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A parallel, volume-tracking algorithm for unstructured meshes

Description: Many diverse areas of industry benefit from the use of volume of fluid methods to predict the movement of materials. Casting is a common method of part fabrication. The accurate prediction of the casting process is pivotal to industry. Mold design and casting is currently considered an art by industry. It typically involves many trial mold designs, and the rejection of defective parts is costly. Failure of cast parts, because residual stresses reduce the part`s strength, can be catastrophic. Cast parts should have precise geometric details that reduce or eliminate the need for machining after casting. Volume of fluid codes will help designers predict how the molten metal fills a mold and where ay trapped voids remain. Prediction of defects due to thermal contraction or expansion will eliminate defective, trial mold designs and speed the parts to market with fewer rejections. Increasing the predictability and therefore the accuracy of the casting process will reduce the art that is involved in mold design and parts casting. Here, recent enhancements to multidimensional volume-tracking algorithms are presented. Illustrations in two dimensions are given. The improvements include new, local algorithms for interface normal constructions and a new full remapping algorithm for time integration. These methods are used on structured and unstructured grids.
Date: October 1, 1996
Creator: Mosso, S.J.; Swartz, B.K.; Kothe, D.B. & Ferrell, R.C.
Partner: UNT Libraries Government Documents Department

A new 3D computational model for shaped charge jet breakup

Description: This paper reviews prior 1D and 2D axisymmetric, analytical and computational studies, as well as empirical studies of the shaped charge jet particulation problem and discusses their associated insights and problems. It proposes a new 3D computational model of the particulation process, based upon a simplified version of the observed counter-rotating, double helical surface perturbations, found on softly recovered shaped charge jet particles, from both copper and tantalum jets. This 3D approach contrasts with the random, axisymmetric surface perturbations which have previously been used, to try to infer the observed length distribution of jet particles, on the basis of the most unstable wavelength concept, which leads to the expectation of a continuous distribution of particle lengths. The 3D model, by its very nature, leads to a non-random, periodic distribution of potential initial necking loci, on alternate sides of the stretching jet. This in turn infers a potentially periodic, overlapping, multi-modal distribution of associated jet particle lengths. Since it is unlikely that all potential initial necking sites will be activated simultaneously, the 3D model also suggests that longer jet particles containing partial, but unseparated necks, should be observed fairly often. The computational analysis is in its very early stages and the problems involved in inserting the two helical grooves and in defining the initial conditions and boundary conditions for the computation will be discussed. Available initial results from the 3D computation will be discussed and interpreted.
Date: September 1, 1996
Creator: Zernow, L.; Chapyak, E.J. & Mosso, S.J.
Partner: UNT Libraries Government Documents Department

A high resolution finite volume method for efficient parallel simulation of casting processes on unstructured meshes

Description: We discuss selected aspects of a new parallel three-dimensional (3-D) computational tool for the unstructured mesh simulation of Los Alamos National Laboratory (LANL) casting processes. This tool, known as {bold Telluride}, draws upon on robust, high resolution finite volume solutions of metal alloy mass, momentum, and enthalpy conservation equations to model the filling, cooling, and solidification of LANL castings. We briefly describe the current {bold Telluride} physical models and solution methods, then detail our parallelization strategy as implemented with Fortran 90 (F90). This strategy has yielded straightforward and efficient parallelization on distributed and shared memory architectures, aided in large part by new parallel libraries {bold JTpack9O} for Krylov-subspace iterative solution methods and {bold PGSLib} for efficient gather/scatter operations. We illustrate our methodology and current capabilities with source code examples and parallel efficiency results for a LANL casting simulation.
Date: March 1, 1997
Creator: Kothe, D.B.; Turner, J.A.; Mosso, S.J. & Ferrell, R.C.
Partner: UNT Libraries Government Documents Department

Low-speed flow hydrodynamics

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was the inception and development of a new casting simulation tool that is founded in modern, high-order numerical algorithms, accurate physical models, and advanced computational science constructs needed to execute efficiently on parallel architectures. This project has therefore led to the development and application of a new simulation tool (known as Telluride) for the modeling of casting processes used in the manufacture of metal alloy components needed for various Department of Energy (DOE) and Defense Programs (DP) projects. As a result of the efforts undertaken in this project, Telluride can now model key foundry processes in the DOE/DP and in industry. Successes realized over the course of this project have secured funding for further Telluride development by the DOE Accelerated Strategic Computing Initiative (ASCI) Program.
Date: August 1, 1997
Creator: Cerutti, J.H.; Kothe, D.B. & Mosso, S.J.
Partner: UNT Libraries Government Documents Department

Volume tracking of interfaces having surface tension in two and three dimensions

Description: Solution algorithms are presented for tracking interfaces with piecewise linear (PLIC) volume-of-fluid (VOF) methods on fixed (Eulerian) two-dimensional (2-D) structured and three-dimensional (3-D) structured and unstructured grids. We review the theory of volume tracking methods, derive appropriate volume evolution equations, identify and present solutions to the basic geometric functions needed for interface reconstruction and volume fluxing, and provide detailed algorithm templates for modern 2-D and 3-D PLIC VOF interface tracking methods. We discuss some key outstanding issues for PLIC VOF methods, namely the method used for time integration of fluid volumes (operator splitting, unsplit, Runge-Kutta, etc.) and the estimation of interface normals. We also present our latest developments in the continuum surface force (CSF) model for surface tension, namely extension to 3-D and variable surface tension effects. We identify and focus on key outstanding CSF model issues that become especially critical on fine meshes with high density ratio interfacial flows, namely the surface delta function approximation, the estimation of interfacial curvature, and the continuum surface force scaling and/or smoothing model. Numerical results in two and three dimensions are used to illustrate the properties of these methods.
Date: March 1, 1996
Creator: Kothe, D.B.; Rider, W.J.; Mosso, S.J.; Brock, J.S. & Hochstein, J.I.
Partner: UNT Libraries Government Documents Department

MESA: A 3-D computer code for armor/anti-armor applications

Description: We describe a new 3-D computer code, named MESA, developed at the Los Alamos National Laboratory with DARPA/Army/Marine Corps support specifically for simulations of armor and anti-armor systems. MESA is a three-dimensional, cartesian, Eulerian code with hydrodynamics, high explosives, and material strength models. Among special features of MESA are its high-order advection algorithm, its material interface tracking scheme and the van Leer monotonic advection limiting. We will briefly illustrate the code capabilities by showing comparisons of two calculations with experiments. The first problem shown in this paper is the impact of a lead sphere on a thin lead plate at 6.66 km/s, producing a debris cloud composed mostly of vapor. The second problem is the impact of a copper cylinder at 130 m/s on a rigid wall, producing deformation in the cylinder. 17 refs., 5 figs.
Date: January 1, 1989
Creator: Manell, D.A.; Adams, T.F.; Holian, K.S.; Addessio, F.L.; Baumgardner, J.R. & Mosso, S.J. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department