Publications

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The SPARC (Sandia Parallel Aerodynamics and Reentry Code) will provide nuclear weapon qualification evidence for the random vibration and thermal environments created by re-entry of a warhead into the earth’s atmosphere. SPARC incorporates the innovative approaches of ATDM projects on several fronts including: effective harnessing of heterogeneous compute nodes using Kokkos, exascale-ready parallel scalability through asynchronous multi-tasking, uncertainty quantification through Sacado integration, implementation of state-of-the-art reentry physics and multiscale models, use of advanced verification and validation methods, and enabling of improved workflows for users. SPARC is being developed primarily for the Department of Energy nuclear weapon program, with additional development and use of the code is being supported by the Department of Defense for conventional weapons programs.

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This document compares results for isothermal wall cases and observes their stagnation lines.

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High performance computing (HPC) is undergoing a dramatic change in computing architectures. Nextgeneration HPC systems are being based primarily on many-core processing units and general purpose graphics processing units (GPUs). A computing node on a next-generation system can be, and in practice is, heterogeneous in nature, involving multiple memory spaces and multiple execution spaces. This presents a challenge for the development of application codes that wish to compute at the extreme scales afforded by these next-generation HPC technologies and systems - the best parallel programming model for one system is not necessarily the best parallel programming model for another. This inevitably raises the following question: how does an application code achieve high performance on disparate computing architectures without having entirely different, or at least significantly different, code paths, one for each architecture? This question has given rise to the term ‘performance portability’, a notion concerned with porting application code performance from architecture to architecture using a single code base. In this paper, we present the work being done at Sandia National Labs to develop a performance portable compressible CFD code that is targeting the ‘leadership’ class supercomputers the National Nuclear Security Administration (NNSA) is acquiring over the course of the next decade.

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A multi-dimensional finite element solver for decomposing and non-decomposing ablating materials has recently been developed and is discussed in this paper. The underlying mathematical and material models are presented along with its discretization via the finite element method. The governing equations and solution algorithm is based on the one-dimensional control-volume finite element method (CVFEM) Chaleur code, a successful ablation code in use at Sandia National Labs, and this paper represents a multi-dimensional extension of Chaleur. The Equilibrium Surface Thermochemistry (EST) code, an equilibrium gas/surface thermochemistry code for decomposing and non-decomposing materials that was previously developed by the authors is used in conjunction with this new multi-dimensional ablation code to provide ablation thermochemistry information (i.e. B0c and enthalpy tables). This new multi-dimensional ablation response code is first applied to solve two established code-to-code comparison problems with tabular aeroheating data. Another aspect of this work has been to develop the ability to couple CFD-based aeroheating data to the ablation code as a spatial and time variant boundary condition. Towards this end, we have established a one-way passing of aeroheating data from a hypersonic CFD code to the ablation code. We then examine the problem of simulating the ablation response of non-decomposing and decomposing materials in two arc-jet facilities.

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