Cálculo do comprimento do ponto de recolamento das camadas cisalhantes em escoamentos turbulentos

Abstract

The study of shear layer separation is important for engineering because of the variety of cases that this phenomenon occurs, such as flow in combustion chamber diffuser channels, separation bubbles in airfoils, flow in bridges and buildings, etc. A well-studied case of shear layer separation is the flow in a descending step, also known in the literature as Backward-Facing Step (BFS). In this problem a fully developed flow flows through a rectangular channel section until the occurrence of a sudden induced expansion caused by the change of geometry in the channel, which presents the shape of a step. This paper is part of the computational study of turbulent flow in a descending step and aims to evaluate the predictive ability of two RANS turbulence models to calculate the reattachment length, using a two-dimensional geometry with Er = 2 built in the BlockMesh utility of the computational fluid dynamics software OpenFoam. The solver used was PimpleFoam and the flow was considered to be two-dimensional, single-phase, isothermal, turbulent, and treated in the transient regime with Re = 9000. To estimate the simulation time it was used the unit time that is necessary to cover the height of the step (h), this value being estimated at 500s. After the simulation, post-processing was performed using the Paraview tool and the values Xr=6.25h for the k - model and Xr = 8.0h for the SST k - model. The DNS and LES simulations performed by (KOPERA et al., 2011) and (WANG; WU; ZHU, 2019) respectively were used for validation of the results. Keywords: Turbulence, Fluid dynamics, Simulation, Openfoam.