Publications

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CTH is an Eulerian hydrocode developed by Sandia National Laboratories (SNL) to solve a wide range of shock wave propagation and material deformation problems. Adaptive mesh refinement is also used to improve efficiency for problems with a wide range of spatial scales. The code has a history of running on a variety of computing platforms ranging from desktops to massively parallel distributed-data systems. For the Trinity Phase 2 Open Science campaign, CTH was used to study mesoscale simulations of the hypervelocity penetration of granular SiC powders. The simulations were compared to experimental data. A scaling study of CTH up to 8192 KNL nodes was also performed, and several improvements were made to the code to improve the scalability.

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Sandia has invested heavily in scientifc/engineering application development and in the research, development, and deployment of large scale HPC platforms to support the com- putational needs of these applications. As application developers continually expand the capabilities of their software and spend more time on performance tuning of applications for these platforms, HPC platform resources are at a premium as they are a heavily shared resource serving the varied needs of many users. To ensure that the HPC platform resources are being used efciently and perform as designed, it is necessary to obtain reliable data on resource utilization that will allow us to investigate the occurrence, severity, and causes of performance-afecting contention between applications. The work presented in this paper was an initial step to determine if resource contention can be understood and minimized through monitoring, modeling, planning and infrastructure. This paper describes the set of metric defnitions, identifed in this research, that can be used as meaningful and poten- tially actionable indicators of performance-afecting contention between applications. These metrics were verifed using the observed slowdown of IOR, IMB, and CTH in operating scenarios that forced contention. This paper also describes system/application monitoring activities that are critical to distilling vast amounts of data into quantities that hold the key to understanding for an application's performance under production conditions and that will ultimately aid in Sandia's eforts to succeed in extreme-scale computing.

Computational simulation of structures subjected to blast loadings requires integration of computational shock-physics for blast, and structural response with potential for pervasive failure. Current methodologies for this problem space are problematic in terms of e ffi ciency and solution quality. This report details the development of several coupling algorithms for thin shells, with an emphasis on rigorous verification where possible and comparisons to existing methodologies in use at Sandia.

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The Method of Manufactured Solutions (MMS) is used to evaluate the Material Point Method (MPM) implemented in CTH, i.e. Markers. MMS is a verification approach in which a desired deformation field is prescribed and the required forcing function to achieve the prescribed deformation is determined analytically. The calculated forcing function is applied within CTH markers determine if the correct displacement field is recovered. For the cases examined in this study, a ring is subjected to a finite, angular-independent, spatially varying body force, superposed with a rigid-body rotation. This test will assess the solid mechanics response of the MPM within CTH for large deformation problems.

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The modeling of failure in a finite volume shock physics computational code poses many challenges. We recently improved upon our recently implemented numerical technique the Material Point Method (MPM) by adding the Convective Particle Domain Interpolation (CPDI) to our finite volume shock physics computational code CTH. The CPDI technique improves accuracy and efficiency of the MPM for problems involving large tensile deformations and rotations. CPDI provides a method for the particles to remain in communication with each other by expanding the interpolation domain over that of the generalized MPM method. This will in turn prevent numerical fracture where fracture occurs when particles loose communication with one another while under going large tensile deformation. This work will focus on a comparison of the abilities of CPDI and generalized MPM in predicting the penetration of steel into aluminium. Simulations of the experiments will be performed to quantify the two numerical techniques.

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