CFD simulations of drag reduction from a square bluff body in the laminar flow regime

Abstract

Drag reduction in square cylinders is still a serious challenge to fluid mechanics with immediate applications in engineering structures like tall buildings, bridges, and pipelines. Although square and circular cylinders have been studied extensively, the current thesis is particularly concerned with square bluff bodies and explores passive geometric alteration as a strategy for aerodynamic enhancement. This research utilizes Computational Fluid Dynamics (CFD) simulations with ANSYS Fluent to investigate the impact of corner modification, specifically the cut (recessed) corner method on square cylinders' drag behavior under laminar flow conditions. The study systematically investigates how the geometry change of square cylinders by the addition of cut corners affects flow separation, wake patterns, and total drag coefficient over various Reynolds numbers. The findings show that the recessed corner modification successfully postpones the separation of flow, reduces the wake area, and decreases the intensity of turbulence behind the cylinder, resulting in a quantifiable reduction in drag. For instance, at a Reynolds number of 200, the recessed (cut) corner condition realized a maximum drag reduction of 2.92 % over the sharp-cornered baseline. These results are compared against published literature and demonstrate the applicability of the cut corner technique as a simple, passive means for the optimization of bluff body shapes in actual engineering applications where reducing aerodynamic drag is paramount.