External Flow Study Around a Hexagonal Cylinder

Abstract

The external flow around hexagonal cylinder is significant as this type of bluff body can generate high pressure drag and a well-defined wake region. The present work was performed by analyzing the flow phenomena around a 3d hexagonal cylinder by performing CFD simulation in the ANSYS Fluent software with a variation of inlet velocity. The steady state pressure-based solver and SST k-  turbulence model were used. A grid independence test was conducted with coarse, medium and fine mesh before making the comparisons of the two main cases. The result indicates that there is only a small difference in drag coefficient (1.18%) between the medium and fine mesh and so the medium mesh was chosen to reduce the time whilst maintaining acceptable accuracy. The inlet velocity is compared between three velocities, namely 5 m/s, 10 m/s and 15 m/s. The drag coefficient stayed almost constant around 2.03, while the drag force increased from 0.6202 N to 5.6043 N. The pressure contour, velocity contour, and pathline result also depicts the front stagnation point, separated wake and the recirculation region behind the cylinder. This implies that the aerodynamic load is greatly increased with wind speed, despite only a small variation in drag coefficient.