Control of Aeroacoustic Noise Generation during Flow Past a Circular Cylinder using Splitter Plate

Aeolian tone generation during unsteady, two-dimensional flow past a circular cylinder in the presence of splitter plates has been numerically investigated at Reynolds number Re = 150 and Mach number M = 0:2 using direct numerical simulations (DNS ). Computations have been performed for flow over a circular cylinder with and without splitter plates. Arc shaped splitter plates have been placed near the top surface of the cylinder. Compressible Navier-Stokes equations in non-dimensional form have been solved using combination of optimized coupled compact di erence (OCCD) scheme and optimized five stage Runge- Kutta (ORK5) time integration scheme. O-grid topology has been adopted in the present computations to generate refined mesh inside computational domain. Computational domain has been divided into acoustic and bu er zones. Acoustic zone covers up to 100D radius with closely spaced grid points, where, D is the diameter of cylinder. On the other hand, bu er zone has comparatively coarser grid, which helps to dissipate high wavenumber numerical oscillations generated during calculations and thereby avoiding reflections from the outer boundary. Results show amplitudes of fluctuating lift forces are reduced in the presence of splitter plate. Placing the splitter plate near the top surface of cylinder resulted in changes in vorticity contours and delay in flow separation. Due to this reason, mean drag has been decrease on the cylinder in the presence of splitter plates. Disturbance pressure field shows less intensity for the case with splitter plate than without splitter plate. Directivity patterns based on root mean square (RMS ) values of disturbance pressure have also shown that there is a reduction in net acoustic noise radiated from cylinder with splitter plate. Furthermore, acoustic, thermal and hydrodynamic modes have been decomposed using Doak's decomposition theory.