CUBENS: A GPU-accelerated high-order solver for wall-bounded flows with non-ideal fluids - presented by M.Sc. Pietro Carlo Boldini

CUBENS: A GPU-accelerated high-order solver for wall-bounded flows with non-ideal fluids

M.Sc. Pietro Carlo Boldini

M.Sc. Pietro Carlo Boldini

Associated Computer Physics Communications article

P. C. Boldini et al. (2025) CUBENS: A GPU-accelerated high-order solver for wall-bounded flows with non-ideal fluids. Computer Physics Communications
Article of record
CUBENS: A GPU-accelerated high-order solver for wall-bounded flows with non-ideal fluids
M.Sc. Pietro Carlo Boldini
Pietro Carlo Boldini
Delft University of Technology

We present a massively parallel GPU-accelerated solver for direct numerical simulations of transitional and turbulent flat-plate boundary layers and channel flows involving fluids in non-ideal thermodynamic states. While several high-fidelity solvers are currently available as open source, all of them are restricted to the ideal-gas region. In contrast, the CUBic Equation of state Navier-Stokes solver (CUBENS) can accurately model and simulate the non-ideal thermodynamics of single-phase compressible fluids in the vicinity of the vapor-liquid saturation line or the thermodynamic critical point. By employing high-order finite-difference schemes and convective terms in split, kinetic-energy-, and entropy-preserving form, the solver is numerically stable, and robust with minimal numerical dissipation, enabling it to capture the steep variations of non-ideal thermodynamic properties. For cost-effective high-fidelity simulations, in addition to MPI parallelization, CUBENS is GPU-accelerated using OpenACC directives for computation offloading, and asynchronous GPU-aware MPI for efficient GPU-GPU communication. Moreover, CUBENS is compatible with both NVIDIA and AMD GPU architectures, achieving significant performance results while ensuring energy-efficient simulations. For instance, using 64 NVIDIA A100 GPUs compared to 8192 CPUs at the same computational cost results in a speedup of approximately 130×130 \times. In multi-node and multi-GPU configurations ranging from 2 to 128 compute nodes (8 to 512 GPUs), a strong scaling efficiency of around 52% and a weak scaling efficiency of 0.88 with 102431024^3 points per GPU, corresponding to approximately 55 billion degrees of freedom, are achieved. The CUBENS solver is validated against selected cases from the literature, covering transitional to turbulent ideal and non-ideal flows up to the transonic regime. In particular, we demonstrate the solver's suitability and applicability for direct numerical simulations of transitional boundary layers with fluids at supercritical pressure and with buoyancy effects. The development of this high-fidelity solver offers the potential for future fundamental research in non-ideal compressible fluid dynamics.

References
  • 1.
    P. C. Boldini et al. (2025) CUBENS: A GPU-accelerated high-order solver for wall-bounded flows with non-ideal fluids. Computer Physics Communications
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P. Carlo Boldini (2025, February 20), CUBENS: A GPU-accelerated high-order solver for wall-bounded flows with non-ideal fluids
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