Numerical study on the wake characteristics of a square cylinder in linearly stratified flow at a Reynolds number of 200

In this study, the flow structures and hydrodynamic forces acting on a square cylinder in a linearly stratified flow at a fixed Reynolds number of Re = 200 are analyzed using large eddy simulation across a Froude number range of 0.2 ≤ Fr ≤ ∞. This study examines the effects of stratification on flow structures and associated hydrodynamic coefficients, employing both qualitative and quantitative analysis. The findings indicate that the flow patterns can be categorized into two primary types: the V pattern and the W pattern. In the V pattern (2 ≤ Fr ≤ 10), the wake is characterized by large-scale vortices shed from the separated shear layers. In contrast, the W pattern (0.2 ≤ Fr ≤ 1) shows a complete absence of vortex shedding. In this case, internal waves are the primary factor influencing the flow field. A transition between these two patterns is observed at a Froude number of 1. Furthermore, as the strength of stratification increases, the size of the recirculation zone progressively diminishes, signifying a gradual suppression of vertical motion. The analysis of drag and lift coefficients, Strouhal number, and pressure coefficient reveals a dependence on the Froude number, with the transition at Fr = 1 serving to further validate the classification of the flow patterns.