Um modelo de turbulência baseado no conceito de vórtice

Abstract

The turbulence is present in most of the flows observed in industry and nature. There are many considerations regarding the difficulties related to the characterization of turbulent flows. One of the many issues regarding the procedure of analyzing the problem through the statistical description of the fields, which leads to the problem of closure and the modeling of the Reynolds tensor, usually with models based on the turbulent viscosity concept. The turbulence models have some shortcomings in predicting the turbulent flow field, which justifies the research of new approaches to treatment turbulence. In this work, the problem of closure is treated using the modeling based on the concept of turbulent viscosity. The proposed new turbulence model admits the existence of vortexs immersed in the flow and applies concepts and definitions related to the identification of this structure, using the Q - criteria that characterizes the region of flow occupied by the vortex. It is proposed to investigate the applicability of this model, resulting in a new turbulence model called k − ε −Q . The model applicability is evaluated through a numerical code for computational treatment of turbulent flows. The numerical solution was obtained by discretization of the fluid domain, using the finite volume method and the multigrid method was used for solving the resulting linear system. As benchmark, we used the turbulence model to simulate the flow in a square cavity with sliding lid and turbulent flow over a backward-facing step. The results were compared with some experimental data and demonstrated that the model proposed here appears to be more effective than the classical k − ε in the treatment of turbulence in these two problems.