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Title: Nested Dissection Interface Reconstruction in Pececillo

Abstract

A nested dissection method for interface reconstruction in a volume tracking framework has been implemented in Pececillo, a mini-app for Truchas, which is the ASC code for casting and additive manufacturing. This method provides a significant improvement over the traditional onion-skin method, which does not appropriately handle T-shaped multimaterial intersections and dynamic contact lines present in additive manufacturing simulations. The resulting implementation lays the groundwork for further research in contact angle estimates and surface tension calculations.

Authors:
 [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Computer, Computational, and Statistical Sciences Division
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA). Advanced Simulation and Computing Program (ASC)
OSTI Identifier:
1324548
Report Number(s):
LA-UR-16-26997
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
97 MATHEMATICS AND COMPUTING

Citation Formats

Jibben, Zechariah Joel, Carlson, Neil N., and Francois, Marianne M. Nested Dissection Interface Reconstruction in Pececillo. United States: N. p., 2016. Web. doi:10.2172/1324548.
Jibben, Zechariah Joel, Carlson, Neil N., & Francois, Marianne M. Nested Dissection Interface Reconstruction in Pececillo. United States. doi:10.2172/1324548.
Jibben, Zechariah Joel, Carlson, Neil N., and Francois, Marianne M. 2016. "Nested Dissection Interface Reconstruction in Pececillo". United States. doi:10.2172/1324548. https://www.osti.gov/servlets/purl/1324548.
@article{osti_1324548,
title = {Nested Dissection Interface Reconstruction in Pececillo},
author = {Jibben, Zechariah Joel and Carlson, Neil N. and Francois, Marianne M.},
abstractNote = {A nested dissection method for interface reconstruction in a volume tracking framework has been implemented in Pececillo, a mini-app for Truchas, which is the ASC code for casting and additive manufacturing. This method provides a significant improvement over the traditional onion-skin method, which does not appropriately handle T-shaped multimaterial intersections and dynamic contact lines present in additive manufacturing simulations. The resulting implementation lays the groundwork for further research in contact angle estimates and surface tension calculations.},
doi = {10.2172/1324548},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

Technical Report:

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  • A nested dissection method for interface reconstruction in a volume tracking framework has been implemented in Pececillo. This method provides a significant improvement over the traditional onion-skin method, which does not appropriately handle T-shaped multimaterial intersections and dynamic contact lines present in additive manufacturing simulations. The resulting implementation lays the groundwork for further re- search in numerical contact angle estimates.
  • A parallel implementation is presented of Gaussian elimination without pivoting, using the nested dissection ordering for solving Ax=b where A is an N x N symmetric positive definite matrix. If the graph of A is a square root of N x square root of N finite element mesh then Birkhoff and George and Liu have shown that a parallel complexity of 0 (square root of N) can be achieved for Gaussian elimination with the nested dissection ordering. Implementation achieves this parallel complexity on a two-dimensional MIMD processor array with N processors and nearest neighbors interconnections. Thus nested dissection is amore » near-optimal algorithm for this problem on this interconnection topology. The parallel implementation on this architecture requires 158 square root of N + 0 (log of square root of N to base 2) parallel floating point multiplications. It is faster than a Kung-Leiserson systolic array for banded matrices for N greater than or equal to 961, and faster than a serial implementation for N as small as 9.« less
  • Several new methods are presented for the capturing and tracking of material boundary interfaces. All methods belong to the general Volume Of Fluid (VOF) approach, and vary from simple flow aligned algorithms to more complex geometric modeling. The performance of the different methods is evaluated by solving the advection equations for a variant of the canonical multi-fluid ''ball & jacks'' problem.
  • The authors present a second-order algorithm for reconstructing an interface from a distribution of volume fractions in a general orthogonal coordinate system with derivatives approximated using finite differences. The method approximates the interface curve by a piecewise-linear profile. An integral formulation is used that accounts for the orthogonal coordinate system in a natural way. The authors present results obtained using this method for tracking a material interface between two compressible media in spherical coordinates.
  • In this project we implement material interface reconstruction into a large, massively parallel Monte Carlo particle transport code. Here we examine the benefit of resolving a material interface for criticality calculations. Input to the code is a mesh with material and density defined on the mesh. For mesh zones that contain more than one material (mixed zones), the old approximation made in the code is to homogenize the material properties of all the materials in the zone. The neutron mean free path is a function of the material density that the neutron is traveling through, so for mixed zones, wemore » use the average density of the zone, rather than reconstructing a material interface, determining which material within the zone the particle is in and using the correct density based on the position of the particle within the zone. In order to get a better answer, here we implement material interface reconstruction and rather than homogenizing the materials in a mixed zone, we have a material interface divide the zone so we can tell which material the particle is in, based on the particle's position and the location of the material interface.« less