Abstract
This paper studies if adaptive grid refinement combined with finite-volume simulation of the incompressible RANS equations can be used to obtain grid-independent solutions of realistic flow problems. It is shown that grid adaptation based on metric tensors can generate series of meshes for grid convergence studies in a straightforward way. For a two-dimensional airfoil and the flow around a tanker ship, the grid convergence of the observed forces is sufficiently smooth for numerical uncertainty estimation. Grid refinement captures the details of the local flow in the wake, which is shown to be grid converged on reasonably-sized meshes. Thus, grid convergence studies using automatic refinement are suitable for high-Reynolds incompressible flows.
Highlights
One of the trends in computational fluid dynamics today is the highfidelity simulation of more and more complex flows
Multiphysics computations like fluid-structure interaction or the modelling of cavitation become common. The results of such simulations depend on the physical models being used, such as the turbulence model in the Reynolds-averaged Navier-Stokes (RANS) equations. Often, such models are applied in situations which are far more complex than the ones for which they were developed and which may be outside their range of validity
A fit through the finest 5 grids, while not identical to the first fits, is good as shown by its low value of σ. This indicates that Cd behaves as a power law, perturbed only by small-scale noise. This is different for Cl : the power-law fit has no solution for Tr = 0.0884, the coefficients vary for each added point, and Cl0 is always lower than Cl, even though Cl on the finest grids increases with further refinement
Summary
One of the trends in computational fluid dynamics today is the highfidelity simulation of more and more complex flows. Multiphysics computations like fluid-structure interaction or the modelling of cavitation become common The results of such simulations depend on the physical models being used, such as the turbulence model in the Reynolds-averaged Navier-Stokes (RANS) equations. Simulations and grid refinement are performed with the ISIS-CFD unstructured finite-volume incompressible RANS solver developed by the authors from ECN-CNRS This code is used for the realistic simulation of industrial-type flows, it is available as the flow solver of the FINETM /Marine computing suite. The tests in this paper are based on the type of computations usually performed with ISIS-CFD: incompressible RANS flows, unstructured hexahedral grids, refinement by subdivision, and refinement criteria based on second spatial derivatives. The conclusion (section 7) discusses the generality of the results and evaluates the limitations and perspectives of the proposed grid convergence method
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