Evaluation of Boundary Condition Treatments and Simulation Environments for Improved Near-Body Solutions in Lattice-Boltzmann Flow Simulations
Fernandez, Isabel Faith
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In this study, different wall boundary conditions and methodologies for improving near-body flow solutions for more complex geometric shapes in a GPU accelerated Lattice-Boltzmann method (LBM) framework were implemented and assessed by comparison to experimental data. Boundary conditions that account for curved geometry, an interpolated bounce-back method, an extrapolation based ghost method, and a unified boundary treatment, were implemented in the current Lattice-Boltzmann framework and the flow around a ROBIN fuselage body was evaluated based on the surface pressure distribution. The boundary conditions were implemented using both no-slip assumptions and slip/moving-wall assumptions. It was found that different types of boundary treatments had little effect on the near-body flow solution, but the slip vs. no-slip assumption had a significant impact on the near-body results. Applying a boundary treatment with a slip assumption, the flow separation expected around the fuselage was captured and the predicted pressures correlated well with experimental data, whereas the no-slip boundary treatment caused the flow separation region around the object to be over-estimated. For both the no-slip and slip boundary treatments, resolution and domain size were found to have little effect on the near-body flow solution in terms of surface pressure distribution. The no-slip boundary conditions, in addition to giving a less accurate near-body flow solution, also showed greater velocity fluctuations and more turbulent energy downstream, indicating that the wall treatments at the fuselage also have an effect on the flow field further downstream. The GPU accelerated LBM was found to have a significantly lower computational expense than the higher-fidelity Helios solvers being compared against.