Experimental and numerical investigation of flow structure of rotary oscillating smooth and corrugated cylinders

The aim of this thesis is to investigate the flow structure occurring behind the smooth and corrugated cylinders by using rotational oscillation which is one of the active flow control methods experimentally and numerically. The experiments were conducted by using Particle Image Velocimetry (PIV) technique for the smooth circular cylinder at ReD=1000 and ReD=5000 of Reynolds numbers, different oscillation amplitudes (θA) and frequency ratios (FR). PIV and numerical analysis of the stationary and rotary oscillating circular cylinders having different roughness coefficients (ɛ/D=0.02, 0.04 and 0.06) and corrugated geometries (rectangle, circular and triangle) at ReD=5000 were investigated. The numerical study includes stationary and rotary oscillation motions of the smooth and corrugated cylinders at ReD=5000 by using Computational Fluid Dynamics (CFD). The numerical study was carried out by using Reynolds-averaged Navier-Stokes (RANS) equations and 2D time-dependent k-ω Standard turbulence model. Drag coefficient (CD) and pressure coefficient (Cp), which is not involved in the experimental results of the stationary and rotary motion of the smooth and corrugated cylinders, are obtained from the numerical study. It is concluded that the rotary oscillating motion has important effects on the cylinder wake region and changes the near wake region structure and vortex shedding modelling. Significant control of the cylinder wake region and the shear layer instability has been achieved. In addition, the rotary oscillating motion of the cylinder significantly effected the average dimensionless flow structure. All frequency ratios and oscillation amplitudes significantly changed the average velocity profiles in the region of vortex formation.