skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Verification Test of the SURF and SURFplus Models in xRage: Part III Affect of Mesh Alignment

Abstract

The previous studies used an underdriven detonation wave in 1-dimension (steady ZND reaction zone profile followed by a scale-invariant rarefaction wave) for PBX 9502 as a verification test of the implementation of the SURF and SURFplus models in the xRage code. Since the SURF rate is a function of the lead shock pressure, the question arises as to the effect on accuracy of variations in the detected shock pressure due to the alignment of the shock front with the mesh. To study the effect of mesh alignment we simulate a cylindrically diverging detonation wave using a planar 2-D mesh. The leading issue is the magnitude of azimuthal asymmetries in the numerical solution. The 2-D test case does not have an exact analytic solution. To quantify the accuracy, the 2-D solution along rays through the origin are compared to a highly resolved 1-D simulation in cylindrical geometry.

Authors:
 [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1304803
Report Number(s):
LA-UR-16-26317
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
97 MATHEMATICS AND COMPUTING; detonation wave; verification; SURF; curvature effect

Citation Formats

Menikoff, Ralph. Verification Test of the SURF and SURFplus Models in xRage: Part III Affect of Mesh Alignment. United States: N. p., 2016. Web. doi:10.2172/1304803.
Menikoff, Ralph. Verification Test of the SURF and SURFplus Models in xRage: Part III Affect of Mesh Alignment. United States. doi:10.2172/1304803.
Menikoff, Ralph. 2016. "Verification Test of the SURF and SURFplus Models in xRage: Part III Affect of Mesh Alignment". United States. doi:10.2172/1304803. https://www.osti.gov/servlets/purl/1304803.
@article{osti_1304803,
title = {Verification Test of the SURF and SURFplus Models in xRage: Part III Affect of Mesh Alignment},
author = {Menikoff, Ralph},
abstractNote = {The previous studies used an underdriven detonation wave in 1-dimension (steady ZND reaction zone profile followed by a scale-invariant rarefaction wave) for PBX 9502 as a verification test of the implementation of the SURF and SURFplus models in the xRage code. Since the SURF rate is a function of the lead shock pressure, the question arises as to the effect on accuracy of variations in the detected shock pressure due to the alignment of the shock front with the mesh. To study the effect of mesh alignment we simulate a cylindrically diverging detonation wave using a planar 2-D mesh. The leading issue is the magnitude of azimuthal asymmetries in the numerical solution. The 2-D test case does not have an exact analytic solution. To quantify the accuracy, the 2-D solution along rays through the origin are compared to a highly resolved 1-D simulation in cylindrical geometry.},
doi = {10.2172/1304803},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 8
}

Technical Report:

Save / Share:
  • The previous study used an underdriven detonation wave (steady ZND reaction zone profile followed by a scale invariant rarefaction wave) for PBX 9502 as a validation test of the implementation of the SURF and SURFplus models in the xRage code. Even with a fairly fine uniform mesh (12,800 cells for 100mm) the detonation wave profile had limited resolution due to the thin reaction zone width (0.18mm) for the fast SURF burn rate. Here we study the effect of finer resolution by comparing results of simulations with cell sizes of 8, 2 and 1 μm, which corresponds to 25, 100 andmore » 200 points within the reaction zone. With finer resolution the lead shock pressure is closer to the von Neumann spike pressure, and there is less noise in the rarefaction wave due to fluctuations within the reaction zone. As a result the average error decreases. The pointwise error is still dominated by the smearing the pressure kink in the vicinity of the sonic point which occurs at the end of the reaction zone.« less
  • As a verification test of the SURF and SURFplus models in the xRage code we use a propagating underdriven detonation wave in 1-D. This is about the only test cases for which an accurate solution can be determined based on the theoretical structure of the solution. The solution consists of a steady ZND reaction zone profile joined with a scale invariant rarefaction or Taylor wave and followed by a constant state. The end of the reaction profile and the head of the rarefaction coincide with the sonic CJ state of the detonation wave. The constant state is required to matchmore » a rigid wall boundary condition. For a test case, we use PBX 9502 with the same EOS and burn rate as previously used to test the shock detector algorithm utilized by the SURF model. The detonation wave is propagated for 10 μs (slightly under 80mm). As expected, the pointwise errors are largest in the neighborhood of discontinuities; pressure discontinuity at the lead shock front and pressure derivative discontinuities at the head and tail of the rarefaction. As a quantitative measure of the overall accuracy, the L2 norm of the difference of the numerical pressure and the exact solution is used. Results are presented for simulations using both a uniform grid and an adaptive grid that refines the reaction zone.« less
  • The xRage code contains three HE ignition models: Forest Fire, Cerro Grande and Ignition and Growth. After describing these models we present results of verification and validation (V and V) tests. These include simulations to determine the Pop-plot for each model and comparision with embedded velocity gauge data for shock-to-detonation transition (SDT) experiments. The data for the SDT experiments on PBX 9502 is taken from the recently developed high explosive database (HED). The HED data files contains additional meta-data with the key experimental parameters. This enables the use of scripts to automate testing: generating xRage input file, running simulation andmore » generating comparison plots with experimental and simulated data. The simulations show that the models are robust. But there is a mesh dependence with the time for transition-to-detonation varying by several tenths of microseconds. After the transition to a detonation wave, the detonation speed and pressure may vary by a few per cent.« less
  • High explosives are energetic materials that release their chemical energy in a short interval of time. They are able to generate extreme heat and pressure by a shock driven chemical decomposition reaction, which makes them valuable tools that must be understood. This study investigated the accuracy and performance of two Los Alamos National Laboratory hydrodynamic codes, which are used to determine the behavior of explosives within a variety of systems: xRAGE which utilizes an Eulerian mesh, and FLAG with utilizes a Lagrangian mesh. Various programmed and reactive burn models within both codes were tested using a copper cylinder expansion test.more » The test was based on a recent experimental setup which contained the plastic bonded explosive PBX 9404. Detonation velocity versus time curves for this explosive were obtained using Photon Doppler Velocimetry (PDV). The modeled results from each of the burn models tested were then compared to one another and to the experimental results. This study validate« less
  • Poor reproducibility among laboratories that use the ASTM D2274 test for the storage stability of distillate fuels has long been a problem. Different operators who use the same equipment obtained different average results even within a single laboratory. A questionnaire relating to the method was sent to users to elicit information about variations in practice among laboratories and to gain insight into the causes. This Center began a task to identify the critical variables in the test procedure by testing three fuels. It was concluded that there is negligible effect from variations in the bath temperature of less than 0.2more » C, in oxygen flow rate of less than 0.3 L/hr, and of time-in-bath of less than 0.25 hr. However, each of these variables (especially the temperature) has a major impact if the limits are exceeded.« less