Elimination of artificial grid distortion and hourglass-type motions by means of Lagrangian subzonal masses and pressures
- Los Alamos National Lab., NM (United States)
The bane of Lagrangian hydrodynamics calculations is premature breakdown of the grid topology that results in severe degradation of accuracy and run termination often long before the assumption of Lagrangian zonal mass ceased to be valid. At short spatial grid scales this is usually referred to by the terms hourglass mode or keystone motion associated in particular with underconstrained grids such as quadrilaterals and hexahedrons in two and three dimensions, respectively. At longer spatial scales relative to the grid spacing there is what is referred to ubiquitously as spurious vorticity, or the long-thin zone problem. In both cases the result is anomalous grid distortion and tangling that has nothing to do with the actual solution, as would be the case for turbulent flow. In this work the authors show how such motions can be eliminated by the proper use of subzonal Lagrangian masses, and associated densities and pressures. These subzonal masses arise in a natural way from the fact that they require the mass associated with the nodal grid point to be constant in time. This is addition to the usual assumption of constant, Lagrangian zonal mass in staggered grid hydrodynamics scheme. The authors show that with proper discretization of subzonal forces resulting from subzonal pressures, hourglass motion and spurious vorticity can be eliminated for a very large range of problems. Finally the authors are presenting results of calculations of many test problems.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- OSTI ID:
- 332728
- Report Number(s):
- SAND-98-1591; CONF-9709141-PROC.; ON: DE99000778; TRN: IM9916%%30
- Resource Relation:
- Journal Volume: 142; Journal Issue: 2; Conference: 5. joint Russian-American computational mathematics conference, Albuquerque, NM (United States), 2-5 Sep 1997; Other Information: PBD: [1997]; Related Information: Is Part Of Proceedings of the 5. joint Russian-American computational mathematics conference; PB: 312 p.
- Country of Publication:
- United States
- Language:
- English
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