; Royl, P.; Wilson, T. L.
1998-10-01
Los Alamos National Laboratory (LANL) and Forschungszentrum Karlsruhe (FzK) are developing GASFLOW, a three-dimensional (3D) fluid dynamics field code as a best-estimate tool to characterize local phenomena within a flow field. Examples of 3D phenomena include circulation patterns; flow stratification; hydrogen distribution mixing and stratification; combustion and flame propagation; effects of noncondensable gas distribution on local condensation and evaporation; and aerosol entrainment, transport, and deposition. An analysis with GASFLOW will result in a prediction of the gas composition and discrete particle distribution in space and time throughout the facility and the resulting pressure and temperature loadings on the walls and internal structures with or without combustion. A major application of GASFLOW is for predicting the transport, mixing, and combustion of hydrogen and other gases in nuclear reactor containment and other facilities. It has been applied to situations involving transporting and distributing combustible gas mixtures. It has been used to study gas dynamic behavior in low-speed, buoyancy-driven flows, as well as sonic flows or diffusion dominated flows; and during chemically reacting flows, including deflagrations. The effects of controlling such mixtures by safety systems can be analyzed. The code version described in this manual is designated GASFLOW 2.1, which combines previous versions of the United States Nuclear Regulatory Commission code HMS (for Hydrogen Mixing Studies) and the Department of Energy and FzK versions of GASFLOW. The code was written in standard Fortran 90. This manual comprises three volumes. Volume I describes the governing physical equations and computational model. Volume II describes how to use the code to set up a model geometry, specify gas species and material properties, define initial and boundary conditions, and specify different outputs, especially graphical displays. Sample problems are included. Volume III
Müller, C.; Hughes, E. D.; Niederauer, G. F.; Wilkening, H.; Travis, J. R.; Spore, J. W.; Royl, P.; Baumann, W.
1998-10-01
Los Alamos National Laboratory (LANL) and Forschungszentrum Karlsruhe (FzK) are developing GASFLOW, a three-dimensional (3D) fluid dynamics field code as a best- estimate tool to characterize local phenomena within a flow field. Examples of 3D phenomena include circulation patterns; flow stratification; hydrogen distribution mixing and stratification; combustion and flame propagation; effects of noncondensable gas distribution on local condensation and evaporation; and aerosol entrainment, transport, and deposition. An analysis with GASFLOW will result in a prediction of the gas composition and discrete particle distribution in space and time throughout the facility and the resulting pressure and temperature loadings on the walls and internal structures with or without combustion. A major application of GASFLOW is for predicting the transport, mixing, and combustion of hydrogen and other gases in nuclear reactor containment and other facilities. It has been applied to situations involving transporting and distributing combustible gas mixtures. It has been used to study gas dynamic behavior in low-speed, buoyancy-driven flows, as well as sonic flows or diffusion dominated flows; and during chemically reacting flows, including deflagrations. The effects of controlling such mixtures by safety systems can be analyzed. The code version described in this manual is designated GASFLOW 2.1, which combines previous versions of the United States Nuclear Regulatory Commission code HMS (for Hydrogen Mixing Studies) and the Department of Energy and FzK versions of GASFLOW. The code was written in standard Fortran 90. This manual comprises three volumes. Volume I describes the governing physical equations and computational model. Volume II describes how to use the code to set up a model geometry, specify gas species and material properties, define initial and boundary conditions, and specify different outputs, especially graphical displays. Sample problems are included. Volume
NASA Astrophysics Data System (ADS)
Krebs, Isabel; Jardin, Stephen C.; Igochine, Valentin; Guenter, Sibylle; Hoelzl, Matthias; ASDEX Upgrade Team
2014-10-01
We study sawtooth reconnection in ASDEX Upgrade tokamak plasmas by means of 3D non-linear two-fluid MHD simulations in toroidal geometry using the high-order finite element code M3D-C1. Parameters and equilibrium of the simulations are based on typical sawtoothing ASDEX Upgrade discharges. The simulation results are compared to features of the experimental observations such as the sawtooth crash time and frequency, the evolution of the safety factor profile and the 3D evolution of the temperature. 2D ECE imaging measurements during sawtooth crashes in ASDEX Upgrade indicate that the heat is transported out of the core through a narrow poloidally localized region. We investigate if incomplete sawtooth reconnection can be seen in the simulations which is suggested by soft X-ray tomography measurements in ASDEX Upgrade showing that an (m = 1, n = 1) perturbation is typically observed to survive the sawtooth crash and approximately maintain its radial position.
NASA Technical Reports Server (NTRS)
Chang, Chau-Lyan
2003-01-01
During the past two decades, our understanding of laminar-turbulent transition flow physics has advanced significantly owing to, in a large part, the NASA program support such as the National Aerospace Plane (NASP), High-speed Civil Transport (HSCT), and Advanced Subsonic Technology (AST). Experimental, theoretical, as well as computational efforts on various issues such as receptivity and linear and nonlinear evolution of instability waves take part in broadening our knowledge base for this intricate flow phenomenon. Despite all these advances, transition prediction remains a nontrivial task for engineers due to the lack of a widely available, robust, and efficient prediction tool. The design and development of the LASTRAC code is aimed at providing one such engineering tool that is easy to use and yet capable of dealing with a broad range of transition related issues. LASTRAC was written from scratch based on the state-of-the-art numerical methods for stability analysis and modem software technologies. At low fidelity, it allows users to perform linear stability analysis and N-factor transition correlation for a broad range of flow regimes and configurations by using either the linear stability theory (LST) or linear parabolized stability equations (LPSE) method. At high fidelity, users may use nonlinear PSE to track finite-amplitude disturbances until the skin friction rise. Coupled with the built-in receptivity model that is currently under development, the nonlinear PSE method offers a synergistic approach to predict transition onset for a given disturbance environment based on first principles. This paper describes the governing equations, numerical methods, code development, and case studies for the current release of LASTRAC. Practical applications of LASTRAC are demonstrated for linear stability calculations, N-factor transition correlation, non-linear breakdown simulations, and controls of stationary crossflow instability in supersonic swept wing boundary
The first transport code simulations using the trapped gyro-Landau-fluid model
Kinsey, J. E.; Staebler, G. M.; Waltz, R. E.
2008-05-15
The first transport code simulations using the newly developed trapped gyro-Landau-fluid (TGLF) theory-based transport model are presented. TGLF has comprehensive physics to approximate the turbulent transport due to drift-ballooning modes in tokamaks. The TGLF model is a next generation gyro-Landau-fluid model that improves the accuracy of the trapped particle response and the finite Larmor radius effects compared to its predecessor, GLF23. The model solves for the linear eigenmodes of trapped ion and electron modes, ion and electron temperature gradient modes, and electromagnetic kinetic ballooning modes in either shifted circle or shaped geometry. A database of over 400 nonlinear gyrokinetic simulations using the GYRO code has been created. A subset of 83 simulations with shaped geometry has been used to find a model for the saturation levels. Using a simple quasilinear (QL) saturation rule, remarkable agreement with the energy and particle fluxes from a wide variety of GYRO simulations is found for both shaped or circular geometry and also for low aspect ratio. Using this new QL saturation rule along with a new ExB shear quench rule for shaped geometry, the density and temperature profiles have been predicted in over 500 transport code runs and the results compared against experimental data from 96 tokamak discharges. Compared to GLF23, the TGLF model demonstrates better agreement between the predicted and experimental temperature profiles. Surprisingly, TGLF predicts that the high-k modes are found to play an important role in the central core region of low and high confinement plasmas lacking transport barriers.
High-performance computational fluid dynamics: a custom-code approach
NASA Astrophysics Data System (ADS)
Fannon, James; Loiseau, Jean-Christophe; Valluri, Prashant; Bethune, Iain; Náraigh, Lennon Ó.
2016-07-01
We introduce a modified and simplified version of the pre-existing fully parallelized three-dimensional Navier–Stokes flow solver known as TPLS. We demonstrate how the simplified version can be used as a pedagogical tool for the study of computational fluid dynamics (CFDs) and parallel computing. TPLS is at its heart a two-phase flow solver, and uses calls to a range of external libraries to accelerate its performance. However, in the present context we narrow the focus of the study to basic hydrodynamics and parallel computing techniques, and the code is therefore simplified and modified to simulate pressure-driven single-phase flow in a channel, using only relatively simple Fortran 90 code with MPI parallelization, but no calls to any other external libraries. The modified code is analysed in order to both validate its accuracy and investigate its scalability up to 1000 CPU cores. Simulations are performed for several benchmark cases in pressure-driven channel flow, including a turbulent simulation, wherein the turbulence is incorporated via the large-eddy simulation technique. The work may be of use to advanced undergraduate and graduate students as an introductory study in CFDs, while also providing insight for those interested in more general aspects of high-performance computing.
