Experimental Study on Wake Characteristics of Secondary Grooved Cylinders with Different Depths

In this study, the flow field of a new secondary-grooved cylinder is determined by using particle image velocimetry (PIV) to understand the wake characteristics at different depths of the secondary grooved cylinders. In order to analyze the wake characteristic behind the secondary grooved cylinder with different depths, timeaveraged streamlines, time-averaged velocity, RMS velocity, Reynolds stress, turbulent kinetic energy, and instantaneous flow structures are employed. The recirculation zone for secondary grooved cylinders with different depths decreases when compared to the smooth cylinder; the peak magnitudes of flow velocity fluctuation intensity and transverse velocity fluctuation intensity for secondary grooved cylinders with different depths are reduced and the locations appear delayed. Furthermore, in contrast to the smooth cylinder, the secondary grooved cylinders with different depths Reynolds stress and turbulent kinetic energy are increased by the wake flow, and the transient large-scale vortex is split into several smaller-scale vortices behind the secondary grooved cylinders. The results obtained for the above flow structure are more significant when h/D = 0.05 for the secondary grooved cylinder.