The Shear Layer of D-65° Type Bluff Body in Effect of Main Cylinder as Passive Control Flow Modification: A Numerical Analysis

This chapter delves into the intricate world of airflow dynamics over cylinders, presenting a groundbreaking hypothesis that modifying the shape of a hydraulic brake line to a D-65° cylinder upstream of a main cylinder can lead to extraordinary drag reduction. Through a meticulous two-dimensional unsteady flow numerical simulation, the study explores the aerodynamic benefits of this configuration, setting the distance between the cylinder center points at s / D = 1.375 and the relative diameter at d / D = 0.125, with a Reynolds number of Re = 5.3 × 10^4. The research builds on extensive prior work, including studies by Triyogi et al. and Lee et al., and employs advanced numerical methods such as the RANS-based equations and the k-kl-ω turbulence model. The results reveal a significant reduction in drag force, with the drag coefficient decreasing by 46.95% and the lift coefficient undergoing a notable directional shift. The chapter also provides detailed pressure and velocity contours, highlighting the delayed separation phenomenon and the reattachment of the shear layer to the cylinder’s surface. This comprehensive analysis not only validates the hypothesis but also paves the way for future research in three-dimensional numerical approaches and the financial benefits of such aerodynamic improvements.