Two-fluid 2.5D code for simulations of small scale magnetic fields in the lower solar atmosphere
NASA Astrophysics Data System (ADS)
Piantschitsch, Isabell; Amerstorfer, Ute; Thalmann, Julia Katharina; Hanslmeier, Arnold; Lemmerer, Birgit
2015-08-01
Our aim is to investigate magnetic reconnection as a result of the time evolution of magnetic flux tubes in the solar chromosphere. A new numerical two-fluid code was developed, which will perform a 2.5D simulation of the dynamics from the upper convection zone up to the transition region. The code is based on the Total Variation Diminishing Lax-Friedrichs method and includes the effects of ion-neutral collisions, ionisation/recombination, thermal/resistive diffusivity as well as collisional/resistive heating. What is innovative about our newly developed code is the inclusion of a two-fluid model in combination with the use of analytically constructed vertically open magnetic flux tubes, which are used as initial conditions for our simulation. First magnetohydrodynamic (MHD) tests have already shown good agreement with known results of numerical MHD test problems like e.g. the Orszag-Tang vortex test, the Current Sheet test or the Spherical Blast Wave test. Furthermore, the single-fluid approach will also be applied to the initial conditions, in order to compare the different rates of magnetic reconnection in both codes, the two-fluid code and the single-fluid one.
Automatic Generation of OpenMP Directives and Its Application to Computational Fluid Dynamics Codes
NASA Technical Reports Server (NTRS)
Yan, Jerry; Jin, Haoqiang; Frumkin, Michael; Yan, Jerry (Technical Monitor)
2000-01-01
The shared-memory programming model is a very effective way to achieve parallelism on shared memory parallel computers. As great progress was made in hardware and software technologies, performance of parallel programs with compiler directives has demonstrated large improvement. The introduction of OpenMP directives, the industrial standard for shared-memory programming, has minimized the issue of portability. In this study, we have extended CAPTools, a computer-aided parallelization toolkit, to automatically generate OpenMP-based parallel programs with nominal user assistance. We outline techniques used in the implementation of the tool and discuss the application of this tool on the NAS Parallel Benchmarks and several computational fluid dynamics codes. This work demonstrates the great potential of using the tool to quickly port parallel programs and also achieve good performance that exceeds some of the commercial tools.
Simulating Magnetic Reconnection Experiment (MRX) with a Guide Field using Fluid Code, HiFi
NASA Astrophysics Data System (ADS)
Budner, Tamas; Chen, Yangao; Meier, Eric; Ji, Hantao; MRX Team
2015-11-01
Magnetic reconnection is a phenomenon that occurs in plasmas when magnetic field lines effectively ``break'' and reconnect resulting in a different topological configuration. In this process, energy that was once stored in the magnetic field is transfered into the thermal velocity of the particles, effectively heating the plasma. MRX at the Princeton Plasma Physics Laboratory creates the conditions under which reconnection can occur by initially ramping the current in two adjacent coils and then rapidly decreasing with and without a guide magnetic field along the reconnecting current. We simulate this experiment using a fluid code called HiFi, an implicit and adaptive high order spectral element modeling framework, and compare our results to experimental data from MRX. The purpose is to identify physics behind the observed reconnection process for the field line break and the resultant plasma heating.
GANDALF: Graphical Astrophysics code for N-body Dynamics And Lagrangian Fluids
NASA Astrophysics Data System (ADS)
Hubber, David; Rosotti, Giovanni
2016-02-01
GANDALF, a successor to SEREN (ascl:1102.010), is a hybrid self-gravitating fluid dynamics and collisional N-body code primarily designed for investigating star formation and planet formation problems. GANDALF uses various implementations of Smoothed Particle Hydrodynamics (SPH) to perform hydrodynamical simulations of gas clouds undergoing gravitational collapse to form new stars (or other objects), and can perform simulations of pure N-body dynamics using high accuracy N-body integrators, model the intermediate phase of cluster evolution, and provide visualizations via its python interface as well as interactive simulations. Although based on many of the SEREN routines, GANDALF has been largely re-written from scratch in C++ using more optimal algorithms and data structures.
Development and application of a multi-fluid simulation code for modeling interpenetrating plasmas
NASA Astrophysics Data System (ADS)
Khodak, M.; Berger, R. L.; Chapman, T.; Hittinger, J. A. F.
2015-11-01
A multi-fluid model, with independent velocities for all species, is developed and implemented for the numerical simulation of the interpenetration of colliding plasmas. The Euler equations for fluid flow, coupled through electron-ion and ion-ion collisional drag terms, thermal equilibration terms, and the electric field, are solved for each ion species with the electrons treated under a quasineutrality assumption. Fourth-order spatial convergence in smooth regions is achieved using flux-conservative iterative time integration and a Weighted Essentially Non-Oscillatory (WENO) finite volume scheme employing an approximate Riemann solver. Analytic solutions of well-known shock tube tests and spectral solutions of the linearized coupled system are used to test the implementation, and the model is further numerically compared to interpenetration experiments such as those of J.S. Ross et al. [Phys. Rev. Lett. 110 145005 (2013)]. This work has applications to laser-plasma interactions, specifically to hohlraum physics, as well as to modeling laboratory experiments of collisionless shocks important in astrophysical plasmas. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project code 15-ERD-038.
Not Available
1984-10-01
STEALTH is a family of computer codes that can be used to calculate a variety of physical processes in which the dynamic behavior of a continuum is involved. The version of STEALTH described in this volume is designed for calculations of fluid-structure interaction. This version of the program consists of a hydrodynamic version of STEALTH which has been coupled to a finite-element code, WHAMSE. STEALTH computes the transient response of the fluid continuum, while WHAMSE computes the transient response of shell and beam structures under external fluid loadings. The coupling between STEALTH and WHAMSE is performed during each cycle or step of a calculation. Separate calculations of fluid response and structure response are avoided, thereby giving a more accurate model of the dynamic coupling between fluid and structure. This volume provides the theoretical background, the finite-difference equations, the finite-element equations, a discussion of several sample problems, a listing of the input decks for the sample problems, a programmer's manual and a description of the input records for the STEALTH/WHAMSE computer program.
NASA Technical Reports Server (NTRS)
Shapiro, Wilbur; Chupp, Raymond; Holle, Glenn; Scott, Thomas
2004-01-01
The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allow the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines
NASA Astrophysics Data System (ADS)
Massimo, F.; Marocchino, A.; Rossi, A. R.
2016-09-01
The realization of Plasma Wakefield Acceleration experiments with high quality of the accelerated bunches requires an increasing number of numerical simulations to perform first-order assessments for the experimental design and online-analysis of the experimental results. Particle in Cell codes are the state-of-the-art tools to study the beam-plasma interaction mechanism, but due to their requirements in terms of number of cores and computational time makes them unsuitable for quick parametric scans. Considerable interest has been shown thus in methods which reduce the computational time needed for the simulation of plasma acceleration. Such methods include the use of hybrid kinetic-fluid models, which treat the relativistic bunches as in a PIC code and the background plasma electrons as a fluid. A technique to properly initialize the bunch electromagnetic fields in the time explicit hybrid kinetic-fluid code Architect is presented, as well the implementation of the Flux Corrected Transport scheme for the fluid equations integrated in the code.
NASA Technical Reports Server (NTRS)
Liang, Anita D. (Technical Monitor); Artiles, Antonio
2004-01-01
The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allow the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines.
Viriato: a Fourier-Hermite spectral code for strongly magnetised fluid-kinetic plasma dynamics
NASA Astrophysics Data System (ADS)
Loureiro, Nuno; Dorland, William; Fazendeiro, Luis; Kanekar, Anjor; Mallet, Alfred; Zocco, Alessandro
2015-11-01
We report on the algorithms and numerical methods used in Viriato, a novel fluid-kinetic code that solves two distinct sets of equations: (i) the Kinetic Reduced Electron Heating Model equations [Zocco & Schekochihin, 2011] and (ii) the kinetic reduced MHD (KRMHD) equations [Schekochihin et al., 2009]. Two main applications of these equations are magnetised (Alfvnénic) plasma turbulence and magnetic reconnection. Viriato uses operator splitting to separate the dynamics parallel and perpendicular to the ambient magnetic field (assumed strong). Along the magnetic field, Viriato allows for either a second-order accurate MacCormack method or, for higher accuracy, a spectral-like scheme. Perpendicular to the field Viriato is pseudo-spectral, and the time integration is performed by means of an iterative predictor-corrector scheme. In addition, a distinctive feature of Viriato is its spectral representation of the parallel velocity-space dependence, achieved by means of a Hermite representation of the perturbed distribution function. A series of linear and nonlinear benchmarks and tests are presented, with focus on 3D decaying kinetic turbulence. Work partially supported by Fundação para a Ciência e Tecnologia via Grants UID/FIS/50010/2013 and IF/00530/2013.
