A Variable Explicit/Implicit Numerical Method for Calculating Advection on Unstructured Meshes

O’Rourke, P.J.; Sahota, Manjit S.

doi:10.1006/jcph.1998.5903

Cited by 36 publications

(12 citation statements)

References 22 publications

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“…(10), and use elastoplastic properties (2) for the zirconium sample and isotropic properties for the half-hard copper impactor. This flyer-plate problem was spatially discretized in three-dimensions for subsequent simulation using the time-dependent CHAD FVM code (11). An axisymmetric mesh with a total of 21,120 cells (165 TT cells, 8 radial cells and 16 azimuthal cells) was generated with the sample modeled as a two-material (specimen and ring) composite.…”

Section: Hugoniot Elastic Limit Analysismentioning

confidence: 99%

Influence of crystallographic anisotropy on the Hopkinson fracture “spallation” of zirconium

Gray¹,

Bourne²,

Zocher³

et al. 2000

AIP Conference Proceedings

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The influence of texture on the spallation (Hopkinson fracture) of low-symmetry metals (e.g. Zr, U, or Sn) has seen limited study. In this study, the Hopkinson fracture of annealed, high-purity Zr has been probed as a function of crystallographic texture. The quasi-static yield strength of the Zr studied is ≈2.5x higher in the plate's through-thickness direction compared to that measured in-plane due to a pronounced basal texture. The pullback signals of each orientation shocked to 5 GPa were found to be insensitive to the texture, although the HEL's and the soft-recovered, incipiently-spalled samples exhibited differences in their damage evolution. The VISAR wave profiles were modeled using a 3-D finite-volume method (FVM) continuum code. The VISAR, post-spallation metallographic observations, and modeling analysis are discussed with reference to the HEL and texture.

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Section: Hugoniot Elastic Limit Analysismentioning

confidence: 99%

Influence of crystallographic anisotropy on the Hopkinson fracture “spallation” of zirconium

Gray¹,

Bourne²,

Zocher³

et al. 2000

AIP Conference Proceedings

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“…the flux going through this face, and u f is the velocity vector interpolated at face f . Using (19) we obtain the corresponding expression for the advection integrated over the control area of each face. In this way, a staggered advection scheme can be derived with a local momentum balance that is equal to that of the collocated scheme:…”

Section: Conservative Scheme Based On Perot's Schemementioning

confidence: 99%

A conservative unstructured scheme for rapidly varied flows

Kramer

Stelling

2008

Numerical Methods in Fluids

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SUMMARYThis article introduces a new semi-implicit, staggered finite volume scheme on unstructured meshes for the modelling of rapidly varied shallow water flows. Rapidly varied flows occur in the inundation of dry land during flooding situations. They typically involve bores and hydraulic jumps after obstacles such as road banks. Near such sudden flow transitions, the grid resolution is often low compared with the gradients of the bathymetry. Locally the hydrostatic pressure assumption may become invalid. In these situations, it is crucial to apply the correct conservation properties to obtain accurate results. An important feature of this scheme is therefore its ability to conserve momentum locally or, by choice, preserve constant energy head along a streamline. This is achieved using a special interpolation method and control volumes for momentum.The efficiency of inundation calculations with locally very high velocities, and in the case of unstructured meshes locally very small grid distances, is severely hampered by the Courant condition. This article provides a solution in the form of a locally implicit time integration for the advective terms that allows for an explicit calculation in most of the domain, while maintaining unconditional stability by implicit calculations only where necessary.The complex geometry of flooded urban areas asks for the flexibility of unstructured meshes. The efficient calculation of the pressure gradient in this, and other semi-implicit staggered schemes, requires, however, an orthogonality condition to be put on the grid. In this article a simple method is introduced to generate unstructured hybrid meshes that fulfil this requirement.

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“…Like KMB, pressure boundary conditions at the walls are linearly interpolated from pressures near the walls. The inversion method for the pressure matrix remains the conjugate residual iteration method (O'Rourke and Amsden, 1986) with a diagonal preconditioner. Although memory is not a limiting factor in engine's CFD for today's computers, we have taken care to never use this matrix (and all the others along the phase B) globally but only few elements at each time, which means that KIFP needs not very more memory than KMB.…”

Section: Lagrangian Phasementioning

confidence: 99%

Reactive Cfd in Engines with a New Unstructured Parallel Solver

Zolver

Klahr

Bohbot

et al. 2003

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Mécanique des fluides numérique dans les moteurs à l'aide d'un nouveau code parallèle non structuré -KIFP, un code hexaédrique, parallèle et non structuré est en cours de développement à l'IFP depuis deux ans. Certains algorithmes de KMB, code IFP basé sur le logiciel KIVA II, ont été implantés dans KIFP. De part le nouveau formalisme non structuré, d'autres algorithmes (volumes finis sur grille décalée, pas de temps fractionné, boucle itérative SIMPLE, convection par souscycles, modèles de turbulence et de spray, etc.) ont dû être modifiés. De nouveaux algorithmes, comme le mouvement de maillage par interpolation temporelle conditionnée, l'algorithme permettant de changer de maillage en cours de simulation, les limiteurs de pentes de Van Leer et Superbee dans la phase de convection, le modèle de transferts thermique de Kays et Crawford et le modèle de combustion essence ECFM ont été ajoutés. Les machines superscalaires étant très utilisées et développées, KIFP a été optimisé pour être employé sur ce type de machines. De nombreux ordinateurs et compilateurs ont été testés. Dû à son faible coût d'implantation, le standard de directive OPEN-MP est utilisé pour paralléliser le code. Une accélération de 3 sur 4 processeurs a été atteinte. KIFP est maintenant capable de simuler correctement la combustion tridimensionnelle dans des moteurs automobiles. Comme exemple, nous montrons dans cet article des calculs sur un banc volute stationnaire à pipe hélicoïdale, une admission/compression/combustion dans un moteur à injection indirecte à allumage commandé avec une chambre en toit, et une compression/injection dans un moteur à injection directe Diesel. Des comparaisons avec des résultats expérimentaux pour les cas moteurs (vitesse de rotation et coefficient de swirl pour la simulation stationnaire, et des courbes de pressions moyennes pour les simulations instationnaires) ou avec des résultats analytiques pour les cas tests académiques ont été réalisées autant que possible. Abstract

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A Variable Explicit/Implicit Numerical Method for Calculating Advection on Unstructured Meshes

Cited by 36 publications

References 22 publications

Influence of crystallographic anisotropy on the Hopkinson fracture “spallation” of zirconium

Influence of crystallographic anisotropy on the Hopkinson fracture “spallation” of zirconium

A conservative unstructured scheme for rapidly varied flows

Reactive Cfd in Engines with a New Unstructured Parallel Solver

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