Escoamento turbulento sobre obstrução: influência da malha na análise espectral e estrutural

Abstract

The fidelity of numerical simulations of turbulent flows, conducted under the Finite Volume Method (FVM) methodology, is directly dependent on the quality of the computational mesh. An inadequate spatial discretization can lead to inaccurate predictions of critical physical phenomena. This work presents a systematic and quantitative analysis of the influence of mesh refinement on the spectral and structural characteristics of the incompressible turbulent flow over a rectangular obstacle, configured at a Reynolds number of Re ≈ 5×10⁵. The simulations were performed using the open-source software OpenFOAM, with the PISO algorithm and the Large Eddy Simulation (LES) turbulence model featuring the WALE subgrid-scale model. The mesh independence study was conducted by comparing four refinement levels. Convergence was assessed through the analysis of temporal autocorrelation and the power spectral density (PSD) of velocity fluctuations. The results demonstrate that coarse meshes introduce excessive nume rical dissipation, suppressing small-scale structures. Conversely, the reference (Medium) and Refined meshes achieved a converged solution, evidenced by the overlap of their autocorrelation functions. The spectral analysis, based on the Fast Fourier Transform, revealed that only the refined mesh was able to capture an extensive inertial subrange with an energy decay consistent with Kolmogorov’s theoretical −5/3 power law, thereby validating the simulation’s ability to reproduce the energy cascade. It is concluded that mesh resolution is a first-order parameter that governs the simulation’s ability to correctly capture vortex dynamics and the physics of turbulence, making its systematic verification an essential step for the validation of the numerical model.