Aceves, S M; Flowers, D L; Chen, J; Babaimopoulos, A
2006-08-29
We have developed an artificial neural network (ANN) based combustion model and have integrated it into a fluid mechanics code (KIVA3V) to produce a new analysis tool (titled KIVA3V-ANN) that can yield accurate HCCI predictions at very low computational cost. The neural network predicts ignition delay as a function of operating parameters (temperature, pressure, equivalence ratio and residual gas fraction). KIVA3V-ANN keeps track of the time history of the ignition delay during the engine cycle to evaluate the ignition integral and predict ignition for each computational cell. After a cell ignites, chemistry becomes active, and a two-step chemical kinetic mechanism predicts composition and heat generation in the ignited cells. KIVA3V-ANN has been validated by comparison with isooctane HCCI experiments in two different engines. The neural network provides reasonable predictions for HCCI combustion and emissions that, although typically not as good as obtained with the more physically representative multi-zone model, are obtained at a much reduced computational cost. KIVA3V-ANN can perform reasonably accurate HCCI calculations while requiring only 10% more computational effort than a motored KIVA3V run. It is therefore considered a valuable tool for evaluation of engine maps or other performance analysis tasks requiring multiple individual runs.
Friedel, Michael J.
2001-01-01
This report describes a model for simulating transient, Variably Saturated, coupled water-heatsolute Transport in heterogeneous, anisotropic, 2-Dimensional, ground-water systems with variable fluid density (VST2D). VST2D was developed to help understand the effects of natural and anthropogenic factors on quantity and quality of variably saturated ground-water systems. The model solves simultaneously for one or more dependent variables (pressure, temperature, and concentration) at nodes in a horizontal or vertical mesh using a quasi-linearized general minimum residual method. This approach enhances computational speed beyond the speed of a sequential approach. Heterogeneous and anisotropic conditions are implemented locally using individual element property descriptions. This implementation allows local principal directions to differ among elements and from the global solution domain coordinates. Boundary conditions can include time-varying pressure head (or moisture content), heat, and/or concentration; fluxes distributed along domain boundaries and/or at internal node points; and/or convective moisture, heat, and solute fluxes along the domain boundaries; and/or unit hydraulic gradient along domain boundaries. Other model features include temperature and concentration dependent density (liquid and vapor) and viscosity, sorption and/or decay of a solute, and capability to determine moisture content beyond residual to zero. These features are described in the documentation together with development of the governing equations, application of the finite-element formulation (using the Galerkin approach), solution procedure, mass and energy balance considerations, input requirements, and output options. The VST2D model was verified, and results included solutions for problems of water transport under isohaline and isothermal conditions, heat transport under isobaric and isohaline conditions, solute transport under isobaric and isothermal conditions, and coupled water
NASA Technical Reports Server (NTRS)
Liang, Anita D. (Technical Monitor); Shapiro, Wilbur
2004-01-01
The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allow the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines.
NASA Technical Reports Server (NTRS)
Athavale, Mahesh; Przekwas, Andrzej
2004-01-01
The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allow the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines.
Ramshaw, J D
2000-10-01
A simple model was recently described for predicting the time evolution of the width of the mixing layer at an unstable fluid interface [J. D. Ramshaw, Phys. Rev. E 58, 5834 (1998); ibid. 61, 5339 (2000)]. The ordinary differential equations of this model have been heuristically generalized into partial differential equations suitable for implementation in multicomponent hydrodynamics codes. The central ingredient in this generalization is a nun-diffusional expression for the species mass fluxes. These fluxes describe the relative motion of the species, and thereby determine the local mixing rate and spatial distribution of mixed fluid as a function of time. The generalized model has been implemented in a two-dimensional hydrodynamics code. The model equations and implementation procedure are summarized, and comparisons with experimental mixing data are presented.
Joseph, Ilon
2014-05-27
Jacobian-free Newton-Krylov (JFNK) algorithms are a potentially powerful class of methods for solving the problem of coupling codes that address dfferent physics models. As communication capability between individual submodules varies, different choices of coupling algorithms are required. The more communication that is available, the more possible it becomes to exploit the simple sparsity pattern of the Jacobian, albeit of a large system. The less communication that is available, the more dense the Jacobian matrices become and new types of preconditioners must be sought to efficiently take large time steps. In general, methods that use constrained or reduced subsystems can offer a compromise in complexity. The specific problem of coupling a fluid plasma code to a kinetic neutrals code is discussed as an example.
Greg Flach, Frank Smith
2011-12-31
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.
Energy Science and Technology Software Center (ESTSC)
2011-12-31
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less
NASA Astrophysics Data System (ADS)
Lotsch, Bettina V.
2015-07-01
Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chemistry perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major—yet largely disjunct—developments in 2D heterostructures, which are firmly rooted in solid-state chemistry or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.
GEO2D - Two-Dimensional Computer Model of a Ground Source Heat Pump System
James Menart
2013-06-07
This file contains a zipped file that contains many files required to run GEO2D. GEO2D is a computer code for simulating ground source heat pump (GSHP) systems in two-dimensions. GEO2D performs a detailed finite difference simulation of the heat transfer occurring within the working fluid, the tube wall, the grout, and the ground. Both horizontal and vertical wells can be simulated with this program, but it should be noted that the vertical wall is modeled as a single tube. This program also models the heat pump in conjunction with the heat transfer occurring. GEO2D simulates the heat pump and ground loop as a system. Many results are produced by GEO2D as a function of time and position, such as heat transfer rates, temperatures and heat pump performance. On top of this information from an economic comparison between the geothermal system simulated and a comparable air heat pump systems or a comparable gas, oil or propane heating systems with a vapor compression air conditioner. The version of GEO2D in the attached file has been coupled to the DOE heating and cooling load software called ENERGYPLUS. This is a great convenience for the user because heating and cooling loads are an input to GEO2D. GEO2D is a user friendly program that uses a graphical user interface for inputs and outputs. These make entering data simple and they produce many plotted results that are easy to understand. In order to run GEO2D access to MATLAB is required. If this program is not available on your computer you can download the program MCRInstaller.exe, the 64 bit version, from the MATLAB website or from this geothermal depository. This is a free download which will enable you to run GEO2D..
Brittle damage models in DYNA2D
Faux, D.R.
1997-09-01
DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.
Users manual for CAFE-3D : a computational fluid dynamics fire code.
Khalil, Imane; Lopez, Carlos; Suo-Anttila, Ahti Jorma
2005-03-01
The Container Analysis Fire Environment (CAFE) computer code has been developed to model all relevant fire physics for predicting the thermal response of massive objects engulfed in large fires. It provides realistic fire thermal boundary conditions for use in design of radioactive material packages and in risk-based transportation studies. The CAFE code can be coupled to commercial finite-element codes such as MSC PATRAN/THERMAL and ANSYS. This coupled system of codes can be used to determine the internal thermal response of finite element models of packages to a range of fire environments. This document is a user manual describing how to use the three-dimensional version of CAFE, as well as a description of CAFE input and output parameters. Since this is a user manual, only a brief theoretical description of the equations and physical models is included.
Duda, L.E.
1987-01-01
The high temperatures of geothermal wells present severe problems for drilling, logging, and developing these reservoirs. Cooling the wellbore is perhaps the most common method to solve these problems. However, it is usually not clear what may be the most effective wellbore cooling mechanism for a given well. In this paper, wellbore cooling by the use of circulation or by fluid injection into the surrounding rock is investigated using a wellbore thermal simulator computer code. Short circulation times offer no prolonged cooling of the wellbore, but long circulation times (greater than ten or twenty days) greatly reduce the warming rate after shut-in. The dependence of the warming rate on the penetration distance of cooler temperatures into the rock formation (as by fluid injection) is investigated. Penetration distances of greater than 0.6 m appear to offer a substantial reduction in the warming rate. Several plots are shown which demonstrate these effects.
Rahatgaonkar, P. S.; Datta, D.; Malhotra, P. K.; Ghadge, S. G.
2012-07-01
Prediction of groundwater movement and contaminant transport in soil is an important problem in many branches of science and engineering. This includes groundwater hydrology, environmental engineering, soil science, agricultural engineering and also nuclear engineering. Specifically, in nuclear engineering it is applicable in the design of spent fuel storage pools and waste management sites in the nuclear power plants. Ground water modeling involves the simulation of flow and contaminant transport by groundwater flow. In the context of contaminated soil and groundwater system, numerical simulations are typically used to demonstrate compliance with regulatory standard. A one-dimensional Computational Fluid Dynamics code GFLOW had been developed based on the Finite Difference Method for simulating groundwater flow and contaminant transport through saturated and unsaturated soil. The code is validated with the analytical model and the benchmarking cases available in the literature. (authors)
A fluid-particle hybrid framework for the PLUTO code: applications to non-thermal emission in jets.
NASA Astrophysics Data System (ADS)
Vaidya, B.; Mignone, A.; Bodo, G.; Massaglia, S.
2016-05-01
We present an implementation of a fully parallel hybrid framework for the evolution of Lagrangian particles coupled to a MHD fluid for the PLUTO code. For the applications of interest, particles represent ensembles of electrons whose spectral energy distribution is governed by a kinetic transport equation that takes into account different physical processes such as diffusive shock acceleration, synchrotron emission and adiabatic expansion. An application to model non-thermal emission from extragalactic jets shows the effectiveness and strength of the approach in describing not only the dynamics but also the radiation properties of jets and, in general, of high-energy astrophysical plasma environments.
