Numerical simulation of bluff body turbulent flows using hybrid RANS/LES turbulence models

Bluff body characteristic flows are employed in many engineering applications, including both gas turbine combustors and industrial burners. Since these flows exhibit an inherently unsteady dynamics, their numerical modeling is challenging. Therefore, the main goal of this work is to assess the predicting capabilities of hybrid RANS/LES approaches to properly predict bluff body turbulent flows. Accordingly, accounting for a circular bluff body flow configuration, three different turbulence modeling approaches are investigated in this work, (i) RANS, (ii) LES, and (iii) hybrid RANS/LES. Regarding the hybrid approaches, two variants of the detached eddy simulation (DES) one, delayed DES (DDES) and improved delayed DES (IDDES), are studied. As RANS model, the-ω is utilized here. This RANS model is also used as the background one for both DDES and IDDES. Wall-adaptive local eddy viscosity (WALE) is used in turn as the subgrid scale (SGS) model for LES. When compared to experimental data, the obtained numerical results indicate that RANS overestimates the recirculating bubble length by over 18% and is not capable of describing the turbulent kinetic energy and the flow anisotropy in agreement with the experimental data. In contrast, LES, DDES, and IDDES are all within 1% of the recirculating bubble length, while predicting both the Reynolds stress tensor components and the corresponding flow anisotropy in agreement with the measurements. Besides, normalized anisotropy tensor invariants maxima in the shear layer are reproduced by all scale resolving models studied here, but they fail to yield the local extrema measured within the wake recirculation region. Some of the contributions of this work relate to the anisotropic turbulence invariants analyses carried out and the performance assessment of different DES alternatives in comparison to more proven LES techniques