On the symmetry-preserving regularization model on complex flows using unstructured grids

Abstract

Traditionally turbulence modeling of industrial flows in complex geometries have been solved using RANS models and unstructured meshes based solvers. The lack of precision of RANS models in these situations and the increase of computer power, together with the emergence of new high-efficiency sparse parallel algorithms, make possible the use of more accurate turbulent models such as Large Eddy Simulation models (LES). Recently, relevant improvements on turbulence modeling based on symmetry-preserving regularization models for the convective (non-linear) term have been developed. They basically alter the convective terms to reduce the production of small scales of motion by means of vortex-stretching, preserving all inviscid invariants exactly. To do so, symmetry and conservation properties of the convective terms are exactly preserved. This requirement yields a novel class of regularizations that restrain the convective production of smaller and smaller scales of motion by means of vortex stretching in an unconditional stable manner, meaning that the velocity can not blow up in the energy-norm (in 2D also: enstrophynorm). The numerical algorithm used to solve the governing equations must preserve the symmetry and conservation properties too. At this stage, results using regularization models at relatively complex geometries and configurations are of extreme importance for further progress. The main objective of the present paper is the assessment of regularization models on unstructured meshes. To do this, three different test cases have been studied: the impinging jet flow, the flow past a circular cylinder and a simplified Ahmed car. In order to analyse the influence of the filter, the cases have been solved using the Gaussian and the Helmholtz filters. Furthermore, the performance of the model considering the influence of the grid parameters and the filter ratio are also analysed.