Energy Science and Technology Software Center (ESTSC)
2002-01-31
This program solves the two-dimensional mechanical equilbrium configuration of a core restraint system, which is subjected to radial temperature and flux gradients, on a time increment basis. At each time increment, the code calculates the irradiation creep and swelling strains for each duct from user-specified creep and swelling correlations. Using the calculated thermal bowing, inelastic bowing and the duct dilation, the corresponding equilibrium forces, beam deflections, total beam displacements, and structural reactivity changes are calculated.
Code System for Two-Dinensional Sn-Neutronics and Fluid Dynamics.
Energy Science and Technology Software Center (ESTSC)
2003-07-28
Version 00 SIMMERII is designed to predict the neutronic and fluid-dynamic behavior of an LMFBR during a hypothetical core-disruptive accident. Cross sections depend on temperature and background cross sections. The structure, liquid, and vapor fields are modeled to predict the fluid-dynamic behavior of the reactor. Each field consists of density components to follow the material motion and energy components to predict the material temperatures. For typical accident calculations, the materials are fertile fuel, fissile fuel,more » stainless steel, sodium, control material, and fission gas. Heat, mass, and momentum transfer among the three fields and their components are calculated.« less
SCISEAL: A CFD code for analysis of fluid dynamic forces in seals
NASA Technical Reports Server (NTRS)
Athavale, Mahesh; Przekwas, Andrzej
1994-01-01
A viewgraph presentation is made of the objectives, capabilities, and test results of the computer code SCISEAL. Currently, the seal code has: a finite volume, pressure-based integration scheme; colocated variables with strong conservation approach; high-order spatial differencing, up to third-order; up to second-order temporal differencing; a comprehensive set of boundary conditions; a variety of turbulence models and surface roughness treatment; moving grid formulation for arbitrary rotor whirl; rotor dynamic coefficients calculated by the circular whirl and numerical shaker methods; and small perturbation capabilities to handle centered and eccentric seals.
A Two-Dimensional Compressible Gas Flow Code
Energy Science and Technology Software Center (ESTSC)
1995-03-17
F2D is a general purpose, two dimensional, fully compressible thermal-fluids code that models most of the phenomena found in situations of coupled fluid flow and heat transfer. The code solves momentum, continuity, gas-energy, and structure-energy equations using a predictor-correction solution algorithm. The corrector step includes a Poisson pressure equation. The finite difference form of the equation is presented along with a description of input and output. Several example problems are included that demonstrate the applicabilitymore » of the code in problems ranging from free fluid flow, shock tubes and flow in heated porous media.« less
The Proteus Navier-Stokes code. [two and three dimensional computational fluid dynamics
NASA Technical Reports Server (NTRS)
Towne, Charles E.; Schwab, John R.
1992-01-01
An effort is currently underway at NASA Lewis to develop two and three dimensional Navier-Stokes codes, called Proteus, for aerospace propulsion applications. Proteus solves the Reynolds-averaged, unsteady, compressible Navier-Stokes equations in strong conservation law form. Turbulence is modeled using a Baldwin-Lomax based algebraic eddy viscosity model. In addition, options are available to solve thin layer or Euler equations, and to eliminate the energy equation by assuming constant stagnation enthalpy. An extensive series of validation cases have been run, primarily using the two dimensional planar/axisymmetric version of the code. Several flows were computed that have exact solution such as: fully developed channel and pipe flow; Couette flow with and without pressure gradients; unsteady Couette flow formation; flow near a suddenly accelerated flat plate; flow between concentric rotating cylinders; and flow near a rotating disk. The two dimensional version of the Proteus code has been released, and the three dimensional code is scheduled for release in late 1991.
MPI implementation of PHOENICS: A general purpose computational fluid dynamics code
Simunovic, S.; Zacharia, T.; Baltas, N.; Spalding, D.B.
1995-04-01
PHOENICS is a suite of computational analysis programs that are used for simulation of fluid flow, heat transfer, and dynamical reaction processes. The parallel version of the solver EARTH for the Computational Fluid Dynamics (CFD) program PHOENICS has been implemented using Message Passing Interface (MPI) standard. Implementation of MPI version of PHOENICS makes this computational tool portable to a wide range of parallel machines and enables the use of high performance computing for large scale computational simulations. MPI libraries are available on several parallel architectures making the program usable across different architectures as well as on heterogeneous computer networks. The Intel Paragon NX and MPI versions of the program have been developed and tested on massively parallel supercomputers Intel Paragon XP/S 5, XP/S 35, and Kendall Square Research, and on the multiprocessor SGI Onyx computer at Oak Ridge National Laboratory. The preliminary testing results of the developed program have shown scalable performance for reasonably sized computational domains.
MPI implementation of PHOENICS: A general purpose computational fluid dynamics code
NASA Astrophysics Data System (ADS)
Simunovic, S.; Zacharia, T.; Baltas, N.; Spalding, D. B.
1995-03-01
PHOENICS is a suite of computational analysis programs that are used for simulation of fluid flow, heat transfer, and dynamical reaction processes. The parallel version of the solver EARTH for the Computational Fluid Dynamics (CFD) program PHOENICS has been implemented using Message Passing Interface (MPI) standard. Implementation of MPI version of PHOENICS makes this computational tool portable to a wide range of parallel machines and enables the use of high performance computing for large scale computational simulations. MPI libraries are available on several parallel architectures making the program usable across different architectures as well as on heterogeneous computer networks. The Intel Paragon NX and MPI versions of the program have been developed and tested on massively parallel supercomputers Intel Paragon XP/S 5, XP/S 35, and Kendall Square Research, and on the multiprocessor SGI Onyx computer at Oak Ridge National Laboratory. The preliminary testing results of the developed program have shown scalable performance for reasonably sized computational domains.
SCISEAL: A CFD Code for Analysis of Fluid Dynamic Forces in Seals
NASA Technical Reports Server (NTRS)
Althavale, Mahesh M.; Ho, Yin-Hsing; Przekwas, Andre J.
1996-01-01
A 3D CFD code, SCISEAL, has been developed and validated. Its capabilities include cylindrical seals, and it is employed on labyrinth seals, rim seals, and disc cavities. State-of-the-art numerical methods include colocated grids, high-order differencing, and turbulence models which account for wall roughness. SCISEAL computes efficient solutions for complicated flow geometries and seal-specific capabilities (rotor loads, torques, etc.).
A Supersonic Argon/Air Coaxial Jet Experiment for Computational Fluid Dynamics Code Validation
NASA Technical Reports Server (NTRS)
Clifton, Chandler W.; Cutler, Andrew D.
2007-01-01
A non-reacting experiment is described in which data has been acquired for the validation of CFD codes used to design high-speed air-breathing engines. A coaxial jet-nozzle has been designed to produce pressure-matched exit flows of Mach 1.8 at 1 atm in both a center jet of argon and a coflow jet of air, creating a supersonic, incompressible mixing layer. The flowfield was surveyed using total temperature, gas composition, and Pitot probes. The data set was compared to CFD code predictions made using Vulcan, a structured grid Navier-Stokes code, as well as to data from a previous experiment in which a He-O2 mixture was used instead of argon in the center jet of the same coaxial jet assembly. Comparison of experimental data from the argon flowfield and its computational prediction shows that the CFD produces an accurate solution for most of the measured flowfield. However, the CFD prediction deviates from the experimental data in the region downstream of x/D = 4, underpredicting the mixing-layer growth rate.
Static & Dynamic Response of 2D Solids
Energy Science and Technology Software Center (ESTSC)
1996-07-15
NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surfacemore » contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.« less
Compact 2-D graphical representation of DNA
NASA Astrophysics Data System (ADS)
Randić, Milan; Vračko, Marjan; Zupan, Jure; Novič, Marjana
2003-05-01
We present a novel 2-D graphical representation for DNA sequences which has an important advantage over the existing graphical representations of DNA in being very compact. It is based on: (1) use of binary labels for the four nucleic acid bases, and (2) use of the 'worm' curve as template on which binary codes are placed. The approach is illustrated on DNA sequences of the first exon of human β-globin and gorilla β-globin.
Mason, W.E.
1983-03-01
A set of finite element codes for the solution of nonlinear, two-dimensional (TACO2D) and three-dimensional (TACO3D) heat transfer problems. Performs linear and nonlinear analyses of both transient and steady state heat transfer problems. Has the capability to handle time or temperature dependent material properties. Materials may be either isotropic or orthotropic. A variety of time and temperature dependent boundary conditions and loadings are available including temperature, flux, convection, radiation, and internal heat generation.
THE PLUTO CODE FOR ADAPTIVE MESH COMPUTATIONS IN ASTROPHYSICAL FLUID DYNAMICS
Mignone, A.; Tzeferacos, P.; Zanni, C.; Bodo, G.; Van Straalen, B.; Colella, P.
