Numerical investigation of turbulent flow structure in a channel with sudden expansion

Abstract

Separation flows are common in many process units, so the question of modeling these flows is relevant to date, just as the search for the most suitable turbulence models for them. In this paper, the structure of a viscous incompressible turbulent flow in a channel with sudden expansion was calculated. To compare the results, the experimental data were taken. The mathematical model is based on the use of the Reynolds averaged Navier-Stokes equation, represented in the Eulerian form. To obtain the results of numerical simulation, the $k-\epsilon$ turbulence model is chosen. The solution of the task was carried out by the finite volume method in the open package OpenFOAM. The procedure for constructing grids is worked out, where among the three is selected with a rational grid step. The obtained velocity results showed the best result when compared with experiment. The values of turbulent kinetic energy have good indices, however, some disagreements between the data of theory and experiment are observed at the wall in some sections. The reduced pressure coefficient, whose data is obtained along the bottom wall of the channel, showed a deviation of the values towards the obstacle, which is the starting point for future studies and model properties. The attachment area has a length comparable with the results of the experiment. Comparison of the results of numerical simulation with experimental data has shown that this model satisfactorily describes separation currents, and the proposed approach is relevant for the simulation of turbulent flows.