Numerical investigations on the flow control over bumped surface circular cylinders

External flow-induced forces on bumped surface circular cylinders in laminar flow regimes are studied at a range of Reynolds numbers up to 200. This study examines three types of bumped surface cylinders, including square, triangular, and dimpled surfaces. The bumped surfaces are set at the top surface of the cylinder. The bumps are arranged between theta = 0 degrees and 90 degrees from the front stagnation point of the cylinder. It is shown that the presence of a bump on the leading edge of the cylinder manipulates the vortex dynamics and leads to significant changes in flow-induced forces. The results show that due to asymmetrical imposed pressure on the cylinder, the generated negative vorticity of the square bumped surface is approximately 28% stronger than those of triangular and dimpled surfaces once theta = 90 degrees. Comparing to a smooth cylinder, significant reductions in drag and lift coefficients are obtained at Re = 150 once a bump is created on the surface of the cylinder apart from the type of geometry. It is found that the maximum time-mean lift coefficient is produced once the bump is located at theta >= 45 degrees. Furthermore, the minimum drag force is generated for the bumped surface cylinder with theta = 0 degrees and Re = 150.

Automated summary

This study investigates external flow-induced forces on circular cylinders with bumped surfaces in laminar flow regimes, revealing that the presence of bumps significantly alters vortex dynamics and reduces drag and lift coefficients. Among the square, triangular, and dimpled surfaced cylinders examined, the square bumped surface exhibits the strongest negative vorticity when theta = 90 degrees compared to the others. Additionally, maximum lift coefficient is achieved when the bump is located at theta >= 45 degrees, while minimum drag force occurs at theta = 0 degrees and Re = 150.