2012-01-01
We present a description of the adaptive mesh refinement (AMR) implementation of the PLUTO code for solving the equations of classical and special relativistic magnetohydrodynamics (MHD and RMHD). The current release exploits, in addition to the static grid version of the code, the distributed infrastructure of the CHOMBO library for multidimensional parallel computations over block-structured, adaptively refined grids. We employ a conservative finite-volume approach where primary flow quantities are discretized at the cell center in a dimensionally unsplit fashion using the Corner Transport Upwind method. Time stepping relies on a characteristic tracing step where piecewise parabolic method, weighted essentially non-oscillatory, or slope-limited linear interpolation schemes can be handily adopted. A characteristic decomposition-free version of the scheme is also illustrated. The solenoidal condition of the magnetic field is enforced by augmenting the equations with a generalized Lagrange multiplier providing propagation and damping of divergence errors through a mixed hyperbolic/parabolic explicit cleaning step. Among the novel features, we describe an extension of the scheme to include non-ideal dissipative processes, such as viscosity, resistivity, and anisotropic thermal conduction without operator splitting. Finally, we illustrate an efficient treatment of point-local, potentially stiff source terms over hierarchical nested grids by taking advantage of the adaptivity in time. Several multidimensional benchmarks and applications to problems of astrophysical relevance assess the potentiality of the AMR version of PLUTO in resolving flow features separated by large spatial and temporal disparities.
Validation of a Computational Fluid Dynamics (CFD) Code for Supersonic Axisymmetric Base Flow
NASA Technical Reports Server (NTRS)
Tucker, P. Kevin
1993-01-01
The ability to accurately and efficiently calculate the flow structure in the base region of bodies of revolution in supersonic flight is a significant step in CFD code validation for applications ranging from base heating for rockets to drag for protectives. The FDNS code is used to compute such a flow and the results are compared to benchmark quality experimental data. Flowfield calculations are presented for a cylindrical afterbody at M = 2.46 and angle of attack a = O. Grid independent solutions are compared to mean velocity profiles in the separated wake area and downstream of the reattachment point. Additionally, quantities such as turbulent kinetic energy and shear layer growth rates are compared to the data. Finally, the computed base pressures are compared to the measured values. An effort is made to elucidate the role of turbulence models in the flowfield predictions. The level of turbulent eddy viscosity, and its origin, are used to contrast the various turbulence models and compare the results to the experimental data.
The PLUTO Code for Adaptive Mesh Computations in Astrophysical Fluid Dynamics
NASA Astrophysics Data System (ADS)
Mignone, A.; Zanni, C.; Tzeferacos, P.; van Straalen, B.; Colella, P.; Bodo, G.
2012-01-01
We present a description of the adaptive mesh refinement (AMR) implementation of the PLUTO code for solving the equations of classical and special relativistic magnetohydrodynamics (MHD and RMHD). The current release exploits, in addition to the static grid version of the code, the distributed infrastructure of the CHOMBO library for multidimensional parallel computations over block-structured, adaptively refined grids. We employ a conservative finite-volume approach where primary flow quantities are discretized at the cell center in a dimensionally unsplit fashion using the Corner Transport Upwind method. Time stepping relies on a characteristic tracing step where piecewise parabolic method, weighted essentially non-oscillatory, or slope-limited linear interpolation schemes can be handily adopted. A characteristic decomposition-free version of the scheme is also illustrated. The solenoidal condition of the magnetic field is enforced by augmenting the equations with a generalized Lagrange multiplier providing propagation and damping of divergence errors through a mixed hyperbolic/parabolic explicit cleaning step. Among the novel features, we describe an extension of the scheme to include non-ideal dissipative processes, such as viscosity, resistivity, and anisotropic thermal conduction without operator splitting. Finally, we illustrate an efficient treatment of point-local, potentially stiff source terms over hierarchical nested grids by taking advantage of the adaptivity in time. Several multidimensional benchmarks and applications to problems of astrophysical relevance assess the potentiality of the AMR version of PLUTO in resolving flow features separated by large spatial and temporal disparities.
Validation of a Computational Fluid Dynamics (CFD) code for supersonic axisymmetric base flow
NASA Astrophysics Data System (ADS)
Tucker, P. Kevin
1993-07-01
The ability to accurately and efficiently calculate the flow structure in the base region of bodies of revolution in supersonic flight is a significant step in CFD code validation for applications ranging from base heating for rockets to drag for protectives. The FDNS code is used to compute such a flow and the results are compared to benchmark quality experimental data. Flowfield calculations are presented for a cylindrical afterbody at M = 2.46 and angle of attack a = O. Grid independent solutions are compared to mean velocity profiles in the separated wake area and downstream of the reattachment point. Additionally, quantities such as turbulent kinetic energy and shear layer growth rates are compared to the data. Finally, the computed base pressures are compared to the measured values. An effort is made to elucidate the role of turbulence models in the flowfield predictions. The level of turbulent eddy viscosity, and its origin, are used to contrast the various turbulence models and compare the results to the experimental data.
An advanced combustion research facility for validating computational fluid dynamics codes
NASA Astrophysics Data System (ADS)
Bullard, J. B.; Hurley, C. D.; Eccles, N. C.
1991-12-01
The Sector Combustion Rig (SCR), built to obtain experimental data which could be used to verify computational fluid dynamic programs and to investigate the formation and consumption of combustion products through a combustor, is described. This rig was designed to accommodate sectors of full size engine combustion chambers and to test them at real or simulated engine operating conditions. Changes made to improve the operating, measurement, and data handling capabilities of the rig as a result of experience from several years of operations are described together with some of the features which contribute to the uniqueness of the SCR. The SCR gas analysis system and instrumentation are described. Extracts from some results obtained during a recent program of tests on a Rolls-Royce RB211 combustor are given.
NASA Astrophysics Data System (ADS)
Wang, Jin; Ma, Jianyong; Zhou, Changhe
2014-11-01
A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.
Khajeh, Masoud; Safigholi, Habib
2016-03-01
A miniature X-ray source has been optimized for electronic brachytherapy. The cooling fluid for this device is water. Unlike the radionuclide brachytherapy sources, this source is able to operate at variable voltages and currents to match the dose with the tumor depth. First, Monte Carlo (MC) optimization was performed on the tungsten target-buffer thickness layers versus energy such that the minimum X-ray attenuation occurred. Second optimization was done on the selection of the anode shape based on the Monte Carlo in water TG-43U1 anisotropy function. This optimization was carried out to get the dose anisotropy functions closer to unity at any angle from 0° to 170°. Three anode shapes including cylindrical, spherical, and conical were considered. Moreover, by Computational Fluid Dynamic (CFD) code the optimal target-buffer shape and different nozzle shapes for electronic brachytherapy were evaluated. The characterization criteria of the CFD were the minimum temperature on the anode shape, cooling water, and pressure loss from inlet to outlet. The optimal anode was conical in shape with a conical nozzle. Finally, the TG-43U1 parameters of the optimal source were compared with the literature. PMID:26966563
Khajeh, Masoud; Safigholi, Habib
2015-01-01
A miniature X-ray source has been optimized for electronic brachytherapy. The cooling fluid for this device is water. Unlike the radionuclide brachytherapy sources, this source is able to operate at variable voltages and currents to match the dose with the tumor depth. First, Monte Carlo (MC) optimization was performed on the tungsten target-buffer thickness layers versus energy such that the minimum X-ray attenuation occurred. Second optimization was done on the selection of the anode shape based on the Monte Carlo in water TG-43U1 anisotropy function. This optimization was carried out to get the dose anisotropy functions closer to unity at any angle from 0° to 170°. Three anode shapes including cylindrical, spherical, and conical were considered. Moreover, by Computational Fluid Dynamic (CFD) code the optimal target-buffer shape and different nozzle shapes for electronic brachytherapy were evaluated. The characterization criteria of the CFD were the minimum temperature on the anode shape, cooling water, and pressure loss from inlet to outlet. The optimal anode was conical in shape with a conical nozzle. Finally, the TG-43U1 parameters of the optimal source were compared with the literature. PMID:26966563
NASA Astrophysics Data System (ADS)
Tamain, P.; Bufferand, H.; Ciraolo, G.; Colin, C.; Galassi, D.; Ghendrih, Ph.; Schwander, F.; Serre, E.
2016-09-01
The new code TOKAM3X simulates plasma turbulence in full torus geometry including the open field lines of the Scrape-off Layer (SOL) and the edge closed field lines region in the vicinity of the separatrix. Based on drift-reduced Braginskii equations, TOKAM3X is able to simulate both limited and diverted plasmas. Turbulence is flux driven by incoming particles from the core plasma and no scale separation between the equilibrium and the fluctuations is assumed so that interactions between large scale flows and turbulence are consistently treated. Based on a domain decomposition, specific numerical schemes are proposed using conservative finite-differences associated to a semi-implicit time advancement. The process computation is multi-threaded and based on MPI and OpenMP libraries. In this paper, fluid model equations are presented together with the proposed numerical methods. The code is verified using the manufactured solution technique and validated through documented simple experiments. Finally, first simulations of edge plasma turbulence in X-point geometry are also introduced in a JET geometry.
Wang, C.Y.
