A massively-parallel, unstructured overset method for mesh connectivity

Journal Article · Thu Oct 04 00:00:00 EDT 2018 · Journal of Computational Physics

DOI:https://doi.org/10.1016/j.jcp.2018.09.053· OSTI ID:1614483

Horne, Wyatt James ^[1]; Mahesh, Krishnan ^[1]

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1. University of Minnesota, Minneapolis, MN (United States)

Here we present a method that dynamically and efficiently performs connectivity calculations between many O(10⁵) moving, unstructured overset meshes in parallel. In order to connect overset meshes, elements exterior to the solution domain must be removed from the simulation. In regions with many overlapping meshes, elements must be selectively removed to reduce redundancy while maintaining a solution over the entire domain. Around masked regions interpolation partner pairing is required between meshes to provide boundary conditions. For general unstructured meshes, these steps involve challenging computational geometry calculations which must be efficient and automatic. For many moving meshes each step must be massively parallelized and scalable to large numbers of computational cores. To establish communication patterns a parallelized master/slave algorithm is used which minimizes global communication and storage. To remove elements a parallel ‘Forest Fire’ flood-fill algorithm is used to set a masking variable. For interpolation partner pairing, and other necessary searches, k-dimensional tree data structures (k-d trees) are extensively used. Often in a calculation, the connectivity between overset meshes remains largely the same between time steps. The temporal coherence of the various objects in the connectivity calculation is directly used to only update necessary information with time, resulting in substantial cost savings. Details of the different algorithms are presented. Resulting connectivity and timings are shown for complex geometries. Parallel scaling is demonstrated for 100,000 spherical particles within a channel up to 492,000 processors.

• Research Organization: Stanford Univ., CA (United States); Univ. of Minnesota, Minneapolis, MN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
• Grant/Contract Number: NA0002373; CBET-1510154.; CBET-1510154
• OSTI ID: 1614483
• Alternate ID(s): OSTI ID: 1635918
• Journal Information: Journal of Computational Physics, Vol. 376, Issue C; ISSN 0021-9991
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

97 MATHEMATICS AND COMPUTING
overset
unstructured
O(hundred thousand) meshes
connectivity
dynamic
parallel