Simulating the flow around a baseball: Study of a 2D-cylinder with a single bump

The seams of a baseball have a large influence in the dynamics of non-spinning balls, so that the Navier–Stokes equations must be solved if one wants to have a full description of the throw. However, the rugosity of the baseball makes difficult to study computationally the flow around it. Therefore only a few investigations have been reported on the subject. In this work, the flow around a ball is studied in a two dimensional domain by means of direct numerical simulations. The goal of this investigation is to characterize the effects produced by a single seam on the flow around the ball. In our 2D simulations the air flow is perpendicular to the cross section of the ball. In this context, the problem coincides with the flow around a circular cylinder with a bump on its surface that mimics the seam. The methodology consists in solving the compressible Navier–Stokes equations using a finite-difference method. The implementation was carried out using the ZEUS-3D magnetohydrodynamic code, originally designed for astrophysical purposes. Here we adapted the code to include a solid body (the ball), this will extend the potential use of the code to engineering problems. The flow is validated by comparison of the smooth case with previous findings reported in literature for smooth circular cylinders at similar Re. Near the surface of the ball, the results for the pressure coefficient are in agreement with previous studies for the front face however, we found some differences at the rear side of the ball. A systematic study is performed with a seam located at different angles from 0°to 90°. The resulting flow features are compared to the results of the smooth ball. Each seam produces large disturbations in pressure around it and smooth disturbations along the surface of the ball. We found a direct relationship between the local effects in pressure and the pressure drag and with the lift coefficient. The seams located at the angles of 30°, 85°and 90°produce the large effects in the aerodynamic coefficients and the wake. The results provide a better understanding of the dynamics of baseballs and other sport balls and might have direct application to the flow around modified cylinders.