1993-06-01
This paper describes fluid-structure-interaction and structure response analyses of a reactor vessel subjected to loadings associated with postulated accidents, using the hybrid Lagrangian-Eulerian code ALICE-II. This code has been improved recently to accommodate many features associated with innovative designs of reactor vessels. Calculational capabilities have been developed to treat water in the reactor cavity outside the vessel, internal shield structures and internal thin shells. The objective of the present analyses is to study the cover response and potential for missile generation in response to a fuel-coolant interaction in the core region. Three calculations were performed using the cover weight as a parameter. To study the effect of the cavity water, vessel response calculations for both wet- and dry-cavity designs are compared. Results indicate that for all cases studied and for the design parameters assumed, the calculated cover displacements are all smaller than the bolts` ultimate displacement and no missile generation of the closure head is predicted. Also, solutions reveal that the cavity water of the wet-cavity design plays an important role of restraining the downward displacement of the bottom head. Based on these studies, the analyses predict that the structure integrity is maintained throughout the postulated accident for the wet-cavity design.
Wang, C.Y.
1993-01-01
This paper describes fluid-structure-interaction and structure response analyses of a reactor vessel subjected to loadings associated with postulated accidents, using the hybrid Lagrangian-Eulerian code ALICE-II. This code has been improved recently to accommodate many features associated with innovative designs of reactor vessels. Calculational capabilities have been developed to treat water in the reactor cavity outside the vessel, internal shield structures and internal thin shells. The objective of the present analyses is to study the cover response and potential for missile generation in response to a fuel-coolant interaction in the core region. Three calculations were performed using the cover weight as a parameter. To study the effect of the cavity water, vessel response calculations for both wet- and dry-cavity designs are compared. Results indicate that for all cases studied and for the design parameters assumed, the calculated cover displacements are all smaller than the bolts' ultimate displacement and no missile generation of the closure head is predicted. Also, solutions reveal that the cavity water of the wet-cavity design plays an important role of restraining the downward displacement of the bottom head. Based on these studies, the analyses predict that the structure integrity is maintained throughout the postulated accident for the wet-cavity design.
NASA Technical Reports Server (NTRS)
Beutner, Thomas John
1993-01-01
Porous wall wind tunnels have been used for several decades and have proven effective in reducing wall interference effects in both low speed and transonic testing. They allow for testing through Mach 1, reduce blockage effects and reduce shock wave reflections in the test section. Their usefulness in developing computational fluid dynamics (CFD) codes has been limited, however, by the difficulties associated with modelling the effect of a porous wall in CFD codes. Previous approaches to modelling porous wall effects have depended either upon a simplified linear boundary condition, which has proven inadequate, or upon detailed measurements of the normal velocity near the wall, which require extensive wind tunnel time. The current work was initiated in an effort to find a simple, accurate method of modelling a porous wall boundary condition in CFD codes. The development of such a method would allow data from porous wall wind tunnels to be used more readily in validating CFD codes. This would be beneficial when transonic validations are desired, or when large models are used to achieve high Reynolds numbers in testing. A computational and experimental study was undertaken to investigate a new method of modelling solid and porous wall boundary conditions in CFD codes. The method utilized experimental measurements at the walls to develop a flow field solution based on the method of singularities. This flow field solution was then imposed as a pressure boundary condition in a CFD simulation of the internal flow field. The effectiveness of this method in describing the effect of porosity changes on the wall was investigated. Also, the effectiveness of this method when only sparse experimental measurements were available has been investigated. The current work demonstrated this approach for low speed flows and compared the results with experimental data obtained from a heavily instrumented variable porosity test section. The approach developed was simple, computationally
Nichols, B.D.; Mueller, C.; Necker, G.A.; Travis, J.R.; Spore, J.W.; Lam, K.L.; Royl, P.; Redlinger, R.; Wilson, T.L.
1998-10-01
Los Alamos National Laboratory (LANL) and Forschungszentrum Karlsruhe (FzK) are developing GASFLOW, a three-dimensional (3D) fluid dynamics field code as a best-estimate tool to characterize local phenomena within a flow field. Examples of 3D phenomena include circulation patterns; flow stratification; hydrogen distribution mixing and stratification; combustion and flame propagation; effects of noncondensable gas distribution on local condensation and evaporation; and aerosol entrainment, transport, and deposition. An analysis with GASFLOW will result in a prediction of the gas composition and discrete particle distribution in space and time throughout the facility and the resulting pressure and temperature loadings on the walls and internal structures with or without combustion. A major application of GASFLOW is for predicting the transport, mixing, and combustion of hydrogen and other gases in nuclear reactor containments and other facilities. It has been applied to situations involving transporting and distributing combustible gas mixtures. It has been used to study gas dynamic behavior (1) in low-speed, buoyancy-driven flows, as well as sonic flows or diffusion dominated flows; and (2) during chemically reacting flows, including deflagrations. The effects of controlling such mixtures by safety systems can be analyzed. The code version described in this manual is designated GASFLOW 2.1, which combines previous versions of the United States Nuclear Regulatory Commission code HMS (for Hydrogen Mixing Studies) and the Department of Energy and FzK versions of GASFLOW. The code was written in standard Fortran 90. This manual comprises three volumes. Volume I describes the governing physical equations and computational model. Volume II describes how to use the code to set up a model geometry, specify gas species and material properties, define initial and boundary conditions, and specify different outputs, especially graphical displays. Sample problems are included
Formulation, Implementation and Validation of a Two-Fluid model in a Fuel Cell CFD Code
Kunal Jain, Vernon Cole, Sanjiv Kumar and N. Vaidya
2008-11-01
Water management is one of the main challenges in PEM Fuel Cells. While water is essential for membrane electrical conductivity, excess liquid water leads to ooding of catalyst layers. Despite the fact that accurate prediction of two-phase transport is key for optimal water management, understanding of the two-phase transport in fuel cells is relatively poor. Wang et. al. [1], [2] have studied the two-phase transport in the channel and diffusion layer separately using a multiphase mixture model. The model fails to accurately predict saturation values for high humidity inlet streams. Nguyen et. al. [3] developed a two-dimensional, two-phase, isothermal, isobaric, steady state model of the catalyst and gas diffusion layers. The model neglects any liquid in the channel. Djilali et. al. [4] developed a three-dimensional two-phase multicomponent model. The model is an improvement over previous models, but neglects drag between the liquid and the gas phases in the channel. In this work, we present a comprehensive two- fluid model relevant to fuel cells. Models for two-phase transport through Channel, Gas Diffusion Layer (GDL) and Channel-GDL interface, are discussed. In the channel, the gas and liquid pressures are assumed to be same. The surface tension effects in the channel are incorporated using the continuum surface force (CSF) model. The force at the surface is expressed as a volumetric body force and added as a source to the momentum equation. In the GDL, the gas and liquid are assumed to be at different pressures. The difference in the pressures (capillary pressure) is calculated using an empirical correlations. At the Channel-GDL interface, the wall adhesion affects need to be taken into account. SIMPLE-type methods recast the continuity equation into a pressure-correction equation, the solution of which then provides corrections for velocities and pressures. However, in the two-fluid model, the presence of two phasic continuity equations gives more freedom and
Akcay, Cihan; Victor, Brian S.; Jarboe, Thomas R.; Kim, Charlson C.
2013-08-15
We present a comparison study of 3-D pressureless resistive MHD (rMHD) and 3-D presureless two-fluid MHD models of the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI). HIT-SI is a current drive experiment that uses two geometrically asymmetric helicity injectors to generate and sustain toroidal plasmas. The comparable size of the collisionless ion skin depth d{sub i} to the resistive skin depth predicates the importance of the Hall term for HIT-SI. The simulations are run with NIMROD, an initial-value, 3-D extended MHD code. The modeled plasma density and temperature are assumed uniform and constant. The helicity injectors are modeled as oscillating normal magnetic and parallel electric field boundary conditions. The simulations use parameters that closely match those of the experiment. The simulation output is compared to the formation time, plasma current, and internal and surface magnetic fields. Results of the study indicate 2fl-MHD shows quantitative agreement with the experiment while rMHD only captures the qualitative features. The validity of each model is assessed based on how accurately it reproduces the global quantities as well as the temporal and spatial dependence of the measured magnetic fields. 2fl-MHD produces the current amplification (I{sub tor}/I{sub inj}) and formation time τ{sub f} demonstrated by HIT-SI with similar internal magnetic fields. rMHD underestimates (I{sub tor}/I{sub inj}) and exhibits much a longer τ{sub f}. Biorthogonal decomposition (BD), a powerful mathematical tool for reducing large data sets, is employed to quantify how well the simulations reproduce the measured surface magnetic fields without resorting to a probe-by-probe comparison. BD shows that 2fl-MHD captures the dominant surface magnetic structures and the temporal behavior of these features better than rMHD.
NASA Astrophysics Data System (ADS)
Akcay, Cihan; Kim, Charlson C.; Victor, Brian S.; Jarboe, Thomas R.
