Optimising the OpenFOAM Overset Mesh Solver for Offshore Renewable Applications

Qian, Ling ORCID: https://orcid.org/0000-0002-9716-2342, Rai, Ranjodh, Ma, Zhihua, Bai, Wei, Song, Xianglei and Linxing, Shi (2025) Optimising the OpenFOAM Overset Mesh Solver for Offshore Renewable Applications. In: ISOPE-2025 The 35th International Ocean and Polar Engineering Conference, 1 June 2025 - 6 June 2025, Seoul/Goyang, Korea. (In Press)

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Abstract

The overset mesh method has gained significant popularity for use in computational fluid dynamics (CFD) due to its ability to handle large amplitude motion of structures with complex geometries. However, solvers employing this method can be computationally expensive, so the primary objective of this work is to optimise the open-source ESI-OpenCFD OpenFOAM overset mesh solver for offshore renewable applications by improving its efficiency. A secondary objective is to also establish whether the updated hole-cutting procedure released in OpenFOAM v2212 improves the accuracy of solutions and reduces computational time. A profiling investigation of the solver establishes that the method for donor searching is the primary efficiency bottleneck; hence, a new optimised method is developed that reduces the number of donors that have to be found and consequently reduces the number of necessary inter-processor communications. The new method is validated through two test cases: regular wave interaction with a two-dimensional T-shaped floating body and the aerodynamic modelling of an offshore wind-turbine rotor in constant wind. It is found that the new method reduces computational time in the T-body case by 14 and 7 % on 128 and 256 cores respectively—a modest amount but to be expected for a simple case with only small amplitude motion. For the wind turbine case, the new method reduces computational time by 64.6 % on 1024 cores—approximately 3x faster. For the secondary objective, it is found that the updated hole-cutting method does indeed improve the accuracy of solutions for the T-body case but not necessarily for the wind turbine case. The effect on computational time is small.