Numerical study of the turbulent unsteady wake behind a partially enclosed square cylinder using RANS

Flow past a square cylinder placed centrally in a parallel plate channel has been numerically simulated at a Reynolds number of 21 400. Although turbulence is an essentially three-dimensional (3D) phenomenon, an effort has been made to capture the essence of time-averaged flow quantities through the turbulence models in two dimensions. Three turbulence models namely the standard k-ε, Kato-Launder k-ε and the RNG k-ε have been taken up for this purpose. The results so obtained, have been subsequently compared with the experiments for flow past a square cylinder in an unbounded medium. All the three models clearly reveal the vortex shedding phenomena at nearly identical Strouhal numbers. The predicted lift and drag coefficients due to the standard k-ε and Kato-Launder k-ε models are quite close. However, the predicted lift and drag coefficients due to the RNG k-ε model are different. A detailed comparison in terms of the time-averaged velocities at specified locations and the kinetic energy of the fluctuations reveals Kato-Launder k-ε to be the best. The numerical results were compared with the experimental observations of Lyn et al. [18]. A good match between the kinetic energy peaks shows that the Kato-Launder k-ε model has the correct estimation of the production term in the modelled turbulence equations