2013-08-01
We present a comparison study of 3-D pressureless resistive MHD (rMHD) and 3-D presureless two-fluid MHD models of the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI). HIT-SI is a current drive experiment that uses two geometrically asymmetric helicity injectors to generate and sustain toroidal plasmas. The comparable size of the collisionless ion skin depth di to the resistive skin depth predicates the importance of the Hall term for HIT-SI. The simulations are run with NIMROD, an initial-value, 3-D extended MHD code. The modeled plasma density and temperature are assumed uniform and constant. The helicity injectors are modeled as oscillating normal magnetic and parallel electric field boundary conditions. The simulations use parameters that closely match those of the experiment. The simulation output is compared to the formation time, plasma current, and internal and surface magnetic fields. Results of the study indicate 2fl-MHD shows quantitative agreement with the experiment while rMHD only captures the qualitative features. The validity of each model is assessed based on how accurately it reproduces the global quantities as well as the temporal and spatial dependence of the measured magnetic fields. 2fl-MHD produces the current amplification Itor/Iinj and formation time τf demonstrated by HIT-SI with similar internal magnetic fields. rMHD underestimates Itor/Iinj and exhibits much a longer τf. Biorthogonal decomposition (BD), a powerful mathematical tool for reducing large data sets, is employed to quantify how well the simulations reproduce the measured surface magnetic fields without resorting to a probe-by-probe comparison. BD shows that 2fl-MHD captures the dominant surface magnetic structures and the temporal behavior of these features better than rMHD.
Bullock, James H.; Youchison, Dennis Lee; Ulrickson, Michael Andrew
2009-08-01
Enhanced radial transport in the plasma and the effect of ELMS may increase the ITER first wall heat loads to as much as 4 to 5 MW/m{sup 2} over localized areas. One proposed heatsink that can handle these higher loads is a CuCrZr hypervapotron. One concept for a first wall panel consists of 20 hypervapotron channels, each measuring 1400 mm long and 48.5 mm wide. The nominal cooling conditions anticipated for each channel are 400 g/s of water at 3 MPa and 100 C. This will result in boiling over a portion of the total length. A two-phase thermalhydraulic analysis is required to predict accurately the thermal performance. Existing heat transfer correlations used for nucleate boiling are not appropriate here because the flow does not reach fully developed conditions in the multi-segmented channels. Our design-by-analysis approach used two commercial codes, Fluent and Star-CCM+, to perform computational fluid dynamics analyses with conjugate heat transfer. Both codes use the Rensselear (RPI) model for wall heat flux partitioning to model nucleate boiling as implemented in user-defined functions. We present a comparison between the two codes for this Eulerian multiphase problem that relies on temperature dependent materials properties. The analyses optimized the hypervapotron geometry, including teeth height and pitch, as well as the depth of the back channel to permit highly effective boiling heat transfer in the grooves between the teeth while ensuring that no boiling could occur at the back channel exit. The analysis used a representative heat flux profile with the peak heat flux of 5 MW/m{sup 2} limited to a 50 mm length. The maximum surface temperature of the heatsink is 415 C. The baseline design uses 2 mm for the teeth height, a 3 mm width and 6 mm pitch, and a back channel depth of 8 mm. The teeth are detached from the sidewall by a 2-mm-wide slot on both sides that aids in sweep-out and quenching of the vapor bubbles.
Pigarov, A Y; West, W; Soukhanovskii, V; Rognlien, T; Maingi, R; Lipschultz, B; Krasheninnikov, S; LaBombard, B
2003-11-25
Fast intermittent transport has been observed in the scrape-off layer (SOL) of major tokamaks including Alcator C-Mod, DIII-D, and NSTX. This kind of transport is not diffusive but rather convective. It strongly increases plasma flux to the chamber walls and enhances the recycling of neutral particles in the main chamber. We discuss anomalous cross-field convection (ACFC) model for impurity and main plasma ions and its relation to intermittent transport events, i.e. plasma density blobs and holes in the SOL. Along with plasma diffusivity coefficients, our transport model introduces time-independent anomalous cross-field convective velocity. In the discharge modelling, diffusivity coefficients and ACFC velocity profiles are adjusted to match a set of representative experimental data. We use this model in the edge plasma physics code UEDGE to simulate the multi-fluid two-dimensional transport for these three tokamaks. We present simulation results suggesting the dominance of anomalous convection in the far SOL transport. These results are consistent with the hypothesis that the chamber wall is an important source of impurities and that different impurity charge states have different directions of anomalous convective velocity.
Castro-Chavez, Fernando
2012-01-01
Background Three binary representations of the genetic code according to the ancient I Ching of Fu-Xi will be presented, depending on their defragging capabilities by pairing based on three biochemical properties of the nucleic acids: H-bonds, Purine/Pyrimidine rings, and the Keto-enol/Amino-imino tautomerism, yielding the last pair a 32/32 single-strand self-annealed genetic code and I Ching tables. Methods Our working tool is the ancient binary I Ching's resulting genetic code chromosomes defragged by vertical and by horizontal pairing, reverse engineered into non-binaries of 2D rotating 4×4×4 circles and 8×8 squares and into one 3D 100% symmetrical 16×4 tetrahedron coupled to a functional tetrahedron with apical signaling and central hydrophobicity (codon formula: 4[1(1)+1(3)+1(4)+4(2)]; 5:5, 6:6 in man) forming a stella octangula, and compared to Nirenberg's 16×4 codon table (1965) pairing the first two nucleotides of the 64 codons in axis y. Results One horizontal and one vertical defragging had the start Met at the center. Two, both horizontal and vertical pairings produced two pairs of 2×8×4 genetic code chromosomes naturally arranged (M and I), rearranged by semi-introversion of central purines or pyrimidines (M' and I') and by clustering hydrophobic amino acids; their quasi-identity was disrupted by amino acids with odd codons (Met and Tyr pairing to Ile and TGA Stop); in all instances, the 64-grid 90° rotational ability was restored. Conclusions We defragged three I Ching representations of the genetic code while emphasizing Nirenberg's historical finding. The synthetic genetic code chromosomes obtained reflect the protective strategy of enzymes with a similar function, having both humans and mammals a biased G-C dominance of three H-bonds in the third nucleotide of their most used codons per amino acid, as seen in one chromosome of the i, M and M' genetic codes, while a two H-bond A-T dominance was found in their complementary chromosome, as seen
Adaptive entropy coded subband coding of images.
Kim, Y H; Modestino, J W
1992-01-01
The authors describe a design approach, called 2-D entropy-constrained subband coding (ECSBC), based upon recently developed 2-D entropy-constrained vector quantization (ECVQ) schemes. The output indexes of the embedded quantizers are further compressed by use of noiseless entropy coding schemes, such as Huffman or arithmetic codes, resulting in variable-rate outputs. Depending upon the specific configurations of the ECVQ and the ECPVQ over the subbands, many different types of SBC schemes can be derived within the generic 2-D ECSBC framework. Among these, the authors concentrate on three representative types of 2-D ECSBC schemes and provide relative performance evaluations. They also describe an adaptive buffer instrumented version of 2-D ECSBC, called 2-D ECSBC/AEC, for use with fixed-rate channels which completely eliminates buffer overflow/underflow problems. This adaptive scheme achieves performance quite close to the corresponding ideal 2-D ECSBC system. PMID:18296138
WFR-2D: an analytical model for PWAS-generated 2D ultrasonic guided wave propagation
NASA Astrophysics Data System (ADS)
Shen, Yanfeng; Giurgiutiu, Victor
2014-03-01
This paper presents WaveFormRevealer 2-D (WFR-2D), an analytical predictive tool for the simulation of 2-D ultrasonic guided wave propagation and interaction with damage. The design of structural health monitoring (SHM) systems and self-aware smart structures requires the exploration of a wide range of parameters to achieve best detection and quantification of certain types of damage. Such need for parameter exploration on sensor dimension, location, guided wave characteristics (mode type, frequency, wavelength, etc.) can be best satisfied with analytical models which are fast and efficient. The analytical model was constructed based on the exact 2-D Lamb wave solution using Bessel and Hankel functions. Damage effects were inserted in the model by considering the damage as a secondary wave source with complex-valued directivity scattering coefficients containing both amplitude and phase information from wave-damage interaction. The analytical procedure was coded with MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local finite element model (FEM) with artificial non-reflective boundaries (NRB). The WFR-2D analytical simulation results were compared and verified with full scale multiphysics finite element models and experiments with scanning laser vibrometer. First, Lamb wave propagation in a pristine aluminum plate was simulated with WFR-2D, compared with finite element results, and verified by experiments. Then, an inhomogeneity was machined into the plate to represent damage. Analytical modeling was carried out, and verified by finite element simulation and experiments. This paper finishes with conclusions and suggestions for future work.
NASA Technical Reports Server (NTRS)
Liang, Anita D. (Technical Monitor); Walowit, Jed; Shapiro, Wilbur
2004-01-01
The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allow the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines.
Characterization of Porous Medium Properties Using 2D NMR
NASA Astrophysics Data System (ADS)
Sun, Boqin; Dunn, Keh-Jim
2003-03-01
We have successfully applied the concept of 2D NMR to the characterization of properties of fluid-saturated porous medium. Using a two-windowed modified CPMG pulse sequence, we were able to explore the magnetic internal filed gradient distribution within the pore space of a fluid-saturated porous medium due to magnetic susceptibility contrast between the solid matrix and pore fluid. Similar scheme is used to identify and quantify different types of pore fluids, such as oil, water, and gas, based on the contrast in their diffusion coefficients. The magic angle spinning technique (MAS) can also be applied in the 2D NMR framework for delineating the chemical shift spectra of the pore fluids in a porous medium at different T1 or T2 relaxation times. The results can be displayed in a two-dimensional plot, with one axis being the T1 or T2 relaxation times, the other axis being the internal field gradient, diffusion coefficient, or chemical shift, and the third axis being the proton population. Our preliminary laboratory work indicates that the 2D NMR approach can be a powerful tool for the characterization of properties of fluid-saturated porous medium, such as fluid typing, oil viscosity determination, surface wettability, etc.
