CFD Simulation of Airflow Around a Circular Cylinder

Abstract

This study presents a numerical investigation of fluid flow characteristics around a circular cylinder using ANSYS Fluent software. The main objective is to analyse the effects of different inlet velocities on pressure distribution, flow structure, and velocity field around the body. The cylinder is modelled with a diameter of 5 mm and an extrusion length of 30 mm, placed at the centre of a rectangular computational domain with a uniform distance of 30 mm from all outer boundaries. The numerical simulation employs the automatic meshing method with tetrahedral elements, where the element size ranges from 12.0 mm to 2.0 mm. A grid independence test is conducted to verify accuracy, and a mesh size of 2.0 mm is selected for all final analyses to ensure high resolution and consistency. The SST k ω turbulence model is applied together with the finite volume method to solve the governing equations of fluid flow, while boundary conditions are defined as velocity inlet, pressure outlet, wall, and pipe surfaces accordingly. Simulations are performed at three different inlet velocities: 10 m/s, 50 m/s, and 80 m/s, to observe changes in flow behaviour as speed increases. The results show that velocity magnitude has a significant influence on the overall flow physics. At 10 m/s, the pressure distribution is mostly uniform with only a small high-pressure zone at the front stagnation point, while streamlines follow the surface smoothly with no separation. As velocity rises to 50 m/s and further to 80 m/s, the pressure difference between the front and rear surfaces becomes much larger, creating a stronger drag force acting on the cylinder. The streamline patterns indicate wider deflection, earlier separation, and a broader wake region behind the body at higher speeds. Velocity contours reveal that the flow accelerates strongly along the curved sides, reaching a maximum value of 91.21 m/s at 80 m/s, accompanied by steep gradients near the surface and a large low-velocity area downstream. All results maintain symmetrical distribution, confirming stable and balanced flow conditions throughout the study. In conclusion, this work successfully demonstrates how increasing velocity directly leads to greater pressure variation, larger flow disturbance, and more intense acceleration around the cylinder. The numerical setup used is proven reliable and capable of producing physically meaningful data, providing a clear understanding of flow characteristics that can support engineering design and analysis involving cylindrical structures.