NASA Astrophysics Data System (ADS)
Mayor, Louise
2016-05-01
Graphene might be the most famous example, but there are other 2D materials and compounds too. Louise Mayor explains how these atomically thin sheets can be layered together to create flexible “van der Waals heterostructures”, which could lead to a range of novel applications.
Roy, C.; Ohana, M.; Host, Ph.; Alemann, G.; Labani, A.; Wattiez, A.; Lang, H.
2014-01-01
Objective The goal of this prospective study was to compare the efficiency of two types of MRU after diuretic administration to identify the non-dilated ureter. Methods MR pelvic examinations were performed in 126 patients after receiving furosemide. Each patient underwent in addition to their protocol for context, two types of MRU: 2D T2-weighted FSE (T2w-MRU) and 3D Gd T1-weighted GE (CE-MRU). Four segments were checked for each ureter. For the first part of the analysis, readers evaluated the whole image quality using a four points subjective scale and for the second part, they were asked to score separately each ureteral segment as present or absent. Results 1008 ureteral segments were checked. For the image quality, readers did not find any significant difference (3.8 ± 0.5 vs 3.6 ± 0.7, p value: 0.13) between MRU methods. The interobserver agreement was excellent with a κ correlation coefficient as high as 0.89 for T2w-MRU and 0.92 for CE-MRU, respectively. For the detection of the segments and considering the 9 rotations for the T2W MRU, there were no statistically significant differences between the two groups. Conclusion T2-weighted MRU with multiple orientations and diuretic is sufficient to identify the non-dilated ureter. It offers information on ureteral peristaltism. It can be suggested that this sequence is able to detect an initial obstruction before hydronephrosis occurs. PMID:26937423
NASA Astrophysics Data System (ADS)
Yoshida, Hiroyuki; Misawa, Takeharu; Takase, Kazuyuki
Two-fluid model can simulate two-phase flow by computational cost less than detailed two-phase flow simulation method such as interface tracking method or particle interaction method. Therefore, two-fluid model is useful for thermal hydraulic analysis in large-scale domain such as a rod bundle. Japan Atomic Energy Agency (JAEA) develops three dimensional two-fluid model analysis code ACE-3D that adopts boundary fitted coordinate system in order to simulate complex shape flow channel. In this paper, boiling two-phase flow analysis in a tight-lattice rod bundle was performed by ACE-3D code. The parallel computation using 126 CPUs was applied to this analysis. In the results, the void fraction, which distributes in outermost region of rod bundle, is lower than that in center region of rod bundle. The tendency of void fraction distribution agreed with the measurement results by neutron radiography qualitatively. To evaluate effects of two-phase flow model used in ACE-3D code, numerical simulation of boiling two-phase in tight-lattice rod bundle with no lift force model was also performed. From the comparison of calculated results, it was concluded that the effects of lift force model were not so large for overall void fraction distribution of tight-lattice rod bundle. However, the lift force model is important for local void fraction distribution of fuel bundles.
Energy Science and Technology Software Center (ESTSC)
2012-01-05
Code is for a layered electric medium with 2d structure. Includes air-earth interface at node z=2.. The electric ex and ez fields are calculated on edges of elemental grid and magnetic field hy is calculated on the face of the elemental grid. The code allows for a layered earth with 2d structures. Solutions of coupled first order Maxwell's equations are solved in the two dimensional environment using a finite- difference scheme on a staggered spationamore » and temporal grid.« less
Energy Science and Technology Software Center (ESTSC)
2001-01-31
This software reduces the data from two-dimensional kSA MOS program, k-Space Associates, Ann Arbor, MI. Initial MOS data is recorded without headers in 38 columns, with one row of data per acquisition per lase beam tracked. The final MOSS 2d data file is reduced, graphed, and saved in a tab-delimited column format with headers that can be plotted in any graphing software.
Faudot, E.; Heuraux, S.; Colas, L.
2005-09-26
Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a 'test map' having initially a Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude {phi}0 (normalized to a characteristic length for transverse transport and to the local temperature). A 'peaking factor' is built from the DC peak potential normalized to {phi}0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the 'peaking factor' for ITER will be presented for a given configuration.
Nanoimprint lithography: 2D or not 2D? A review
NASA Astrophysics Data System (ADS)
Schift, Helmut
2015-11-01
Nanoimprint lithography (NIL) is more than a planar high-end technology for the patterning of wafer-like substrates. It is essentially a 3D process, because it replicates various stamp topographies by 3D displacement of material and takes advantage of the bending of stamps while the mold cavities are filled. But at the same time, it keeps all assets of a 2D technique being able to pattern thin masking layers like in photon- and electron-based traditional lithography. This review reports about 20 years of development of replication techniques at Paul Scherrer Institut, with a focus on 3D aspects of molding, which enable NIL to stay 2D, but at the same time enable 3D applications which are "more than Moore." As an example, the manufacturing of a demonstrator for backlighting applications based on thermally activated selective topography equilibration will be presented. This technique allows generating almost arbitrary sloped, convex and concave profiles in the same polymer film with dimensions in micro- and nanometer scale.
Shadowfax: Moving mesh hydrodynamical integration code
NASA Astrophysics Data System (ADS)
Vandenbroucke, Bert
2016-05-01
Shadowfax simulates galaxy evolution. Written in object-oriented modular C++, it evolves a mixture of gas, subject to the laws of hydrodynamics and gravity, and any collisionless fluid only subject to gravity, such as cold dark matter or stars. For the hydrodynamical integration, it makes use of a (co-) moving Lagrangian mesh. The code has a 2D and 3D version, contains utility programs to generate initial conditions and visualize simulation snapshots, and its input/output is compatible with a number of other simulation codes, e.g. Gadget2 (ascl:0003.001) and GIZMO (ascl:1410.003).
Wavelet characterization of 2D turbulence and intermittency in magnetized electron plasmas
NASA Astrophysics Data System (ADS)
Romé, M.; Chen, S.; Maero, G.
2016-06-01
A study of the free relaxation of turbulence in a two-dimensional (2D) flow is presented, with a focus on the role of the initial vorticity conditions. Exploiting a well-known analogy with 2D inviscid incompressible fluids, the system investigated here is a magnetized pure electron plasma. The dynamics of this system are simulated by means of a 2D particle-in-cell code, starting from different spiral density (vorticity) distributions. A wavelet multiresolution analysis is adopted, which allows the coherent and incoherent parts of the flow to be separated. Comparison of the turbulent evolution in the different cases is based on the investigation of the time evolution of statistical properties, including the probability distribution functions and structure functions of the vorticity increments. It is also based on an analysis of the enstrophy evolution and its spectrum for the two components. In particular, while the statistical features assess the degree of flow intermittency, spectral analysis allows us not only to estimate the time required to reach a state of fully developed turbulence, but also estimate its dependence on the thickness of the initial spiral density distribution, accurately tracking the dynamics of both the coherent structures and the turbulent background. The results are compared with those relevant to annular initial vorticity distributions (Chen et al 2015 J. Plasma Phys. 81 495810511).
NASA Astrophysics Data System (ADS)
Zaghi, S.
2014-07-01
OFF, an open source (free software) code for performing fluid dynamics simulations, is presented. The aim of OFF is to solve, numerically, the unsteady (and steady) compressible Navier-Stokes equations of fluid dynamics by means of finite volume techniques: the research background is mainly focused on high-order (WENO) schemes for multi-fluids, multi-phase flows over complex geometries. To this purpose a highly modular, object-oriented application program interface (API) has been developed. In particular, the concepts of data encapsulation and inheritance available within Fortran language (from standard 2003) have been stressed in order to represent each fluid dynamics “entity” (e.g. the conservative variables of a finite volume, its geometry, etc…) by a single object so that a large variety of computational libraries can be easily (and efficiently) developed upon these objects. The main features of OFF can be summarized as follows: Programming LanguageOFF is written in standard (compliant) Fortran 2003; its design is highly modular in order to enhance simplicity of use and maintenance without compromising the efficiency; Parallel Frameworks Supported the development of OFF has been also targeted to maximize the computational efficiency: the code is designed to run on shared-memory multi-cores workstations and distributed-memory clusters of shared-memory nodes (supercomputers); the code’s parallelization is based on Open Multiprocessing (OpenMP) and Message Passing Interface (MPI) paradigms; Usability, Maintenance and Enhancement in order to improve the usability, maintenance and enhancement of the code also the documentation has been carefully taken into account; the documentation is built upon comprehensive comments placed directly into the source files (no external documentation files needed): these comments are parsed by means of doxygen free software producing high quality html and latex documentation pages; the distributed versioning system referred